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Development of critical-area criteria for protecting Microwave Landing System azimuth and elevation antenna guidance signals

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DEVELOPMENT OF CRITICAL-AREA CRITERIA FOR PROTECTING
MICROWAVE LANDING SYSTEM AZIMUTH AND ELEVATION
ANTENNA GUIDANCE SIGNALS
A Dissertation Presented to
The Faculty of the
Fritz J. and Dolores H. Russ
College of Engineering and Technology
Ohio University
In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy
by
Michael Francis DiBenedetto
March 1999
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UMI Number: 9919216
Copyright 1999 by
DiBenedetto, Michael Francis
All rights reserved.
UMI Microform 9919216
Copyright 1999, by UMI Company. All rights reserved.
This microform edition is protected against unauthorized
copying under Title 17, United States Code.
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THIS DISSERTATION ENTITLED
DEVELOPMENT OF CRITICAL-AREA CRITERIA FOR PROTECTING
MICROWAVE LANDING SYSTEM AZIMUTH AND ELEVATION
ANTENNA GUIDANCE SIGNALS
by Michael Francis DiBenedetto
has been approved
for the School o f Electrical Engineering and Computer Science
and the
Fritz J. and Dolores H. Russ
College of Engineering and Technology
Roge/D. Radcliff
Professor of Electrical Engineering and Computer Science
lih
im
/ )
>
£/
Warren K. Wray, Dean
Fritz J. and Dolores H. Russ
College o f Engineering and Technology
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ACKNOWLEDGMENTS
The research presented in this dissertation was funded by the Federal Aviation
Administration (FAA) under Contracts DTRS-57-C-00097, DRTS-57-85-C-00063,
Scientific Systems, Inc subcontract 86:1088.001, DTRS-57-87-P-80906, and DTRS-57-87C-0006.
The author extends his sincere gratitude to the FAA Navigation and Landing Team,
the MLS research team at the FAA Technical Center, and to the Members and Technical
Advisors of the All Weather Operations Panel (A WOP) of the International Civil Aviation
Organization for their support of, and sincere interest in, this research. I offer my sincere
thanks to Mr. Seymour Everett, U.S. Member to the A WOP, for the mentoring he provided
and the privilege of serving as one of his technical advisors.
The assistance of the staff of the Avionics Engineering Center was key to the
completion of this dissertation. Mr. David A. Dudding, Mr. Dennis E. Dudding, Mr. Paul
L. Ewing, Dr. Robert W. Lilley, and Dr. Michael S. Braasch are acknowledged for their
assistance with collecting the data required for validation of the critical-area criteria
presented herein.
The United Parcel Service is acknowledged for providing a Boeing B-747 aircraft and
ground crew, which enable the validation of the critical-area criteria presented herein.
I offer my sincere thanks to the members of my dissertation committee for providing
a thorough review of this dissertation, specifically: Dr. Jerrel R. Mitchell, Dr. Jeffrey C. Dill,
Dr. Frank van Graas, and Dr. Robert L. Williams II. To my advisor, Dr. Roger D. Radcliff,
thank you for your guidance, perseverance and continued encouragement.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
To my wife, Beth, and children, Michael, Joseph, and Stan, thank you for your
support, interest and understanding that “extra” time away was required for completing this
dissertation. To my mom and dad, who have given me so much, I am eternally grateful for
all that you have done.
In memory of Dorothy Virginia DiBenedetto.
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TABLE OF CONTENTS
Page
List o f Tables
iii
List o f Figures
iv
List o f Acronyms
I.
INTRODUCTION
A. Ground Equipment
1.
Angle Equipment
2.
Range Equipment
B. Airborne Equipment
C. Angle and Range Measurement Techniques
1.
Angle Measurement Concept
2.
Range Measurement Concept
II.
PROBLEM BACKGROUND
A. Siting Manual Overview
B. Author’s Contribution to the MLS Siting Manual Development
C. MLS Multipath Phenomena
1.
Angle Equipment
2.
Range Equipment
viii
1
1
4
16
18
22
23
23
26
27
29
31
31
36
III.
NEED FOR MLS CRITICAL AREAS AND SCOPE OF RESEARCH EFFORT
43
A. Assessing Requirement for MLS Critical Areas
43
B. Establishing Scope and Priorities
44
IV.
DEVELOPMENT OF AZIMUTH AND ELEVATION CRITICAL-AREA
CRITERIA
A. Development of Criteria for Basic Procedures
1.
Standard Approach Procedures
2.
Validation and Model Refinement
3.
Finalization of Results for Straight-in Procedures
4.
Dynamic Interfering Aircraft
5.
Offset-Azimuth Procedures
B. Computed-Centerline Approach Procedure
C. Advanced Procedures
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49
49
56
63
80
80
81
88
96
ii
V.
DEVELOPMENT OF DME/P CRITICAL-AREA CRITERIA
105
VI.
CONCLUSIONS AND RECOMMENDATIONS
A. Azimuth and Elevation Critical-Area Criteria
B. DME/P Critical-Area Criteria
108
108
110
VII.
REFERENCES
112
APPENDIX A: Multipath Error Equation For Angle Equipment
130
APPENDIX B: Critical Area Error Allocations for Azimuth and Elevation
132
APPENDIX C: Critical Area Criteria Published in FAA Order 6830.5
135
APPENDIX D: Critical Area Criteria Published in ICAO Annex 10
144
APPENDIX E: Derivation of Principle Shadowing Equation Used by MLSMM
160
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iii
List o f Tables
Page
Table 1. MLS Guidance Function Rates.
13
Table 2. DME/P Pulse Code Parameters.
17
Table 3. Azimuth-Error-Contour Plots Analyzed for Standard Approach Procedure.
57
Table 4. Elevation-Error-Contour Plots Analyzed for Standard Approach Procedure.
58
Table 5. Azimuth Critical-Area Lengths Versus Approach Radial Angle.
88
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iv
List o f Figures
Page
Figure 1. Illustration o f ICAO Precision Approach and Landing Operational
Categories.
2
Figure 2. MLS Approach and Landing Operations.
3
Figure 3. Preferred and Alternate Areas for Siting of the Azimuth and DME/P
Equipment.
5
Figure 4. Siting o f the Elevation Equipment.
6
Figure 5. Typical Azimuth/Elevation Ground Equipment Designs.
7
Figure 6. Typical DME/P Ground Equipment Designs.
8
Figure 7. Typical Ground Equipment Structures.
9
Figure 8. MLS Guidance Signal Coverage Volume.
10
Figure 9. Time-Multiplexed Signal Format.
11
Figure 10. Existing Function Sequences.
12
Figure 11. Azimuth Antenna Scan Conventions.
14
Figure 12. Elevation Antenna Scan Convention.
14
Figure 13 OCI Lateral Coverage.
15
Figure 14. Differential Phase Shift Keying.
16
Figure 15. DME/P Coverage and Modes of Operation.
19
Figure 16. Typical MLS Avionics Installations for Baasic and RNAV Procedures.
20
Figure 17. MLS Angle Receiver and DME/P Interrogator Designs.
21
Figure 18. Example MLS Avionics.
22
Figure 19. Angular Measurements Using the Time Reference Scanning Beam
Technique.
24
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Figure 20. The DME Slant Range Measurement Technique.
25
Figure 21. MLS Multipath Phenomena.
32
Figure 22. The Effect o f Multipath on the Angular Measurement Process.
34
Figure 23. Angle Equipment Error as a Function o f Multipath Signal Strength and
Separation Angle.
35
Figure 24. Illustration o f In-Beam and Out-of-Beam Multipath.
37
Figure 25. Illustration of Three-Dimensional Characteristic o f Multipath Propagation. 38
Figure 26. Effect o f Multipath on the DME Range Measurement.
40
Figure 27. Illustration of Short and Long Time-Delay Scatterers for DME.
41
Figure 28. DME/P Equipment Error as a Function of Multipath Signal Strength and
Time Delay.
42
Figure 29. MLS Approach Procedure Types.
46
Figure 30. Azimuth and Elevation Critical Area Problem Definition - Basic
Procedures.
50
Figure 31. Annotated Example Error-Contour Plot.
51
Figure 32. Overview o f Process Used to Generate Error Contour Plot Data - Azimuth. 53
Figure 33. Standard Filter Characteristics for Generating PFE and CMN Data From the
Static Error Data.
54
Figure 34. Methodology Used for Generating 95% Sliding Window Data.
55
Figure 35. Azimuth Critical-Area Criteria for Standard Approach Procedures.
60
Figure 36. Elevation Critical-Area Criteria for Standard Approach Procedures.
61
Figure 37. Measured and Modeled PFE Magnitude Data for Atlantic City Scattering
Position #3.
65
Figure 38. Measured and Modeled PFE Magnitude Data for Atlantic City Scattering
Position #5.
67
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Figure 39. Measured and Modeled PFE Magnitude Data for Standiford Field Elevation
Scattering Position # 1.
69
Figure 40. Overview of Process Used for Generating Measured PFE and CMN data.
70
Figure 41. Ground-Base Optical-Theodolite Reference System.
71
Figure 42. Repeatability o f Measured Data for Standiford Field Elevation Scattering
Position#!.
72
Figure 43. Rectangular Plates Used by MLSMM to Represent Shadowing Boeing B-747,
Viewed from SDF Elevation Antenna.
74
Figure 44. Overview of Theory Used by MLSMM to Estimate Elevation Error Due to
Shadowing by a Rectangular Plate.
75
Figure 45. Measured and Modeled PFE Magnitude Data for SDF Elevation Scattering
Position #1, Modified Tail Fin.
79
Figure 46. Procedure Types Supported by an Offset Azimuth Installation.
83
Figure 47. Plan View Considerations for Elevation Critical Areas. Offset-Azimuth
Procedure.
84
Figure 48. Plan View Consideration for Azimuth Critical Area - Offset Azimuth
Procedure.
86
Figure 49. Error Contour Plots for 0- and 10-Degree Rotation Angles. B-747.
87
Figure 50. Azimuth Line-of-Sight Migration Region for the Computed-Centerline
Approach.
90
Figure 51. Construction o f Azimuth Critical Area for Multiple Offset-Azimuth
Procedures.
91
Figure 52. Construction o f Azimuth Critical Area for Computed-Centerline
Procedures.
92
Figure 53. Verification: Detailed Methodology for Constructing Azimuth Critical Area
for Computed-Centerline Procedures.
94
Figure 54. Verification: Simplified Methodology for Constructing Azimuth Critical
Area for Computed-Centerline Procedures.
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95
vii
Figure 55. Standard Approach and OfF-Centerline Critical-Area Considerations.
97
Figure 56. Expansion of Basic Procedure Elevation Critical Area for OfF-Centerline
Procedures.
99
Figure 57. Elevation Error Contour Plot Comparing Length for Basic and
OfF-Centerline Procedures.
101
Figure 58. Sample Application of OfF-Centerline Critical-Area Requirements.
102
Figure 59. Simulation Set-Up for Developing Azimuth OfF-Centerline Critical-Area
Criteria - Minimum Height.
104
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List of Acronyms
ALS - Approach Lighting System
AWOP - All Weather Operations Panel
AZ - Azimuth
BAZ - Back Azimuth
CCL - Computed Centerline
CMN - Control Motion Noise
DH - Decision Height
DME - Distance Measuring Equipment
DME/N - Distance Measuring Equipment/Narrow
DME/P - Precision Distance Measuring Equipment
DPSK - Differential Phase Shift Keying
EL - Elevation
FA - Final Approach
FAA - Federal Aviation Administration
IA - Initial Approach
ICAO - International Civil Aviation Organization
ILS - Instrument Landing System
M/D - Multipath to Direct
MLS - Microwave Landing System
MLSMM - Microwave Landing System Mathematical Model
OCI - Out-of-Coverage Indication
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PFE - Path Following Error
PFN - Path Following Noise
PMDT - Portable Monitor/Data Termincal
RF - Radio Frequency
RMMS - Remote Maintenance and Monitoring System
RNAV - Area Navigation
SLS - Side Lobe Supression
SW - Sliding Window
TRSB - Time Reference Scanning Beam
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I.
INTRODUCTION
The Microwave Landing System (MLS) is an internationally standardized all-weather
precision approach and landing system that can provide three-dimensional guidance [1 ]. The
MLS is capable o f meeting International Civil Aviation Organization (ICAO) requirements
for Category IRC (Figure 1) precision instrument approach and landing operations [2]. The
MLS consists o f ground-based and airborne equipment operating on specified Aeronautical
Mobile (R) Service frequencies at L-band and C-band (Figure 2). Also, the MLS provides
a ground-to-air digital data link for transmission of operationally essential parameters (basic
data), and auxiliary data for use by other components of the airborne installation [1]. The
Federal Aviation Administration (FAA) MLS specifications provide a single standard for
accuracy which is suitable for supporting Category III operations [3-5]. However, the
standards for integrity, continuity and availability are specific to the category o f operation
(Category I, II, or III). At this writing, only systems certified for supporting Category I
approach and landing operations have been commissioned by the FAA.
A technical overview of the MLS is presented in the following sections, and this
overview emphasizes the MLS concepts germane to the investigation discussed herein.
Additional technical information and key developmental milestones are presented in
References 2 and 6.
A.
Ground Equipment
The basic MLS ground equipment configuration includes an Azimuth (AZ) system,
an Elevation (EL) system, a Distance Measuring Equipment (DME) transponder, and a
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w
I f
RUNWAY
■«
= 4 - 6 n mi
►
“ 1 0 - 1 5 n mi
PLAN VIEW
G l i d e P ath I n t e rc e p t P o in t
I nitial A p p r o a c h Fix
C a te g o r y II O p e r a ti o n : A p recisio n in stru m e n t a p p ro a c h and
la n d in g w ith a D ll < 2 0 0 ' b u t a 100' a n d w i t h a R V R 2 1 1 4 8 '
C a te g o r y I O p e r a ti o n : A p re c isio n in stru m e n t a p p ro a c h
an d la n d in g w ith a d e c is io n h e ig h t ( D ll) 2 2 0 0 ' a n d w i t h
e ith e r a v i sib ility
( R V R ) 2 18 0 4 ’.
2
2 6 2 4 ' o r r u n w a y v isu a l r a n g e
C a te g o r y I I I A O p e r a ti o n : A p recisio n in stru m e n t a p p ro a c h
a n d lan d in g w ith a D H < 100' an d w ith a R V R 2 6 ) 6 '.
C a te g o r y III B O p e r a ti o n : A p re c isio n in stru m en t
a p p ro a c h and la n d in g w ith a D H < 3 0 ' an d w ith a
R V R 2 636'.
l \ \ \ \ \ \ \ \ v ||\
RUNWAY
G l i d e P ath A n g l e = 3 .0 " (g e n e r a lly )
C a t e g o r y I I I C O p e r a t i o n : A p re c isio n in stru m e n t a p p ro a c h and
lan d in g w ith no d ec isio n h e ig h t an d no R V R lim itatio n s.
P RO F I L E VIEW
Figure 1. Illustration of ICAO Precision Approach and Landing Operational Categories.
M DB9803220I
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2D O R 3D CU RVED A P P R O A C H E S
(C O M P U T E D G UID A NCE)
N O IS E
ABATEM ENT
M LS TERMINAL AREA ENTRY GATE
INITIATE MLS GUIDANCE
CAT I
D E C ISIO N H EIG HT
^
&
A*
CAT II
D EC ISIO N HEIGHT
A
A PPR O A C H
REFERENCE
DATUM
y'
iq o '
Y
^— Jl
O PTIO N A L BACK AZIMUTH
(C -B an d )
ELEVATION
(C -B and)
DISTANCE
M EA SU RIN G EQ U IPM EN T
(L -B and)
A P P R O A C H AZIMUTH
(C- B an d )
N OT TO SCALE
M D B 31484.B
Figure 2. MLS Approach and Landing Operations.
200'
4
Remote Maintenance Monitoring System (RMMS). A back azimuth (BAZ) system may be
included in order to provide missed approach or departure guidance. Typical AZ, BAZ, EL
and DME ground equipment locations are shown in Figures 3 and 4 , typical equipment
designs are shown in Figures 5 and 6, and typical equipment structures are shown in Figure
7. Each system includes an antenna array, integral and field monitoring equipment, and
remote control and status indicator equipment. The ground equipment is divided further into
the angle equipment, i.e., AZ, EL, and BAZ, and the range equipment, i.e., DME.
1.
Angle Equipment
The angle equipment provide guidance information and digital data throughout the
coverage volume shown in Figure 8 by using a time-multiplexed signal format (Figure 9).
Since the function identification is transmitted as part o f the preamble, a specific function
transmission sequence is not required by the airborne receiver. However, several sequences
(Figure 10) have been developed which provided the average function rates given in Table
1, while precluding any function from being repeated at a fixed period, i.e., jitter. The
jittering of the function transmissions provides resistance against synchronous error
mechanisms.
The angle equipment operates on one of 200 C-band channels between 5.0310 GHz
and 5.0907 GHz, with a channel spacing of 300 KHz [2,3]. Additional spectrum to 5.150
GHz is available to provide an additional 198 channels for future system growth.
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5
LEG EN D 1
| P referred A re a 1
i A lternate A rea
± 3.0 ° ANGLE FROM POINT
DESCRIBED IN FAA ORDER
8260.36. CIVIL UTILIZATION
OF MLS
500’ CATEGORY I
800' CATEGORY II. Ill
RUNWAY
STOP END*
■* 1.000’
TO RUNWAY
THRESHO LD ’
1,000'
R equired C om pliance with A ccuracy S tan d ard s
1 ° Beam w idth AZ A n ten n a: 16,000’ Max
2° Beam w idth AZ A n ten n a: 10,000' Max
3° Beam w idth AZ A n ten n a:
7 ,5 0 0 'Max
PLAN VIEW
S u rfa c e 50:1 Slope-
Obstacle Clearance
20 0 ’
- ►
AZ/DME E q u ip m e n t M ust
Not P e n e tra te O b sta c le
C learan ce S u rfac e
Notos
1) Additional criteria applies when
collocating wtth an Instrument
Landing System or Approach Lighting
System. See FAA Order 6830.
DME A ntenna*■*
2) For the Back Azimuth, this criteria
is applied using the threshold end of
the runway
3) 50:1 Slope Is the
predominant requirement
4) Collocation of AZ and DME
equipment Is the preferred option
■*— AZ A ntenna S y stem
I;
5) The OME antenna may be offset
laterally up to 400' to avoid
penetrating obstacle clearance
surface
NOT TO SCALE
M D B31094
PRO FILE VIEW
Figure 3. Preferred and Alternate Areas for Siting of the Azimuth and DME/P
Equipment.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
6
1) H. 6 ; Oov w nH by Fight Standards and FAA Ordar
S2SO J4. typical valuea are H*SO ^<r. 6 • 3.0 .
2) OS: C an ran oahom 250*- S O tr.wdh *OOr-SOCT
prafarrad. must sattsfy obstndn ctearanca raqidramsRL
( S n SHow lafQ
ELEVATION
ANTENNA
3) APCH: DMarana hataraan M isfit at antenna pftaaa
OF
APPROACH
REFERENCE DATUM (ARO)
4) SB: Calculated knowing H. 6 . APCH
SB • H .APCH (PlanarCalndallon)
tan O
5) HO*: Odfccanca hatwaan hypatoole glda p ati and
taiaar Asyw piBBLJltflMld ha mlntenad (*10*>. (Saa
8 H o w righQ *
HO(F ■ ( SB2 *08*) (tan 9 ) • APCH - H
ANTENNA
PHASE CENTER
APPROACH SURFACE
BASE PLANE
CONVENTION FOR
POSITIVE VALUED
APCH
ELEVATION SITE
TERRAIN HEIGHT
T H e 3:1 TRANSITIONAL SURFACE IS THE COMTROILMQ SURFACE FO R ELEVATION
SITING. THE PRESEN CE O F TAXIWAYS ANO AOJACENTJCROSSINO RUNWAYS
WOULD PROVIDE AOOfTIONAL RESTRICTIONS.
RUNWAY
CENTERLINE
FOR REASONABLY FLAT TERRAIN (APCH ■ 7 . V . 9 • 3 O'). THE AREA 0EF1NED
BELOW WILL MAINTAIN THE A SYMPTOTE AT A HEIGHT O F 80 FEET ABOVE
THRESHOLD W H EE KEEPING THE PATH HEIGHT TO LESS THAN « 0 FEET
ABOVE THRESHOLD-
kk
RUNWAY
•80.0*
-
-►
«200V-«200V
*<-
I
500*
-►
PRIMARY
SURFACE
ELEVATION STATION
{FRONT VIEW)
CURVE SATISFYING
EQUATION
(OS)3 • (S B )2 - ( 1 0 1 1 3 J 2
(n M n u a , Flat Ground)
Figure 4. Siting o f the Elevation Equipment.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
NOT TO SCALE
M0S431S4.1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
In terface
P h a se
S h e lte r s
A
Pow er
Divider
h
OCI
Sw itch
A ntenn a
S w itch
PM DT
A
R a d io
I DistributionI
InteBral
Monitor
RF
AMP
J P an el J
A
| OCI
I Ant
DPSK
*
STcst/S
W ire
T
Array
LCSU
Fiber
Exciter
R e c e iv e r ;
D e te c to r
j
A
s /w
A
Timing
&
Control
COMM
B SU
t
1
E xec
Mon
F ield |
M onitor I
Monitor
! (hardw are)
Analog
l
S/W
ERP
D e te c to r
s /w
SAW
D ata
t
Mf>Hy811)2602
Figure 5. Typical Azimuth/Elevation Ground Equipment Designs.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A n ten n a
Antenna
Fi m i M
Power
Reelotance
Kiml*
>1
Oetecter
- I n te r fa c e
RF
Recelver-T ranemltter
y :
Receiver!
Trenemit
leoieDonr
RF
DtolhbuOeA
aoc
XMT
>1
RF To IF
TfAMltttOA I
>1
w ]
if To
|
Video
TfOAOltOOA
> n j IntorropoNon
Tim* at
Arrival
wJ
Detection
>
>
V
I. Reply Delay
AppSeaSan
AOC Ceabratwn
ADC AppSealton
Reply Encoding
Squtter Oeneratten
Identify Oanaiatton |
2
3
4
6
fl
> .
Reply
Traneoileelon
Local Control and Status
w l
Statue And
Central
|^ >
' w T e /F ro m
k^
R6U
Monitor
Tool Reply
Cemm
Interface
And Statue
Panel
MDB98I02603
Figure 6. Typical DME/P Ground Equipment Designs.
00
9
Lightning
Air Term inal
O bstruction Lights
C B and S y n c R adom e
R ad o m e (not visible)
Elevation E lectronics
C ab in et
--------
M ovable L adder
A.C. P o w er Box —
0
Battery Box
a)
ELEVATION SYSTEM
O bstruction Lights
Ice S e n so r
DME A n ten n a
S o la r S hield
Lightning Air Term inal
H eat Sink
O u t o f C o v e ra g e
Indicator
(OCI) A n ten n a
D oor
R ad o m e
B attery Box
MDB33094.1
b) AZIMUTH AND DME SY STEM S
Figure 7. Typical Ground Equipment Structures.
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10
(26.000n
00)0010 _____
20 *
_ HORIZONTAL - '
APPROACH
AZMUTHANTENNA
I_______
Back Azimuth
— A p p ro a c h
A z im u th /E le v a tio n
-40
Range Requirem ent
22.5nm from the
Back Azimuth -----
/ -40°
(Typical)
+62°
(max)
Fan-shaped Beam (AZ)
♦40°
(Typical)
Range Requirement
14nm from Threshold
(16.5nm from Azimuth)
Range Requirement
20nm from Threshold
(22.5nm from Azimuth)
MOT TO SCALE
MDB33094_2
Figure 8. MLS Guidance Signal Coverage Volume.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
11
S
TIME
Function
Preambles
V
w
/
EL
BAZ
EL
AZ
V
^
X
VDATA
EL
V
a) Overview ofTime-Multiplexed Signal Format
* Azimuth Functions ONLY
S
f—
( ) Number of BITS
c.
_
«*
O
cc
mm
S
o
I
n
Cx.
Sector
Signals
T o " Scan
Time Slot
3
•Fro' Scan
Time Slot
Pause
Time
Ground Radiated Test
(*Fro* Poise)*
Function
Guard Time
b) Detail of Angle Function Format
BASIC DATA’
32 Bits
Auxiliary Data
(Digital Data)
76 Bits
Auxiliary Data
(Alpha-Numeric)
76 Bits
PARITY
(7 Bits)
DATA TRANSMISSION
(18 Bits)
DATA
(49 Bits)
ADDRESS
(8 Bits)
ADDRESS
(8 Bits)
PARITY
(7 Bits)
# I
(8 Bits)
(8 Bits)
(8 Bits)
(8 Bits)
(8 Bits)
(8 Bits)
ASCII Characters
M db51894.1
c) Detail o f Data Function Format
Figure 9. Time-Multiplexed Signal Format.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
*7
(8 Bits)
12
Num ber o f Auxiliary Data W ords That Could be Transmitted
SEO.
SEQ.
fl
#2
SEQ.
SEQ.
SEQ.
SEQ.
SEQ.
#1
•2
*1
#1
#1
SEQ.
SEQ.
*1
*2
FULL CYCLE ■ 615 m ate. (MAXIMUM)
a) Complete Multiplex Transmission Cyde
TIME
(msec )
TIM E
(awec.)
SEQUENCE NO 2
SEQUENCE NO. 1
SEQUENCE NO I
SEQUENCE NO 2
APPROACH
ELEVATION
APPROACH
ELEVATION
APPROACH
ELEVATION
APPROACH
ELEVATION
(NOTE 2)
(NOTE 2)
10
APPROACH
AZIMUTH
HIGH RATE
APPROACH
AZIMUTH
HIGH RATE
APPROACH
AZIMUTH
APPROACH
AZIMUTH
20
(NOTE 2)
(NOTE 2)
APPROACH
ELEVATION
APPROACH
ELEVATION
BASIC DATA
WORDS (NOTE 2)
GROWTH
I t .2 msec
M IN .
(No'e2)
BACK
AZIMUTH
<*O T E 2>
60
6 6 .7 ..
HIGH RATE
APPROACH
AZIMUTH
APPROACH
ELEVATION
APPROACH
ELEVATION
HIGH RATE
APPROACH
AZIMUTH
(NOTE 2)
APPROACH
ELEVATION
BACK
AZIMUTH
HIGH RATE
APPROACH
AZIMUTH
(NOTE 3)
APPROACH
ELEVATION
APPROACH
ELEVATION
(NOTE 2)
(NOTE 3)
HIGH RATE
APPROACH
AZIMUTH
60
w e
APPROACH
ELEVATION
NOTES:
1) Total time duration for sequence I plus
sequence 2 m ust not exceed 124 msec.
3) When back azimuth is provided, basic data
word #2 must be transmitted only in this
position.
2) Basic data words may be transmitted in any
open time periods.
b) Sequence Pairs
MDB98102604
Figure 10. Existing Function Sequences.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
13
Table 1. MLS Guidance Function Rates.
FUNCTION
Average Rate (Hz) Measured over
any 10 Second Interval
Azimuth
13.00 ±0.50
High-Rate Azimuth
39.00 ± 1.50
Back Azimuth
Elevation
DME/P (LA Mode)
DME/P fFA Mode)
6.50 ± 0.25
39.00 ± 1.50
16
40
The AZ, BAZ and EL systems provide angular guidance by employing a Time
Referenced Scanning Beam (TRSB) technique, which is discussed further in Section I.C.l.
The AZ antenna scans a vertical fan-shaped beam laterally (Figure 11) through a maximum
horizontal displacement o f ±62° about the antenna boresight. Similarly, the EL antenna
scans a horizontal fan-shaped beam vertically (Figure 12) through a maximum vertical
displacement o f 30 °.
If required, the angle equipment can support out-of-coverage indication (OCI)
antennas, which radiate signals to protect against false courses resulting from reflection of
the angular guidance signal (Figure 13). Additional information on the OCI capability can
be found in References 3 and 5.
The digital data are provided using Differential Phase Shift Keying (DPSK) o f the
radio frequency carrier with a modulation rate of 15,625 baud [3,5]. The encoding/decoding
procedure is shown in Figure 14. The data transmitted include the function preamble, six
basic data words, and the auxiliary data words.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
14
•42 M u
*40 T y p c a I
•10 Ma'
0 .0 ' A n u k , T ypically
A ttgacd W ith K a m y
LEG EN D /N O T ES
*02 M u
*40 Typical
*10 M ia '
• S c u Ia tta ffa a A a tfe
A S o t T c m ia w rtop Amglc
<*>
1) Chw u i Signal* fnwrirt a
I — taller o f C avcnga V ataac
MOT TO SCALE
MDB4im2
Figure 11. Azimuth Antenna Scan Conventions.
1 5 .0 * T y p i c a l
2 9 .3 *
M ax
E l e v a ti o n
A n te n n a
0 .9 * T y p ic a l
- I .S * M in
LEGEND
" F R O * S c a n D ire c tio n
•
S c a n In itia tio n A n g le
A S c a n T e r m in a tio n A n g le
(▼)
"T O * S c a n D ire c tio n
NO T TO SCA LE
M D B 4 1 9 9 4 .1
Figure 12. Elevation Antenna Scan Convention.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
15
S « r* Stgfct (Cfc
Am b A Ondwt RipM
* 4 0 to * 4 2 '
1) U ^ i o i a O C I »
2) toqwremstfe
4 4 v r a g Piaffe In tp rc ti— « f
1> H ig h p » O C I — »■■■■■ pw w J i 20 « f k
w i H ». 5 v cro cal
m d to protect
OCI i
IS
AZIMUTH
N««4 for O C I N « A a te p ittd
b rT fcia ft*(M a
N O T TO SCALB
M D B 4IS44 2
E te v a n m A i t e n i
ELEV A TIO N
Figure 13 OCI Lateral Coverage.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
16
I ) " Z e r o " .‘ p h a s e s h i f t o f
0°±!0a
o
0
1
1
0
1
0
-> " O n e *
." p h a s e s h i f t o f
I 8 0 ', * l 0 “
E ncoded
D a ta
-4 - 1 B it
►
------------------
6 4 (i s e c
36^8757413
S ig n a l
P hase
D a t a F r e q u e n c y 1 5 .6 2 5 K H z
NOT TO SCALE
M D B04IS94.I
Figure 14. Differential Phase Shift Keying.
2.
Range Equipment
The DME transponder can be either a precision DME (DME/P) or an enroute DME
(DME/N), depending on the approach and landing operation to be supported. The DME
transponder must at least support the coverage volume shown in Figure 8, and it typically
provides omni-directional coverage laterally. DME function rates are also shown in
Table 1.
The DME transponder can operate on one of 200 paired L-band channels (960-1215
MHz), with a channel spacing o f 1 MHz [1,3,6]. Each channel has an uplink (transponder)
and downlink (interrogator) frequency pair, which are separated by 63 MHz. In the case o f
the transponder, spectrum efficiency is increased by using pulse pairs with one of four
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
17
possible pulse pair spacings (pulse code), which provides four channels for a given frequency
pair. The pulse pair coding is provided in Table 2.
Table 2. DME/P Pulse Code Parameters.
CHANNEL
X
Y
W
Z
INTERROGATOR
PULSE CODE
(/isec)
TRANSPONDER
PULSE CODE
(^tsec)
TRANSPONDER
REPLAY DELAY
18
12
56
12
12
50
FA
---------------------IA
42
30
62
36
30
56
FA
---------------------IA
30
24
56
24
24
50
27
15
62
21
15
56
OPERATING
MODE
FA
---------------------IA
FA
---------------------IA
(pisec)
The transponder acts as a radar beacon in that upon receiving an interrogator pulse
pair it transmits a corresponding pulse pair after waiting a fixed delay time. The slant range
between the interrogator and transponder can be determined by measuring the elapsed time
between the transmission o f the interrogator pulses and receipt o f the transponder pulses.
This range measurement concept is discussed further in Section I.C.2.
In order to support advanced landing operations, the DME/P must be capable o f
providing accurate range information (±100 feet, Standard I) in the final approach and
landing phases of flight.
During these flight phases, multipath, i.e., undesired signal
reflection by the environment, is the dominate error source, thus the DME/P is designed to
minimiVfi effects of multipath on the range accuracy. Since the multipath signals arrive later
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
18
than the direct signal, the key to achieving high accuracy in the presence of multipath is
using a low threshold on the leading edge of a fast rise-time pulse (cos/cos2 pulse shape).
Adjacent channel spectrum requirements, which are designed to limit the interference from
a neighboring facility, are satisfied by careful specification o f the pulse rise time and
restricting the maximum range at which the low-threshold, fast rise-time technique can be
used. Thus, the concept discussed above results in the DME/P having two modes of
operation, which are based on the range o f the aircraft from the transponder. Figure 15
illustrates the Initial Approach (IA) and Final Approach (FA) regions associates with the
DME/P.
B.
Airborne Equipment
The basic airborne equipment installation includes an angle receiver, DME/N or
DME/P interrogator, control heads, associated antennas and cables, and display systems.
The angle receiver provides the AZ, EL, and BAZ angle information, as well as
Basic/Auxiliary Data. The DME interrogator provides the slant range between the aircraft
and ground transponder. Depending on the guidance capability desired, RNAV equipment
may be added to the airborne installation to provide guidance along segmented or curved
flight paths.
Typical airborne installations are shown in Figure 16, typical
receiver/interrogator designs are shown in Figure 17, and example hardware are shown in
Figure 18.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
19
215.0°
20.000'
0.85°
=3000’
VERTICAL COVERAGE
Transition
Region
N O T E : T jrp tc a l b o r a o o i i l c o v c n g t
is 3 6 0 * . m o s t c o v t r A s i a u h s a d
B * ck A x x m ath c o v s n g s v o h m u .
y
DME/P
T ra n s p o n d e r
.
22 n®L
^
RUNWAY --------------- •
■ < -
Region
>■
*<
IA
HORIZONTAL COVERAGE
NOTE h c n u d
EXAMPLE OF DIFFERENTIAL DATA
M DB52394
Figure 15. DME/P Coverage and Modes o f Operation.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
OFF8ETAZ
(OPTIONAL)
A2
ML8
RCVR
CDI
ML8
RCVR
HSj
RNAV CIRCUITS
CONTROL
PANEL
WP 2
WP 1
CONTROL
PANEL
DME/P
(™j
W
RANGE READOUT
RANGE REAOOUT
L e v e l I M L S / R N A V (O ptional 2 -W a y p o in t Capability)
B a s ic M L S
FORE
ANTENNA ANTENNA
(OPTIONAL)
MLS
RCVR
RNAV
AFT
FORE
ANTENNA ANTENNA
[CD
t D]
H8
CONTROL
PANEL
Hi
/ X
\
WP 3
FD AND H8I
FUNCTION8
J
ML8
RCVR
FLIGHT
MGMT
6YSTEM
L
EFia| | e FI8
lONTRO
PANEL
I---
OME/P
CCD
RANGE REAOOUT
DME/P
WP 1
L e v e l II M L S /R N A V
MDBS19B4.2
Figure 16. Typical MLS Avionics Installations for Baasic and RNAV Procedures.
-H i
RANGE READOUT
L e v e l III M L S / R N A V
ALTERNATE
WP i WAYPOINTS
ASSIGNED BY
►WP 2 ATC FOR PATH
STRETCHING
»WP 3
iWP 4
21
C-BAND
ANTENNA AND
FRONT END
CONTROL HEAD
CHANNEL SELECT
AZIMUTH SELECT
ELEVATION SELECT
IF CIRCUITS
ANO CHANNEL
FILTER
A
LOG AMP AND
VIDEO DETECT
26kHz FILTER
ID
OECOOE
SAMPLE SLS
ENVELOPE
PRCOESSOR
V
ACQUISITION/
VALIDATION
CHECKS
MICROPROCESSOR
4
ANGLE
PROCESSING
^
10 RAD/SEC FILTER *<
DISPLA Y
(C DI)
Y
ANGLE OUTPUT
a) Aitgte Racalvar
Y__
TRANSMITTER
RECEIVER
ENCOOER
TRIGGER
RANGING
CIRCUIT
ZERO MILE DELAY
MOBS19M 1
b ) In te rro g a to r
Figure 17. MLS Angle Receiver and DME/P Interrogator Designs.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
22
Basic Receiver, Cabin Class
Basic Receiver, ARINC
(Air Carrier) Specifications
Figure 18. Example MLS Avionics.
C.
Angle and Range Measurement Techniques
This section provides an overview of the angle and range measurement techniques.
In general, the MLS guidance signals are processed by the airborne equipment to obtained
highly accurate time measurements which are then converted directly into angular and slant
range information. This information is compared to desired values in order to generate the
guidance information to be displayed to the pilot or provided to the flight control system.
The angle and range measurement techniques are conceptually simple, however, the actual
hardware/software implementations are complex, particularly when considering mitigation
of the effects due to noise.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
23
1.
Angle Measurement Concept
The AZ, BAZ and EL stations provide angular guidance by employing a Time
Referenced Scanning Beam (TRSB) technique. The TRSB technique for the approach
azimuth function is illustrated in Figure 19. After the preamble and sector signals have been
radiated (not shown), the approach azimuth antenna scans a vertical fan-shaped beam
laterally, "TO" and "FRO", through the appropriate portion o f the MLS coverage volume
(Figure 8). The scan initiations times and velocities are carefully controlled. The MLS angle
receiver measures the time between the "TO" and "FRO" scans, and this time is used to
calculate the azimuth angle as illustrated. Except for different values for the angle guidance
parameters, the same measurement technique is used for the back azimuth and elevation
(scans vertically) functions.
2.
Range Measurement Concept
The DME range measurement technique is shown in Figure 20.
The range
measurement is initiated by the interrogator transmitting a pulse pair and starting a “timer.”
After the ground-based transponder receives the interrogator pulses, it waits a fixed-delay
time, and then transmits a reply pulse pair. The interrogator receives the reply pulses and
then measures the elapsed time between the transmission o f its pulses and receipt of the
transponder's reply. The elapsed time is used to determine the slant range.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
.0
S c a n B aam
C o n c a p l E x am p la
ANGLE EQUATION
©- Mr-*T V,t
♦ ©
= I t R - d F - l T) ] , ' 4 c.n 12
-T O ' SCA N
W INDOW
B aam C an tro ld
"FR O " 8C A N
W INDOW
B a a m C an tro ld
H
i
e u n p i r hmaaz (Hl0h -R a tt A pproach Azimuth)
MI0-4CAN ro m i
* 1 0 ' SCA N
•FR O * SCA N
TIME (tT)
TIME (1,1
6
■
(8600
•
(9700
•
3600)1
* ( 0 . 02)/2
e« to1
•40
SY STEM PA R A M ETER S
Slop e G ives S een
Velocity (VtCAH)
•»
* R
S y atam
"• R eference Time ( I , )
V »can
(f8 « c )
•
jo
H R A A Z
6 ,8 0 0
+ 0 .0 2 0
A A Z
4 ,6 0 0
+ 0 .0 2 0
BA Z
4 ,8 0 0
- 0 .0 2 0
EL
3 ,3 5 0
+ 0 .0 2 0
Duration ( » I)
'M easuring Angle*
0
MDB90894 IB
Not to Scale
13,000
Figure 19. Angular Measurements Using the Time Reference Scanning Beam Technique.
to
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
T ran sm issio n R ecaption
R
Flxad ------T ran ap o n d a r Delay
■Tranam laalon R aoaptlon
In terro g ato r P ulaa P air
("Interrogation”)
(Tfo)
T ran ap o n d a r P u laa Pair
("Raply")
Interrogator
T ran ap o n d e r
D iui lse
Ia a R
D ae Ife
a p a
’P
rence
Point
<
P ro p o g a tlo n Delay
(Down Link)
P ro p o g a tlo n D e l a y ------(Up Link)
E la p se d Time M e asured By Interrogato r (T(r)
T
bt;
E la p s e d tim e m e a s u r e d by In terrog ator
T fo: T r a n s p o n d e r fixed delay time
SLANT RANGE
(t e t '
t f q )* v p
Vp = Velocity of P r o p o g a tlo n
SF -
S c a le f a c to r to provid e r a n g e in
d e s ire d un its (I.e., feet, m e te r s , nautical
miles)
MDB61886.1B
Figure 20. The DME Slant Range Measurement Technique.
N>
26
n.
PROBLEM BACKGROUND
In order to ensure proper operation, the MLS transmitters, i.e., AZ, BAZ, EL and
DME, must be sited properly at the facility to be serviced. For most facilities, proper
equipment siting is achieved by following a prescribed set of guidelines, which have been
consolidated into a siting manual [7]. Through FAA sponsored research, the author has led
extensive research efforts in order to develop MLS siting criteria. These criteria have been
adopted as a national standard and are published in the FAA MLS Siting Manual [8].
Further, these criteria have received extensive review by the All Weather Operations Panel
(AWOP) of the International Civil Aviation Organization (ICAO), and as a result have been
adopted and published internationally [1].
The results of the research presented herein have furnished the aviation community
with an essential element of the MLS siting manual. The contributions of these results are
best understood once one realizes the overall requirements for developing a siting manual
for a ground-based precision approach navigational aids such as the MLS. Thus, the balance
of this section provides an overview of the material typically contained in a siting manual
and discusses how the author’s research aided the completion of the MLS siting manual.
Furthermore, the development of protective-zoning requirements for the MLS requires
mitigating the effect of multipath errors due to scattering by transient vehicles. Thus, this
section concludes with a discussion o f the MLS multipath phenomenon.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
27
A. Siting Manual Overview
Generally, the siting manual for ground-based navigational aids will provide
introductory material, a technical description o f the navigational aid, installation
requirements, and siting requirements. Although the content may be the same for different
types of navigational aids, the format and organization of the information does vary from
manual to manual. Additional discussion of siting manual content is proved in the balance
o f this section.
The introductory material typically provides information on the purpose and content
of the document. Also, information related to revision, distribution, and the applicability of
the material to new and existing facilities may be provided. Navigational-aid-specific
terminology is introduced and defined, and references to other sources o f requisite
information are provided.
Typically, the technical description of the navigational aid is limited to an overview
of major system components, since detailed descriptions are provided in either the owner’s,
installation, operator’s, or maintenance manuals. Guidance-signal formats, signal-in-space
characteristics, and coverage requirements are discussed. Data transmission requirements
for such items as facility identification and other operationally required information are
provide, as appropriate.
The discussion of installation requirements focuses on addressing electrical and
mechanical requirements. Specific requirements are provided for the type o f primary
electrical service required (120/240 volts, 3 wire, single-phase 60 Hz); tolerances for AC
voltage and line frequency drift also may be included. The maximum power requirement
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28
(capacity) will normally be equipment-type specific. Depending on continuity-of-service
specifications, requirements for alternate or battery backup o f the primary electrical service
may be provided. The range of environmental conditions (temperature, humidity, wind/snow
loading, vibration, etc.) under which electronic and mechanical equipment must perform
normally are specified.
Physical site requirements (soil bearing strength, clearing o f
trees/brush, grading, preparation of equipment foundations, access roads, etc.) are provided,
as appropriate.
The siting requirements or criteria provided in the manual, for the most part, are
specific to the navigational aid being addressed. These criteria make up a significant portion
o f the manual: it is not unusual for half of the manual to address these criteria. The three
major topics addressed are: the identification of the data needed for site selection; the
coordination o f installation activities and system utilization among specific governmental
entities; and, the procedures to be used in selecting specific equipment locations. Generally,
the majority of the information will be dedicated to addressing the last topic. The process
o f selecting specific equipment locations requires: ensuring that relevant obstacle-clearance
and safety-zone requirements are satisfied; providing the proper geometry between the
equipment and the procedure so that the guidance signal is “interpreted” correctly; and,
ensuring that reflections o f the navigational aids’ signal by objects in the environment, i.e.
multipath, will not result in unacceptable guidance errors along the approach procedure.
Due to the demanding accuracy requirements for precision approach navigational
aids, equipment locations must be carefully selected in order to ensure that the degradation
o f the guidance signal accuracy, due to multipath, does not exceed tolerable levels.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
29
Therefore, significant effort is directed at the development o f procedures or guidelines for
successfully selecting such locations so that the equipment installation, and thus the
provision of the particular navigational service, can be performed in a cost-effective manner.
Such an effort was undertaken when developing the MLS siting manual [7].
B.
Author’s Contribution to the MLS Siting Manual Development
The author has conducted extensive research to support the development o f an FAA
MLS siting manual [7,9-13]. This research was initiated in spring of 1984 and produced the
initial version of the FAA MLS siting manual by January 1995 [9]. This version provided
a technical description of the MLS, installation requirements, and preliminary siting criteria.
These preliminary criteria addressed the selection of equipment locations under nominal
conditions.
The results of the research performed during this initial phased identified five areas
were further research was required in order to complete the development of the MLS siting
manual. These areas were:
i) Criteria o f the collocated siting of MLS Azimuth and Approach Lighting System
(ALS) equipment;
ii) Criteria of the collocated siting of MLS and Instrument Landing System (ILS)
equipment;
iii) Criteria for the MLS azimuth equipment siting at humped-runway airports;
iv) Guidance material for application of the MLS Mathematical Model (MLSMM)
for estimating install equipment performance; and,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
30
v) Criteria for establishing MLS critical area boundaries (protective zoning
requirements) for basic, off set, computed-centerline and advanced MLS
approach procedures.
The author has conducted research that resulted in the revision o f the criteria initially
produced by Mathias [14] for item i above. In addition, these results provided guidance on
the application o f these criteria, as well as how to apply the MLSMM to develop site-specific
adaptations o f these criteria [15,16]. During the past 15 years, the author has led extensive
research efforts, and the results of these effort have produced nationally and internationally
accepted criteria for items ii - iv above [17-43].
This dissertation documents the research conducted by the author for the purpose o f
producing MLS critical-area criteria for basic, off-centerline, computed-centerline, and
advanced MLS procedures (item v above). Producing these criteria implies: developing
protective zoning requirements for the azimuth, elevation and DME/P equipment; validating
requirements; and, generating guidance material to aid in the proper application o f these
criteria by the end user. In this case, the end user is assumed to have a basic understanding
o f installation requirements for ground-based, non-visual, precision-approach aids and
familiarity with the MLS to the extend presented in this dissertation.
As previously stated, the development of protective-zoning requirements for the MLS
requires mitigating the effect of multipath errors due to electromagnetic scattering by
transient vehicles. Accomplishing such a goal requires that one first understand how
multipath affects the accuracy of the MLS guidance signal and the parameter germane to
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
31
characterizing the extent o f the effect. Thus, this section concludes with a discussion o f the
MLS multipath phenomenon.
C. MLS Multipath Phenomena
The presence o f objects (hangars, buildings, aircraft, and hilly terrain) within the
vicinity o f the MLS ground equipment will result in electromagnetic scattering of the MLS
signals (Figure 21). This electromagnetic scattering is commonly referred to as multipath,
which may result in detectable distortion of the direct MLS signals. When present, this
distortion degrades the accuracy of the time measurements, and thus the accuracy of the MLS
guidance information.
The design of the MLS makes it very resistant to multipath effects; however, there
are conditions under which multipath can produce unacceptable degradation of the MLS
guidance information. Proper equipment siting is essential in order to avoid such multipath
conditions. Multipath effects and equipment siting requirements are addressed in detail in
References 8, 9, and 11, and an overview is provided in the following two sub-sections.
1.
Angle Equipment
For the angle equipment (azimuth, back-azimuth and elevation), such multipath
conditions can be identified by examining how multipath affects the receiver’s ability to
measure the time between the “TO” and “FRO” scans. In general, the angle receiver
processes the “TO” and “FRO” scan receiver video in order to determine the location of
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
2D/3D Curved Segment to
8tralghtan Centerline Approach
R E F L E C T IO N S FR O M
B U IL D IN G S A N D
P A R K E D A IR C R A F T
A
V
S H A D O W IN G BY
O V E R F L Y IN G
A IR C R A F T
D IS T A N C E
M E A S U R IN G E Q U IP M E N T
ELEVATION
T E R R A IN
R E F L E C T IO N S
D I R E C T /D E S I R E D S IG N A L S
M U L T IP A T H S IG N A L S
NOT TO SCALE
A Z IM U T H
Figure 21. MLS Multipath Phenomena.
M D B 1217 1
33
the main-beam centroid (Figure 22) during each portion of the scan. These locations equate
to times, which then are used to determine an angular value as discussed previously. As
illustrated in Figure 22, the presence o f multipath introduces perturbations in the receiver
scan video which may be classified as in-beam or out-of-beam.
In-beam multipath results when side lobe and/or reflected mainbeam multipath arrive
at the receiver close enough in time such that the direct (actual) mainbeam shape detected
by the receiver is distorted. This distortion can cause an error in determining the location of
the true mainbeam centroid which gives rise to error in the angle measurement. The
magnitude of the error is a function o f the multipath-to-direct signal ratio, the time-of-arrival
of the multipath relative to the direct signal (time-delay), the phase o f the multipath signal
relative to the direct, and the multipath scalloping frequency resulting from receiver motion
in the dynamic case [44].
For the TRSB technique employed by the angle equipment, the time-delay between
the arrival of the direct signal and a multipath signal corresponds to a particular separation
angle (Figure 23). In this case, it is more effective to used the separation-angle concept for
assessing the potential of an object to cause unacceptable multipath errors. Figure 23
provides an example of the error caused as a function of multipath signal strength and
separation angle. Additional information on multipath error parameters and the analysis of
multipath effects can be found in References 8, 15 and 44. The basic error equation is
provided in Appendix A.
Since the presence of in-beam multipath from antenna side lobes can not be avoided
for operational equipment, the error resulting from this type of multipath is
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
S e p a r a tio n '
A n g le
F o r th e T R S B T e c h n iq u e , T h e T iroeD elay B e tw e e n th e A rriv a l o f th e D irect
an d a M u ltip a th S ig n al C o rre sp o n d s to a
S e p a ra tio n A n g le
■ A n gt i l a r Er r o r
" "I
I’r a c k i n g ( i dl e
►
(5) T r u e
Main Beam
Centroid
•
A ctu al/R e ceiv ed
Dire c t / De si r ed
M e a s u re d M ain
B e am C e n tro id
M a i n l . obe. O u t n l Beam Multipath
M ain l.o b e.
In-B cam ^‘ ‘
S i d e l . o be,
Si d e Loi re. O u l - o l
Beam ^
I n- I J c um M u l t i p a t h
T IM E
MDB980B3I0I
Figure 22. The Effect of Multipath on the Angular Measurement Process.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Angle System Multipath Error as a Function of Separation Angle and Strength
0.8
0.6
The traces where the normalized error starts with
'positive values is for the case where the multipath
is in-phase with the direct signal.
0.4
0.2
k
E
w
e
I -0.2
The traces where the normalized error starts with
negative values is for the case where the multipath
is out-of-phase with the direct signal.
•0.4
•o.e
0
0.5
1
1.5
2
2.5
3
3.5
4
Separation Angles (Beamwidths)
Figure 23. Angle Equipment Error as a Function of Multipath Signal Strength and Separation Angle.
4.5
5
m u u v k o v iio i
36
controlled by requiring the antenna to have very low side lobe levels (= 30 dB down from
main lobe). In-beam multipath from the antenna main lobe is avoided by proper equipment
siting based on the procedure to be supported. Considering the TRSB technique used by the
angle equipment, the in-beam multipath region may be defined as an angular region 1.7 times
the antenna beamwidth (1.7 BW) about the direct-signal path as shown in Figure 24. It
should be noted that a scatterer can be located in the in-beam multipath region, but not
subject the receiver to in-beam multipath (Figure 25). That is, the in-beam multipath will
exist in a specific volume o f space and the receiver may or may not pass through this
volume.
Out-of-beam multipath results when side lobe and/or reflected mainbeam multipath
arrive at the receiver sufficiently separated in time such that the direct (actual) mainbeam
shape detected by the receiver is not distorted (Figure 22). That is, the scatterer lies outside
the in-beam multipath region. Provided that the receiver is in a region where it receives the
direct signal (no shadowing), this type of multipath does not introduce error in the angle
measurement. Reception of the direct signal is ensured by proper equipment siting, which
takes into consideration the operational procedure to be supported.
2.
Range Equipment
For the range equipment (DME/P or DME/N), the multipath conditions that can
produce unacceptable degradation of the ranging signal can be identified by examining how
multipath affects the ability o f the interrogator and transponder to measure the time-
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
37
Beam Locaboa That Gcaeratcs Multipath at
Receiver Locatioa White Beam u Still
[Ilamiaatng Reciever fa-Beam
Scaaamg Beam Locatioa That Gcaeratcs
Miltipadi at Receiver Locanoa After Bca
has niamiaated Reciever: Oat-of-Beam
Aagalar Scparatioa o f 1.7*(Aateaaa
Beam) for Rcccvier Locatioa
“ 1.7-Beam width Boaadary-
Receiver Locatioa
—
Aximath Aatcaaa
Aagalar Sepaiatioa o f l.7*(Aateaaa
Beam) for Recevtcr Locaboa
A ZIM U TH CASE - Plan View
t .7-Bcamwidth Boaadary
Receiver Locatioa
Elevatioa Aatcaaa
Aircraft Hold tag oo Taxiway
ELEV A TIO N CASE - Profile View
(Sec Azinath Case for Explaiastioe)
Figure 24. Illustration of In-Beam and Out-of-Beam Multipath.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MDB9712I202
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
INSERT
.
B u ild in g \
AZ
PLAN VIEW
B u ild in g
M D B97121201
Not to S c a le
Figure 25. Illustration o f Three-Dimensional Characteristic of Multipath Propagation.
u>
00
39
of-arrival of the ranging pulses. In general, a particular portion of the received pulse will be
processed in order to estimate the pulse time-of-arrival.
As illustrated in Figure 26,
mutlipath the affects the receiver video can be classified as “short-delay” or “long-delay.”
Multipath which has a “short” time-delay will distort the portion o f the pulse used
to estimate the time-of-arrival. This situation, which is analogous to in-beam multipath for
the angle equipment, can result in ranging errors. Again, the magnitude o f the error is a
function o f the multipath-to-direct signal ratio, the time-of-arrival of the multipath relative
to the direct signal (time-delay), the phase o f the multipath signal relative to the direct, and
the multipath scalloping frequency resulting from receiver motion in the dynamic case [6].
In this case, echo ellipsoids for a given time-delay value are used to assess a
scatterer’s potential for causing ranging errors (Figure 27). The specific values used depends
on the type of pulse processing being used, that is, whether it is DME/P (300 nsec) or
DME/N (2400 nsec) type equipment. Figure 28 provides an example o f the error caused as
a function of multipath signal strength and time delay. Additional information on multipath
error parameters and the analysis o f multipath effects can be found in References 6, 8, and
15.
Multipath with a “long” time-delay does not cause a ranging errors (Figure 26), since
it does not distort the portion of the direct-signal pulse that is processed to estimate the pulse
time-of-arrival. As with the angle equipment, this statement assumes that the direct signal
path between the interrogator and transponder is not blocked.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
- M ultipath A rriving In T his T im e Block D iitorta Portion of Received
P ulie U ied to D eterm ine T he T lm c-of-A rlval " R anging E rro r
- T he E xact D uration of the T im e Block ii a Function of P u lie Shape
and the R eceiver P ro c e iiin g Technique Uied
M ea su red T h re s h o ld P o lo l/A rriv o l T im e
^
T ru e T h re s h o ld P o lo l/A rrlv e l T im e
C om posite Pulse V ideo, R eceived Pulse
Direct Pulse
M ulitpath Pulse w ith “ Short” D elay-Tim e
(In-P hase w/ D irect)
T im e-of-A rrival Threshold Level
M ulitpath Pulse w ith "L o n g ” D elay-Tim e
(In-Phase w / D irect)
Echo Ellipsoid Tim e*uelay Value
Used for M ultipath Analysis
MDBBB01140S
Figure 26, Effect of Multipath on the DME Range Measurement.
■fc.
o
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Echo Ellipsoid _ Locus of
Points G iving C o n stan t
M ultipath T im e'D elay
P R O F IL E VIEW
B u ild in g O u litd c a n d B e lo w
E llip s o id * N o P ro b le m
B u ild in g Inaidc a n d A b o v e
E llip so id “ P o ssib le P ro b lem
I
B u ild in g In a id c b u t B elow
E llip s o id • N o P ro b lem
P L A N V IE W
Figure 27. Illustration of Short and Long Time-Delay Scatterers for DME.
MOB9B0114.06
Not to Scale
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
DME/P lfrror Versus Time Delay and Fixed M/D Ratio
M/D = Multipath-to-Direct Signal Ratio
Relative RF Phase: 0.0 Degrees
M/D » +3 dB
M/D = -I dB
M/D = -6 dB
M/D “ -20 dB
100
150
200
250
300
lim e Delay (ns)
MDB9809020I
Figure 28. DME/P Equipment Error as a Function of Multipath Signal Strength and Time Delay.
43
III.
NEED FOR MLS CRITICAL AREAS AND SCOPE OF RESEARCH EFFORT
As discussed in the previous section, objects in the airport environment can produce
multipath, and these objects are commonly referred to as scatterers. For the purpose of this
discussion, there are two main classes o f scatterers: permanent and transient. A permanent
scatterer refers to fixed objects whose signal reflections can subject the MLS receiver to
multipath. Examples of permanent scatterers are aircraft hangars, equipment enclosures, and
sloping terrain. The selection of the appropriate equipment characteristics (beamwidth,
pulse-shape, etc.) and proper equipment siting are essential in avoiding unacceptable
multipath signal levels in operationally significant airspace. A transient scatterer refers to
objects that can be stationary or mobile, but are only present in the environment for a short
duration o f time. These objects can subject the MLS receiver to unacceptable multipath
signal levels as well. Transient scatterers can be an airborne aircraft, moving service
vehicles, taxiing aircraft, parked/holding aircraft, and parked vehicles. Protection from this
type of signal scatterer may require protective zoning requirements called critical areas.
A. Assessing Requirement for MLS Critical Areas
Based on typical equipment locations, large transient scatterers (commercial jet
aircraft) certainly could be located in close proximity to the MLS transmitting antennas. A
qualitative multipath analysis performed by Kelly and Laberge, initial flight tests conducted
in Brussels, and experience with the Instrument Landing System (ILS) indicate that the MLS
likely will require critical areas about the antennas in order to ensure sufficient protection
from transient scatterers [44,45]. Initial work in this area using an early version of the MLS
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
44
Mathematical Model was performed by Lincoln Laboratory and produced results consistent
with the qualitative analysis and flight test results [46]. However, the Lincoln Laboratory
work assessed only the multipath errors resulting at decision height. Although the results
obtained from this preliminary study were useful, it was concluded that they were not
sufficient for developing critical area requirements. This conclusion was reached for several
reasons. One of the more compelling reasons is that the accuracy of the guidance provided
by a precision approach aid must result in the aircraft being at an acceptable location and in
an acceptable attitude when the aircraft reaches decision height so that a safe landing can be
made without undue pilot workload. This reason indicates that the multipath error due to
transient vehicles must be assessed over the last several miles of the approach procedure in
order to establish critical area requirements.
Subsequently, the FAA sponsored an extensive research program with the purpose
of producing MLS critical-area criteria. The program objective was to define critical areas
that provide adequate protection for the MLS signal while not unnecessarily restricting the
movement of ground-based aircraft. This program ended successfully with the inclusion of
the critical-area criteria in the FAA siting manual [8], and adoption of this criteria
internationally by the International Civil Aviation Organization [1]. An overview of the
program objective is provided in the next section.
B.
Establishing Scope and Priorities
The initial stages of the critical-area program involved assessing what research
activities would need to be undertaken.
This assessment considered three types of
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
45
operational procedures envisioned to be supported by the MLS. The first type is referred to
as basic MLS procedures (Figure 29) and implies that the vertical and lateral guidance are
based on raw MLS (receiver outputs) information. This type includes the “standard” MLS
approach and the “offset-azimuth” approach. The standard approach is taken as a threedegree glide path along the runway centerline extended, with the azimuth antenna sited on
the extended runway centerline. For the offset-azimuth procedure, the lateral track is along
a constant azimuth radial which may not be aligned with the runway centerline and the
azimuth antenna may not necessarily be sited on the runway centerline extended.
The second type o f MLS procedure is referred to as a “computed-centerline”
approach (Figure 29). This procedure can be used to provide a three-degree centerline
approach when the azimuth antenna is sited offset from the runway centerline. Normally,
the DME will be collocated with the azimuth antenna. Raw elevation information is used
to provide the vertical guidance. In the simplest case, the lateral guidance is provided by
processing the azimuth and DME information in order to determine the aircraft’s offset from
centerline.
Based on this offset and range (DME), the appropriated lateral guidance
information can be generated.
The third type o f MLS procedure is the “advanced” procedure (Figure 29). This
procedure type is divided further into three levels based upon the complexity o f the
procedure and the avionics suite required for performing the operation. These procedures
are comprised o f segmented and/or curved elements, and the two/three dimensional
“computed” guidance is obtained from processing azimuth, elevation, and DME information.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
46
G U ID A N C E IN F O R M A T IO N
CONTROL
MLS
RCVR
R a w A z im u th , E le v a tio n ,D M E
u s e d for G u id a n c e
(IL S -L ik e P r o c e d u r e s )
PANEL
CDI
RANGE READOUT
Basic MLS
|A Z /D M E
G U ID A N C E IN F O R M A T IO N
‘ /"v
MLS
RCVR
4
[coi,
R a w E le v a tio n fo r V e r tic a l
A z im u th /D M E - C o m p u te d L a te r a l
RNAV CIRCUITS
CONTROL
PANEL
DME/P
on
RANGE R EA D O U T
Computed Centerline Procedure
AFT
ANTENNA
7 FORE
AZ/DME
FD A N D HSI
FU N C T IO N S
0
O ff C e n te r lin e : A z im u th ,
E le v a tio n , D M E /P — C o m p u te d
V e r tic a l, L a te ra l, a n d A lo n g T r a c k
A N TE N N A
MLS
RCVR
/
FLIGHT
MGMT
SYSTEM
G U ID A N C E IN F O R M A T IO N
F in al S e g m e n t R a w A z im u t h ,
E le v a tio n , D M E
CONTROL
PANEL
DME/P
RANGE REA D OU T
M D B 9 8 0 1 2 2 .0 2
* or sp e cia l pu rp ose
RNAV com puter
Advanced MLS Procedures
Figure 29. MLS Approach Procedure Types.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
47
It was determined that critical-area criteria would be needed for equipment supporting
basic, computed-centerline, and advanced MLS approach procedures. The majority of MLS
installations planned would be sited to support basic procedures. Although these same
installations could be used to support computed-centerline and advanced procedures, the
initial use would be limited to supporting basic procedures. Thus, development of criticalarea criteria for basic procedures was given first priority.
Based on the procedure
development, airborne equipment specification, flight worthiness certification, and flight
inspection activities that had to be completed before advanced MLS procedures could be
implemented; development of criteria for computed-centerline procedures was given second
priority.
For each of these three procedure types, priorities had to be established in terms of
developing criteria for azimuth, elevation, or DME/P. For basic procedures, the DME/P
provides information that will enable the pilot to determine the distance from threshold or
when an operationally significant location along the approach, e.g., decision height, has been
reached. For the Instrument Landing System (ILS), this function is provided by either
DME/N or marker beacons [45]. Thus for ILS, the effective ranging accuracy is on the order
o f300 - 500 feet. Based on a preliminary analysis by Kelly and Cusick [6], the ranging error
due to severe multipath (M/D = -3dB) was not expected to exceed 33 feet. This result is
consistent with the results shown in Figure 28. Further, the error for an M/D ratio of +3 dB
would not be expected to exceed 60 feet. These result, plus the realization that the azimuth
critical area also would provide some protection of a collocated DME/P, placed the priority
on developing critical-area criteria for the azimuth and elevation antennas instead of DME/P.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
48
Similar conclusions were reached for the case of computed-centerline and advanced
procedures. Therefore, development o f critical-area criteria for the azimuth and elevation
antennas for these procedures was given a higher priority than the development of DME/P
criteria. That is, development of criteria for DME/P would be initiated once criteria for each
procedure type had been developed for azimuth and elevation.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
49
IV.
DEVELOPMENT OF AZIMUTH AND ELEVATION CRITICAL-AREA
CRITERIA
Initially, this section discusses the development and validation o f azimuth and
elevation critical-area criteria for basic MLS procedures. Then, the focus is placed on how
the results obtained for the basic procedures were used to aid the development o f critical-area
criteria for computed-centerline procedures. The section concludes with a discussion of the
development o f criteria for advanced procedures.
A. Development o f Criteria for Basic Procedures
The development of azimuth and elevation antenna critical-area criteria involves two
distinct steps (Figure 30). For azimuth, the first step is to characterize the guidance signal
errors caused along the standard precision approach profile due to an interfering aircraft
located ahead of the azimuth antenna.
The error must be characterized in terms of
magnitude, duration, scalloping frequency, and location along the approach profile as a
function of interfering aircraft type, location, and orientation. The second step involves
determining the area that bounds all the locations that have the potential to produce
guidance-signal errors that exceed acceptable limits. Once this area has been determined,
the final step is to develop criteria that clearly and concisely describes the area that needs to
be protected. The same process is required for developing elevation critical-area criteria.
Error-contour plots can be used to characterize the error caused along the approach
procedure due to scattering of the MLS guidance signal by a stationary ground-based aircraft
(Figure 31). Thus, the critical-area criteria developed for basic procedures are based on the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A zim uth C ritical-Area Problem
1) C h a r a c t e r i z e A z i m u t h E r r o r C a u s e d A l o n g S t a n d a r d ( B a s i c ) A p p r o a c h P r o f i l e
' D u e to a n In terferin g A ircra ft L o c a te d A h e a d o f the A z im u th A n te n n a
2 ) D e t e r m i n e A r e a T h a t B o u n d s A l l L o c a t i o n s T h a t H a v e t h e P o t e n t i a l to
P ro d u c e E rro rs th at E x c e e d A c c e p ta b le L im its
S ta n d a rd A p p r o a c h P rofile:
Lateral T ra c k o n C e n te r,
V ertical T ra c k A lo n g a
T hree-d eg ree G lide P ath
A zim uth A ntenna
E le vation A n te n n a
Elevation C ritical-Area Problem
1) C h a r a c t e r i z e E l e v a t i o n E r r o r C a u s e d A l o n g S t a n d a r d ( B a s i c ) A p p r o a c h P r o f i l e ■
D u e to a n I n t e r f e r i n g A i r c r a f t L o c a t e d A h e a d o f t h e A z i m u t h A n t e n n a
2 ) D e t e r m i n e A r e a T h a t B o u n d s A l l L o c a t i o n T h a t H a v e th e P o t e n t i a l to
P r o d u c e E r r o r s th a t E x c e e d A c c e p t a b l e L i m i t s
PLAN VIEW
Figure 30. Azimuth and Elevation Critical Area Problem Definition - Basic Procedures.
MDB9809090I
o
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A n tenn a Location Relative to R unw ay Stopend
A nte nn a B cam width an d T y p e -
'2 . 0
Decision Height — ^ - 2
DEGREE AZIMUTH SYSTEM1; 1 - 1 0 0 0 . 0 , 0 . 0 , 6 , D1
5 0 F T . DH “ PFE CONTOURS FOR R B ~ 7 4 7
I nterfe ring A irc ra ft T ype
RIRCRRFT ROTATION ANGLE « 270
3 DEGREE C .L. RPPRORCHn 9000 FT. RUNWAYi
A p proa ch Profile ( S t a n d a r d ------------A p p ro a ch in this Case)
R un Length for A zim uth Sim ulatio ns •
C O N V EN T IO N S
EXAMPLE
T h e m a s im u m I’FE e r r o r observed along a
s t a n d a r d a p p r o a c h down to a decision height of
250 feet due to M ultipa th for a Boeing B-747
c en ter at this location and oriented with its nose
in the +Y direction would be less than 0.090*
0.000
-0 .4 2 0 _ ~ 0.300
,.0-JO
V O . I S O ^ O . I jin
1000.0
30
RUNW AY
R O TA T ON l
IN T E R P R E T A T IO N
0 .2 1 0
X -y J
v
0.Q&0 o
2 0 00.0
T
3000.0
DISTANCE
-The c o n to u r plots describes the m a s im u m e r r o r , on a 95%
sliding w indow basis, observed along the specified a p p ro ac h
profile due to m ultipath caused by the specified in terfering
a irc r a ft, which is centered at a selected location on the plot
an d in the orientation specified.
- T h e a p p r o a c h profile sta rts 5 nmi from runw a y threshold
and ends at the decision height given in the plot h e ad e r
T
40 0 0 .0
T
5 0 0 0 .0
IN FRONT DF THE ANTENNA
6000.0
7000.0
IN FEET
NOTE i CONTOUR LIN ES ARE IN INCREMENTS OF 0 .0 3 0 DEGREES
PLOT STORED ON 015K F IL E
flEC ML5 MODELING
Figure 31. Annotated Example Error-Contour Plot.
: AC0NE24.PLT
M D H 9 B 0 9 I6 0 3
52
analysis o f error contour plots. An overview of the process used to generate an azimutherror-contour plot is provided in Figure 32. The same process is used for analysis of error
contour plots. An overview o f the process used to generate an generating an elevation-errorcontour plot, but in this case the runway length is not an essential parameter. Also, the
search grid is located ahead o f the elevation antenna as shown in Figure 30.
The process starts with an initialization stage: where the parameters that remain
constant during the process are specified. The next four stages form a process loop, thus
representing the majority of the process. During the second stage, the interfering aircraft is
centered at the appropriate search-grid point in the orientation specified during the
initialization stage. During the next stage the MLS Mathematical Model (MLSMM) is used
to estimate the guidance-signal errors that would occur along the specified approach
procedure due to multipath caused by the interfering aircraft. During the fourth stage, the
Path Following Error (PFE) and Control Motion Noise (CMN) data are generated and
analyzed. The PFE and CMN data are generated by filtering the static error data generated
by the MLSMM as shown in Figure 33. The multipath scenarios being considered will not
generate a bias error, thus the PFE data do not require any additional processing in order to
obtain PFN data (PFE = PFN + bias). The resulting PFE/N and CMN data are analyzed
using the MLS error-measurement methodology specified in Reference 3, which is based on
a 95% sliding-window (95%_SW) requirement (Figure 34). The maximum 95%_SW PFE/N
and 95%_SW CMN values obtained from this analysis process, along with the current
search-grip coordinates, are written to a data file during the fifth stage. Once error data have
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
53
'
‘
*'
E rr a r C u l i i r D m G n e r a M ti f m m
---------- Interfering Arcnft Location.
Imttelieerioii
Type and Orientation?
---------------------------------------------I) Place Interfering
Aircraft At Next G nd Point
2) Perform Sunnfaoon to Determine
Error Induced Along Approach Due
to Scattering by Interfering Aircraft
3) Analyze PFE
CMN to
D eterm ine M axim um Error V alues
No
4) Write Interfering Aircraft
Location and Error Data to Data
Last Grid
Point?
F ile
Locatioa
Grid Location.
Size and Spacing?
Yes
Create Contoor Plot
Approach Procedure —
Profile?
— Approach Aircraft Speed and
Receiver Type?
Interfering Aircraft —
Glide Path Angle?
Decision Height?
— Runway Leagth(s)?
2-D egree A zim uth and Interfering B-747
95% Sliding Window Analysis
HEADER BLOCK
S cen ario Descrition
Sim 6
Distance from Threshold (am i)
2-D egree A zim uth and Interfering B-747
95% Sliding Window Analysis
01
02
03
04
05
06
07
06
09
10
S c a tte r
X«100
X=100
X*100
X *100
X «100
X «100
X »100
X »100
X *150
X «150
Location
Y=50
Y*100
Y«1S0
Y«200
Y «250
Y*300
Y*350
Y*400
Y«50
Y *100
9996
9997
9996
X *1000 Y«50
X *1000 Y»50
X *1000 Y*50
Max PFE
Max CMN
0.0457
0.0534
0.0496
0.0572
0.0657
0.0527
0.0457
0.0557
0.0397
0.0287
0 .0667
0.0721
0 .0657
0 .0 5 6 7
0 .0 5 3 7
0 .0 4 6 9
0 .0523
0.0451
0 .0 4 6 7
0 .0398
0 .0057
0.0132
0.0019
0 .0 2 0 7
0 .0107
0 .0 0 6 7
MDB98012201
Distance from Threshold (nmi)
Figure 32. Overview o f Process Used to Generate Error Contour Plot Data - Azimuth.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Receiver Output Filter
\
Static Error Data
Generate by MLSMM
S + (0
R a d /S c c
u - 10
Dynamic Error
Data
K
v /
CMN Filter
PFE Filter
P ro v id es p o rtio n o f g u id a n ce sig n al e rro r th at
co u ld ca u se aircraft d isp la cem en t from
d esire d co u rse
P ro v id es p o rtio n o f g u id a n ce s ig n al erro r w h ich could
a ffec t aircraft attitu d e an d cause co n tro l su rface m o tio n ,
b ut does not disp lace aircraft from d esire d co u rse
We­
s' +2(0, + (i),'
S
S + (0
0
Rid/Scc
R a d /S e c
A p p ro a c h A B a c k A z im u th , • - O J
Approach A Back A zim uth,« • O.S
Blevation A DME/P: *» - 0.S
E le v a tio n A D M E /P : • - 1.5
CMN Data
PFE Data
Scenarios Modeled
do not Generate
Bias Component
Where;
(0 = 0 . 6 4 ( 0 .
PFN Data
M D B 9809270I
Figure 33. Standard Filter Characteristics for Generating PFE and CMN Data From the Static Error Data.
iyt
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
SLIDING
O U T P U T O F P FB O R C M N F IL T E R
■ iT
>
DISTANCE FROM THRESHOLD (■»!)
SLIDING WINDOW CRITERIA
W
T« WIDTH OF
w|
SLIDING WINDOW
e . - MINIMUM VALUE FOR WHICH THE
INEQUALITY BELOW IS TRUE
(T l » T J * T J » . )
T
N O T E : T U B V A L U E (£■
)
O B T A IN E D F O R E A C H IN T E R V A L
IS P L O T T E D A T T H E D IS T A N C E
A S S O C IA T E D W IT H T H E
T H R B S H O L D E N D O F T H E S L ID IN O
W IN D O W .
I
f“
>oos
WHERE:
T - EVALUATION INTERVAL DURATION
T 1 .T 2 .T 3 - TIME INTERVALS THAT
THE ERROR EXCEEDS E.
*
£.
9 5% S L ID IN G
W IN D O W ER R O R
TRACE
-►
DISTANCE FROM THRESHOLD (ami)
T H E M A X IM U M V A L U E O B T A IN E D F R O M T H E 95% SL ID IN G W IN D O W
E R R O R T R A C E I S R E C O R D E D IN T H E E R R O R C O N T O U R D A T A F I L E
M b B v io m o ;
Figure 34. Methodology Used for Generating 95% Sliding Window Data.
LA
LA
56
been generated for every search-grid point, the resulting data file is processed in order to
produce an error-contour plot. Generally, about 1,200 approaches are simulated for each
azimuth-error-contour plot generated, and about 500 are simulated for each elevation-errorcontour plot.
1.
Standard Approach Procedures
As illustrated in Figure 32, values for a number o f parameters must be specified
during the execution o f the process. These parameters were reviewed and specific values
were developed [47-50]. Subsequently, the process of generating error contour plots for the
purpose of developing critical-area criteria for standard approach procedures was initiated
[51-55]. Extensive simulation work was performed and numerous error contour plots were
generated [56].
To facilitate the analysis of these contour plots, the azimuth and elevation system
error budgets for PFE/N and CMN were reviewed. As a result o f this review, allocations
were made for the multipath error permitted to be caused by interfering ground-based
aircraft, and the resulting PFN and CMN allocations are provided in Appendix B [54,55].
Since multipath from interfering aircraft will not generate a bias error, it would be
inappropriate to make an allocation based on system requirements for PFE (PFE = PFN +
bias).
Based on these allocations, the contour plots were analyzed and interfering aircraft
locations which result in error levels that exceed the error-budget allocations were identified.
Tables 3 and 4 provide a listing of the error contour plots that were analyzed.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
57
Table 3. Azimuth-Error-Contour Plots Analyzed for Standard Approach Procedure.
Interfering Aircraft
Beamwidth
[.O'
Orientation
Type
Perpendicular to
Runway
Centerline 0
Boeing B-747
Runway
Length
(Feet)
12,000
1,000
10,000
Boeing B-727
12,000
1,000
Decision Height(s)
(Feet)
50, 100, 150,200,250,
300, 350, 400, 500, 600,
700, 800, 900, 1000
For Selected Cases:
Touchdown, Rollout Down
Runway
10,000
2. 0 '
Perpendicular to
Runway
Centerline 0
Boeing B-747
9,000
8,000
7,000
6,000
5,000
Boeing B-727
50, 100, 150,200,250,
300, 350, 400, 500, 600,
700, 800.900,1000
For Selected Cases:
Touchdown, Rollout Down
Runway
9,000
8.000
7.000
6,000
5,000
NOTES:
n A parallel orientation, nose pointed towards stop end, was simulated
for selected cases, but these results were not the driving factor in
determining the critical-area lengths.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
58
Table 4. Elevation-Error-Contour Plots Analyzed for Standard Approach Procedure.
Interfering Aircraft
Decision Height(s)
(Feet)
Beamwidth
Rotation Angle
Type
1.0°
Boeing B-747
Boeing B-727
0.0°
50, 100, 150,200
270°
Note: 3.0° glide-path angles
was used for all elevation
work
0.0°
270°
1.5°
Boeing B-747
0.0°
50, 100, 150,200
270°
Note: 3.0° glide-path angles
was used for all elevation
work
300°
315°
330°
340°
350°
Boeing B-727
0.0°
270°
CON VEN TION F O R R O TA T IO N ANGLE
RUNWAY
270'
E le v atio n
A n ten n a
I*"
180'
H -
G rid P oint
90°
M FD TM P012
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
59
The characteristics o f these unacceptable error locations, along with runway safety zone
requirements and operational considerations, form the basis for the critical-area criteria that
have been developed for the standard approach case.
Generalized descriptions o f the critical-area criteria for azimuth and elevation
antennas are provided in Figures 35 and 36, respectively. Although the terminology “critical
area” has been used, mainly due to existing terminology that was used for the ILS, the
criteria actually define a volume. Several factors must be considered in order to apply the
generalized critical-area criteria to a specific site. In each case, the length (L) o f the critical
area must be determined. References 1, 8, 54, and 55 contain tables which provide lengths
based on the antenna beamwidth, size of the largest aircraft type expected to operate at the
facility, and the severity of the multipath environment. As discussed in the following
paragraph, this information is provide in Appendices C and D. Since the location o f the field
monitor is site dependent, the criteria must be adapted as shown to ensure that the area
between the antenna and monitor is protected. The profile view must be adjusted to account
for the specific glide-path angle(s) for which an approved approach procedure exists.
It should be noted that in most cases the elevation critical area will be elevated off
the ground. In particular, most aircraft fuselages will fit under this area when a 1.0°
beamwidth elevation antenna is used. For the case of a 1.5 ° beamwidth elevation antenna,
criteria have been developed that enable site-specific tailoring of the elevation critical area
when the site meets specified requirements [57]. Typically, such tailoring is performed when
an increase in capacity, that is an increase in the number of takeoffs and landings performed
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
60
Azimuth Antenna
To Field Monitor Pole as Required
/
X
RUNWAY
CENTERLINE
Azimuth Critical Area — ^
(Standard Approach Procedures)
L - 1,000’ - 2,700’
Exact length depends on antenna beam width.
azimuth-to-threshold distance, and interfering
aircraft type, and multipath environment
Flight Path Deviation
Allowance: ± 0.2°
B W ■ B eam w id th
P L A N V IE W
Azimuth Antenna
m
Frcsacl
RUNW AY
Values for a a n d 0 (Feet)
6 1 - 3.0°
NOTES
* As required to protect
field monitor
1 M ost all published results assume 6 ■ 3.0°,
5 should equal the maximum glide path angle
for which an approved approach procedure
exists
1 M easured horizontally from front o f azimuth
antenna
’ Measured vertically from bottom o f azimuth
antenna aperture
p1
i i j
250
8 .7
500
17.5
" 750
2415
1 0 0 0 ' 2 8 . 3'
Where
34.3
5 6 ^2
76.0
94 . 8
a - 0.03S*X X < 656’
a - iWlX X 2 656'
P - X*Tan(S) 3V0.2X
M O B98022301
P R O P IL E V IE W
Figure 35. Azimuth Critical-Area Criteria for Standard Approach Procedures.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
61
N - 250 ft. -«l
RUNWAY
E L E V A T IO N
ANTENNA
T O F IE L D M O N IT O R A S R E Q U I R E D
( S e e T a b l e B e lo w )
For G lide Path A n g les
BEAMWIOTH
CLEAN SITE
2
3 .0 ’
COMPLEX SITE
747
727
747
1.0*
1050 ft.
560 n.
1260 ft.
600 ft
1.5’
1310 ft
820 ft
1860 ft.
990 ft.
a)
727
P L A N V IE W
T H IS V O L U M E E X IS T S O N LY
W H ERE A PPRO A CH PR O C E D U R ES
F O R M U L T IP L E E L E V A T IO N
A NG LES A RE A PPRO VED
M AX G P
E L E V A T IO N
ANTENNA
F L IG H T PA T H
D E V IA T IO N
ALLOW ANCE
( 0 . 2 °)
M IN G P
U 3.0 ’)
7 BW
M IN IM U M
G L ID E P A T H
M A X IM U M E L E V A T IO N A N G L E F O R
W H IC H A N A P P R O V E D A P P R O A C H
P R O C E D U R E E X IS T S
r ////
A S R E Q U IR E D T O
P R O T E C T F IE L D M O N IT O R
b) P R O F IL E V IE W
M DB98022706
Figure 36. Elevation Critical-Area Criteria for Standard Approach Procedures.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
62
per hour, is required at a site that is currently serviced by a 1.5° beamwidth elevation
antenna.
The results obtained throughout this research effort received extensive review by the
FAA and the All Weather Operations Panel (A WOP) of ICAO [58,64]. In accordance with
FAA and A WOP recommendations, the critical-area criteria presented herein have been
adopted as national and international standards. The published descriptions of these criteria
contained in Reference 1 and Reference 8 are provided in Appendices C and D, respectively.
Based on these published descriptions, there are three points which need to be
emphasized. First, the lengths provided for the elevation critical area are valid only for glidepath angles o f 3.0° or greater, and for decision heights not less than 50 feet. Since the vast
majority of civil operations was expected to use a 3.0° or higher glide-path angle, the
development o f the lengths for lower glide-path angles had a very low priority. This work
was never performed due to the FAA decision in the fall of 1994 to focus on implementation
o f MLS, thus deferring further MLS research and development. Elevation critical-area
criteria that protect MLS operations to a decision height of 50 feet were considered
sufficient, since radar altimeter data, and inertial data when available, are used normally for
vertical guidance below this height. Second, the upper boundary of the azimuth profile view
must be adjusted to accommodate the highest glide-path angle for which an approved
approach procedure exists. Normally, absolute values for this boundary are provided: these
values assume a 3.0° glide-path angle. The equation provided in Figure 35 can be used to
determine values for other glide-path angles, as required. Finally, the critical-area criteria
were developed with the emphasis on protecting the last five nautical miles of the approach
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
63
procedure. That is, the last five miles are protected to the level associated with the criticalarea error allocations; larger error levels were considered acceptable for the portion o f the
procedure prior to the glide-slope intercept point.
2.
Validation and Model Refinement
During the development of the critical-area criteria, flight tests were performed to
validate the results obtained [65-68]. Test plans were developed in order to detail the flight
tests and data analysis activities necessary to accomplish two objectives. The first objective
was validation of the criteria that had been developed, thus far, for the standard-approach
case. These criteria were still considered preliminary criteria at the time the testing was
conducted. In general, interfering aircraft locations on both sides of the critical-area
boundaries were used during the testing. A review o f selected error contour plots indicated
that these locations would be expected to cause minimal error. Error levels that would be
indistinguishable in terms of comparing system performance with and without the interfering
aircraft present. The second objective was validation of the MLS Mathematical Model’s
ability to estimate the error due to multipath from interfering aircraft. In this case, selected
error-contour plots were reviewed in order to identify high-error regions. The intent was to
locate the interfering aircraft at locations which would produce error signatures that could
be distinguished easily from the composite effect o f other commonly present error sources,
e.g. other multipath, thermal, transmitter, receiver, measurement, etc.
The initial validation work consisted of a joint effort between the FAA Technical
Center and the Avionics Engineering Center; this work occurred during the fall o f 1987. For
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
64
this work, an FAA Technical Center Boeing B-727 was used as the interfering aircraft, and
the FAA’s MLS equipment installed on Runway 04 at the Adantic City International Airport
(identifier = ACY) provided the guidance information. The flight test and data reduction
work were performed by the Avionics Engineering Center.
A total o f 67 flight
measurements were performed with precision tracking o f the test aircraft. Measured PFE
and CMN data were compared to model estimates. Through this comparison it was
demonstrated that the MLS Mathematical Model can estimate the effects o f interfering
aircraft on the MLS guidance signal. Generally, the amplitudes o f the estimated error
differed from the measured by ten to twenty percent with a few exceptions where the
difference was about fifty percent.
Based on these findings, several factors were investigated in order to determine the
reasons for the differences between the model and measured data. In this case, the intent was
to determine the extent to which the differences were due to deficiencies with the MLSMM
as opposed to the validation process. The first factor was the magnitude o f the multipath
errors. The magnitude o f the multipath errors generated by signal scattering from the
interfering Boeing B-727 was generally on the order of 0.020°to 0.035° (Figure 37). This
magnitude is comparable to the error magnitudes observed for the baseline performance data
(no interfering aircraft). This situation indicates that the error levels generate due to
multipath from the interfering Boeing B-727 are comparable to the composite multipath error
levels generated by all other error sources. These error sources include ground reflection,
sidelobe reflections, thermal noise, disperse scattering, beampointing, etc. Thus, isolation
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED VERSUS MODELED ERROR - ACY POSITION #3
0.04
SCATTERING GEOMETRY
0.035
0.03
S- 0.025
P O S IT IO N 3. ACY
UJ
£
0.02
£
I 0.015
9
~
0.01
0.005
0
0
0.5
1
1.5
2
2.5
3
3.5
4
D istance from Threshold (nmi)
▲Measured
■ Modeled
Figure 37. Measured and Modeled PFE Magnitude Data for Atlantic City Scattering Position #3.
M D B98092901
66
of the multipath error signature due to scattering by the interfering aircraft would not be
feasible in this case.
However, the situation discussed above does not explain the differences observed
between the measured and model data for the scattering geometries that generated multipath
errors with magnitudes of 0.20° to 0.40°. These error levels were generated by shadowing
or diffraction of the guidance signal by the aircraft tail fin, which produced a noticeable error
spike in the error data (Figure 38). Further investigation revealed that the location and
magnitude of the error spike was sensitive to several factors including the difference
(accuracy) of the modeled versus actual interfering aircraft location, differences between the
model and actual receiver flight path, and, the method used to represent the tail fin in the
MLSMM. Thus, it was concluded that further testing was required before the accuracy of
the MLSMM could be evaluated completely.
For the purpose of further model validation, flight measurements were performed at
Standiford Field (identifier = SDF), Louisville. Kentucky during the spring o f 1988. The
MLS ground equipment was installed and aligned by Avionics Engineering Center personnel
prior to the scheduled flight-test period. For the interfering aircraft, Avionics personnel had
access to a Boeing B-747 and associated ground crew, which were provided without charge
by the United Parcel Service. A total of 83 approaches, 40 for azimuth and 43 for elevation,
were flown during this validation effort. The approaches consisted of 3.0° centerline
approaches with baseline measurements performed before and after each test session in order
to assess system stability.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED VERSUS MODELED ERROR - ACY POSITION #5
0.4
S C A T T E R IN G G E O M E T R Y
0.35
0.3
o>
q
• C O O R D IN A T E REFERENC E
0.25
P O S I T I O N 5. A C Y
N O IR
_CX. vt*_
Ui
a
TAM.
(X, VI*
(M l. .101)
0.2
£3
|
015
0.1
0.05
0
0.5
1.5
1
2
2.5
3
3.5
4
Distance from Threshold (nmi)
a
M easured
■ M odeled
M D B 9809300I
Figure 38. Measured and Modeled PFE Magnitude Data for Atlantic City Scattering Position #5.
o\
68
Measured PFE and CMN data were compared to model estimates; and, in comparison
to the first validation effort, an overall improvement was achieved. However, it was
observed that the MLSMM significantly over estimates the error generated due to scattering
by the aircraft tail fin (Figure 39). As shown in Figure 39, the peak magnitude o f the model
estimate is almost three times that o f the measured data and exists for a longer duration. This
situation would result in an overly conservative estimate o f the area that needs to be
protected for the elevation antenna, which may unnecessarily restrict the movement of
ground-based aircraft. Thus, more representative error estimates are desired and further
investigation was initiated.
The measured PFE data are obtained using the process shown in Figure 40. The
aspect of this process relevant to the validation effort is that the truth data are provided by
a joystick controlled optical theodolite reference system (Figure 41). That is, a human
operator manipulates the joystick such that the theodolite crosshairs remain on the MLS
antenna o f the flight-test aircraft. Since the operator does not track the aircraft antenna
perfectly, there is error in the measured data. The instantaneous error introduced by an
experienced operator is about 0.02° to 0.03 ° when proper quality control measures are taken.
One of the quality control measure involves repeating the flight measurement and confirming
the repeatability of the measured data. In addition to ensuring that the aircraft was tracked
properly, it also characterizes the sensitivity of the measured error to variation in receiver
position, since the flight-test aircraft flies a slightly different path in space each time the
measurement is performed. The repeatability of the measured data for SDF elevation
position number 1 is shown in Figure 42 and it provides confident that the measured data are
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED VERSUS MODELED ERROR - SDF POSITION #1
S C A T T E R IN G G E O M E T R Y
* C iir d la iu R if tm c i
2> 0.8
^ - B U v t i i o a A b K o d * B o r « itg k i
S ttn d lfo rd F ield • P oailon f I
0
0.5
1
1.5
2
2.5
3
3.5
4
D istance from T h resh o ld (nmi)
A Measured
■ Modeled
Figure 39. Measured and Modeled PFE Magnitude Data for Standiford Field Elevation Scattering Position #1.
MDB98093002
ON
NO
D A T A P R O C E S S IN G :
L in e a rly In te rp o la te T ru th D a ta
S a m p le s to M L S S a m p le T im e s
T ra n s la te T ru th D ata to M L S an d
D M E A n te n n a P h ase C e n te r
L o c a tio n s
• G e n e ra te D iffe re n tia l E rro r D a ta
Differential
Error Data
TRUTH DATA:
(T h e o d o lite A n g le s , M in ira n g e r R a n g e , F la g s an d
A sso c ia te d T im e T a g s)
Analigous to Dynaimic Error
Data Genereated by MLSMM
PFE Filter
CMN Filter
I
1
- ifnqdiY
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A IR B O R N E D A T A :
(M L S A n g le s /F la g s , D M E
R a n g e /F la g s an d A s so c ia te d
T im e T a g s)
iS + CO
*
(0.
ia
S
$
7 \
S ’ + 2 c o . + co.
•
Rad/Sec
CMN Data
Rad/Scc
Approach A Back Azimuth, • - 0.5
Elevation A DME/P: • - 1.5
Ap preach A Back Azimuth, • * 0.3
Etc valion a DME/P: a - 0.5
W h ere:
to “ 0 .6 4 co.
PFN Data
PFE Data
Remove Bias
Component
M D B 9 S 1 0 0 I0 I
Figure 40. Overview of Process Used for Generating Measured PFE and CMN data.
o
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
THEODOLITE
AND STAND
( Wa r re n- Kn i gh t )
C O M M RADI O ( King)
G R O UN D D A T A
MANAGER
I
j
J
-JOYSTICK
CONTROLLER
M I N I - R A N G E R III
(Motorola)
M D B 9 M O 0 I0 2
Figure 41. Ground-Base Optical-Theodolite Reference System.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED DATA REPEATABILITY - SDF POSITION #1
S CATTERI NG G E O M ET R Y
* C e s rd ia s u R if tria c a
~ 0.35
111Imi
^ m t v a i l o n A a i « m >«
in i
r«n
0.25
5
S iM d lfo rd r i c l d • ro i t i o n #1
0.2
“ 0.15
1.5
2
NOSE (X, Y)*
TAIL <X,Y)
(fed)
(1069. 64)
(1069,291)
2.5
3
Distance From Threshold (nmi)
i Run 15
« Run 16
« Run 17
Figure 42. Repeatability of Measured Data for Standiford Field Elevation Scattering Position #1.
MDB98093003
73
representative of the actual error. In addition, the repeatability achieved between each of the
flight measurements establishes the benchmark to be used in assessing the accuracy o f the
MLSMM. This is, the model estimates should be considered representative if they agree
with the measured data to the same degree as one measurement (run) agree with another. At
this point, the investigation focused on improving the error estimates provided by the
MLSMM.
For SDF elevation position number 1, the multipath error is generated by diffraction
o f the guidance signal by the aircraft tail fin and fuselage. In this case, the MLSMM uses
two rectangular plates to represent that aircraft fuselage and tail fin (Figure 43). Analysis o f
the scattering geometry indicates that the large error spikes in Figure 42 are due to signal
diffraction by the aircraft tail fin, since the line-of-sight from the antenna to the receiver
migrates across the upper portion of the tail fin as the receiver approaches threshold (Figure
43). For this migration route, the width o f the plate used in the model is almost twice the
width o f the actual tail fin. In order to understand how such a difference will effect the error
estimate, one must understand the electromagnetic theory used by the model.
The MLSMM is based on a unique combination of Physical and Geometrical Optics
[15].
The theory developed for estimating the error produced due to diffraction by
rectangular plate is detailed in Appendix E and outlined in Figure 44. This theory is applied
whenever line-of-sight from the antenna to the receiver passes through, or close to, a
rectangular shadowing plate. In this case, the theory used is obtained by starting with the
equation provided in Sommerfeld for Fraunhofer and Fresnel diffraction through an infinite
slit [69]. Then, the equation is adapted to account for diffraction through an electrically-
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
------------------ 296' ------------------------TO RUNWAY CENTERLINE
<------ 40'(1)
TRACE OF WHERE LINE OF SIGHT FROM
ELEVATION ANTENNA TO RECEIVER
CROSSES THB TAIL FIN AS RECEIVER
APPROACHES ON 3.0" GLIDE PATH,
CENTBRL1NE APPROACH
1)STANDARD TAIL FIN
WIDTH USED IN MODEL.
OVERLY CONSERVATIVE
PREDICTIONS FOR
ELEVATION SCATTERING
<2I'(2) >
2)GEOMETRY DEPENDENT
ADJUSTMENT OF TAIL FIN
WIDTH USED TO IMPROVE
MODEL PREDICTION
PLATES USED BY MODEL
TO REPRESENT AIRCRAFT
ACTUAL AIRCRAFT
STRUCTURE
TAXIWAY SURFACE
11 111 I I I Lit
BACK OF
ELEVATION
ANTENNA
I
i
325'
TO RUNWAY CENTERLINE
MDB9809180I
Not to Scale
Figure 43. Rectangular Plates Used by MLSMM to Represent Shadowing Boeing B-747, Viewed from SDF Elevation Antenna.
^
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1) DI FF RA CT IO N BY I N FI NI TE T WO
D IMENSI ONAL SLIT
3) APPLYING BABINET’S PRINCIPLE YIELDS
SHADOWING BY RECTANGULAR PLATE
SHADOWED REGION
RECEIVER
RECEIVER
(V,)
SLIT APERTURE
■TRANSMITTER
TRANSMITTER
SHADOWED REGION
v.„ = 1 - (j/2)[F(zn -F(z[)][F(y^) -F(y,)l
V ,= '/i (l-j)lF (z ;) -F(Zi)]
FRESNEL INTEGRAL, See Appendix E
for D etailed D lic u n lo n
2) DIFFRACTION BY RECTANGULAR
APERTURE
4) APPLY SHADOWING-GEOMETRY
DEPENDENT ADJUSTMENT
RECEIVBR^S
RECEIVER
EDGE RAYS
TRANSMITTER
TRANSMITTER
ADJUSTED TAIL
FIN WIDTH
V. = 0/2)[F(zi) -F(z7)][F(yI> -F(y-)]
.STANDARD TAIL
FIN WIDTH
M D B 9 8 I0 2 6 0 I
Figure 44. Overview of Theory Used by MLSMM to Estimate Elevation Error Due to Shadowing by a Rectangular Plate.
L /l
76
large rectangular aperture. However, the field desired is the field due to blockage by a
rectangular plate, that is the complementary problem to diffraction through a rectangular
aperture. According to Babinet’s Principle, the blockage by the plate can be expressed as the
unperturbed field (direct) minus the field propagating through the aperture. Now having an
expression for the field behind the plate, it must be decomposed into components in order
to provide an error estimate.
Methods for decomposing the field into edge rays have been developed based on the
unique physical aspects of the signal scattering, which result from the fact that the angle
equipment generate scanning beams [70-74]. For electrically-Iarge plates, the particular
method used depends on where line-of-sight from the antenna to the receiver passes relative
to the rectangular plate. The three cases are: line-of-sight passes through the plate; line-ofsight passes close to a vertical edge; and, line-of-sight passes close to a horizontal edge.
Although the implementation is specific to the case being considered, the concept employed
to the same in each case.
For example, consider the case where line-of-sight between the elevation antenna and
the receiver passes through the plate. As the elevation antenna performs the “TO” scan, the
beam will be diffracted by the top horizontal edge of the tail fin. As the scan continues,
signal will be diffracted by the vertical edges when the proper diffraction geometry results.
Finally, the scan continues and the signal is diffracted by the bottom horizontal edge. The
sequence is reversed on the “FRO” scan. Considering the TRSB technique, the signals
diffracted by the vertical edges will arrive at the receiver at nearly the same time as the direct
signal would have if the plate were not present. Thus, the signal diffracted by the vertical
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
77
edges may be represented as the “unperturbed field” mentioned during the earlier discussion
of Babinet’s Principle. Now, according to Babinet’s Principle the signal blocked by the plate
must be “subtracted” from the unperturbed field to obtain the total field behind the plate.
This subtraction is done in a manner that enables an error estimate to be computed. That is,
it accounts for the signal diffracted by the plate edges which have a non-zero separation
angle relative to the direct signal. In the case of the elevation antenna, the signal blocked
by the plate is represented by two edge rays; one for the top horizontal edge and one for the
bottom. Based on the concept o f equivalent currents, the magnitude and phase o f the top
edge ray are obtained by integating the field over strip A. Similarly, the bottom edge ray is
obtained by integrating over strip B. In addition to determining the amplitude and phase of
these rays, the separation angles (Figure 44) must be taken into consideration when
computing the resulting multipath error.
Based on the rectangular plate used to represent the tail fin versus the actual physical
characteristics of the tail fin (Figure 43) and the theory employed by the MLSMM, one
would expect the model to estimate both the magnitude and duration of the error produce for
SDF position number 1 scattering geometry. Further, the Physical/Geometrical Optics
theories used by the model would be expected to provide accurate estimates for shadowing
by rectangular plates with dimension that are large compared to the source wavelength. At
MLS angle equipment frequencies (5 GHz), the wavelength is about 0.2 feet. Accordingly,
accurate estimates would be expected for plates with dimensions exceeding 2 feet.
Therefore, the problem is that the 40-foot width of the rectangular plate used to represent the
tail fin is not representative of the actual scattering geometry when line-of-sight passes
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
78
through the upper portion o f the tail fin. Thus, it was asserted that the estimate could be
improved by appropiately adjusting the width of the tail fin based on where line-of-sight
passes through the tail fin. To verify this assertion, the scattering geometry for SDF
elevation position number 1 was reviewed. The width o f the tail fin where line-of-sight
passes through the tail fin is about 21 feet (Figure 43). Therefore, the width of the plate used
in the model was adjusted from 40 feet to 21 feet and the results obtained are provided in
Figure 45. These results show a noticeable improvement compared to the results obtained
in Figure 39.
In addition to the tail fin adjustment discussed in the above paragraph, it was shown
that the model’s performance could be improved by adjustment o f the aircraft dimension
parameters used in the model, and by the user modeling “secondary” structures (engine pods,
etc.) with shadowing and scattering plates [68]. These findings promoted confidence that
the propagation theory used in the model is accurate enough but limited by the default
aircraft silhouettes used. The final conclusion o f the validation efforts was that the aircraft
silhouette is a limiting factor in the model’s accuracy.
However, the objective of the critical-area work is to identify errors typical of
interfering wide-body and standard commercial aircraft, and to bound the areas where the
errors are expected to exceed error allocations. Therefore, it was concluded that a detailed
silhouette of a particular aircraft was not required for developing critical area criteria
provided the errors predicted for first-order scattering mechanisms (fuselage, wings, tail fin)
were realistic [68]. In addition, margins were provided in the error allocations to compensate
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED VERSUS MODELED ERROR - SDF POSITION #1
0.4
SC A TTER IN G G EO M ETR Y
’* C m i I U i Ii l U f m i o
0.3
ao
Q
’BMi
III
U.
“ ■
c
0.2
V
0
S u ad lfo rd F ield ♦ fo iiH o n
tl
1
iS
(10**.
0
0.5
1
1.5
2
2.5
3
3.5
4.5
4
Distance from Threshold (nmi)
a
Measured
■ Modeled
MDB98093004
Figure 45. Measured and Modeled PFE Magnitude Data for SDF Elevation Scattering Position #1, Modified Tail Fin.
80
for remaining model limitations. Thus, it was decided that the model could be used with
confidence for developing critical-area criteria.
3.
Finalization o f Results for Straight-in Procedures
A final simulation effort was performed [75.76], which took into account the findings
o f the validation work. This effort revisited the scenarios list in Tables 3 and 4. The
resulting simulation data were used to generate error contour plots, and these plot were
analyzed to refine and finalize the critical-area criteria for standard-approach procedures.
Again, these criteria are provided in Appendices C and D.
4.
Dynamic Interfering Aircraft
Since the research performed to this point considered only stationary interfering
aircraft, a preliminary study was performed to investigate the errors caused by dynamic
interfering aircraft [77]. The interest centered around aircraft exiting or traveling through
the runway region. The results o f 426 simulations performed using the MLSMM indicate,
that depending on the orientation and direction o f travel o f the interfering aircraft, the error
can be reduced or increased over the results obtained in the stationary case.
Significant error reduction is achieved for situations involving an aircraft on a taxi
path which is perpendicular to the receiver lateral track. The reduction is due to additional
motion averaging resulting from the interfering aircraft motion, and a decreasing amount of
time the interfering aircraft is in the in-beam multipath region. An example of this situation
is an aircraft exiting or crossing the runway while an approaching aircraft is performing a
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
81
standard-approach procedure. Similarly, an error reduction is achieved for aircraft with a
taxi path parallel to the receiver lateral track and moving in the direction opposite to the
receiver. In this case, the reduction results from the shorter duration o f multipath error which
is due to the motion o f the interfering aircraft. An example of this situation would be a
previously landed interfering aircraft taxing from the runway stop end to the gate area while
an approach aircraft is performing an offset-azimuth approach.
An increase in the error is observed, however, when the interfering aircraft taxi path
is oriented parallel to the lateral track of the receiver and moving in the same direction as the
receiver. In this case, the receiver can be exposed to multipath for a longer duration o f time.
An example of this situation is a landed aircraft on roll-out with an aircraft making a standard
approach. Since this situation represents the “normal” landing situation, a careful review o f
the results was performed. First, this interfering aircraft orientation is not a driver in defining
the critical-area boundary, thus there is margin available in the critical-area error allocation.
In addition, the results indicate that for operationally representative conditions, the error
levels would not be expected to exceed the critical-area error allocations.
5.
Offset-Azimuth Procedures
There are two types o f basic approach procedures that can be supported by an
azimuth antenna that is sited offset from the extended runway centerline (Figure 46). For
one type, the lateral track of the procedure is along an azimuth radial which is parallel to the
runway centerline. For the other type, the lateral track is along a radial which is not aligned
with the runway centerline. For either type, raw azimuth and elevation information are used
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
82
to provide the guidance information for the procedure. If the equipment is supporting
operations for fixed-wing aircraft, the angle between the runway centerline and the
procedural radial generally will be 3.0° or less. This angle may be larger when the
equipment is used to support rotorcraft operations to remote helipads.
As shown in Figure 46, the elevation antenna can be sited to either side o f the runway
regardless o f which side the azimuth antenna has been offset. Thus, each procedure type
provides two cases to consider in terms o f elevation critical-area criteria. The profile view
o f the elevation critical area (Figure 36) protects the procedure from in-beam multipath due
to main beam reflections caused by aircraft ahead o f the antenna. The same protection is
required for the offset-azimuth procedure, thus the same requirement applies. As the plan
view (Figure 36) indicates, the critical area must extend a distance "L" ahead of the antenna.
The specific value depends on the antenna beamwidth, multipath environment, largest
aircraft operating at the facility, etc., and specific lengths have been developed and
published. These lengths protect the MLS operation to decision heights o f not less than 50
feet. Since the offset-azimuth procedure will have a decision height greater than 50 feet
(likely greater than 250), the lengths developed for the standard-approach case can be used.
Finally, the lateral boundaries must be considered. As the receiver approaches threshold, the
line-of-sight between the elevation antenna and the receiver will migrate through a specific
region, as shown in Figure 47. Provided the region for the standard approach procedure fully
encompasses the region for the offset approach procedure, the criteria for the standard
approach procedure will provide sufficient protection o f the offset procedure.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
If the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Possible Elevation
A ntenna Location
Runway
O ffset Azim uth
A nlcnne
CASE 1: Offset Azimuth Antenna Supports Procedure with Lateral
Track offset from and Parallel to the Runway Centerline
Possible Elevation
Antenna Location
Possible Elevation
Antenna Location
Runway
O ffs e t A z im u th
A n te n n a
CA SE 2: O ffset A zim uth A ntenna S upports P rocedure with Lateral
Track offset from and Parallel to the R unw ay C enterline
Figure 46. Procedure Types Supported by an Offset Azimuth Installation.
Possible Elevation
Antenna Location
M DB 9I02I10I
00
u>
Taxiwa
Possible Elevation Antenna Location
~
To Receiver at Glide Path
Intercept Point
Liaa-of-Sigkt Migration Regions
O fb et Aximath Procedure
Standnrd Approach Procedure
D ecision H eight P oint Used for
Standard-A pproach Procedure
R unw ay
Decision Height
For Offset
Azimuth
Procedure
Procedure Lateral Track
Possible Elevation
Antenna Location
Taxiway
To Receiver at Glide Path
Intercept Point
► To Receiver at Glide Path
Intercept Point
Possible Elevation
Antenna Location
L lne-of-S ight M ig ra tio n R egions
O ffset A zim u th P ro c e d u re
- S ta n d a r d A p p ro a c h P ro c e d u re
Runway
Procedure Lateral Track
Possible Elevation
Antenna Location
m
\
Taxiway
Decision Height
For Offset
Azimuth
Procedure
► ■To Receiver at Glide Path
Intercept Point
M D B 9S 0I270I
Figure 47. Plan View Considerations for Elevation Critical Areas, Offset-Azimuth
Procedure.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
85
preceding stipulation is not satisfied, the lateral boundaries must be adjusted as described for
the case o f an advanced procedure, see Section IV .C.
Regarding the profile view o f the azimuth critical area (Figure 35), the same
considerations exist for an offset azimuth antenna as exists for an azimuth antenna sited on
the centerline extended [53,55,76,78]. Thus, the profile view descriptions will be the same.
For the standard approach, the azimuth signal is protected from in-beam multipath (main
beam) by the ±1.7 beamwidth area shown in the plan view o f Figure 35. This same
protection must be provided for the offset azimuth procedure, thus a ± 1.7 beamwidth sector
must be provided about the offset azimuth procedure as shown in Figure 48. The final
consideration is the length o f the critical area for the offset azimuth procedure. For the
standard approach, the length is mainly a function of the azimuth to threshold distance,
decision height, and size of the interfering aircraft. Since these same considerations drive
the length required for the offset-azimuth procedure, the length required for the offsetazimuth case should be the same as the standard approach, given a common set of
conditions. To investigate the assertion, error contour plots were generated for several
selected scenarios [79]. The results obtained for the length o f the critical areas are
summarized in Table 5. As indicated by the table note, the accuracy for estimating the length
o f the critical area from the error contour plot is ±100 feet. This accuracy is 5.6% o f the
length for the B-727 case (0.0° rotation) which implies about 7.9% change would be
expected for the comparison o f two lengths. Similarly, a 4.2% change would be expected
for the B-747 case. In addition, the characteristics of the high-error region rotated as the
radial for the approach procedure was rotated (Figure 49). Based on these results, it was
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
F or S tandard A p p ro ach , ± 1.7-B eam w idth A rea is C en tered A b o u t
P rocedure L ateral T rack - R u n w ay C enterline.
P ro ced u re L ateral T rack
N orm ally Sited
A zim uth A ntenna
,
—. _ m a T
H MMB »
k h l l B N B M *
---------g
T I T 'l '
a u ■ ■ m r
Runw ay
O ffic t A zim uth
A ntenna
For O ffset A zim uth A p p ro ach , ± 1,7-B eam w idth
A rea is C entered A bout P rocedure L ateral T rack.
F or S tandard A pproach, ± 1.7-B cam w idth A rea is C entered
A bout P rocedure L ateral T rack - R unw ay C enterline.
j
P ro ced u re L ateral T rack
O ffict A zim uth
A ntenna
For Offset Azimuth Approach, ± 1,7-Beamwidth
M D B 9 I0 IU 0 1
A rea is C entered A bout P rocedure L ateral T rack.
Figure 48. Plan View Consideration for Azimuth Critical Area - Offset Azimuth Procedure.
00
O s
2 .0 OEGREE AZIMUTH SYSTEM; -1 0 0 0 .0 ,0 .0 ,6 .0
250 FT. OH - PFE CONTOURS FOR R 8-747
AIRCRAFT ROTRTION ANGLE : 270
3 DEGREE C .L . HPPRORCH - 9000 FT. RUNHRY
8
I
Like a Topographical Map Where
“Height'’ Represents Error M agnitudes
z
s i-
E rror C ontour "Ridge" Oriented Parallel to
Runw ay Centerline - Approach Radial
UJ
5
Horizontal Axis Represents Runway
Centerline
1000.0
2000.0
300 0.0
4000.0
5000.0
I
DISTANCE IN FRONT OF THE ANTENNA IN FEET
NOTE : CONTOUR LINES ARE IN INCREMENTS OF 0.030 DECREES
PLOT STORED ON DISK FILC ; AC0NE24.PLT
ACC U S nOOELlNC
- —
■
10 °
2 .0 OEGREE AZIMUTH SYSTEM; -8 2 1 ,2 0 4 2 ,6 .0
2SU H .
UM -
rtL
L U N IU U K S U K
tl 8 - / 4 /
ORIENTED PERPENDICULAR TO APPROACH RROIRL : 100 OEG
HZ. ROT. ANGLE; 10 OEGREE - 9000 FT. RUNWAY
N o te C h a n g e in
A xis S calin g
Error Contour "R idge" Oriented Parallel to 10
Approach Radial
■2 1 .0
IS 2 I.0
2 3 2 1 .0
3321.0
3821.0
DISTANCE IN FRONT OF THE ANTENNA IN FEET
4821.0
NOTE : CONTOUR LACS ARC IN INCREMENTS OF 0.030 DEGREES
PLOT STORED ON DISK FILE : C0N385.PLT
ACC MLS MODELING
M O B 9 8 0 2 I3 0 4
Figure 49. Error Contour Plots for 0- and 10-Degree Rotation Angles, B-747.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
88
Table 5. Azimuth Critical-Area Lengths Versus Approach Radial Angle.
CRITICAL-AREA LENGTH
% Change from 0.0°
Interfering Boeing B-727
Interfering Boeing B-747
0
©
o
(Length 1790.0 feet1)
(Length 3337.0 feet1)
1.0°
-8.0
0.6
LO
O0 o0
APPROACH RADIAL ANGLE
(Deg. Relative to Centerline)
8.8
1.6
6.9
2.6
10.0°
6.2
-3.6
0 The accuracy for estimating the length of the critical area from the error contour plots is
±100 feet.
concluded that the information developed for the standard approach could be applied to
develop criteria for the offset-azimuth procedure. The resulting criteria are provided in [8,1].
B. Computed-Centerline Approach Procedure
As discussed earlier, the "computed-centerline" approach (Figure 29) procedure can
be used to provide a standard approach profile when the azimuth antenna has been sited
offset from the runway centerline extended. Raw elevation information is used to provide
the vertical guidance. Azimuth, DME, and possibly elevation guidance information are
processed in order to determine the offset of the aircraft from centerline. Based on this offset
the appropriate lateral guidance information can be generated.
In this case, the elevation antenna is sited as for a standard approach. Since the
interfering aircraft considerations are identical for the standard approach and the computed-
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
89
centerline approach, the elevation critical-area requirements are the same. Thus, the criteria
developed for the standard-approach procedure are used.
For azimuth, an additional level o f complexity is added in comparison to the offsetazimuth case. Instead of providing in-beam multipath protection along one azimuth radial,
a larger area must be protected for the computed centerline procedure since the line-of-sight
between the azimuth antenna and the receiver will migrate through a large region (Figure
50). Given this reality, the initial critical-area criteria for computed-centerline procedures
were based on prohibiting in-beam multipath and maintaining optical line-of-sight to the
receiver at each point along the approach [53, 76, 80]. Subsequent research indicated that
the initial criteria needed to be refined since it appeared to be unnecessarily restricting the
movement of ground-based aircraft.
Based on the results o f the offset azimuth work, it was hypothesized that a better
estimate of the critical area could be obtained by developing a methodology using the
available information from the basic-procedures work. Such a methodology was developed
in the following manner. First, consider an offset azimuth antenna supporting an approach
procedure to a decision height o f 100 feet. The radial for this procedure is selected such that
the decision height point is located on the extended runway centerline and on a three-degree
glide-path angle. The resulting azimuth critical area is shown in Figure 51a. Then, the same
azimuth antenna is used to support a second procedure, but a 150-foot decision height is
used. The critical area required is shown in Figure 51b. Now, consider a third procedure
with a 200-foot decision height (Figure 51c). If the azimuth antenna is to support all three
Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission.
90
AZIMUTH
ANTENNA
LINE-OF-SIGHT
MIGRATION AREA
DECISION
HEIGHT
TYPICAL STRAIGHT-IN
APPROACH
‘
RECEIVER AT A V
HEIGHT OF
1000 FEET
MDB980Z0201
Not to Scale
Figure 50. Azimuth Line-of-Sight Migration Region for the Computed-Centerline
Approach.
procedures, then the critical area can be obtained from the union o f the individual critical
areas as shown in Figure 5Id.
If offset azimuth procedures were “established” for each height listed in Table 3, the
resulting critical area (Figure 52) appears to protect a large portion o f the line-of-sight
migration region for the computed-centerline approach. The entire migration region is
obtained by adding the requirement to provide in-beam multipath protection out to the initial
approach fix, as illustrated in Figure 52. Now the fact that the approach paths for the offsetazimuth and computed-centerline procedures will be different must be addressed. Therefore,
consider a specific decision height, 400 feet for example The multipath error that exists at
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
AREA OBTAINED
FOR HEIGHT OF
100*
AREA OBTAINED
FOR HEIGHT OF
160'
ro° « C i
Y DECISION
HEIGHT
\
•
RUNWAY
RUNWAY
c) HEIGHT « 200’
a) HEIGHT a 100"
THE COVERAGE VOLUME TO BE PROTECTED FROM
INTERFERING AIRCRAFT 16 THE UNION OF ALL THE
AREA8 OBTAINED FROM THE ANALY8ES AT EACH
HEIGHT.
AREA OBTAINED
FOR HEIGHT
OF 100'
DECISION
HEIGHT
RUNW AY
b) HEIGHT- 1 5 0 '
d) PROTECTED COVERAGE VOLUME
MDB98020202
Not to Scale
Figure 51. Construction of Azimuth Critical Area for Multiple Offset-Azimuth Procedures.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
O Shaded Region » Azimuth critical area (or
computed-centerline approach
1) Radlala from the azimuth antenna, which Intercept the
approach procedure at preacrlbad halghta, plua to the
Initial approach Ox are conitructed;
2) The length to be protected (dlatince ahead ol the
azimuth antenna) along each radial la taken from
publiahed tablaa baaed on Interfering aircraft type, error
allocation, antenna beamwidth, and azlmuth-tothraahold dietance.
Azimuth
Antenna
■SJS!I!4^Kao1CHrl
3) A t.7-Beamwldth margin la added about the
outer radlala, the length ol thla area la baaed on
the correapondlng radial;
4) 'Connect-the-dota* to conatruct the critical
area.
•JO
q
?
’•c"*<0
7°o-
*v
*»/
Azimuth
TO INITIAL APPROACH FIX
1.7 BW
AZIMUTH ANTENNA OFFSET
EXAOOERATEO FOR PURPOSE OF
ILLUSTRATION
PLAN VIEW
PROFILE VIEW
600'*
600'-
700’J
800J
BW 8 Beamwidth
MDB98020203
Not to S cale
Figure 52. Construction of Azimuth Critical Area for Computed-Centerline Procedures.
93
this point in space is only a function o f the interfering aircraft and azimuth antenna geometry.
As the receiver passes through this point from different directions, the error at the receiver
output could be different due to differences in the receiver output-filter history prior to
reaching this point.
However, there are two factors that mitigate the concern about the different receiver
paths. First, the angle between the radial to the azimuth antenna and the centerline extended
will be small (< 5°). The multipath error in the near vicinity of the point will be similar to
the multipath error at the point due to the continuous nature of electromagnetic fields. Thus,
similar filter histories would be expected, and similar error levels would be expected at the
receiver output.
Based on the above concept, a detailed methodology for developing critical-area
criteria for the computed-centerline procedure was developed [81, 82]. Error contour plots
were generated for selected computed-centerline scenarios in order to validate the
methodology [76, 83, 84]. The critical-area boundaries given by the methodology were
superimposed on the contour plots (Figure 53).
Then a verification boundary is
superimposed based on the interfering aircraft orientation used for the particular scenario.
Such an adjustment is required since the contours are relative to the aircraft center and the
critical area represents the area where no portion of the aircraft is permitted to penetrate. For
the 16 scenarios examined, it was noted that the critical areas obtained were conservative
[76, 83].
As a result, a simplified methodology was developed and validated as described in
the above paragraph [83]. An example o f the results obtained is provided in Figure 54. This
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1.0 DEGREE AZIMUTH SJfSTEM; -1000.0,200.0.6.0
CRT II DH - PFE CONTOURS FOR B-747
RIRCRRFT ROTATION ANGLEi 270
3 DEGREE C.C.L. APPROACH - 11000 FT. RUNWAT
------ _
_i
O.OTJ........................................................
............
^
O il
•< > )
<•’ ’•......V..X
f\
*i *
C ritical A rcai Boundary Constructed Using Detailed M ethodology
(Solid Line)
• C ritic a l a rea re p re s e n ts the a re a w e re n o p a n o f th e airc ra ft ca n p en e tra te
• B ito t co n to u r p lo t g iv e s erro r re la tiv e to th e lo c a tio n o f th e in te rfe rin g a irc ra ft's center
• T h u s, a n ad ju s tm e n t (so lid lin e to d a sh e d lin e ) b ase d o n th e in te rfe rin g a u c ra A o rie n ta tio n is
re q u ired to a c c o u n t fo r th is d iffe re n c e ( w a s n o t p e rfo rm e d to a c c o u n t for w in g sp a n )
• F o r v a lid a tio n , erro r co n to u rs m u s t b e in sid e d a sh e d line
1QOO.O
T
2000.0
T
3000.0
"T
<1000.0
T
5000.0
6000.0
7000.0
DISTRNCE IN FRONT OF THE ANTENNR IN FEET
NOTE i CONTOUR LINES ARE IN INCREMENTS OF 0.033 DECREES
PLOT STORED ON D13K FILE i CQNG0L7.PLT
REC MLS MODELINB
Figure 53. Verification: Detailed Methodology for Constructing Azimuth Critical Area for Computed-Centerline Procedures.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1.0 DEGREE AZIMUTH SYSTEM; -1000 .0 ,200.0.6.0
CAT II DH - PFE CONTOURS FOR B-747
AIRCRAFT ROTATION ANGLEi 270
3 DEGREE C.C.L. APPRORGH - tlOOO FT. RUNWAY
./ • • " e ; 0 .0 3 3 - - a e
Critical Areas Boundary Constructed Using Simplified Methodology
(Solid Line)
• C ritic a l a r e a re p re s e n ts th e a r e a w e re n o p a r t o f th e a irc ra ft e a n p e n e tra te .
• E rro r c o n to u r p lo t g iv e s e rro r re la tiv e to th e lo c a tio n o f th e in te rf e rin g a i r c r a f t 's c e n te r
• T h u s , a n a d ju s tm e n t (s o lid lin e to d a s h e d lin e ) b a s e d o n th e in te rf e rin g a irc ra ft o rie n ta tio n is
re q u ire d to a c c o u n t fo r th is d iffe re n c e ( w a s n o t p e rfo rm e d to a c c o u n t fo r w in g s p a n )
• F o r v a lid a tio n , e r ro r c o n to u rs m u s t be in s id e d a s h e d lin e
— r—
1000.0
2000.0
T
3000.0
— i----4000.0
— I---6000.0
— I----
DISTANCE IN FRONT OF THE RNTENNA IN FEET
NOTE i CONTOUR LINES ARE IN INCREMENTS OF 0.033 DECREES
PLOT STORED ON DISK FILE • CQNQOL0.PLT
RED MLS MODELING
eooo.o
7000.0
M D B 9I021306
Figure 54. Verification: Simplified Methodology for Constructing Azimuth Critical Area for Computed-Centerline Procedures.
iS
96
methodology has been adopted and published internationally [I], but the results have not
been published in the FAA Siting Manual [8]. A copy o f these criteria are provided in
Appendix D.
C. Advanced Procedures
Advanced procedures are comprised of segmented and/or curved elements and the
two/three dimensional “computed” guidance is obtained from processing azimuth, elevation,
and DME information (Figure 55). Critical-area criteria for the azimuth, elevation, and DME
antennas are required in order to ensure sufficient protection of the guidance signals.
Discussions in this section pertain to azimuth and elevation; DME is discussed in Section V.
In addition, the type of advanced procedures addressed herein terminate with a standard
approach procedure as the final segment of the procedure [76]. Thus, in the referenced
literature one may find the phrase off-centerline procedure used. Although advanced
procedures can include precision approaches to secondary runways, for example, this
capability was not expected to be implemented in the near future. Consequently, work to
develop critical-area criteria for this type of advanced procedure had a very low priority, and
the work was never initiated as efforts focused on the implementation of MLS research and
development.
There are two factors that need to be considered when developing criteria for
advanced procedures [53,85]. First, the portion of the critical area protecting the offcenterline portion of the procedure could cover active taxiways or movement areas,
particularly for azimuth. Without careful planning from the inception of the advanced
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
2D, 3D
CURVED
RUNWAY
THRESHOLD
AZIMUTH
ANTENNA
1
FINAL LEG
STRAIGHT-IN
RUNWAY
STOP END
KS5
S T A N D A R D CRITICA L A R EA
REGION FOR OFF-CENTERLINE
CRITICAL A R E A INVE STIG AT ION
MDB98020206
Not to Scale
Figure 55. Standard Approach and Off-Centerline Critical-Area Considerations.
sO
98
procedure, unacceptable restriction of ground-aircraft movement can result. Second, the
critical-area error allocations made for the basic and computed-centerline procedures are
overly conservative for the off-centerline portion of the advanced procedure. The following
explains specifically how these factors were taken into consideration for developing azimuth
and elevation criteria for advanced procedures.
For elevation, the profile view must protect the procedure from in-beam multipath
as is done for the basic procedure case [54]. Thus, the profile view will have the same type
o f description as for the basic procedure (Figure 36). The difference is that for the offcenterline portion the 1.7-beamwidth sector must extend below the vertical track o f the
procedure, not simply the minimum glide-path angle, as is specified for the basic-procedure
case. Depending on the particular procedure to be supported, the plan view may need to be
expanded as illustrated in Figure 56. A procedure for constructing the expanded portion is
provided in References 1 and 54.
It should be noted that the critical-area lower boundary for the off centerline portion
may be closer to the ground than for the centerline portion. In some cases, it may be feasible
to increase the height of the procedure vertical track to mitigate this situation. However,
there may be cases where such a height increase is not suitable, and thus, the vertical angle
for the line-of-sight between that elevation antenna and receiver will be less than 3.0°.
Initially, this realization raised concern about the length required for the off-centerline
portion, since the lengths developed to date were for glide-path angles of 3.0° or greater.
However, these lengths were developed based on the more stringent error allocation
associated with the basic procedures. The guideline to be used in developing advanced
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MLS DATUM POINT
RUNWAY
— APPROACH
TAX IWAY
2D, 3D APPROACH
CRITICAL AREA FOR 3 .0 ‘ CENTERLINE APPROACH
Y /A
EXTENSION R EQUIRED TO E N S U R E
E L EV AT IO N S IG N A L QUALITY O F O F F - C E N T E R L I N E
P O R T IO N O F ADVANCE A PP R O A C H
PROCEDURES.
APPROACH
FOR PROFILE VIEW:
THE CRITICAL AREA EXTENDS TO 1.7
BEAMWIDTHS BELOW THE AIRCRAFT TRACK.
MDB88020208
Not to Scale
USE OF ELEVATION GUIDANCE
BEGINS HERE.
Figure 56. Expansion of Basic Procedure Elevation Critical Area for Off-Centerline Procedures.
vO
o
100
procedure criteria (off- centerline) is that the PFE and CMN error magnitudes should not
exceed 0.10° [85]. Based on a preliminary analysis o f selected error contour plots (Figure
57), it was concluded that the lengths developed for the basic-procedure case should provide
sufficient protection for the off-centerline portion o f the advanced procedure. The work
required to rigorously verify this conclusion was never performed.
For azimuth, the plan view of the azimuth critical area (Figure 35) must be expanded
in order to protect the off-centerline portion o f the procedure from in-beam multipath
[85,86]. As illustrated in Figure 58, the manner in which the critical area is expanded will
depend on the particular lateral track o f the procedure. The profile view o f the off-centerline
portion o f the critical area is defined in the same way as for the basic procedure (Figure 35).
Since the off-centerline portion of the critical area may lay over active taxiways and
movement areas, it is desirable to keep the length as short as practical [87]. In addition, it
was realized that there would be a benefit in developing criteria with the flexibility to trade
off requirements between the length o f the critical area and the height o f the off-centerline
portion o f the procedure. Thus, the objective was to define the slope o f a minimum height
surface as a function of critical-area length. That is, for a given critical-area length, the slope
of a conical surface originating from the azimuth antenna could be defined (Figure 58).
Then, the off-centerline portion of the procedure would need to lie at or above this surface
in order to ensure sufficient protection o f the azimuth signal.
Based on optics principles, the magnitude o f the error would be expected to correlate
with the extent to which line-of-sight between the azimuth antenna and receiver is blocked
[85]. Furthermore, the extent of the blockage should be able to be characterized in terms of
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
1 .5 DEGREE ELEVATION SYSTEM; 8 1 9 0 , - 3 2 5 , 7 . 5
STANDARD APPROACH - CAT 1 1 FC - PFE CONTOURS
B- 7 4 7 , ROTATION ANGLE : 270
USING EFFECTIVE T A IL F IN LENGTH
LJ
LJ
>
!<=>W
c
LJ
(Y
g -
LJ
Oo
o r i-» .
CXL o
1 -o c
z: 8 -
oc
O y'
U
“ C r i t i c a l A r e a L e n g t h Tor O f f - c c m c r l i n c P r o c e d u r e ,
E rro r A llocation o f 0 . 1 0 “ ( H 5 0 ' - 9 8 ' “ 1052)
L lr “ C ritical A re a L e n g th for S ta n d a rd A p p r o a c h
P ro c e d u re ( 1 9 5 4 ' - 9 8 ' - 1856')
o
zC8m
-<
C
I—
1
lo „
oc
T h e 9 8 ' R e p r e s e n t s t h e A d j u s t m e n t for
□
A ircraft W i n g S p an
to
0.0
500,0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
4000.0
DI5TANCE IN FRONT OF THE ANTENNA IN FEET
NOTE i CONTOUR LINES ARE IN INCREMENTS OF 0 .0 3 0 DEGREES
PLDT STORED ON DISK FILE : C0N25B.PLT
HEC MLS MODELING
Figure 57. Elevation Error Contour Plot Comparing Length for Basic and Off-Centerline Procedures.
M DB9S021307
102
□ 2 STA N D A R D . STRAIGHT-IN
A PPR O A C H CRITICAL AREA
“I
1.7 BW
I
OFF-CENTERLINE CRITICAL
AREA REQUIREM ENT
J
1.7 BW
S T O P END
L*. See Table Below
- 1 . 7 BW
—
PLAN VIEW
O F APPROACH
>
runway
•
l17B-wtX
1.7 BW
.
.lni». E p giac. itP r a ts Q w a pjl _
Standard-A pproach Critical Area
;r.onicafL
AZIMUTH
ANTENNA
PCH
THESE EQUATIONS CAN BE USED TO DETERMINE THE
SLOPE FOR ARBITRARY CRITICAL-AREA LENGTH ’L \
Units = Feet
*L
0 = tan'
TFH t - V ^
PCH
34 ♦ v ° ? (L) - PCH
4
Boeing B-727: 0 = tan’’
WHERE:
TFH - INTERFERING TAIL FIN HEIGHT
A* MLS WAVELENGTH
PCH » PHASE CENTER HEIGHT
L - OFF-CENTERLINE CRITICAL AREA LENGTH
6 3.4 +v
Boeing B -747:0 = ta n '1
__________
4
- PCH
___________
MDB98020209
Not to Scale
Figure 58. Sample Application o f Off-Centerline Critical-Area Requirements.
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103
a fractional portion o f the first Fresnel zone (Figure 59). Simulations were performed based
on this philosophy and the resulting PFE and CMN data were analyzed [85]. This analysis
indicates that the error allocations (±0.10°) would not be exceeded if, at every point along
the off-centerline segments o f the procedure, optical line-of-sight to the receiver exists over
the aircraft tail fin by at least one-quarter of a Fresnel zone radius. This finding is the basis
for the equations provided in Figure 58, which provide the slope of the minimum height
surface as a function of the critical-area length. It is important to realize that the minimum
height surface requirement applies only to the off-centerline portion o f the advanced
procedure. In addition, the associated critical-area length applies only to the off-centerline
portion of the critical area (Figure 58). Also, the criteria presented is intend for procedures
with segments intercepting the centerline extended five miles or further from threshold. For
low-height, close-in procedures, one may need to consider the specific profile when
developing the critical-area requirement.
These criteria has been adopted and published internationally [1 ], but the results have
not been published in the FAA Siting Manual [8]. A copy of these criteria are provided in
Appendix D.
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
PROFILE
VIEW
INTERFERING
AIRCRAFT
(1 0 0 0 -2 5 0 0 ft)
PLAN
VIEW
RECEIV ER PATH
VELOCITIES 16. 70,
135 KNOTS
MDB98020207
Not to S e a e
2 2 1 6 2 FT
104
Figure 59. Simulation Set-Up for Developing Azimuth Off-Centerline Critical-Area Criteria - Minimum Height.
105
V.
DEVELOPMENT OF DME/P CRITICAL-AREA CRITERIA
The work performed for developing DME/P critical-area criteria was very limited.
Preliminary error allocations to be used in conjunction with the error contour data were
developed [88]. Specific values for some of the parameters to be used when generating the
error contour data were developed. These parameters include search-grid size for various
runway lengths, search-grid sample spacing, and determining worst-case aircraft orientations
[89]. The DME/P work was delayed when a deficiency in the MLS mathematical model was
discovered [15].
This deficiency was related to DME/P error estimates for the case of signal
diffraction, and from an initial investigation of the problem it was determined that the error
in this case could be significantly underestimated [90]. A review o f the theory used for
estimating DME/P error caused by signal diffraction, or shadowing, revealed two limitations.
The first limitation was that the time-delay for edge-diffracted rays was assumed to be zero.
This assumption is of little consequence when computing azimuth and elevation errors due
to signal diffraction/shadowing, but the time delay is a fundamental parameter when
computing DME/P error estimates. The second limitation was that the total (composite)
electromagnetic field is constructed using the same methodology used for azimuth and
elevation. That is, the total field is composed of an “unperturbed” field and two edgediffracted rays, when the line-of-sight between the transponder and receiver is blocked by,
or passes close to, a rectangular plate. For DME/P, it was concluded that an edge-diffracted
ray needed to be calculated for each edge in order to ensure that a reliable estimate would be
provided [91].
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106
The author led research efforts that successfully corrected the two limitations
discussed in the previous paragraph [92]. However, an additional limitation was discovered
during this research effort. This limitation was traced to the DME/P system processing
module of the MLSMM. In the case of DME/P signal shadowing, there appears to be a
problem with how the composite (direct + multipath components) DME pulse is generated
and/or processed when computing the error.
Correction of the problem was never
accomplished due to the FAA decision in 1994 to focus on implementation of MLS and to
defer further research and development activities. As a consequence, formal DME/P criticalarea criteria were never developed.
Although critical-area criteria have not been developed specifically for DME/P, the
following factors from Section III.B. should be considered. For basic procedures, the
DME/P provides information that will enable the pilot to determine the distance from
threshold or when an operationally significant location along the approach, e.g., decision
height, has been reached. The ranging accuracy required to support this function is on the
order of 300 - 500 feet. The error for an M/D ratio of +3 dB would not be expected to
exceed 60 feet, which is nearly an order of magnitude below the required accuracy.
In order to produce the 60-foot error, the direct signal would have to be blocked and
the time-delays for all of the multipath components would have to exceed 150 nanoseconds
(Figure 28). For shadowing by a Boeing B-747, the dominate multipath components would
have time-delays that are less than 40 nanoseconds given the physical size of the aircraft.
For a DME/P that is collocated with the azimuth antenna (preferred siting configuration),
such shadowing geometries would result in violating the azimuth critical area. For a DME/P
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107
that is not collocated with the azimuth antenna, the siting criteria provided in Reference 8
prevents the DME/P from being sited at any location that would permit aircraft within 600
feet o f the transponder antenna. This requirement in combination with obstacle clearance
and safety zone requirements should preclude worst-case shadowing geometries from
occurring.
Given the above discussion, one may wonder why an effort was even initiated to
develop DME/P critical-area criteria. The DME/P is specified to provide a ranging accuracy
of 100 feet in Final Approach Mode [3,5]. In order to meet this accuracy requirement, the
error due to multipath from interfering aircraft would need to be limited to about 30 feet [88].
In this case, there is the potential for interfering aircraft to be in locations that would cause
errors which exceeding the error allocation. Thus, the research to develop DME/P criticalarea criteria was initiated.
For computed-centerline and advanced procedures, the DME/P provides ranging
information, which may be used in combination with azimuth and elevation information, to
provide both lateral and vertical guidance. In this case, analysis and computer simulations
should be performed to assess DME/P critical-area requirements needed to protect the
specific procedure.
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108
VI.
CONCLUSIONS AND RECOMMENDATIONS
As significant amount of research has been performed to develop and validate critical
area criteria for MLS azimuth and elevation antennas. Conclusions and recommendations
pertaining to this research are presented in Section VT.A. Conversely, a relatively limited
amount o f research has been performed in terms of developing DME/P critical-area criteria.
Thus, conclusions and recommendations related to DME/P critical area development are
presented separately in Section VLB.
A. Azimuth and Elevation Critical-Area Criteria
The MLSMM has been utilized to generate extensive simulation data that
characterize the effect on the MLS guidance signals due to electromagnetic scattering of
these radiated signals by ground-based aircraft. Herein, electromagnetic scattering is referred
to as multipath, and the ground-based aircraft are referred to as interfering aircraft.
The capability of the MLSMM to provide accurate estimates of the multipath errors
caused by interfering aircraft has been validated by comparison to measured flight data. The
validation effort revealed that some modifications to the model were required in order to
obtain error estimates with accuracies sufficient for the purpose o f developing critical-area
criteria. At MLS frequencies, the electromagnetic theory employed by the model was shown
to be suitable for estimating the multipath generated by interfering aircraft. However, its was
shown that modifications were required to improve how the model represents the aircraft tail
fin for the case of signal shadowing or diffraction. A method for improving how the
MLSMM represents the aircraft tail fin was developed successfully.
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109
Subsequent to the model validation effort, the MLSMM was used to generate PFE
and CMN contour data that characterize the effect of interfering aircraft on the MLS
guidance signals for basic MLS approach procedures. The analysis o f these data were
facilitated by the development o f critical-area error allocations and the use o f contour plots.
Approximately 1,700 error contour plots were analyzed to develop the critical-area criteria
for basic, offset-set azimuth, and computed-centerline approach procedures. Each of these
contour plots presents the data resulting from the analysis of as many as 2,000 simulated
approaches. In addition, the MLSMM was used to generated simulation data which aided
in the development of criteria for advanced (off-centerline) procedures.
The critical-area criteria resulting from this extensive research effort has received
extensive review by government and industry experts at both the national and international
levels. As a result of these reviews, the critical-area criteria presented herein have been
adopted and published by the Federal Aviation Administration and the International Civil
Aviation Organization, Throughout this research effort the author enjoyed the privilege of
being invited by the U.S. State Department to serve as a Technical Advisor to the U.S.
Member o f the All Weather Operation Panels of the International Civil Aviation
Organization.
At this writing, the criteria presented herein are currently in use at 32 airports; 29 are
in the United States. Although these criteria have been validated by flight measurements,
it is recommended that these criteria be reviewed and refined as indicated by the operational
experience that will gained in the near future. As of this writing, it is the author’s
understanding that the FAA intends to continue to operate the MLS’s that have been installed
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110
and commissioned in the United States. Internationally, MLS programs are still active,
including research and development activities. At this writing, the author is completing an
eighteen-month, critical-area study sponsored by the National Air Traffic Services, LTD,
United Kingdom and continues to work with international companies.
B. DME/P Critical-Area Criteria
The research performed to develop DME/P critical-area criteria was very limited in
comparison to the effort undertaken for azimuth and elevation. This situation resulted from
the DME/P research being assigned a lower priority than the azimuth and elevation research
for the reasons presented in Section IIIB and the cancellation o f further MLS research and
development on the part of the FAA.
However, the results obtained from this limited research effort indicate that DME/P
siting criteria currently contained in the FAA MLS siting manual, in combination with
standard obstacle clearance and safety zone requirements, should provide sufficient
protection of the DME/P signal when it is used to support basic procedures. That is, it is
possible for the multipath caused by interfering aircraft to result in ranging errors that exceed
the published DME/P FA mode accuracy requirements, however the probability this situation
occurring is considered to be very low. Furthermore, the available analyzes indicate that the
ranging error generated by these rare worst-case multipath conditions would still be well
within operationally acceptable limits.
For computed-centerline and advanced procedures, the DME/P provides ranging
information, which may be used in combination with azimuth and elevation information, to
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Ill
provide both lateral and vertical guidance.
In this case, it is recommended that the
requirement for establishing a DME critical area be assessed prior to implementing such
procedures.
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112
VII.
REFERENCES
[1]
International Standards. Recommended Practices and Procedures for Air Navigation
Services. Aeronautical Telecommunications. Annex 10 to the Convention on
International Civil Aviation. Fourth Edition of Volume 1. July 1996.
[2]
Redlien, Henry W. and Robert J. Kelly, '"Microwave Landing System: The New
International Standard,” The Bendix Corporation Communication Division, 1300 E.
Joppa Road, Baltimore, Maryland, Copyright Academic Press, Inc, 1981.
[3]
Microwave Landing System (MLS) Interoperability and Performance Requirements.
Department of Transportation. Federal Aviation Administration. FAA-STD-022d,
June 30, 1989.
[4]
Microwave Landing System (MLSi Specification. Department o f Transportation,
Federal Aviation Administration, FAA-E-2721B, August 30, 1990.
[5]
Microwave Landing System fMLS) General Requirements. Department of
Transportation, Federal Aviation Administration, FAA-E-2721/1 la, June 30, 1989.
[6]
Kelly, Robert J., and Danny R. Cusick. "Distance Measuring Equipment and Its
Evolving Role in Aviation,” Advances in Electronic and Electron Physics, Volume
68, Copyright 1986, Academic Press, Inc.
[7]
DiBenedetto, Michael F., "Overview of the Development of Microwave Landing
System (MLS) Siting Criteria Relevant to Signal-in-Space Considerations,” OU/EER
98-01, Avionics Engineering Center, School of Electrical Engineering and Computer
Science, Ohio University, Athens, Ohio, December 1997.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
113
[8]
"Criteria for Siting Microwave Landing Systems (MLS)," FAA Order 6830.5,
Federal Aviation Administration (ANN-500), Department o f Transportation, July
1993.
[9]
Radcliff, R. and M.F. DiBenedetto, "Siting Criteria for Microwave Systems (MLS),"
DOT/FAA/PM-86/18, January 1985, available from the National Technical
Information Service, Springfield, Virginia 22161.
[10]
Radcliff, Roger D. and Michael F. DiBenedetto, "Siting Criteria for Microwave
Landing Systems (MLS)," OU/AEC EER 81-1, Avionics Engineering Center,
Department of Electrical and Computer Engineering, Ohio University, Athens, Ohio,
June 1986.
[11]
Vickers, Douglas B. and Michael F. DiBenedetto, Technical Memorandum OU/AEC
24-90TM0006/38-2, “MLS Siting Manual Update,” Avionics Engineering Center,
Department of Electrical and Computer Engineering, Ohio University, Athens, Ohio,
March 1990.
[12]
DiBenedetto, Michael F., "TTD-38 MLS Siting Manual Update: Report on Oral
Briefing,” Precis No. 125, Avionics Engineering Center, Department of Electrical
and Computer Engineering, Ohio University, Athens, Ohio, March 1990, Rev,
February 1991.
[13]
DiBenedetto, Michael F., “Performance Plan: Siting Criteria Activities (Revision 1),”
Technical Memorandum OU/AEC 94-30TM94-00006/1-2, Avionics Engineering
Center, Department of Electrical and Computer Engineering, Ohio University,
Athens, Ohio, November 1994.
Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission.
[14]
Mathias, Sally A., "Development o f Siting Criteria for the Collocation o f the
Microwave Landing System (MLS) and the Approach Lighting System (ALS),”
Technical Memorandum OU/AEC 85-88TM00006/12-1, Avionics Engineering
Center, Department of Electrical and Computer Engineering, Ohio University,
Athens, Ohio, June 1988.
[15]
DiBenedetto. Michael F., “Documentation of the Status o f the Microwave Landing
System (MLS) Mathematical Model,” Technical Memorandum OU/AEC 9633TM94-00006/5-2, Avionics Engineering Center, School of Electrical Engineering
and Computer Science, Ohio University, Athens, Ohio, December 1996.
[16]
DiBenedetto, Michael F. and Eric R. Maurer, "Results o f Modeling to Determine the
Effects of Approach Lighting System Light Structures on the MLS Azimuth Signal
at Toulouse Airport, France,” Technical Memorandum OU/AEC 67-88TM, Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, March 1988.
[17]
DiBenedetto, Michael F. and Roger D. Radcliff, "Effects o f Simulated MLS
Installations on the Capture Effect Glide Slope and 14-Element Log-Periodic
Localizer at Airborne Express Air Park, Wilmington, OH,” Technical Memorandum
OU/AEC R-l TM, Avionics Engineering Center, Department of Electrical and
Computer Engineering, Ohio University, Athens, Ohio, August 1985.
[18]
DiBenedetto, Michael F., "Localizer Signal Sensitivity to Non-Symmetrical
Placement of the MLS Azimuth Antenna About Localizer Centerline,” Precis No. 45,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
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115
Ohio University, Athens, Ohio, August 1985.
[19]
DiBenedetto, Michael F., "Presentation o f Guidelines for the Collocated Siting o f
MLS and ILS Equipment,” Technical Memorandum OU/AEC 44-87TM00006/9A-2,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, October 1987.
[20]
DiBenedetto, Michael F., "Proposed Refinements to the MLS/ILS Collocation
Guidelines,” Technical Memorandum, OU/AEC 20-90TM00006/2C-13/ICAO,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, November 1989.
[21]
DiBenedetto, Michael F. and David A. Quinet, "Synopsis of Results Which
Established the MLS/ILS Collocation Siting Guidelines,” Technical Memorandum
OU/AEC 18-89 TM00006/2&2A, Avionics Engineering Center, Department o f
Electrical and Computer Engineering, Ohio University, Athens, Ohio, April 1989.
[22]
DiBenedetto, Michael F., "Criteria for Siting the Azimuth Antenna Behind the ILS
Localizer,” Technical Memorandum OU/AEC 91-23 TM00006/2B-19/ICAO,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, January 1990.
[23]
DiBenedetto, Michael F., "Proposed Refinements to the MLS/ILS Collocation
Guidelines,” Technical Memorandum OU/AEC 47-90TM00006/2C-16/ICAO,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, December 1990.
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116
[24]
Braasch, Michael S., David A. Quinet and Michael F. DiBenedetto. "A Synopsis of
Results Which Established the MLS/ILS Collocation Guidelines,” Technical
Memorandum OU/AEC 92-IOTM00006/2&2A, Avionics Engineering Center,
Department of Electrical and Computer Engineering, Ohio University, Athens, Ohio,
March 1992.
[25]
DiBenedetto, Michael F. and Roger D. Radcliff, "Results for a Study on MLS-ILS
Collocation,” Technical Memorandum OU/AEC EER 85-1, Avionics Engineering
Center, Department o f Electrical and Computer Engineering. Ohio University,
Athens, Ohio, August 1987.
[26]
DiBenedetto, Michael F. and Roger D. Radcliff, "Final Results for a Study on
MLS/ILS Collocation,” Technical Memorandum OU/AEC R-6 TM, Avionics
Engineering Center, Department of Electrical and Computer Engineering, Ohio
University, Athens, Ohio, August 1986.
[27]
Edwards, Jamie S. and Michael F. DiBenedetto, "Comparison of the Effects of Two
Simulated MLS Azimuth and Elevation Station Configurations on the Side-band
Reference Glide Slope and 8-element V-ring Localizer at the Tamiami Airport,
Tamiami, Florida,” Technical Memorandum OU/AEC 38-87TM86:l088.001/6-FR,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, September 1987.
[28]
DiBenedetto, Michael F., "Test Design:
Validation of Previous MLS/ILS
Collocation Results for New MLS Antenna Structures,” Technical Memorandum
OU/AEC 2-87TM 80658, Avionics Engineering Center, Department of Electrical and
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117
Computer Engineering, Ohio University, Athens, Ohio, February 1987.
[29]
DiBenedetto, Michael F., "Validation of Siting Criteria for the Collocated Siting o f
the MLS Elevation and ILS Glide Slope Antennas at Grenier-Manchester Airport,
Runway 35,”
Technical Memorandum OU/AEC 23-87TM00006/2-5/ICAO,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, February 1988.
[30]
DiBenedetto, Michael F., "Effects of Simulated MLS Azimuth Station on the
GRN-27 Localizer at Dayton International Airport, Dayton. OH,” Technical
Memorandum OU/AEC R-4 TM, Avionics Engineering Center, Department o f
Electrical and Computer Engineering, Ohio University, Athens, Ohio, February
1986.
[31]
DiBenedetto, Michael F., "Effects of Simulated MLS Azimuth Station o f the
8-Element V-Ring Localizer at Tamiami Airport, Tamiami, Florida,” Technical
Memorandum OU/AEC R-5 TM, Avionics Engineering Center, Department o f
Electrical and Computer Engineering, Ohio University, Athens, Ohio, March 1986.
[32]
Edwards, Jamie S. and Michael F. DiBenedetto, "Effects of a Simulated MLS
Azimuth Station Constructed of Sheet Metal on the 8-element V-ring and 8-element
LPD Localizer Arrays at the Tamiami Airport, Miami, Florida,” Technical
Memorandum OU/AEC 64-87TM00006/2A-6/ICAO, Avionics Engineering Center,
Department of Electrical and Computer Engineering, Ohio University, Athens, Ohio,
December 1987.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
118
[33]
DiBenedetto, Michael F, "Flight Measurement Results Quantifying the Effect on the
Redlich Dual-frequency, Wide-aperture Localizer Array Due to Siting an MLS
Azimuth Antenna in Front of the Array,” Technical Memorandum OU/AEC
09-89TM00006/2B/ ICAO, Avionics Engineering Center, Department o f Electrical
and Computer Engineering, Ohio University, Athens, Ohio, April 1989.
[34]
Dudding, Dennis and Michael F. DiBenedetto, "MLS-ILS Collocation Criteria
Validation: Flight Test and Data Collection Plan for a Rotated Azimuth Antenna
Located
Ahead
of
the
Localizer,”
Technical
Memorandum
OU/AEC
91-26TM00006/2-20, Avionics Engineering Center, Department of Electrical and
Computer Engineering, Ohio University, Athens, Ohio. July 1991.
[35]
Edwards, Jamie S. and Michael F. DiBenedetto, "Effects of a Simulated MLS
Azimuth Station Constructed of Sheet Metal on the 8-element V-ring Localizer at the
Tamiami Airport,” Technical Memorandum OU/AEC 17-87TM00006/2-1, Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, Revised December 1987.
[36]
Quinet, David A. and Michael F. DiBenedetto., "MLS/ILS Collocation Criteria:
MLS Azimuth Sited Abeam the 8-element and 14-element LPD Localizer Arrays,”
Technical
Memorandum
OU/AEC
42-90TM00006/2C- 14/ICAO,
Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, November 1989.
[37]
Braasch, Michael S., David A. Quinet and Michael F. DiBenedetto, "Development
of Criteria for Siting the Azimuth Antenna Behind or Abeam the ILS Localizer,”
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
119
Technical Memorandum OU/AEC 92-11TM00006/2B, Avionics Engineering Center,
Department o f Electrical and Computer Engineering, Ohio University, Athens, Ohio,
March 1992.
[38]
Dudding, Dennis and Michael F. DiBenedetto, "MLS-ILS Collocation Criteria
Validation: Flight Test and Data Collection Plan for an Azimuth Antenna Located
Abeam the Localizer,” Technical Memorandum, OU/AEC 92-05TM00006/2-22,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, July 1991, Revised January 1992.
[39]
Quinet, David A. and Michael F. DiBenedetto., "MLS Computer Model Validation:
Effect o f the V-ring Localizer Array Structures on the MLS Azimuth Guidance
Signal,” Technical Memorandum, OU/AEC 43-90TM00006/2B- 15/ICAO, Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, November 1989.
[40]
DiBenedetto, Michael F., "Development of Criteria for Siting the Azimuth Antenna
Behind the ILS Localizer,” Technical Memorandum OU/AEC 17-90TM00006/2B-3/
ICAO, Avionics Engineering Center, Department o f Electrical and Computer
Engineering, Ohio University, Athens, Ohio, March 1990.
[41]
DiBenedetto, Michael F., "Development of a Geometrical Theory of Diffraction
Model for Calculating Microwave Landing System Azimuth Signal Attenuation at
Humped Runway Facilities,” Technical Memorandum OU/AEC EE-2 TM, Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, January 1987.
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120
[42]
DiBenedetto, Michael F., "Development o f a Geometrical Theory of Diffraction
Model for Calculating Microwave Landing System Azimuth Signal Attenuation at
Humped
Runway
Facilities,”
Technical
Memorandum
OU/AEC
32-87TM86:1088.001/5-1, Avionics Engineering Center, Department o f Electrical
and Computer Engineering, Ohio University, Athens, Ohio, August 1987.
[43]
DiBenedetto, Michael F., “Siting Criteria for the Microwave Landing System (MLS):
MLS/ILS Collocation and Runway Hump Shadowing,” Master o f Science Thesis,
College o f Engineering and Technology, Ohio University, Athens, Ohio. August
1988.
[44]
Kelly, Robert J. and Chuck LaBerge, “MLS Error Relations.” Letter No. MLSICAO-058, Revisions A, Bendix Communication Division, Baltimore Maryland,
August 1979.
[45]
Siting Criteria for Instrument Landing Systems. FAA Order 6750.16C, Federal
Aviation Administration, United States Department o f Transportation, October 31,
1995.
[46]
Evans, J.E., R.S. Orr and R.C. Burchsted, "TRSB Critical Areas Studies Part I:
Reflection Effects,” ATC Working Paper 44WP-5028, Massachusetts Institute of
Technology, Lincoln Laboratory, Boston, Massachusetts, November 1975.
[47]
Chamberlin, Kent A., "Analysis of Spatial Sampling Interval of Aircraft Ground
Scatterer Necessary to Characterize MLS Errors as a Function o f Scatterer Position,”
Technical Memorandum OU/AEC M-22 TM, Avionics Engineering Center,
Department of Electrical and Computer Engineering, Ohio University, Athens, Ohio,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
September 1984.
[48]
Chamberlin, Kent A., "Computer Model Study of MLS Derogation Due to Scattering
from Aircraft on the Ground,” Technical Memorandum OU/AEC M-24 TM,
Avionics Engineering Center, Department o f Electrical and Computer Engineering,
Ohio University, Athens, Ohio, July 1985.
[49]
DiBenedetto, Michael F., “Identification and Preliminary Investigation of Parameters
Germane to Critical Areas Modeling,” Technical Memorandum EE-1, Avionics
Engineering Center, Department of Electrical and Computer Engineering, Ohio
University, Athens, Ohio, January 1987.
[50]
Quinet, David A., "Evaluation of Aircraft Dimensions to Determine if Two Classes
of Aircraft are Adequate to Define the Critical Areas,” Technical Memorandum
OU/AEC 25-89TM-00006/9D-2/ICAO, Avionics Engineering Center, Department
of Electrical and Computer Engineering, Ohio University, Athens, Ohio. May 1989.
[51]
DiBenedetto, Michael F. and Michael S. Braasch, "MLS Azimuth and Elevation
Volumes of Protection to be Used in Conjunction with Operational and Obstacle
Clearance Requirements in Refining MLS Critical Area Definitions,” Technical
Memorandum OU/AEC 65-88TM00006/9-3/ICAO, Avionics Engineering Center,
Department of Electrical and Computer Engineering, Ohio University, Athens, Ohio,
August 1988.
[52]
DiBenedetto, Michael F. and Michael S. Braasch, "Validation Results Obtained to
Date on MLS Critical and Sensitive Areas,” Technical Memorandum OU/AEC
91-88TM00006/ 9B/ICAO, Avionics Engineering Center, Department of Electrical
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
122
and Computer Engineering, Ohio University, Athens, Ohio, August 1988.
[53]
DiBenedetto, Michael F., "Results Obtained to Date on MLS Critical and Sensitive
Areas,” Technical Memorandum OU/AEC 06-89TM00006/9D/ICAO, Avionics
Engineering Center, Department of Electrical and Computer Engineering, Ohio
University, Athens, Ohio, January 1989. Revised May 1989.
[54]
DiBenedetto, Michael F., "Development o f Microwave Landing Systems (MLS)
Elevation Antenna Critical Area Requirements: An Analysis o f Errors Caused by
Parked
and
Taxiing
Aircraft,”
Technical
Memorandum
OU/AEC
18-90TM00006/9D-3/ICAO, Avionics Engineering Center, Department of Electrical
and Computer Engineering, Ohio University, Athens, Ohio. September 1989.
[55]
DiBenedetto, Michael F., "MLS Critical Areas: Azimuth Requirements for Basic
A pproach
P ro file s,”
T echnical
M em orandum
OU/AEC
21-90TM00006/9D&E-X/ICAO, Avionics Engineering Center, Department of
Electrical and Computer Engineering, Ohio University, Athens, Ohio, November
1989.
[56]
DiBenedetto, Michael F., and Aaron A. Wilson, “Data Report: MLS Critical Area
Error Contour Data Plots, Volume 1 of 3,” Technical Memorandum OU/AEC 9615TM94-00006/1-14, Avionics Engineering Center, School of Electrical Engineering
and Computer Science, Ohio University, Athens, Ohio, April 1996.
[57]
DiBenedetto, Michael F., and Aaron A. Wilson, “Assessing the Effects o f Aircraft
Infringement into the Microwave Landing System (MLS) Azimuth and Elevation
Critical Areas,” OU/AEC EER 98-02, Avionics Engineering Center, School of
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123
Electrical Engineering and Computer Science, Ohio University, Athens, Ohio, May
1998.
[58]
All Weather Operations Panel, Working Group A, “Report on the First Meeting”
AWOP-WG/A-WP/31, Washington DC. United States of America, November 1986.
[59]
All Weather Operations Panel, Working Group A, “Report on the Second Meeting”
AWOP-WG/A-WP/74, Leningrad, USSR, June 1987.
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All Weather Operations Panel, “Report on the Twelfth Meeting,” AWOP-WP/561,
Montreal, Canada, November 1987.
[61]
All Weather Operations Panel, Working Group A, “Report on the Third Meeting”
AWOP-WG/A-WP/115, Toulouse, France, September 1988.
[62]
All Weather Operations Panel, Working Group A, “Report on the Fourth Meeting”
AWOP-WG/A-WP/179, Canberra, Australia, June 1989.
[63]
All Weather Operations Panel, Working Group A, “Report on the Fifth Meeting”
AWOP-WG/A-WP/247, Amsterdam, Kindom of the Netherlands, November 1989.
[64]
All Weather Operations Panel, “Report on the Thirteenth Meeting,” AWOP/13WP/619, Montreal, Canada, March 1990.
[65]
Braasch, Michael S. and Eric R. Maurer, "Preparations for MLS Azimuth Critical
Areas Flight Evaluation Using the MLS Computer Model,” Technical Memorandum
OU/AEC 27-87TM86:1088.001/2-2, Avionics Engineering Center, Department of
Electrical and Computer Engineering, Ohio University, Athens, Ohio, August 1987.
[66]
DiBenedetto, Michael F., Eric R. Maurer and David Dudding, "Final Report on
Results Obtained From MLS Critical Area Flight Evaluations Using a Boeing 727,”
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Technical Memorandum OU/AEC 88-88TM86:1088.001/2-l/ICAO, Avionics
Engineering Center, Department of Electrical and Computer Engineering, Ohio
University, Athens, Ohio, February 1988, Revised August 1988.
[67]
DiBenedetto, Michael F., "Presentation of Flight Data Collected at Standiford Field,
Louisville, Kentucky to Measure the Effects of an Interfering Boeing B-747 on the
MLS Azimuth and Elevation Signals/’ Technical Memorandum OU/AEC
96-88TM00006/9B-3, Avionics Engineering Center, Department of Electrical and
Computer Engineering, Ohio University, Athens, Ohio, October 1988.
[68]
DiBenedetto, Michael F. and Michael S. Braasch, "Analysis of Simulation Data and
Flight Data Collected At Standiford Field, Louisville, KY, To Investigate the Effects
o f an Interfering Boeing B-747 on the MLS Azimuth and Elevation Signals,”
Technical Memorandum OU/AEC 97-88TM-00006/9C-01, Avionics Engineering
Center, Department o f Electrical and Computer Engineering, Ohio University,
Athens, Ohio, October 1988, Revised May 1989.
[69]
Flynn, Charles W„ Michael F. DiBenedetto and Kevin L. Johnson, “DME Routines:
Implementation Strategy for the Model Modifications to Correct the Time-delay
Calculations for the Case of Shadowing Buildings,” Technical Memorandum
OU/AEC 94-14TM0039/Ray-4, Avionics Engineering Center, Department of
Electrical and Computer Engineering, Ohio University, Athens, Ohio, September
1994.
[70]
Shindman, David A., "The Logan MLS Multipath Experiment,” AD-AO17083,
FAA- RD-75-180, Project Report ATC-55, MIT, Lincoln Lab, September 1975.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
125
[71]
Evans, James E., Burchsted, Jack Capon, R. S. Orr, David A. Shindman, S.M.
Sussman, "MLS Multipath Studies Vol. I - Mathematical Models and Validation,
Lincoln Laboratory, MIT,” FAA-RD-76-3 Project Report ATC-63, MIT, Lincoln
Lab, February 1976.
[72]
Capon, Jack, "Multipath Parameter Computation for MLS Simulation Computer
Program, 9DDC AD-A024350/1 Project Report ATC-68, Lincoln Laboratory, MIT,”
FAA-RD-76-55, MIT, Lincoln Lab, April 1976.
[73]
Evans, James E., "MLS Multipath Studies, Phase 3. Volume 1, Final Report,
Overview and Propagation Model Validation/Refinement Studies, M.I.T,”
FAA-RD-79-2I Project Report ATC-88-Vol-l, MIT, Lincoln Lab, 1979.
[74]
Evans, James E., Samuel J. Dolinar, David A. Shnidman, D. F. Sun,
"MLS
Multipath Studies, Phase 3, Final Report, Vol. II: Development and Validation of
a Model for MLS Techniques,” FAA-RD-79-21 Project Report ATC-88-Vol-2, MIT,
Lincoln Lab, February 1980.
[75]
DiBenedetto, Michael F., Michael S. Braasch and Herman W. Hill, "MLS Azimuth
and Elevation Volumes of Protection,” Technical Memorandum OU/AEC
92-73TM00006/9- FR, Avionics Engineering Center, Department of Electrical and
Computer Engineering, Ohio University, Athens, Ohio, October 1992.
[76]
DiBenedetto, Michael F., Michael S. Braasch and Herman W. Hill, "MLS Critical
Area Criteria Development and Refinement,” Technical Memorandum OU/AEC
92-74TM00006/9D-FR, Avionics Engineering Center, Department o f Electrical and
Computer Engineering, Ohio University, Athens, Ohio, October 1992.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
126
[77]
Braasch, Soo Y. and Michael F. DiBenedetto, "Investigation Regarding Reduction
of Critical/Sensitive Areas Through Exploitation of Interfering Aircraft Dynamics,”
Technical Memorandum OU/AEC 92-68TM00006/52-3. Avionics Engineering
Center, Department of Electrical and Computer Engineering, Ohio University,
Athens, Ohio, October 1992.
[78]
DiBenedetto, Michael F. and Dennis Dudding., "Discussion of Azimuth Critical Area
Requirements for Rotated Azimuth Approach Profiles,” Technical Memorandum
OU/AEC 23-89TM00006/9D-01/ICAO, Avionics Engineering Center, Department
o f Electrical and Computer Engineering, Ohio University, Athens, Ohio, May 1989,
Revised April 1990.
[79]
DiBenedetto, Michael F., and Aaron A. Wilson, "Data Report: MLS Critical Area
Error Contour Data Plots, Volume 2 of 3,” Technical Memorandum OU/AEC
96-16TM94- 00006/1-15, Avionics Engineering Center, School of Electrical
Engineering and Computer Science, Ohio University, Athens, Ohio, April 1996.
[80]
Braasch, Michael S. and Michael F. DiBenedetto, "Areas of Protection Derived for
an Offset Azimuth Antenna Which Supports a Computed Centerline Approach,”
Technical
Memorandum
OU/AEC
90-88TM00006/9B-1/ICAO,
Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, August 1988.
[81]
DiBenedetto, Michael F., "MLS Critical Areas:
Azimuth Requirements for
Computed-Centerline Approach Profiles,” Technical Memorandum OU/AEC
22-90TM 00006/9D&E/ICAO, Avionics Engineering Center, Department of
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
127
Electrical and Computer Engineering, Ohio University, Athens, Ohio, November
1989.
[82]
DiBenedetto, Michael F., "MLS Critical Areas:
Azimuth Requirements for
Computed-Centerline Approach Profiles/’ Technical Memorandum OU/AEC
45-90TM00006/9E-17/ICAO, Avionics Engineering Center, Department of Electrical
and Computer Engineering, Ohio University, Athens, Ohio. November 1989.
[83]
DiBenedetto, Michael F., "Development o f Guidance Material for Determining
A zim u th Critical and Sensitive Areas for the Computed Center Line Procedure,”
Technical
Memorandum
OU/AEC
9 1-20TM00006/9E- 19/ICAO,
Avionics
Engineering Center, Department o f Electrical and Computer Engineering, Ohio
University, Athens, Ohio, June 1991.
[84]
DiBenedetto, Michael F., and Aaron A. Wilson, "Data Report: MLS Critical Area
Error Contour Data Plots, Volume 3 of 3,” Technical Memorandum OU/AEC
96-17TM94- 00006/1-16, Avionics Engineering Center, School o f Electrical
Engineering and Computer Science, Ohio University, Athens, Ohio, April 1996.
[85]
DiBenedetto, Michael F., "MLS Critical Areas:
Advanced
Approach
Profiles,”
Technical
Azimuth Requirements for
Memorandum
OU/AEC
46-90TM00006/9E-18/ICAO, Avionics Engineering Center, Department of Electrical
and Computer Engineering, Ohio University, Athens, Ohio, November 1989.
[86]
DiBenedetto, Michael F., "Preliminary Information on MLS Azimuth Critical Areas
for
Advanced
Approach
Profiles,”
Technical
Memorandum
OU/AEC
04-89TM00006/ 9D-1/ ICAO, Avionics Engineering Center, Department of
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
128
Electrical and Computer Engineering, Ohio University, Athens, Ohio, April 1989
[87]
DiBenedetto, Michael F., "Summary o f Preliminary Information on MLS Azimuth
Critical Areas for Advanced Approach Profiles,” Technical Memorandum OU/AEC
13-89TM00006/9D-1/ICAO, Avionics Engineering Center, Department of Electrical
and Computer Engineering, Ohio University, Athens, Ohio, April 1989.
[88]
DiBenedetto, Michael F., "DME/P Critical Areas: Proposed Error Budgets and
Outline
of
Future
Activities,”
Technical
Memorandum
OU/AEC
91-07TM00006/44-1/ICAO, Avionics Engineering Center, Department of Electrical
and Computer Engineering, Ohio University, Athens, Ohio, March 1991.
[89]
Rajendran, J., "DME/P Critical Areas: Parameter Specification for Error Contour
Data Generation,” Technical Memorandum OU/AEC 92-61TM00006/44-FR,
Avionics Engineering Center, Department of Electrical and Computer Engineering,
Ohio University, Athens, Ohio, October 1992.
[90]
DiBenedetto, Michael F„ Stephan J, Kruger, “DME/P Module Validation: The
Comparison of Measured and Modeled Multipath Errors due to Signal Scattering by
the DOT/FAA Technical Center Hangar,” Technical Memorandum OU/AEC 9275TM00006/51-4, Avionics Engineering Center, Department o f Electrical and
Computer Engineering, Ohio University, Athens, Ohio, August 1993.
[91]
Flynn, Charles W., Michael F. DiBenedetto and Kevin L. Johnson, “DME Routines:
Implementation Strategy for Model Modifications to Correct the Time-delay
Calculations for the Case of Shadowing Buildings,” Technical Memorandum
OU/AEC 94-14TM0039/RAY-4, Avionics Engineering Center, Department of
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
129
Electrical and Computer Engineering, Ohio University, Athens, Ohio, September
1994.
[92]
DiBenedetto, Michael F., *‘DME Routines: Validation of Model Modifications to
Correct the Time-delay Calculations for the Case of Shadowing Buildings,”
Technical Memorandum OU/AEC 94-28TM0039/RAY-7, Avionics Engineering
Center, Department of Electrical and Computer Engineering, Ohio University,
Athens, Ohio, September 1994.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
130
APPENDIX A
MULTIPATH ERROR EQUATION FOR ANGLE EQUIPMENT
(AZIMUTH AND ELEVATION)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
131
Multipath Error Formula. The peak in-beam multipath error depends on several
factors. The peak of the error envelope can be estimated using the formula:
p0_
57.37rt
^ s in [ ,
M]
1-79.BW
2fg '
P s 0.707 (-3
dB)
(1)
where:
E
0SA
0B W
= peak error (Degrees)
= multipath separation angle from direct signal
as viewed from the ground antenna (< 1.7 beamwidths)
= antenna beamwidth
g
= data rate ; if f > 1.6 Hz
2 x FNB
= 1 ; if f < 1.6 Hz
FNB
= output filter noise bandwidth
= 1.6 k !2 H z
data rate
= 13 Hz (Azimuth);
39 Hz (High Rate Azimuth and Elevation)
p
= ratio of multipath to direct signal level
f
= multipath scalloping frequency (Hz)
= (VA.)(cosa - cosp)
V
= aircraft velocity (nominally 200 ft/sec)
X
= wavelength (0.2 ft)
a
= angle between the aircraft direction and the guidance
antenna as viewed from the aircraft
P
= angle between the aircraft direction and the reflected
signal as viewed from the aircraft
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
132
APPENDIX B
CRITICAL AREA ERROR ALLOCATIONS FOR AZIMUTH AND ELEVATION
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
ERROR ALLOCATIONS FOR MLS AZIMUTH CRITICAL AREA DEVELOPMENT
(distances are in feet; error values are in degrees)
Azimuth to threshold distance (feet)
Antenna beamwidth
a)
Svstem hudeet for PfN“
b)
c)
Ground equipment error allowance
Ground reflection allowance
d)
11,5ft
■ Clean site error allocation
[d =
6,000
7,000
8,000
9,000
10,000
11,000
12,000
2°
2°
2"
2"
2*
le
1°
0.1098
0.0120
0.0400
0.0941
0.0120
0.0400
0.0824
0.0120
0.0400
0.0732
0.0120
0.0400
0.0659
0.0120
0.0400
0.0599
0.0120
0.0200
0.0549
0.0120
0.0200
l#
0.0507 |
0.0120
0.0200
0.1016
0.0844
0.0710
0.0601
0.0510
0.0552
0.0497
0.0450
13,000
6*- o*]
e)
ALS/monitor pole allowance
0.0300
0.0300
0.0300
0.0300
0.0300
0.0150
O.OISO
O.OISO
0
Complex site multipath error allocation
0.0970
0.0788
0.0643
0.0521
0.0412
0.0531
0.0474
0.0424
[ f • Jd* -
•*]
s)
70% complex site multipath error allocation
■ Complex site error allocation
0.0679
0.05S2
0.0450
0.0365
0.0288.
0.0372
0.0332
0.0297
a)
Svstem budget for CMN - 10.5 ft
Ground equipment error allowance
Airborne equipment error allowance
Allowance for structure vibration
0.1003
0.03 IS
0.01S0
0.0320
0.08S9
0.0270
0.01 SO
0.0320
0.0752
0.0236
O.OISO
0.0320
0.0668
0.0210
0.0150
0.0320
0.0602
0.0189
0.0150
0.0320
0.0547
0.0172
0.0150
0.0320
0.0501
0.0158
0.0150
0.0320
0.0463
0.0145
O.OISO
0.0320
■ Clean site error allocation
Also, complex multipath error allocation
0.0884
0.0735
0.0620
0.0527
0.0449
0.0380
0.0319
0.0261
0.0619
0.0515
0.0434
0.0369
0.0314
0.0266
0.0223
0.0183 j
b)
c)
d)
e)
[ e ■ i/a1 -
0
b* - o *-
d1]
70% complex site multipath error allocation
“ Complex site error allocation
U>
U>
134
ERROR ALLOCATIONS FOR MLS ELEVATION CRITICAL AREA DEVELOPMENT
(all allocation values are in degrees)
Antenna beamwidth
a)
b)
c)
d)
Svstem budget for PFN = 1.3 ft.
Ground equipment error allowance
Sidelobe reflections allowance
—Clean site error allocation
[
1.5°
1.0°
0.083
0.010
0.055
0.083
0.010
0.037
0.061
0.073
d= }Ja2- b2- c2]
e)
f)
Vertical diffractions (field monitors)
Lateral reflections allowance
0.030
0.031
0.030
0.043
g)
Complex site multipath error allocation
0.043
0.051
[
g= Jd2- e2- f2]
h)
70% complex site error allocation
= Complex site error allocation
0.030
0.036
a)
b)
c)
d)
e)
Svstem budget for CMN = 1.0 ft
Ground equipment error allowance
Airborne equipment error allowance
Sidelobe reflections allowance
Allowance for structure vibration
0.064
0.032
0.010
0.015
0.010
0.064
0.032
0.010
0.010
0.010
f)
= Clean site error allocation
also complex site multipath error allocation
0.052
0.053
0.036
0.037
f yja2- b2- c2- d2- e 2]
[ =
g)
70% complex site error allocation
= Complex site error allocation
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
135
APPENDIX C
This appendix provides a copy o f the critical-area criteria
published in Federal Aviation Administration Order 6830.5,
“Siting Criteria for the Microwave Landing System (MLS)"
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
136
ORDER
6 8 3 0 .5
CHTTKHTA TOR SITIBG
m a n u re
u d ik
systems o ils )
klSTAjj
DEPARTMENT OF TRANSPORTATION
FEDERAL 86
ADMINISTRATION
D istribution:
Initiated By:
A-W
A-X
(T B /SE /M S/U /SK /FS/T O /A S)-2;
(A F/FS/A S)—3
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
AKK-500
7/22/93
6830.5
• •*. * * »
503. CRITICAL AREA. The critical area for the MLS AZ station, shown in figure 5-3, is
intended to maintain the full (Category m) accuracy of the MLS guidance along rmtrrKne
approach procedures. This area around the AZ antenna must be protected from the
unrestricted movement of surface traffic to ensure continuous integrity of the radiated signaL
Surface traffic includes taxiing aircraft and authorized vehicles.
a. Critical Areas for Centerline Approach Procedures. The general formula for
critical angles (± ), on each side of the approach course, to be protected is (BW x 1.7) + 0.2
degrees. As down in figure 5-3, for an AZ antenna which has a 2-degree beamwidth, die
width of the critical area would be 3.6 degrees each side o f antenna boresight pins die small
region indicated to protect the field monitor. The 0.2-degree flight path deviation allowance
is to account for the wander of the aircraft around centerline in the final approach region.
The critical area lengths found in table 5-l(a) are used where the AZ antenna is normally
sited on the runway centerline extended. These lengths provide signal protection far the
approaching aircraft down to a height of 600 feet by which point the landed aircraft should
be dear of the runway. This table accommodates interference by B-747 or B-727 aircraft in
•clean* or ’stressful* propagation environments using AZ antennas with beamwidths of 1 or
2 degrees. The clean and stressful sites represent extreme environments, where the first has
no other interference sources (except the ground reflection) while the second assumes several
reflection and diffraction sources which use op most of the accuracy margin. In the vertical,
the lower boundary typically will intercept the ground near the antenna, although, for a tower
mounted antenna or with depressed terrain in front, traffic can pass under the lower
boundary without causing signal degradations. The upper boundary protects against
helicopter or other airborne traffic moving near the antenna at slow speeds. If the azimuth
antenna is offset from centerline and the critical area overlays off-nmway regions where
moving aircraft or vehicles may exist, the
area lengths given in table 5-l(b) win
provide signal protection for approaching aircraft down to die 250-foot decision-height. The
criteria are primarily based on the tailfin height For aircraft with tailfin heights between B727 and B-747, the latter criteria should be used.
b. Critical Areas for Advanced Procedures with Off-Centeriine Segments. Criteria to
define the critical areas needed to protect mt.s signal quality along procedure segments away
from the centerline region (e.g., on Radio Navigation (RNAV) routes) are under
development by the All Weather Operations Panel of the ICAO.
Chap 5
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IE 5-3. AZTMirm AWTBNWA CRITICAL AREA
mnet
^ncsuyjot
• a p t)
0 a Ok)
i l l
3 .3 0 .4 )
3 .0 0 .4 )
I .K H .3 )
7 .3 0 4 .3 )
0 .3 0 7 .0 )
"S« 8
la m
MCXOO) .
n o w
U tP M l
131(7901
so o a so o )
M a ra t Mu la aaM l
• • i-J O l Z
Z < 300 ■
I ■ 103
3 > 300 ■
1 - 0.0 1 3 z » iVXz
X • 0 .0 0 a (0 .3 33)
Pi*e58
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Chap 5
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TABLE 5.1. AZ CRITICAL AREA MIRTHS
TABLE 5-KA). AZ CRITICAL AREA LENGTHS FOR CENTERLINE APPROACHES
(AZ ANTENNA SUED Off CENTERLINE^
2 O ur** Iw w fd th
AZ to
th ru ta lrf
d istan t*
ldo id! 2**o ITU USA
1 B T C a u u fd th
USA
IB B
5MB
CfiOQO) (TOM) MOOO) (9000) (10000) (11000) (12000) (13000)
1-7*7
*90
320
sao *10 tut
(1*00) (1700) (1900) (2000) (2100)
C70
(2200)
700
(2300)
TOO
(2300)
8-7Z7
ctaan i l t i
300
300
300
300
300
(1000) (1000) (1000) (1000) (1000)
4M
300
(1000) (1300)
*90
(UOO)
•*7*7
• tr u s f u l
*90
530
sao 6*0 700
(MOO) (» 0 0 ) (1900) (2100) (2300)
730
(2(00)
7*0
(2300)
820
(2700)
•*727
■ tru s fu l
(ft*
300
300
300
350
«M
(1000) (1000) (1000) (1300 (1*00)
Uo
to t
(1300) (1*00)
330
(1800)
d u n a lt*
lit*
v Distances an in meters (feet). Values In both units have been rounded.
NOTE: For locations when one degree beamwidths an used instead of the 2
degree, these values still apply although they will be conservative.
TABLE S-inn. AZ CRmCAL AREA LENGTHS FOR CENTERLINE APPROACHES
(OFFSET AZ INSTALLATION)?
2 D soru I d M O
AZ t*
threshold
d istan t*
1 0 * ir u SMMfdt*
SUB
UM
SNA
(6000) (7000) (8000) (9000) (10000) <11000) (12000) (13000)
0-7*7
d u n s ft*
<*0
. 000
730
790
•00
(2100) (2*00) (2*00) (2900) (2900)
9*0
920
(3000) (3100)
1000
(3100)
•-727
c lu n ( I t*
300
(1000)
300
*90
(1000) (M 00)
550
(MOO)
■•7*7
• tr u s f u l
• It*
<20
*70
7*0
1010
no
(2200) (2300) (2700) (2900) (3300)
900
(3200)
1070
(3300)
1130
(3700)
1-727
( tr u s f u l
• it*
300
(1000)
*90
320
(1*00) (1700)
350
(MOO)
300
300
300
300
(1000) (1000) (1000) (1000)
300
330
530
wo
(1000) (1100) (1300) (1S0O)
v Distances an in meters (feet). Values in both units have been rounded.
NOTE: For locations when one degree beamwidths an used instead of the 2
degree, these values still apply although they will be conservative.
C hap 5
P a r 503
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c. Requirements. Parking of surface vehicles in the critical area is prohibited and all
traffic shall remain clear of die area except as provided in the latest edition of
Order 7110.65, Air Traffic Control. Vegetation shall not be permitted to grow to such a
height that it extends up into the critical area.
d. Aircraft Specific Hold Lines. The siting engineer shall coordinate with Air
Traffic and Airports on the desirability for aircraft specific hold lines. In many cases wide
body aircraft (B747, L1011) may be the ooly aircraft which cause signal degradation of die
MLS signal where the taxiway violates die A Z critical area. Actual onsite testing with flight
inspection may be requited to implement this feature.
e. Collocation. If die AZ antenna is located with a localizer, both the ILS and MLS
critical areas must be protected from ground traffic.
SECTION 3. DME/P SITE
504. LOCATION. The preferred location for the DME/P is at the AZ site. However, this
may cause the DME/P antenna to violate obstacle clearance surfaces (Part 77) when
AZ-DME/P site is about 1,400 feet or less from the stop end of the runway and-iocated in
the light lane. The distance from the stop end is found by determining the necessary antenna
height to ensure adequate DME/P signal at 8 feet above the runway surface from figure 5-4,
and checking to see if the 50:1 surface is violated for that particular DME/P antenna site. I f
so, the DME/P antenna may be moved further bade (and its height readjusted) until it does
not penetrate the 50:1 surface. It should be noted that in figure 5-4 a difference of 5 feet
between the phase center and the top of the antenna was assumed. The siting engineer
should always check the manufacturer’s specifications for the particular antenna being
i««t»iw before making siting derisions. In choosing a site for the DME antenna, the
possibility of carrier wave (CW) interference must be considered. This interference is
caused by emissions from the DME interrogators of aircraft in close proximity to the DME
antenna, hi order to minimize these effects, the DME antenna should be located at least 600
feet from any aircraft movement area, Le., taxiways, nunps. Where such siting is not
possible, local restrictions on DME interrogator operations may be required.
505. ANTENNA OfrSciuNG. If the DME/P antenna penetrates the approach light
plane or the 50:1 surface, the antenna may be offset laterally from the AZ station. An offset
greater than 200 feet is required to predude penetration of the obstadc free zone surfaces
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6830-5
9 ) Hie Ideal EL antenna setback would cause the asymptote of the minimum
glidepath to intersect the MLS ARD. This SB is illustrated in figure 5-6 and is calculated
using the formula included in that figure. As the antenna offset from runway centerline
increases, die hyperbolic effect also increases and at offsets approaching 600 feet the effect
may begin to present an operational problem. The difference in height (HDDF) above
threshold between the hyperbolic glidepath and the linear asymptote may be calculated using
the appropriate formula from figure 5-6. This difference is graphically shown in figure 5-7
which plots the hyperbolic threshold crossing height (ICH) as the antenna offset is increased.
The HDIF should be kept to a minimum. If this difference exceeds 10 feet, it could present
an operational problem, and alternative siting should be explored.
(3) Figure 5-8 gives the siting area which will maintain the asymptote at a height
of 50 feet above threshold while keeping the path height to less than 60 feet above threshold
(a phase center height of 7 feet and a 3 degree glidepath were assumed).
508. CRITICAL AREA. The EL station critical area is shown in figure 5-9. This area
must be protected from unlimited movement of surface traffic to ensure the continuous
integrity of the EL signal-in-space.
a. Critical Area for Centerline Approach Procedures. Laterally, the EL critical area
extends from the runway edge to a line parallel to centerline located 33 feet beyond the
antenna and as necessary to include the far field monitor (see figure 5-9 for the specific
geometry). The length of the critical area appropriate for various sites, aircraft sizes, and
antenna beamwidths is found in the table inyJntfot on figure 5-9. It is important to note that
the EL critical area may not extend down to ground level, and thus, in many cases, aircraft
can pass under the critical area or, as a mimrnnm, hold in front of the EL site as long as the
tailfin is excluded. For normal siting of a 1-degree beamwidth antenna and fiat ground, the
fuselage of most aircraft will fit under the lower boundary of the critical area. Far an
antenna with a 1.5-degree beamwidth, limited penetration may be tolerated by an aircraft
fuselage which is perpendicular to centerline. At sites performing well within tolerances,
aircraft may hold in front of the antenna provided: (1) the reparation angle between the
glidepath and the top of the aircraft fuselage is at lost 1.5 degrees; and, (2) the aircraft
tailfin is excluded from the critical area. The criteria are primarily based on the tailfin
height. For aircraft wife tailfin heights between B-727 and B-747, the latter criteria should
be used.
b. Critical Area* frw Arfvanr-t iW hw wife Qff-centeriine Segments. Criteria to
define the critical areas needed to protect MLS signal quality along procedure segments away
Chap 5
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FIGURE 5-9. ELEVATION ANTENNA CRITICAL AREA.
o ju u tra
• u*
LT
Chap 5
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m
mm
QM« 9*m
mm
<DM« 9»m
m
mm
m
M
mm mm
9rnm m»m
mm
mm
om
m vmrn
bX PROHLEVIEW
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from the centerline region (e.g., on KNAV routes) axe under development by the All
Weather Operations Panel of the ICAO.
c. M h rfifica rin n T e c h n iq u e s. If the EL critical area is interfering with operationally
desirable aircraft movements, the « tin g enpm*r can take the following actions:
(1) Raise the phase center. The antenna can be raised and moved towards the
runway threshold in order to move the EL antenna to the threshold side of the offending
taxiway or to assure that taxiing aircraft will not penetrate the lower boundary of the critical
area (see paragraph 308a). Limitations of these tnchniqnes include violation of the 7:1
surfaces, which can be minimized by increasing the offset, and operational concerns about
m Kh i i h
m n tra l
(2) Multiple aircraft hold lines. The siting engineer can coordinate with air
traffic and airports on the desirability for aircraft specific hold lines. In many locations, only
aircraft with very tall tailfins (e.g.,B747, L1011) may be required to hold short of the EL
critical area. Actual onsite testing with flight inspection may be needed to validate this
technique.
d. Collocation. If the EL antenna is located with an 1LS glideslope antenna, both the
ILS and MLS critical areas must be protected.
SECTTONS. FIELD MONITORS
309. GENERAL. Both the AZ and EL stations include field monitors that are w»«t»tfed in
association with the scanning beam antennas. The field monitor’s primary purpose is to
monitor mechanical stability of the antennas. An integral monitor (within the antenna
aperture) is used to monitor the electrical stability.
a. Integral Monitor. The integral monitor sums the signals from each antenna
element to reproduce the antenna pattern as it would be seen in the for field, and it is
designed to monitor at only one angle which cannot be changed.
b. Held Monitor. The field monitor can be placed at any angle within the scan
coverage of the antennas. However, it is requited that either the integral or field monitor (or
both) be within one beamwidth of die zero degree course (AZ) and the minimum glirirpath
(EL). This is to ensure maximum system integrity for the final approach course.
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Chop 3
Par 508
144
APPENDIX D
This appendix provides a copy of the critical-area criteria
published by the International Civil Aviation Organization in
Annex 10 to the convention on international civil aviation
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INTERNATIONAL STANDARDS
AND RECOM M ENDED PRA C TIC ES
AERONAUTICAL
TELECOMMUNICATIONS
ANNEX 10
TO T H E CONVENTION ON INTERNATIONAL C IV IL AVIATION
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4 3 Critical and sensitive treat
taxiways and roadways which penetrate the critical area in
order to restrict the entry o f vehicles and aircraft.
43.1 The ucuw ence of interference 10MLS signals is
depeodent on the reflection and shadowing environment
around the MLS antennas and the antenna beamwidths.
S h a d e s and fixed objects within 1.7 beamw idths o f the
receiver location ate considered “in-beam'’ and w ill cense
main lobe m ultipath interference to the MLS guidance
signals. Typically, the ground equipment beamwidths are
chosen such that no azimuth in-beam reflections exist along
the final approach course and no elevation in-beam multipath
exists along the commissioned glide paths. However,
movable objects may enter the in-beam muldpaah regions and
cauae interfering reflections to or shadowing o f the guidance
signals to the extent that the quality becomes unacceptable.
The areas w ithin which vehicles can cause degraded perform­
ance need to be defined and im p iiM t For the purpose o f
developing protective zoning criteria, these areas can be
divided into two types. Le. critical an as and sensitive areas.
433
r'nrjueurnMnUIUng IwJimqniw ra n he employed
to ralm lw r the magnitude and duration o f signal disturbances
caused by a ntennas o r by aircraft o f various sizes and
orientation at differing locations. Typically, the pan m rtew
required to operate such a model are the antenna beamwitfchs
and the size, location and orientation o f reflecting and
shadowing objects. T dang into account the maximum allowable multipath degradation o f the signal due to aircraft on the
ground, the corresponiflng critical and sensitive areas can be
itm ininM l Such a method has been used in developing
Figures G-23 and G-24. after validation o f compute r models
which included comparisons at selected pomes o f .computed
results with actual field and Sight data an parked aircraft
interference to the MLS guidance signals.
4 3 .4 Control o f critical areas and the designation o f
sensitive areas an the airport proper generally win be
sufficient to protect MLS signals from m ultipath effects
caused by targe, fixed ground structures. This is particularly
sigiifirant whrn rnuridaringthe size o f new buildings. Sttnctnres outside the bounthnies o f the airport generally w ill not
cause difficulty to the MLS signal quality as long as the
structures meet obstacle lim itation criteria.
a) The MLS critical area is an area o f defined dhnensions about the azunudt and elevation antennas where
vehicles, including aircraft, are ntrfuded during all
m t.q opentioos. The a id e d a n t s pfotwsgil by a t t
the presence o f vehicles tod/or aircraft inside its
boundaries w ill cause unacceptable disturbance to the
guidance signals.
4 3 3 The boundary o f the protected zone (Le. the
combined critical and sensitive areas) is defined such that
interference caused by aircra ft and vehicles outride .that
boundary w ill not cause errors io excess o f typical allowances
for propagation effects. T he derivation o f error allowances to
protect centre line approach profiles, as shown in ThMes
G -Ift and G -ll (hr a "dean’’ and “complex’ propagation
environment, proceed a t follows. A llaw m ces fbr arftipm rnt
errors are subtracted (on a root sum square basis (RSS)) from
the system e n o r U nits a t the approach rrfrrrn rr datum
(ARD) and the resulting balance o f the error budget is
available for propagation anomalies. The ground wflartlcn is
accommodated at both d ean and complex sites, while m
complex environments, a margin is reserved to aacaaamodma
additional eno r sources such as support stoacture vibration,
(fiffiacted signals from, for example, approach lighting sydem
(ALS) lights and supports o r more intense lateral reflections.
Finally. 70 per cent o f the remaining error balance is allo­
cated to define the protected zone boundary. Thus, error
halm nni are avaflablB to define protected zone hcundariaa fo r
the extreme caaea-of a very clean pmpagarinu environm ent
with only gwand irflrrtiom and for a very complex eoviroument with several significant sources o f propagation errors.'
b) The MLS sensitive area is an area extending beyond
the critical area where the parking and/or movement
o f vehicles, including aircraft, is controlled to prevent
the possibility o f unacceptable interference to the
MLS signals during MLS operations. The sensitive
area provides protection against interference caused
by huge objects outside the critical area but still
normally within the airfield boundary.
■Vole /.— Where disturbance to the guidanc« signal can
occur only at tome height above the ground the lerm t
"critical volume" or "tentirive volume" are used.
Note 2.— The objective o fdefining critical and sensitive
anas is to qffbrd adequate protection o f the MLS guidance
signals. The manner in which die terminology is applied may
vary between States. In seme States, the term “critical area ”
is also used to describe the area that is referred to herein as
the sensitive area.
4 3 3 Typical examples o f critical and sensitive areas
that need to be protected are shown in Figure G-23 and
Figure G-24. The tabled values asanriaied with Figure G-23
and Figure G-24 apply to approach procedures with elevation
angles o f three degrees or higher. To assure the signal
quality, it is necessary normally to prohibit all entry o f
vehicles and the taxiing or parking o f rircralt within this area
during all MLS operations. The critical area determined for
each arim uth and elevation antenna should be dearly desig­
nated. Suitable signal devices may need to be provided et
7/11/96
4 3 3 The MLS critical areas are smaller than the ILS
critical areas. Where MLS antennas are located in dose
proximity to the ILS antennas, the ILS critical erees in most
cases will protect Ihq MLS for sim ilar approar h paths
Note.— A reduction o f the MLS critical and sensitive
areas may be obtained by measurements or analysis which
M2
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147
Annex 10 — Aeronautical Telecom m unications
Attachm ent G
consider the specific environment. It is recommended that
samples be taken a t least every 15 m (50 ft).
point to the runway centre line w here guidance is
required (point G ):
4 3 .7
Azimuth. For an azim uth antenna supporting an
aligned approach along the zero degree azim uth the region
betw een the azim uth antenna and runway stop end is to be
designated as a critical area. The sensitive area o f Figure
G -23 provides additional signal protection w hen low visibility
landing operation s are in progress. In general, the azim uth
sensitive area w ill fall w ithin the runw ay boundaries such that
attenuate control can be exercised o v e ra ll m oving traffic to
prevent unacceptable interference to the M LS signals. In
developing the sensitive area lengths o f Table G -12A it was
assum ed th at th e landed B-727 (or B-747) type aircraft has
cleared th e runw ay before the landing aircraft teaches a
height erf 9 0 m (300 ft) (or 180 m (600 ft) fo r B -747)). T hat
assum ption resulted from consideration o f the follow ing
factors:
b) locate point C on line AG at a distance from the
azim uth antenna found by entering T able G -12C or
G -I2D w ith azim uth to threshold d istan ce, s ite o f the
largest aircraf t on ground and h eig h t o f point G on
CbC wwwamnqi gfufe path;
c) line AB has the sam e length as lin e A C and fines AC
and AB are angularly separated b y an am ount for
in-beam m ultipath (1.7 beam w idth) and a value fo r
flight path deviation allow ance to accou n t fo r d evia­
tions o f the approaching aircraft aboot th e nom inal
approach track;
d ) determ ine the direction o f line A F from the azim uth
antenna to point F a t a height o f 300 m (1 000 ft) on
the wif ifliu n glide
a) 5.6 km (3 N M ) separation behind B -747 size aircraft;
e) determ ine the direction o f fine A D w hich is angularly
separated by 1.7 BW from line A in
b) 3.7 km (2 N M ) separation behind B -727 size aircraft;
the length o f fine AD is taken from T hble G -12C o r
G-12D w ith inform ation on th e h eig h t o f point F ; and
c) runw ay occupancy tim e fo r the landing aircraft is
30 seconds; and
0
d) approaching aircraft speed is approxim ately 220
km /hr (2 NM /m in).
g) the area to b e protected is bounded b y th e polygon
ABCD.
4 3 .7 .1
F o r an azim uth antenna supporting an offset
approach th e critical and sensitive areas w ill depend an the
azim uth antenna location and the approach track orientation
relative to the zero degree azim uth. The critical area extends
fo r at least 300 m (1 000 ft) in front o f the azim uth antenna.
T o avoid shadow ing w hile landing oper ations are in progress,
additional protection is to be provided in the form o f a sensi­
tive area. T able G -I2B gives sensitive area length fo r use
w ith an o ffset azim uth installation. W hen a procedure is
along an azim uth o ther than the zero degree azim uth, the plan
view definition has to take into account beam spreading.
Figure G -25 show s typical exam ples.
4 3 .7 3 3
Typically the areas o f polygon ABCD in
Figure G-26 w ithin a t least the first 300 m ( t 0 0 0 ft) o r
600 m (2 000 ft) o f the azim uth antenna a te to b e designated ,
respectively, as a critical area w here B -727 o r B -747 size
aircraft are operating T he balance o f th e reg io n is designated
as a sensitive area. W here possible, the azfttm th antenn a is to
be offset to the runw ay side aw ay from th a t o f active
taxiw ays. A t facilities w here the azim uth am rm ia is set back
less than 300 m (1 000 ft) o r located ahead o f th e runw ay
stop end. a detailed analysis and consideration « f dm an p o tt
layout m ay support reductions o f the area to b e p ro te cte d .
4 3 .7 3
C ritical and sensitive areasja r ULS/RNAV pro­
cedures. For MLS/RNAV approach procedures, th e c ritica l
Note.— This guidance material also applies to an azimuth
antenna providing the back azimuth junction.
4 .3 .7 3
C ritical and sensitive areas fo r the computed
centre line approach Figure G -26 provides a general
illustration o f the areas to be protected from uncontrolled
m ovem ent o f ground traffic. T he exact shape o f th at area w ill
depend on the azim uth antenna location. »zimmh to threshold
distance, decision height, type o f aircraft operating at the
facility, and the m ultipath environm ent.
4.3.73 .1
In determ ining the area to be protected, the
follow ing steps are appropriate:
a) determ ine the direction o f line AG (Figure G-26)
from the azim uth antenna (point A ) to the neatest
and sensitive areas w ill require expansion to pro tect against
in-beam m ultipath in th e sectors used. T hese expanded areas
protect approach procedures w hich are n o t possib le w ith ILS.
T he length o f the area to be protected depends o n th e opera­
tional minimum height surface selected from T able G -13.
Inform ation fo r determining the area to be pro tected is given
in Figure G -27. F or a wide range o f p ro files, sim ulation
indicated that, w here B-727 size aircraft a te operating,
adequate protection w ould be afforded i f th e first 3 0 0 ’m
(1 000 ft) o f the protected area is designated as a critical area
and the rem ainder as a sensitive area. F o r B -747 size aircraft,
the corresponding length is 600 m (2 0 0 0 ft). F o r higher
approach profiles, the length derived from T able G -13 o r an
equation therein m ay be less than these v alues; its th is case
the entire expanded area is to be designated a s a c ritical area.
183
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7/11/96
148
A nnex 10— A tromm lic itl Telecommunication*
Votmme I
fc fn terrriatin w sh ip o f
g rou n d eq uipm ent mon ito r
a n d co n tro l actio n s
Increased flexibility m ay be obtained by perforating an
analysis considering the specific approach profile and airport
environm ent.
6.1
The intenclationship o f m onitor and control actions
4 3 .8
Elevation. T he elevation critical area to be
protected results from the critical volum e show n in Figure
is considered necessary to ensure th at aircraft do not receive
incomplete guidance w hich could jeopar di se safety, b ut a t the
G -24. N orm ally no sensitive area is defined fo r the elevation
sam e tim e continue to receive valid guidance w hich may
antenna. A s th e low er surface o f the critical volum e normally
safely be ntflized in the event o f certain functions ceasing to
is w ell above ground level, aircraft m ay bold near the eleva­
ratfiate.
tion antenna as long as the low er boundary o f the critical
volum e is not penetrated.
Afore— The interrelationship o f ground equipment
43 .8 .1
F o r norm al siting o f a 1.0 degree beam width monitor and control actions is presented in Table C-14.
elevation antenna and Bat ground, the fuselage o f m ost
aircraft types w ill fit under the profile low er surface o f the
critical volum e o f Figure G -24.
7 . A irb o rn e eq u ipm ent
4 3 .8 3
F or a 1 3 degree beamwidth elevation antenna,
lim ited penetration o f the profile low er surface o f the critical
7.1 G eneral
volume o f Figure G -24 by an aircraft fuselage m ay be to ler­
ated by defining the low er part o f the critical volum e betw een
7.1.1
T he airborne equipmen t param eters and toler­
1 3 degrees and 1.7 beam width below the minim um g lide
ances included in th is section are intended to enable an inter­
path as sensitive volum e. At sites performing w ell w ithin
pretation o f th e Sf datda contained in Chapter 3, 3.11 and
tolerance, aircraft m ay bold in from o f the antenna provided:
include aDowancea. w here appropriate, fix:
a) the separation angle between the glide path and the
a) variation o f the ground equ ipment param eters w ithin
top o f the aircraft fuselage is a t least 1 3 degrees;
the fintits defined in C hapter 3, 3.11;
b) the aircraft tail fin does not penetra te the low er
b) aircraft m anoeuvres, speeda and sttitudes norm ally
surface o f the critical volume; and
encountere d w ithin the coverage volume.
c ) the fuselage is a t right angle to the centre fine.
Nate I .— The airborne equipment indndtt the aircraft
antennais), the airborne receiver, the pilot interface
4333
F or MLS/RNAV approach procedures, the plan
equipment and the necessary interconnections.
view o f the elevation critical area w ill require expansion to
ensure the elevation signal quality along the nom inal
Note 2.— D etailed “Minimum Performance Spedftcnapproach track (Figure G -28). These expanded areas protect
approach procedures w hich are not passible w ith ILS. T he
dans'’ fo r M LS avionics have bean compiled and co­
ordinated by th e European Organization fo r Civil Aviation
characteristics o f the profile view (Figure G -24) rem ain
Electronics (EUROCAE) and KTCA Inc. ICAO periodically
unchanged , noting th at the low er boundary is referenced to
provides to Contracting Slates current lists o f the
the nom inal approach hack. This guidance m aterial co v en a
publication! o f these organisations in accordance with
w ide tin g e o f profiles. Incressed flexibility m ay be obtained
Recommendations 3/1 8(a) and 6/7(a) o f the Seventh A ir Navi­
by perform ing an analysis considering the specific approach
gation Conf erence.
profile ro d airport environment.
S. O p eratio n al ro n ak trratio u s o n sitin g
o f D M E ground equipm ent
7 .1 3
Function decoding
5.1 T he DM E equipment should, w henever passible,
provide indicated zero range to the pilot a t th e touchdown
point in order to satisfy current operational requirem ents.
7.13 .1
T h e airborne equipm ent is to be capable o f
decoding and pro cessing the approach azim uth, high ram
approach arim nth. back azim uth, and approach elevation
functions, and d ata required fa r the intended operation.
3.1.1
W hen DM E/P is installed w ith the M LS.
indicated zero range referenced to the M LS datum point m ay
be obtained by airborne equipm ent utilizing coordinate
inform ation from the MLS data. DME zero range should be
referenced to the DM E/P site.
7 .1 3 3
In addition, the receiver utilizes trrh n iqnos to
prevent junction processing resulting from the presence o f
function pream bles om hrdded w ithin the data fields o f besic
and auxiliary d a ta w ords and scanning beam side lobe radia­
tion. O ne technique to .’accom plish this is to decode all
7/11/96
184
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
AttackmnUG
A nntx 10 — A tnm m ttical
lfcb le G -ll. E rro r aBocntio— fo r M LS d e ra tio n c ritica l a re a d n r d o p w a t
(ill allocation values n in degrees)
A n ew beamwidth
IJ*
io*
a)
System budget far PFN - 0 4 m (1_3 ft)
0.083
0083
b)
Ground equipment enor allowance
0.010
OJOIO
c)
Siddobe reflections allowance
0055
0037
d)
Clean site enor allocation
0061
0073
\d - Ja* - b1 - c 1
e)
Vertical dfflractioea (Held monaotx)
0030
0030
0
Lateral reflections allowance
0031
0 0 (3
|)
Complex site enor adocatioo
00(3
0051
0030
0036
0064
L - V d 1 - * 2 -/*
b)
70% complex m e enor allocation
a)
System budget for CMN * 0 3 a (1.0 ft)
0064
b)
Ground equipment enor allowance
0032
0032
c)
Airborne equipment enor allowance
0010
0010
d)
Sidelobe reflections allowance
0015
OOIO
e)
Allowance for structure vibration
0010
OOIO
0
Clean/complex site error allocation
0052
0053
0036
0037
\ f - V«2 - b l - e l - rfl - r»
0
70% complex site error allocation
309
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
|
150
Aumtx 10 — Atromamtieal TtUcommuxicrtioms
Vobau I
T able G -12A . T ypical aTtranSh w i lh t a m Im glha
(aligned ap proach a lo n g z ara degree a r i i i t h , m b 4 J.7 )
(distances are in m etres (feet); values in both ra in have been rounded)
1.0* bcahnviddi
2j0* beaanridrit
2 140
(7 000)
2440
(1000)
2750
(9 000)
3 050
(10000)
3 350
(U 000)
3 660
(12 000)
3 960
(13000)
490
(1600)
520
(1700)
580
(1900)
610
a 000)
640
(2 100)
670
(2 200)
700
a 300)
700
a 300)
B-727. dean site
300
(1000)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
300
(1 000)
460
(1 500)
490
(1600)
B-747. complex site
490
(1600)
550
(1100)
580
(1900)
640
a too)
700
(2 300)
730
a 400)
760
(2500)
820
(2 700)
B-727. complex site
300
(1000)
300
(1000)
300
( 1 000)
460
(1 500)
550
(1800)
460
(1 500)
490
(1 600)
550
(1 800)
Azimuth lo threshold
IM K b
1130
(6 000)
B-747. dean site
Table G-12B. Typical arim tk af a ttie r a m lengths
(oflhat appenarh, mm 4 1 7 J)
(distances are in m etres (feet); vaioea in both onits have been rounded)
U T b a m U fc
2J>* beaamMSi
Axutmtb to threshold
1 830
(6000)
2140
(7 000)
2 440
(8 000)
2 750
(9000)
so n
(10 000)
3350
(11000)
3 660
(12 000)
3900
(13000)
B-747. dean site
640
a 100)
730
0400)
790
0600)
880
0900)
880
0900)
920
(3 008)
940
(3 100)
1010
(3 300)
B-727. dean site
300
(1000)
300
(1000)
300
(I 000)
300
(1000)
300
(1 000)
300
(1 000)
490
(1600)
550
(1 800)
B-747, complex site
670
(2 200)
760
0500)
820
0700)
880
0900)
1010
(3 300)
980
(3 200)
1070
(3 500)
1 130
(3 700)
B-727. complrx site
300
(1000)
300
(1000)
330
(1 100)
460
(1 500)
550
(1 800)
490
(1600)
520
(1700)
550
(1 800)
7/11)96
210
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
151
Attachm eutG
Aam tx 10 — Atnm aatU ol
T kbie G -1 2 C T ypical a rim ath searitiv e a m len g th s
(cotapotcd c en tre lin e appca oc h. see 4 J .7 .2 , d e a n sites)
(distances arc in m etres (feet); values in both anils have been rounded)
ID* —nii»W»
2.0* bcaanridth
2750
(9000)
3050
(10 000)
3 660
(12000)
3 960
(13 000)
300
IS30
(6000)
2140
(7 000)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
(loom
300
(1000)
300
(1000)
300
(1000)
75
(250)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
490
(1600)
550
(1800)
60
(200)
300
300
(1000)
300
(1000)
460
(1500)
610
(toon
n eon
a ooo)
610
(2000)
a 200)
45
(150)
300
(1 000)
300
(1000)
490
(1600)
550
(1 800)
610
(2 000)
670
(2 200)
a 500)
760
820
(2 700)
30
(100)
300
(1000)
520
(1700)
a ooo)
610
700
« 300)
820
(2 700)
920
P 000)
980
(3 200)
I too
(3 600)
IS
(50)
610
(2 000)
730
(2 400)
880
(2 900)
1010
(3 300)
1070
(3 500)
1 100
(3 600)
1 040
(3 400)
1 190
(3 900)
300
(1000)
430
(1400)
460
(1500)
490
(1600)
520
(1700)
520
(1700)
550
(1 800)
580
(I 900)
610
a 000)
75
(250)
640
(2 100)
730
(2 400)
790
\2 60Q)
850
(2 800)
880
(2 900)
920
(3 000)
940
(3 100)
1010
(3 300)
60
(200)
700
(2 300)
790
(2 600)
820
(2 700)
920
(3 000)
940
(3 100)
940
(3 100)
1 010
(3 300)
1 010
(3 300)
45
(ISO)
760
(2 500)
820
(2 700)
920
(3 000)
1 010
(3 300)
t 070
(3 500)
1 070
(3 500)
1 190
(3 900)
1400
(4 600)
30
(100)
850
(2 800)
960
(3 100)
I 100
(3 600)
1 250
(4 100)
1 400
(4 600)
I 550
(5 100)
1 710
(5 600)
1 890
(6 200)
15
(50)
I 070
(3 500)
1 340
(4 400)
1 580
(5 200)
1 830
(6 000)
1980
(6 500)
2040
(6 700)
2 070
(6 800)
2 070
(6 800)
Aaaadi a
Aunce
2440
(8 000)
3 350
(II 000)
B-727. clean ale
Height:
490
670
B-747. dean are
2U
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
7 /1 1 /9 6
152
A m ur 10 — Atromauacal TtUcommmniratinKS
Volmmr 1
T able G-1ZD. ty p ic a l
scnailh re a re a lengths
(com puted cen tre fine appconcb . sea 4 J .7 J , t a n pin t aitee)
(distances ate in metres (feet): values in both units have been rounded)
UT bemmwiddi
1ST bi nnairWi
A
^
auw
r—
eA
it
an
a
...—
m
30S0
(ro a n
3 350
(11 000)
3 660
( i 2 oon
3 960
<13 oon
300
(1000)
300
(1 000)
300
(1000)
300
(1000)
300
(I 000)
330
(1 100)
460
(1 500)
550
(1 800)
490
(1600)
520
(1700)
550
(1 800)
330
(1 100)
330
(1 100)
490
(1600)
550
(1800)
580
(1900)
610
(2 o o n
730
a 400)
330
(1 100)
330
(1 100)
490
(1600)
550
(1 800)
670
0200)
700
a 300)
790
(2 600)
880
a 900)
30
(100)
330
(1 100)
550
(1 800)
640
« 100)
730
0400)
I 010
(3 300)
940
a io n
1040
(3 400)
I 160
(3 s o n
IS
(50)
640
(2100)
790
(2 600)
940
(3 100)
1070
(3 500)
I 250
(4100)
1250
(4100)
1280
(4 200)
1430
(4 700)
300
(1 000)
430
(1400)
460
(1500)
490
(1600)
520
(1700)
670
0200)
550
(1 800)
580
(1 900)
a oon
75
(250)
670
(2 200)
760
(2 500)
820
U 700)
880
0900)
1010
(3 300)
980
(3 200)
o son
I 130
C3 7 0 n
60
(200)
730
(2 400)
820
(2 700)
920
(3 000)
1010
(3 300)
1 130
(3700)
1040
(3 400)
1070
(3 s o n
1 220
(4 o o n
45
(150)
820
(2 700)
880
(2 900)
980
(3 200)
1 100
(3 600)
1220
(4 000)
I too
(3 600)
1 190
(3 9 0 n
1430
(4 70n
30
(100)
920
(3 000)
I 010
(3 300)
1 130
(3 700)
1280
(4 200)
1430
(4 700)
1 580
(5 200)
1770
(5 so n
1950
(6400)
15
(50)
1 100
(3 600)
I 370
(4 500)
1620
(5 300)
1830
(6 000)
2130
2230
(7 300)
2 350
croon
(7 70n
2380
(7 800)
2 750
(9 000)
2440
(8 000)
1 130
(6000)
2 140
a 000)
300
(1000)
300
(1000)
300
(1000)
300
(1000)
75
(250)
300
(1000)
300
(1000)
60
(200)
300
(1000)
45
(150)
dacsbold
tja a a
B-727. complea site
H eitbc
B-747, dean die
7/11/96
1070
212
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
610
153
Attachm ent G
A nnex 10 — Aeronautical i
Table G-13. Minimum height surface angle and related protected coverage
volume lenftba for MLSRNAV ap p n aeh procedure!
hMRfed revenge
volume feagdi
UXU1
PCH- 2.0 m
Mnatmnn beigfct surtax angle (degrees). 8
B-727
B-747
300(1000)
1.81
3.49
430(1300)
123
2 J6
600(2000)
0.95
1.79
730(2 300)
0.77
1.44
900(3 000)
N/A
121
The following equation can be used to determine the minimum height surface angle (6 ) in respect to an
aamuth antenna phase centre for arbitrary protected coverage volume length “L".
TPSJ » A o T _ p n t
9 » tan'1
L
where:
TFH = tail fin height;
PCH = phase centre height of MLS antenna;
X
= MLS wave length.
Note.— TFH equals 10.4 m fo r B-727 and 193 m fo r B-747, and X is 0.06 m. PCH and L m ust be in.
metres if TFH and X are in metres.
213
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
rmm
154
A nnex 1 0 — Aeronautical Tt lecomm aairatiim t
Sanartiva araa
To (taid monitor poia m raquirad
f ▼*2* * ♦ a
- . -T- -
».
+«
^ •_
_ RUNWAY
CENTRE UNE
Flight path
davtatten
aHaanaea (0.2*)
■
VALUE FOR a and P
•
mm
xm(R)
30(100)
75asm
190/500)
225(750)
900(1000)
f)m(R)
1.1(35)
»457>
5.3(17.5)
5 7 (1 0 5 )
1 0 .5 (9 0 )
17.1
25208$
2 5 0 (0 1 8 )
7JS0AJ5
5 8 (253)
Whara:
• MEASURED HORIZONTALLY FROM
AZIMUTH ANTENNA
” MEASURED VERTICALLY FROM
BOTTOM OF AZIMUTH ANTENNA
APERTURE
wm
a m (ft)
a - 0.095 X
X < 200m
a - 2^0.00 X
X > 200m
P -X tan 9« ♦ 310.06 X
BW > BEAMWIDTH
Figure G-23. Typical ariaiuth critical and ■rnilliw areaa
239
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
7/11/96
155
A nnex 1 0 — Aeronautical Telecom m unications
Volume 1
7Bn
mimsL
OEMMMDTH
1JB*
IE*
CLEANSITE
B-727
B-747
320 m 170m
(10600) (6000)
COMPLEXSnE
B-747 B-727
366m 100m
(13600) (60001
400m 280m 666m 300m
(13100) (0200) (16600) (0006
PLAN VIEW
FLIGHTPATH
DEVIATION
ALLOWANCE
( 0-2*)
AS REQURED TO— '
PROTECTFIELDMONITOR
PROFILE VIEW
Figure G-24. Typical elevation critical and sensitive areas/volume
7/11/96
240
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
156
A ttachm ent G
A im er 10 — Aeronautical Telecommunications
17771
CRITICALAREA
BBSS SENSITIVEAREA, B-727
lfw w 1
(STATIONARYAIRCRAFTPROHBMTED)
\\V
satSTTIVE AREA. B-747
(STATIONARYAIRCRAFT PROHBITED)
Sm plan vtow of Figure 6-23
for monitor and near-mid
300 m
Note.— Proflls view Is shown in Figure G-23.
Figure G-25. Typical a iim ath critical and m m tire areas
fo r ofbet azimuth inataflation
241
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
7/11/96
157
Am tux 10 — Aeronautical Telecommunication!
Volume I
’ SM 4.3.7.2.1
1.7 BW + flight path
daviation allowance (0.2*)
| DH (MAP)
BW - Beamwidth
INotta
Figure G-26. Typical azmmth critical and w Mw areas/rolmne
for the computed centre line procedure
7/11/96
242
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
158
Attachm ent G
Annex 10 — Aeronautical Telecom m unications
STANDARD STRAIGHTEN
APPROACHCRITICALAREA
1.7 BW
OFF-CBITREUNECRITICAL
AREAREQURBUBfT
SENSITIVEAREA
V
1.73 W
BW
1.73 W
BUM
puprapnoM
M Bn
/ ’mamanoagu*)
IMngm MsMawfeee
ip p ln tolN i Mtfon oiRf
MNMMW^ n O jJ)
PLANVBW
PCH,
PROFEEVEW
Figure G-27. Typical rrtnakw a t arimnth critical and mMMw areaa
for acgmmted and cnrvcd approacbea
243
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
7A1/96
159
Annex 10 — Aeronautical Telecommunications
Volume I
FOR PROFILE VIEW:
THE CRITICAL AREA EXTENDS
BELOWTHE NOMINALTRACK BY
AN ANGLE OF 1.7 BWPLUS AN
ALLOWANCE FOR FLIGHT PATH
DEVIATIONS.
Figure G-28. Typical extension o f the elevation critical area
for segmentrd and curved approach procedures
7/11/96
244
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
160
APPENDIX E
DERIVATION OF ELECTRIC FIELD BEHIND A PLATE
AND MLS MATHEMATICAL MODEL APPLICATION
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
161
This appendix describes the electromagnetic theory used by the MLSMM to estimate
the error due to signal shadowing. Estimates of the errors caused by shadowing o f the MLS
guidance signal by objects in the airport environment are obtained by representing these
objects by one, or more, shadowing rectangular plates when performing a simulation with
the MLSMM. The principal shadowing equation used for estimating the total field when a
shadowing plate is present is derived. This equation forms the basis for the specific
equations used by the MLSMM to compute the associated multipath components for a given
shadowing geometry. The appendix concludes with an overview of how the principal
shadowing equation is applied to a specified shadowing geometry.
The principal shadowing equation is obtained by first considering slit diffraction,
which is then expanded to the case o f diffraction through a rectangular aperture. Then
Babinet’s Principle is applied to obtained the field due to shadowing by a rectangular
aperture.
From Sommerfeld [E-l], the Fraunhofer and Fresnel diffraction through a slit is
(Figure E - l) :
A
(2)
(Note: The leading minus sign may or may not be present depending on the convention
assumed for the frequency variation, i.e., ejwt (requires minus sign) versus e ‘jwt.)
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
162
where:
Y=
2k' ±R* - RL ’'
<P. =
<Py =
«/2J l +_L
/?
/?'
X=wavelength
A
=
constant
For an infinite two-dimensional slit, Equation 1 can be further manipulated (+/ -
-I-
then applying Babinet’s Principle) to obtain the equation for shadowing by an infinite strip.
S H A D O W E D REG IO N
RECEIVER
SLIT A PE R T U R E
Z = Z,
TR A N SM IT T E R
SH A D O W E D REG IO N
Figure E -l. Diffraction Through Two-Dimensional Slit.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
163
However, the Fraunhofer and Fresnel diffraction through an aperture is desired.
So, accounting for an aperture, Equation 1 can be expanded and written as (Figure E-2):
-jXv
p
=
R R
e ‘ ^ Z' d z [ y*~y- e ^ d y
Jz, -z
(3)
Jy, - v
where:
n = yi - a2
cp = ' A & k
1 +—
R
R'
All other parameters are as defined for Equation I
z
A
RECEIVER
*
L .O .S .: Location w here line-of-sigbt
from transm itter to receiver
passes thro u g h p lan e o f the
aperture.
%
z
P L A TE-R E FE R EN C ED
C O O R D IN A T E SY STEM
TRANSMITTER
Figure E-2. Diffraction Through a Rectangular Aperture.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MDB9II02I02
164
Now, one can utilize Fresnel's integral [E-l]:
-T2
F(co) = / V
Jo
(4)
2 dr
and the Change of Variable Theorem [E-2]:
f b A g M ) g '{x)dx = [ # " f{u) du
J a
Where
u = g(x)
jg ( a )
(5)
to re-write the integral:
. 'v
*
(6)
•| "l
as follows:
eJ%zl dz = n
Jo
r :
z’ e]%z2 dz - f Z, Z’ e ^
Jo
dz
(7)
now, using the following change o f variable:
u =
2 <P.
1 z
=>du =
n
\
2<P. dz
K
(8)
and the associated change in the limits o f integration:
z - z z~ z s
u =y\.
=0
U
=
2 <P.
n
K
~z)
(9)
0
the integral:
f
: 2
z ,
(10)
d z
Jo
can be written as:
ry —2*i*.t-v-V e nit
2
du
• <P, Jo
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
(ID
165
which, utilising Fresnel’s Integral and applying further algebraic manipulation, yields:
/
j<
1
F
yN 2
f ' 1'
Jo
(12)
7t
'
'/
RR'
where:
/
=
R + R'
Thus, the integral:
(13)
can be written as:
I
y\
/
/
X/
F
2
2<H
IN 71 '
where:
/
- * '/) J
-
(14)
F
In
(< *
1 .-*)
7C
RR'
=
R + R'
similarly, the integral:
f yrK
Jy, -y,
e 1V,y d y
(15)
can be written as:
I
Xf
il \
/
\
/
2
2 <p
F
In
2
— - (y ,
7t
l>2
-
)
F
In
*')
CD
y
(16)
7t
Now, applying Equations 13 and 15 to Equation 2:
-7 X v
v
=
Jj— yCle J U R ' R )
RR’
\ U
2
Y
N
f
/
2 cp
2 <p
IN - f K
IN -T ('■-*.)
-J
(17)
2(p
n \|
2
IN
- F
\
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Further algebraic manipulation yields:
- j X. v
'
=
—
-
ik{R~R)
IN
RR’
2<p- /
2 cp
IN
\ -
- F
~ r b -'■>
FIN “2T(p
K ' 2')
2 (p
IN
Substituting in for/ and performing further algebraic manipulations:
2(p
f ig '
IN
£ +/?'
In
/
2(p
-
F
i
*
h -y.)
IN
---------2 cp .
kN
/
/
j k i R + R ‘)
.
V
>
~
F
I
2
R + R '
U
2<P- ( r
K
\
\
2 (p v
In
/
F
2%
In
/
F
-
- , )
2
n
1,
r*
- r
i
‘"''J
/
2 tp
\
-
F
In
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Now, letting
2©
s 1-----\ 7i r<
\
2kr, Ri ++ Rr ' t
K
y
-
\
t
K _r.)
\
1
1
~R
R \/
f k
2<P71
(z
U
- z )
')
=
\
71
i
K)
r
R + R't
,1
1
71
+
n 2k
V 't
\
(•>'.
71
( i
+
kr
+
-y.)
r
a 2k
2(f>y
(y
7t
v 2
- y \
-
\
r
\
K
(y, ->.)
The field propagating through an aperture can be written as:
v
j
= —
f
2
A eJ
R+R'
where:
A e
- * f ,) !
[* $ j -
F (r>)]
jt(R-R')
R+R'
is the signal at the receiver if no opaque screen were present (i.e., aperture).
Normalizing the unperturbed signal to 1, (i.e.,
A e
j k ( R - R ' )
R +R
—
= 1)
The diffracted field propagating through the aperture can be written as:
v, - 2 i F f c ) ' F W ]
- F (2".)]
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
168
However, the diffracted field desired is the field due to blockage by a plate (i.e.,
complementary problem of the aperture). So, according to Babinet's Principle, the blockage
by a plate can be expressed as the unperturbed field minus the field propagating through the
aperture [E-3]:
vs h
=
(24)
1 ~ %
Therefore, the principal equation for shadowing by a rectangular plate is:
■ 1 - 1 [ '■ f c i- 'f ,) ]
m
<2s>
As mentioned previously, estimates o f the errors caused by shadowing o f the MLS
guidance signal by objects in the airport environment are obtained by representing these
objects by one, or more, shadowing rectangular plates when performing a simulation with
the MLSMM. Calculation of these errors can be accomplished by spatial decomposition of
the signal received as a results o f shadowing or diffraction by the rectangular plate(s).
Methods for spatial decomposition of the signal into edge rays with complex amplitudes has
been developed based on Equation 24 [E-3]. The specific method used depends on the
particular MLS system being considered and the transmitter-object-receiver geometry
(Figure E-3).
The particular method used for the case of elevation signal shadowing is outlined
below. This case is being considered since it provides insight into the type of adjustments
that can be made to improve the error estimates when the elevation signal is shadowed by
an aircraft tail fin. For this case, the received signal is expressed as the sum of the following
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
A Z IM U T H
SYSTEM?
NOTE
W = Plate Width
H = Plate Hieght
II > F r e s n e l R a d i u s a n d
W > F re sn e l R a d iu i an d
L O S i n t e r i e c t i p la n e
c o n t a in i n g p la te o u tc id e o f
E L E V A T IO N O R D M E
YES
C A S E A Z a : T w o edge
r a y s + D ir e c t
p la te
L O S in t e r s e c t s p la n e
c o n t a in i n g p l a t e o u ts id e o f
p la te
L O S in t e r s e c t s p la n e
c o n t a in i n g p la te in s id e o f
p la te
C A S E E L fD M E * : T w o
e d g e r a y s + D ir e c t
NO
NO
W > F re s n e l R a d iu s an d
YES
II > F r e i n e l R a d i u i a n d
Y ES
L O S in t e r s e c t s p la n e
CASE A
T
wo
Edge R ays +
YES
c o n t a in i n g p la te in s id e o f
p la te
C e n te r R ay
NO
W < F r e s n e l R a d i u i , a ll L O S
NO
C A SE A Z r : O ne
E d g e R a y + D ir e c t
H < F r e s n e l R a d i u i , a ll L O S
C A S E E L / D M E C:
O ne Edge R ay +
D ir e c t
M D B 9 8 I0 2 2 0 I
Figure E-3. Outline of System and Scattering Geometry Parameters versus Signal Decomposition Case - Shadowing Plate.
On
no
170
three “edge” rays: top, bottom, and center (Figure E-3). The equations used to calculate the
complete amplitude for each o f these rays follow:
-
J [F W
- F W ] [F K ) - F H ]
T
L
j-7
Edge RayCenur = I - e 4 [ f ( y 2) - F(y,)]
Note
v7X
* .) = 1 _
<26>
(28)
(29)
ft
The center edge ray is may be interpreted as an attenuated direct signal. Further, the sum of
the complex amplitudes of the three rays is equal to Equation 24.
For shadowing geometries, where line-of-sight passes through the top half of the tail
fin, representing the tail fin as a rectangle with a width equal to the entire horizontal span of
the actual tail fin can result in over estimating the error generated.
This result is
demonstrated by the initial results obtained for SDF elevation position #1 (Figure E-4). This
situation results for two reasons. First, the representation of the tail fin normally used by the
MLSMM yields a center ray that is attenuated more than it would when one accounts for the
actual width of the tail final along the horizontal line containing LOS (Figure E-5). Second,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED VERSUS MODELED ERROR - SDF POSITION #1
S C A T T E R IN G G E O M E T R Y
* C u r d l a i i i R e fe re n c e
ao
Q
y . E le v a tio n A n te n n a B o tc iig h t y
Ui
IL
0.6
c
0
“ ■
S u o d lfo id F ield » P o u io n tfl
!o
N O S H (X ,Y )*
( fecn
ui 0.4
( 1069, 296)
0.2
0
0.5
1
1.5
2
2.5
3
3.5
4
Distance from Threshold (nmi)
A Measured
■ Modeled
M D B 98093002
Figure E-4. Measured and Modeled PFE Magnitude Data for Standiford Field Elevation Scattering Position #1.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Top Edge Ray Diffraction Point
R e c t a n g u l a r P la te
N o r m a l l y U s e d to
R e p r e s e n t T a il F in
More Representative
Location for Y
Location where Lineof-Sight Passes
Through Tail Fin
Attenuated Center Ray
More Representative
Location for Y.
A c tu a l T a il F in - B -747*
X
“ S t a n d a r d ” T a il F in
o
W i d th
“ S h ad o w in g G eo m etry
D e p e n d e n t ” T a il F in
W i d th U s e d to I m p r o v e
A c c u r a c y o f E le v a tio n
E r r o r E s tim a te s
Bottom Edge Ray Diffraction
Point
MDBV8102202
Figure E-5. Illustration o f Shadowing Geometry Depended1!Adjustment of Tail Fin Width for Elevation System.
-0
to
173
the top edge ray that has a stronger amplitude for a similar reason. The end results is that the
center ray, which has a zero separation angle (essentially) relative to the direct path, is
weaker than it is in reality, and the top ray, which has a non-zero separation angle, is stronger
than it is in reality. Thus, the error is over estimated.
Thus, the accuracy o f the error estimate would be expected to improve if the width
o f the rectangular plate used for the tail fin was more representative of the width o f the actual
tail fin along the horizontal line containing LOS. Such a method for respenting the tail fin
was applied, and the results obtained are shown in Figure E-6. As expected, the accuracy of
the estimate improved.
APPENDIX REFERENCES
[E-l]
Sommerfeld, A., Optics. Academic Press, Inc, New York, New York, 1954.
[E-2]
Swokowski, Earl W., Calculus with Analytical Geometry. Copyright by Prindle,
Weber, and Schmidt, Statler Office Building, 20 Providence Street, Boston,
Massachusetts, November 1980.
[E-3]
Capon, Jack, “Multipath Parameter Computation for the MLS Simulation Computer
Program,” Project Report ATC-68, Lincoln Laboratory - M.I.T., Report Number
FAA-RD-76-55, April 1976.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
MEASURED VERSUS MODELED ERROR - SDF POSITION #1
SCATTERING GEOMETRY
• Caerdiaatt R ih r u t i
0.3
O)
«
Q
^
UJ
IL
a.
c
0
W
3a
ui
Elcv.1m.11 A m e n u B o io itlil < £
Suadlfoid FUld • Foittoa H
0.5
1.5
2
2.5
3
3.5
4
4.5
D istance from T h resh o ld (nmi)
AMeasured
■ Modeled
M D B98093004
Figure E-6. Measured and Modeled PFE Magnitude Data for SDF Elevation Scattering Position #1, Modified Tail Fin.
ABSTRACT
DIBENEDETTO, MICHAEL FRANCIS, Ph.D. March 1999
Electrical Engineering
Development of Critical-area Criteria for Protecting Microwave Landing System
Azimuth and Elevation Antenna Guidance Signals (174 pp.)
Director o f Dissertation: Dr. Roger D. Radcliff
This dissertation presents the methodologies used to develop and validate
protective zoning requirements for Microwave Landing System (MLS) azimuth and
elevation guidance signals. Typically, the aviation community refers to these protective
zoning requirements as critical areas. The purpose o f defining critical areas about the
azimuth and elevation antennas is to protect the radiated guidance signals from multipath
errors caused by electromagnetic scattering o f these signals by transient vehicles and
aircraft.
A method for applying the Federal Aviation Administration MLS Mathematical
Model to characterize the guidance signal errors caused by interfering aircraft located
ahead o f the azimuth or elevation antenna is presented. This method was used to generate
error-contour plots characterizing the guidance signal errors caused along a standard
precision approach profile as a function of interfering aircraft type, location, and
orientation. Error budgets were developed, including allocations to the error permitted to
be caused by interfering aircraft. Based on these allocations, error-contour plots were
analyzed to determine the areas that bound all of the interfering aircraft locations that
have the potential to cause guidance-signal error that exceed the allocations. Methods for
adapting these criteria to protect non-standard, computed-centerline, and advanced
approach procedures are presented.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
The dissertation provides azimuth and elevation critical-area criteria for basic,
computed-centerline, and advanced MLS procedures. Also, it presents the status of
critical-area criteria development for Precision Distance Measuring Equipment. The
dissertation recommends that validation and refinement o f the criteria be performed as
indicated by operational experience.
n
Approved:.
iture o f Director
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IMAGE EVALUATION
TEST TARGET (Q A -3 )
150mm
IM /IG E . Inc
1653 East Main Street
Rochester, NY 14609 USA
Phone: 716/482-0300
Fax: 716/288-5989
0 1993. Applied Image. Inc.. All Rights Reserved
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