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Патент USA US2412647

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vec. 17, 1946.
J. K. NORTHROP ET AL
2,412,647
AIRCRAFT
Filed Aug. 8, 1944
5 Sheets-Sheet l_
JOHN K. NORTH-ROP
WlLLlAM R. SEARS
INVENTORS
8*’
‘ WW
M ATTORNEYS
Dec. 17, 1946.
J, K, NORTHROP ET AL
2,412,647
AIRCRAFT
Filed Aug. 8, 1944
FIG.?
15 Sheets-Sheet 2v
FIG. 8
5
FIG. \O
JOHN K.NORTHROP
WILLIAM R. SEARS
INVENTORS
ATTORNEYS
De?- 17, 1946-
_
J. K. NOAFIQTHROP ET Al;
'
2,412,647 I
AIRCRAFT
Filed Aug. 8, 1944
5 Sheets-Sheet 5
JOHN K.NORTHROP
WILLIAM RSEARS
INVENTORS
BY
ATTORNEYS
2,412,647
Patented Dec. 17, 1946
' UNITED ‘I STAT
Es PATENT OFFICE"
: 12,412,647
AIRCRAFT
John K. Northrop, Los Angeles, and William R.
Sears, Inglewood, Calif., assignors to Northrop
Aircraft, Inc., Hawthorne, Cali?, a corporation
of California
Application August 8, 1944, Serial No. 548,586
4 Claims.
This invention relates generally to aircraft-of
the all-winger tailless type, and more particu
larly to devices for reducing the landing speed
of such airplanes.
_
The present application is a continuation-in
part of our original application, entitled Airplane,
?led February 23, 1942, Serial No. 432,016. See
our application entitled Airplane, Serial No.
547,594, ?led August 1, 1944, which is a continua
(Cl. 244-13) .
2
improvements provided by the invention claimed
herein are applicable either in conjunction ‘with
or independently of the low longitudinal static
stability parameter referred to in theforegoing,
and a discussion of that concept will accordingly
be omitted from the ‘present application.
The present‘invention will be understood more
fully by referring to the following detailed {de
scription of an illustrative tailless airplane in
tion-in-part of said original application Serial 10 which the invention ‘has been incorporated. For
such purpose, reference is made to the accom
No. 432,016. Our said original application Serial
No. 432,016 was addressed to the broad’ problem
of reducing the landing speed of tailless air
planes. Since the elevators of such ‘airplanes
panyingdrawings, in which:
~
Fig. l is a top plan'view ‘of the military embodi
ment of our invention as set forth in the para
usually consist of control surfaces incorporated
in the trailing edge of the wing, their upward
de?ection in trimming the airplane for landing
graph just above.
by reduction in the longitudinal static stability
parameter of the airplane to an unconventionally
faces arrangement.
Fig. 2 is a front view of the airplane shownin
Fig. l.
,
Fig. 3 is‘a side view of the airplane shown in
seriously diminishes ‘the lift coefficient of the
Figs. 1 and 2, with the landing gear diagram
wing, with the result that landing speed tends to
become excessive. Our above mentioned original 20 matically indicated in extended position.
Fig. .4 is a-three-quarters front perspective view
application disclosed two means by which this
of the airplane, that is, seen from above and in
excessive landing speed may be reduced, the ?rst
front in flight attitude.
(claimed ‘in said original application) consisting
Fig. 4a, ‘is a fragmentary perspective view of a
ofa minimization of the loss of lift ‘coe?icient
modi?cation
of the control-and-stabilizingsur
resulting from necessary up-elevator de?ection
low value, and the second vconsisting in ‘the use
_
Figs. 5,6, 7, 8, 9 and lOJare diagrams showing
chord-section contours, taken ‘as indicated bylines
'of a novel combinationof landing flaps with pitch
control flaps located near or at the tipsof swept 30 tively, in Fig. 1.
For the purpose of disclosing‘the invention,~we
.back wing panels. The landing flaps increase the
have illustrated and ‘will describe the low sta
vlift coefficient of the wing, but introduce an im
bility airplane disclosed and-claimed in the afore
wanted diving moment. The pitch control flaps
mentioned originalapplication Serial No. 432,016,
are de?ected upwardly to introduce a counter
acting ‘positive moment. These latter flaps, being 35 and the continuation-impart application Serial
typically located at the tips of a sweptback wing,
have a greater moment arm than do the landing
v?aps, hence may be of lesser area than the land
No. 547,594. .It will of course ‘be understood,v
however, ‘that this is for illustrative purposes
on1y,-and that the inventionherein-claimed is ap
plicable to variousother tailless airplanes having
ing flaps, and any loss of‘ lift caused by their
use is therefore less than the gain in lift owing 40 certain essential characteristics as will appear.
The present somewhat detailed description ofan
to the landing flaps.
,
'
illustrative airplane istherefore to be understood
The present application deals particularly with
merely as descriptive of one typical airplane to
the last-described concept, and the general object
which the invention may beapplied with .proven
of the invention claimed herein may be stated as
‘advantage,
and no implied limitation thereto is
45
the provision Of a combination of flaps capable
to be inferred. With this understanding, we
of "increasing the lift coe?icient of a tailless air
proceed to a description-of the illustrative air
plane without introduction cf a substantial div
ing moment.
plane mentioned.
.
.
The airplane illustratedhas-a substantially tri
angular
planform with an angularnose I and
50
:the maximum available lift coe?icient of a tail
sweptback
.wing panels 12, the .latter preferably
.less airplane may be increased during the landing
having wing pro?les designed .‘to have substan
maneuver by use of a low static'longitudinalsta
tially zero center .ofpressure movement through
bility parameter, see our said original applica
out all normal .?ig'htiang‘les of incidence. vThis
tion-‘Serial No. 432,016, .and our said continua
.55 is illustratively and .preferably'thoughnot neces»
7
For a full discussion of the manner in which
.tion-in-partvapplication Serial No. 547,594. The
2,412,647
3
.,;..
.71. '
4
sarily, accomplished by use of substantially sym
metrical wing pro?les from root to tip, giving
substantially constant center of pressure posi
tions one-fourth of the chord length back from
the leading edge. In the illustrative airplane,
the sweptback measured along the 25% chord line
is substantially 22°, though this is subject to
and reinforced on its inner face and hinged suit
ably to a rearward semi-spar or the like.
These ?aps 6-6 are mounted and operated for
de?ection in unison, but only in arcs lying below
UK the lower surface of the wing, and for retraction
into the plane of the lower skin of the wing. The
maximum angle of de?ection of these ?aps, for
variation'depending upon various design con
siderations, as will appear. The dihedral angle,
an airplane embodying the present concepts and
design factors, is on the order of not over sub
also measured along the 25% chord line, may be .10, stantially 60°. This maximum de?ection is em
substantially 2°, and the wing panels may have an
ployed, of course, only in landing. Primarily,
aerodynamic washout of 4°, or somewhat less.
these ?aps e?ectuate an increase in the lift co
_ ye?icient of the airplane, but coincidentally they
increase the drag and deceleration, and thus act
The taper ratio in planform (ratio of root chord
to tip chord) may be in the range from 3:1 to 6:1,
being preferably and as here shown about‘ 4:1. 15 as an aerodynamic brake or decelerator to steepen
As here shown, the aspect ratio is about 7.4:1.
the angle of vertical approach.
The wing panels are tapered in both'planform
For use in takeoif, these ?aps may be de?ected
and thickness, the thickness of the root section,
downwardly, but not to such an extent as in
in percentage of chord, being about 19% in the
landing, e. g., not over about 10°, within which
present airplane, whereas the tip chord section is 20 angle they do not increase the drag detrimentally.
preferably’ of about 15% thickness. In accord
Hence, they increase the available lift coe?icient,
ance with the principles described in our said
and permit taking off a large heavy tailless air
original and continuation-impart applications,
the wing is preferably structurally designed and
plane with a short run, even over high obstacles.
of the wing forwardly of the aerodynamic center
the pitch-control ?aps 4 have been provided.
vIn either case, however, the de?ections of these
loaded to locate its center of gravity not over 25 ?aps set up unbalanced negative pitching
from .01 to .03 of the mean aerodynamic chord
moments, and in order to counteract this e?'ect,
of the wing, giving a designed longitudinal static
These pitch-control ?aps 4 are operable in the
stability parameter of from .01 to .03. As already
sense opposite to that of the de?ection of the
stated, these designed constants are given mere— 30 landing _?aps 6—'6, i. e., upwardly, whenever a
ly for the purpose of disclosing one typical air
net unbalanced pitching moment is set up by
plane to which the ‘improvements of the present
the operation of the landing ?aps. The pitch
invention may be applied. They are in no sense
to be taken as limitative on the invention.
control ?aps are primarily‘intended for opera
> tion with the landing flaps only on landing, but
they may, as indicated, be used also on the take
Each wing panel is shown asprovided with a
trailing edge elevator or “elevon” 3', located out
board of the later described propeller shaft hous
ings.
off, and in fact they may be used in cooperation
with the elevators at any time desired. For in
These elevons are so called because they
combine the functions of'elevator and aileron.
Elevons 3 when moved in opposite directions for 1
roll control operate in the manner of any ordinary
stance, they may be used for trim purposes, de
?ected either in unison or di?erentially.
Attention is directed to the fact that the ?aps
'4, being mounted at the trailing edges of the
trailing edge ailerons to control the airplane in
tip ‘ regions
of ' considerably
sweptback
wing
roll, and when moved together in the same direc
panels, lie substantially farther aft of the air
tion, operate as elevators. Linkages to accom
plane’s center of gravity than do the landing
plish such diversi?ed control are well known in 45 ?aps 6-6, and hence have a substantially longer
the art, and, per se, form no part of the present
moment arm than do the landing ?aps, so they
invention. Since elevons 3 are herein provided
can be constructed smaller in both chord and
for the dual function of elevators and ailerons,
span than the landing flaps, or with provision
elevator surfaces and aileron surfaces are iden- >_
tical and coextensive.
.
Pitch-control ?aps 4 are incorporated in the
trailing edges of the winglpanels, outboard of the
elevons, thus occupying positions on the tip por
tions of sweptback wing panels. These pitch
control flaps 4 are preferably designed for a maxi
mum upward de?ection'angle of the order of 35°
to 40°. If they are to be used additionally for
trim purposes, as they may, provision may also
be made for a downward de?ection of up to ap
proximately 10°.'
,
I
-
Yaw control of any desired type may be em
ployed, though we have here conventionally indi
cated rudders 5 located on the aft 40% of’ each
panel near the tip and understood to be extensi
ble simultaneously above and below the surface of '
the wing to produce drag and/or side force.
Occupying that portion of the span which lies
inboard of the elevons, along the trailing edge
50
for substantially smaller deflection angles, or
both, while still remaining entirely capable of
operation to produce a stalling moment equal to
any negative pitching moment resulting from use
of the landing ?aps. And being of considerably
smaller area than the landing ?aps, or used with
smaller de?ection angles, or both, their ap
propriate upward de?ection in conjunction with
any givenv downward de?ection of the landing
?aps will always leave a substantial net increase
‘in lift coef?cient. That is to say, their proper
coordinated use with the landing ?aps results
always in a net increase in lift coe?icient for
landing and take-off, while counterbalancing any
unbalanced pitching moments produced‘by the
landing ?aps.
Suitable control mechanism of any conven
tional character, unnecessary to illustrate here
in, is provided for operating the landing flaps and
pitch-control ?aps in differential amounts, but
of each wing-half, near the root thereof and,
simultaneously. The same mechanism, or same
therefore, together forming a portion of the cen 70 control, may operate both the pitch-control and
tral area of the trailing edge region of the wing,
is a pair of landing, ?aps 6—-6, preferably, though
landing ?aps, or separate but simultaneously op
not necessarily,;of the conventional hingedf‘split”
The usevof the pitch-control ?aps in coopera
tion with the landing ?aps will now be evident.
type. . ‘Thus each ?ap maybe constituted 'of apoli
tion of the lower skin of the wing, suitably braced
erable controls may of course be provided.
They are extended or de?ected with the landing
2,412,647
.
5
flaps to such de?ection angles as balance the
diving moments resulting from the extended
?aps. At such angles they of course subtract
somewhat from the lift coefficient, but in an
amount that is small as compared with the in
crease in lift coe??cient contributed by the land
6
mounted at the outer ends of said wing and
spaced rearwardly of said landing ?aps, said pitch
control surfaces being de?ectable simultaneously
with said landing ?aps and in the opposite direc
tion therefrom to produce a pitching moment
substantially equal to and opposite in sense from
the pitching moment of the landing ?aps.
ing ?aps. A substantial net increase in lift co
2. In a tailless airplane having a sweptback
e?icient, with no disturbance in moment coeffi
Wing, the combination of landing flaps hinged to
cient, is thus obtained.
Certain of the major components or features 10 the center section of said wing and forming a
part of the trailing edge thereof, said landing
of the illustrative airplane remain unmentioned,
?aps being deflectable downwardly to increase
and will now be given brief attention.
the lift and drag of the wing, elevator surfaces
Each wing panel of the airplane is provided
hinged to said wing laterally outwardly from the
with propeller shaft housings, an outboard hous
ing 1, and in inboard housing 1', terminating in 15 ends of said landing flaps, said elevator surfaces
being controllable for longitudinal control of the
geared dual rotation pusher propellers 9 and II,
airplane, and pitch control surfaces hinged to
respectively, the engines being understood to be
the outer ends of said wing and spaced rear
placed wholly within the wing section.
wardly of said landing flaps, said pitch control
Each wing panel may also carry for military
purposes an upper gun turret I2, and a lower 20 surfaces being controllable independently of said
gun turret l3. The wing also is provided with a
retractable nose wheel [4 and with dual main
elevator surfaces to produce a pitching moment
substantially equal and opposite to the pitching
moment produced by said landing ?aps.
3. In a tailless airplane having a sweptback
wheels 15 retractable into the wing section,
wheels I 4 and I5 forming, when extended, a tri
cycle landing gear. Each wing panel may be 25 wing, the combination of landing flaps hinged
to the center section of said wing and forming
provided with suitable racks for containing ex
a part of the trailing edge thereof, said landing
ternal bombs IS. The leading edge of each wing
?aps being de?ectable downwardly to increase
is shown as provided with inboard and outboard
the lift and drag of the wing, elevator surfaces
motor cooling air inlets i1 and 19, respectively.
Merging with the center section of the airplane 30 hinged to said wing laterally outwardly from the
ends of said landing flaps, said elevator surfaces
is a main cabin 2| which may conveniently
being controllable for longitudinal control of the
terminate rearwardly in a rear cannon turret 22.
airplane, and pitch control surfaces hinged to the
The cabin 2| is shown as provided with upper
outer ends of said wing and spaced rearwardly
observation window 24. In the center section
adjacent the leading edge may be a pilot en 35 of said landing ?aps, said pitch control surfaces
being controllable independently of said elevator
closure 25, as well as suitable control windows,
surfaces for simultaneous deflection with and
as indicated. Upper and lower gun turrets 30
in opposite direction to said landing ?aps where
and 3| may also be positioned ahead of cabin 2|.
As shown in Fig. 4a, the present concepts also
contemplate the substitution, if desired, for the
elevons 3 (that is, the combined elevators and
ailerons), of separate elevators 3’ and ailerons
3". In such case, the operation and functioning
by the diving moment produced by said landing
?aps is substantially counterbalanced by the stall
ing moment of said pitch control flaps.
4. In a tailless airplane having a sweptback
wing, the combination of landing ?aps hinged
of the landing ?aps are the same as hereinbefore
to the center section of said wing and forming a
described and the pitch-control flaps are located,
part of the trailing edge thereof, said landing
flaps being deflectable downwardly to increase
the lift and drag of the wing, elevator surfaces
hinged to said wing laterally outwardly from the
ends of said landing flaps, said elevator surfaces
being operable to control the longitudinal attitude
of the airplane, and pitch control surfaces hinged
operated and function in the same manner as in
the previous embodiment. The separate ailerons
produce no appreciable unbalanced pitching
moments, either positive or negative. The eleva
tors, in this case, are adapted to be operated in
unison by forward and backward swinging of the
control column and the ailerons by right or left
rotation of the wheel on the control column.
The landing flaps and the pitch-control flaps are
adapted to be operated in unison in the manner
described hereinbefore.
Having thus disclosed the inventive concepts
to the outer ends of said wing and de?ectable
simultaneously with said landing flaps in the
opposite direction thereto, said pitch control sur
faces being of smaller area than said landing
flaps but spaced appreciably further aft of the
center of gravity of the airplane than said land
ing ?aps whereby the sum of the aerodynamic
force acting on the pitch control surface times
1. In a tailless airplane having a sweptback 60 the moment arm measured from the action line
wing, the combination of landing ?aps hinged to
of that force to the center of gravity of the air
plane is substantially equal and opposite to the
the center section of said wing and forming a
sum of the greater aerodynamic force acting on
part of the trailing edge thereof, said landing flaps
being deflectable downwardly to increase the lift
the landing ?aps times the lesser moment arm
and drag of the wing, elevator surfaces hinged
measured from the action line of that force to
and two embodiments thereof, what is claimed
as new is:
to said wing laterally outwardly from the ends
of said landing ?aps, said elevator surfaces being
the center of gravity of the airplane.
operable to control the longitudinal attitude of
JOHN K. NORTHROP.
the airplane, and pitch control surfaces pivotally
WILLIAM R. SEARS.
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