Патент USA US2406836код для вставки
Sept. .3, 1946. w. H. T. HOLDEN 2,406,836 ELECTRIC AIR POSITION INDICATOR Filed March 24, 1944 4 Sheets-Sheet 1 b.\ l@ s JW@ ATTORNEY _ Sept 3» 1946- w. H. 'r. HOLDEN 2,406,836 ELECTRIC AIR POSITION INDICATOR , Filed March 24, 1944 4 Sheets-Sheet 2 /Nl/ENTOR W H 7.' HOLDEN www BV . 6?-6. M Arrows/Ey Selma 3, 1946. w. H. T. HQLDEN 2,406,836 ELECTRIC AIR POSITION INDICATOR Filed Marçh 24. 1944 4 Sheets-Sheet 3 / - WHT/HOLDEN BV . f? ¿î M ATTORNEY Sept. 3, 1946. w. H. T. HOLDEN 2,406,836 ELECTRIC AIR POSITION INDICÁTOR Filed March 24, 1944. 4 Sheets-Sheet 4 /Nl/ENTOR I4.’ H. I HOLDEN @6. ¿ma ATTORNEY Patented Sept. 3, 1946 2,405,836 UNITED STATES ATENT OFFICE 2,406,836 ELECTRIC AIR POSITION INDICATOR William H. T. Holden, Woodside, N. Y., assignorV to Bell Telephone Laboratories, Incorporated, . New York, N. Y., a corporation of New York Application March 24, 1944, Serial No. 527,998 I 5 Claims. 1 This invention relates to an air position indi (Cl. 235-61) 2 sufiiciently compact and of light enough weight cator for use on an aircraft for enabling the that it may be readily installed in small air pilot or the navigator to determine at any in planes. stant the latitude and longitude of his position To attain these objects apparatus has been de and the air miles which he has flown from any 5 signed in two parts, an indicator unit and a con speciiied take-oit point. More particularly the trol unit. Most modern airplanes are equipped invention is concerned with the provision of elec with an air mileage unit and with either a re trical equipment for controlling indicators which continuously indicate the aircraft position in de mote control ,earth inductor compass or re mote control magnetic compass unit. From these grees and minutes of latitude and longitude and 10 units information may be secured concerning the the air miles which have been flown. air speed and the compass course of the airplane The utility of apparatus of this character is flight for enabling a control unit to control the quite evident. On ships the problem of deter indicator unit. The indicator unit is provided mining the ship’s position at any instant is not with three indicators `which may be of the count» great due to the slow speed at which surface ing wheel type, one of which is controlled to in~ ships sail and due to the fact that such ships dicate the air miles flown, the second of which always carry a navigator as a member of the indicates the degrees and minutes of latitude of crew who has ample time to make celestial ob the instant position of the airplane, and the third servations, to do the navigational plotting that is of which indicates the degrees and minutes of necessitated from the data secured from such „ longitude cf >the instant position of the airplane. observations and to keep the necessary records of The indicator may also be provided with a pointer course and speed to enable a dead reckoning po and compass rose for indicating the true com sition `to be always known. However, aircraft and pass course of the flight. Provision is made for particularly airplanes which have high cruising enabling the latitude and longitude indicators to speeds present a_more difficult problem for solv ing navigational data to determine positions. This is particularly true of airplanes of the high ' be reset to indicate the latitude and longitude of the positions of the airplane at some known point as, for example, at the take-oiî of a flight and with means for enabling these indicators to be 30 operated in one or the other direction dependent upon whether the flight is being conducted in, tions, evasive action involves such frequent the north or south hemisphere or east or west oi changes of course and speed that a navigator a particular meridian. cannot keep an accurate log from which the dead As disclosed in one modification of the inven reckoning position may be obtained. The appa ratus which is the subject of this invention may . tion the motor-generator sets and gearing for driving the several indicators are enclosed in a be described as an automatic dead reckoning de speed type which may not have space to accom modate a navigator as a part of the crew. Fur thermore in aerial navigation under war condi casing which houses the indicators. Since this assemblage, while relatively compact, does not Apparatus has heretofore been proposed for readily permit of its mounting in the usual in producing indications of the position of an air plane and the air miles flown which may be ob 40 strument panel installed in front of the pilot, a served by the pilot but such apparatus has been simplified form of indicator unit the indicators of which may be operated by remote controls of a complicated mechanical construction, mak vice. ` ing its production slow and costly, and requiring from motor-generator sets located in the con extremely close limits of mechanical dimensions trol unit may be used and is disclosed in the modi to produce an acceptable accuracy of results. 45 ñed form of the invention. This indicator unit is It is therefore an object of the present inven suñîciently compact so that it may be mounted tion to provide apparatus electrically controlled in accordance with the air speed of an aircraft and with the true course of the flight to con in the instrument panel and occupy no greater area in such panel than do the other iiight in struments such as the altimeter or remote in tinuously indicate the latitude and longitude of 50 dicating compass. the air position of the aircraft and the air miles The control unit comprises the amplifier' and which have been flown whereby substantially relay apparatus necessary to control the motor accurate indications are made possible. and generator assemblies of the indicator unit, It is a further object of the invention to pro when installed therein or when installed in the vide air position indicating equipment which is 55 control unit, in response to the operation of the afioaeec a counting wheel type the wheels of which may be viewed through a sight opening in the face of the housing. One of these counters AMC indi air speed motor unit and the compass unit of the airplane. For a clearer understanding ofthe invention cates the air miles or total distance ñown relative to the air. A second one of the counters LC in and the mode of its operation reference may be had to the following detailed description there «en cf when read in connection with the accompany ing drawings in which: Fig. 1 shows schematically the assembly of the apparatus units involved in the present inven dicates the latitude and a third of the counters LOC4 indicates the longitude relative to the air (neglecting wind) oi the flight position of the airplane after these counters have been set at the 10 latitude and longitude of some known point, for tion; example the take-off point of the iiight. Fig. 2 is a circuit diagram showing schematical The circuit diagram of Fig. 2 shows schemati cally the manner in which apparatus embodying the modiiication _of the invention disclosed in Figs. 4 and 5 or apparatus embodying the modi iication of the invention disclosed in Figs. 5 and 6 is interconnected electrically. In this diagram the air mileage unit I is disclosed as mechanically or otherwise coupled to the master generator MG ly the assembly of the apparatus units; Fig. 3 is a vector diagram explanatory of the theoretical aspects of the invention; _ Fig. 4 showsW the apparatus and circuits of the indicator unit constituting` one modification of the invention; Fig. 5 shows the apparatus and circuits of the control unit which may be used with either modi dcation of the invention; and Y 20 Fig. 6 shows the apparatus and circuits of an indicator unit constituting a modification of the invention and control equipment therefor which andeither mechanically or electrically coupled as desired with the air miles counter AMC. Y.if ` the rotational velocity of the input to the mas ter generator is assumed tovbe wo then this rota tional velocity may be expressed in terms of air may be assembled as a part of the control unit speed as KoVt. The master generator has an out disclosed in Fig. 5. put potential En which at the angular speed wo Referring ñrst to Fig. l the several apparatus may be expressed as Kiwa. This output potential ’ units required to carry forward the invention are is impressed upon the input of the resolving unit schematically illustrated. The air mileage unit MR2 which is oriented by the compass servo CS which constitutes a part of the apparatus of an airplane is shown at l. This unit is equipped 30 through the true course angle GN whereupon out put potentials El and Ee are derived, the potential with a tachometer generator which is connected E1 having a value equal t_o_ Eq cos CN and potential by the cable 2 through the junctionbox 3 and E2 having a Value equal to lilo sin CN. cable ll to a tachometer motor which forms part The potential E1 is applied to the input of the of the motor-generator set of the indicator 5 for speed control device AMPI whose output controls the latitude motor LM to drive the latitude feed back generator FGI at an angular speed w1 corre sponding' to the angular speed _wo as modified by the resolving unit MR2. rl‘he shaft of the motor LM may drive the latitude indicator LC either mechanically or electrically as desired. 'I‘he feedback generator FGI generates a potential E’i which is equal‘to Kiwi which‘potential is applied as a íeedback potential upon the input of the driving the air rmiles indicator, or, alternatively, rfrom the junction box 3 through the cable 6 to the control unit 'i if this motor-generator set constitutes a part of the control unit as illus trated in the modified form of the invention dis closed in Fig. 6. If the airplane is equipped with a remote control earth inductor compass control unitß or so-called “flux gate” compass unit, such unit is connected by the cable 9 attached to the cable Ie, through the junction box 3 to the unit speed control device AMPI. ‘ 5 over cable t. If the airplane is equipped The potential E2 is applied to the input of the with a remote indicating compass of the so-called speed control device AMP2 whose output con “magnesyn” control type such as is indicated trols the longitude motor LOM to drivethe longi schematically at il', this compass is associated tude feedback generator FGE at an angular speed with the auxiliary control unit I2 over cable I3 which latter unit is then connected by cable I4 50 402. The rotor shaft ofy motor LOM may drive the longitude indicator LOC either mechanically or attached to cable it, through junctionbox 3 to electrically as desired. The feedback generator the control unit ‘l and to the indicator unit 5. FGE.’ generates a potential E’z equal to Kw2 which If an indicator unit of the type disclosed in Fig. is impressed upon the input of the resolving unit 6 is used then the compass control unit 8 would be connected with a remote control indicating 55 MRI which is oriented from the input shaft of the latitude counter LC either mechanically or compass on the instrument panel of the airplane. electrically as desired through the latitude angle Power for operating the electrical equipment of the air position indicator is obtained over cable I5 extending from the Zß-volt .direct current A whereupon an output potential having a value E'z cos l is derived and impressed as a feedback source and the 40G-cycle 26S-volt alternating cur 60 potential upon the input >,circuit of the speed l control device AMP?. rent supply source of the airplane. For a more detailed disclosure of the invention The air speed motor unit I is driven by an air reference will iirst be. made to Figs. 4 and-5 which motor which is responsive to the difference of pressure between the pilot and the static tubes of the airplane and in turn drives a tachometer gen erator which, being driven at a speed commen 65 disclose Vone embodiment thereof. As previously stated the air mileage unit I, whose motor. speed is 24; revolutions per minute per knot of true air speed and whose'maximum surate with the air speed, generates a potential speed corresponding .to été()v knots would be 10,800 which varies linearly with the air speed and revolutions per minute. is geared down by-a re which potential is utilized to drive a tachometer motor forming a part of the motor-generator set 70 duction gearing having a ratio of 6 to l to drive a tachometer generator at a speed'oi 1800 revo associated with the air miles indicator AMC. lutions per minute whereby the tachometer motor The indicator 5 if of the type disclosed in Fig. 4 TM, electrically associated with the air mileage comprises a housing containing three motor-gen erator sets each coupled by a suitable gear train to an indicator which maybe oi the multiple unit I over the cable 2', is also driven at a speed of 1800 revolutions per minute. In the indicator 2,406,836 ' É the motor TM through the gearing 400 having', 6 the- shaft '418 of` counter _LC should make one a speed-up ratio of ’1 to 4 drives the master gen-y erator MG at four times the speed of the motor TM or, for example, at 7200 revolutions per min ute when the motor TM is operating at a speed of Cl minute or 57,600 to l. This is secured by the 1800 revolutions per minute'. reduction gear box 4I3 which has a reduction - ` revolution for each sixty minutes of latitude. Therefore the gearV reduction required is 7200 revolutions per minute to .125 revolution per The master generator MG is a two-phase, 400 cycle induction motor functioning as an induc ratio of 3600 to 1 followed by the gears 4I6 and 4I'I which introduce a further reduction ratio of tion generator. A potential Whose amplitude is 16 to l. The input wheel of counter LC, gradu proportional to the rotational speed and whose 10 ated 0 to 59 minutes, moves continuously mak phase is substantially constant up to a speed of ing one revolution for each degree j> latitude. 6000 revolutions per minute appears across the The other wheels are advanced by decimal control phase `40| of this generator. This po Geneva movements in the usual manner to tentia1 has the same frequency as the 400-cycie, register the units and tens of the degrees of 26-volt supply AC of alternating current which 15 latitude. . Vis connected to its ñxed phase winding 402. The The shaft 4I8 of the counter is also con generator may be considered as a transformer nected t0 the input shaft of the reduction gear whose ratio is dependent on the rotational speed. box M9 the output shaft 420 of which is con The motor TM, through the gearing 400, the nected to the rotor RI of the magnetic resolver 'reduction gear box 403 ‘having a reduction ratio 20 MRI. The gear box 450 has a reduction gear of 3600 to 1, and `through the further gearing 404 ratio of 360 to 1 so that a complete revolution having a reduction ratio of 24 to 9 drives the air of the rotor RI would result should the counter miles counter AMC. The input wheel of this shaft 4I8 rotate 360 revolutions to cause the counter,` graduated 0 `to 9, moves continuously counter LC to indicate 360 degrees. The lati making one revolution for each ten nautical tude counter LC, however, reads only from 00 de miles. The other wheels are advanced by deci grees 00 minutes to 99 degrees 59 minutes and mal Geneva movements in the usual manner to readings beyond 75 degrees 30 minutes north or register the tens, hundreds, thousands and ten 75 degrees 30 minutes south are not used. There thousands of miles. Since 7200 revolutions per fore the limit switch LS is provided, which is minute ofthe shaft of generator MG corre operated by cam 42| mounted on shaft 420, to sponds to 450 knots or 7.5 nautical miles per open the circuit of motor LM and to close the minute, the input shaft should rotate at 0.75 ' circuit of alarm lamp ALM in the event the rotor revolution per minute and the total reduction RI should be rotated more than 75 degrees 30 gear ratio between the generator shaft and the minutes either side of the position in which the counter should be 9600 to!` 1. This is accom counter LC indicates 00 degrees 00 minutes. plished by the gear box 403 and the gears 404. When a night is being conducted in the The latitude counter LC is driven by a second northern hemisphere the driving gear 4I6 is motor-generator set comprising a. miniature di meshed with the gear 4I? as disclosed and the rect current motor LM of the magneto type, the counter LC will increase its reading as the flight rotor cf which is directly coupled with the rotor - proceeds northward and will decrease its read of the feedback generator FGI. This feedback ing if the flight proceeds southward towards the generator is a two-phase 40G-cycle induction equator. When the equator is crossed a reading motor functioning as a generator and has one of 00 degrees 00 minutes would be followed by a of its phase windings 405 connected in series reading of 99 degrees 59 minutes as the flight with the phase Winding 40| of the master gen proceeds into the southern hemisphere. In order, erator MG and its other phase winding 400 con therefore, that the counter may increase its read nected overY conductors V40'! and 408 ywith the ing through 00 degrees 01 minute, etc., means winding of potentiometer P3 associated with the is provided whereby the navigator or pilot may `input side of the amplifier circuit AMPI of Fig. reverse the rotation of the counter as the flight 5. The feed back generator FGI is identical with 50 crosses the equator.- This means comprises a the master generator MG and serves to hold the pair of connected gears 422 and 423 of the same speed of motor LM, the armature vcircuit of which pitch diameter as the driving gear 4I0, mounted is connected over conductors 409 and 4I0 with on an idler shaft and so positioned that the gear the output side of amplifier circuit AMIPl, to a 422 is normally in mesh with gear 4I'I and that value such that the output of the feedback gen 55 the gear 423 may be meshed with gear 4I0. To erator ‘FGI , is equal to the output of the master reverse the direction of rotation of the counter generator as modified by the magnetic resolver shaft 4I8 the driving gear 4I6 is moved along MR2. A flywheel 4II is mounted on the rotor the driving shaft 4I5 by the control knob 42'4 out shaft of motor LM Vbetween the rotor of the mo of mesh with gear 4I? and into mesh with the tor and the rotor of the generator FGI to delay 60 reversing gear 423. At the same time a shutter speed changes. NS (see Fig. l) in the face of the indicator unit The rotor shaft of motor LM is also connected 5 changes from N to S. In place of the reversthrough a ñexible coupling 4 I 2 to the input shaft ing gears a switch could be employed for con of the reduction gear box M3, the iiexible cou trolling the electrical reversal of the motor LM. pling reducing the rotational shock to the re The control knob 424 has three positions, the duction gear box. The output shaft of the gear right position being for northward flight, the box 4I3 is connected through bevel gears 4I4 left position being for southward iiight and the having a unity ratio, with a shaft 4 I 5 upon which intermediate position being such that the driving the pinion 4I0 is slidable. This pinion in the gear 450 is entirely out of mesh with either the position disclosed meshes with gear 4I‘I which is gear 4I? or the reversing gear 423. In this po mounted on the driving shaft BIB of the latitude sition the reset gear 425 may be meshed with counter LC. When the master generator MG is gear 4I‘I by the operation of the reset knob 426 rotating at a‘speed of 7200 revolutions per minute to permit the setting of .the counter LC as at a or 450 knots on„a true course north -correspond-. dennite fix or landmark the latitude of which is ing to 7.5 minutes of latitude per minute of time, known. ' ‘ 2,406,836: 7 motor-generator set comprising a miniature di rect current motor LoM of the magneto type, the rotor of which is directly coupled with the r'otor of the feedback generator FGZ. 8 and 443 and the knob 444. It is~ assumed that the. right ’positionof knob 444 is `dis-closed as that in which driving gear 436 is in mesh with The longitude counter LOC is driven by a third Ul gear 431 for driving the counter for a flight in the easternhemisphereì that'the'mid-position of the phase windings 421 connected in series with the phase winding 43I of the master generator MG and its other phase winding 428 connected in knob is the position vin'which gear '436 is out of mesh with both gears '431 and 443 and in which position the reset knob '446 may be operated to mesh gear 445 with gear 431 to permit the set ting- of the counter LOC as at a definite iiX or series with the winding of rotor RI of the mag netic resolver MRI. The feedback generator FGZ that the >left position ‘of :knob 444 is .that in which generatorïis a two-phase 40G-cycle induction ino tor functioning as a generator and has one rof its landmark the longitude of which is known, and driving gear 436 is in mesh with reversing gear 443 for driving the counter in theV direction for a night in the western hemisphere. A shutter EW located .in the face of the indicator unit 5 (sce Fig. l.) changes from E to W when the knob 444 is moved to the left. In place of the revers ing 'gears' a switch could be employed for control equal to the output of thev master generator as modified by the magnetic resolver MRI. A 20 ling the electrical reversal ofthe motor LOM. Also located in the indicator unit 5 is a syn fiywheel 43I is mounted on the rotor shaft of ahrc-receiver SR having a Y-type stator the motor LOM between the rotorrof the motor and three windings of l.which are connected over con the rotor of the generator FG2 to delay speed ductors 441, -448 and 449 with the similar wind changes. ings of the stator of a synchro-transmitter (not The rotor shaft of motor LUM is also connected shown) but driven by the remote 'control earth through a flexible coupling 432 to the input shaft inductor compass unit 8. The rotor R3 of the of the reduction gear bo'x 433, the flexible cou synchro-receiver is mounted on the shaft 439 pling reducing the rotational shock to the reduc which moves the compass needle of the compass tion gear box. The output shaft of the gear box is connected through bevel gears 434 having a 30 C and which also moves the rotor R2 of the mag netic resolver MR2. The winding of the rotor unity ratio with a shaft 435 'ur-'on' which the R3 is conneoted over conductors 449 and 450 with pinion 433 is slid'able. This pinion in the posi the rotor winding of the synchro-transmitter tion disclosed meshes with gear 43'! which is driven by the unit 8 and with the Source AC of mounted on the driving shaft 43E of the longi is identical with the master generatorr MG and serves to hold the speed of motor LoM, the ar mature circuit of which is connected over oon ductors 429 and 430 with the output side of am pliñer circuit AMP‘Z of Fig». 5, to a value 'such f that the output of the feedback generator is tude counter LQC. When the master generator MG is rotating at a speed of ’1290 revolutions per minute or 450 knots on a true course correspond ing to '7.5 minutes of longitude per minute of time, the shaft 433 of counter LoCshould re volve four times as fast as the shaft 4I8 of the latitude counter LC since the rate of change of longitude may be four times vas great as the rate or change of latitude. Therefore the gear reduction required is ’1200 revolutions per minute to .599 revolution per minute or 14,400. This is secured by the reduction gear boX 433 which has a reduction ratio of 3600 to l followed by the 400 cycles alternating current. If the airplane is equìpped'with a remote' cori trol magnetic compass òf the sci-'called “mag nesyn” type as disclosed at II in Fig. 1 driven from the auxiliary compass control unit I2è then the synchro-receiver SR would also be of the “magne'syn” type. ’ Í The horizontal stator winding 443 of the mag netic resolver MR2 is cor'inectedI in series with the winding of> potentiometer P2 over conduc tors 45I and 452 and the vertical stator winding 44| is connected in series with the winding of potentiometer Pl over conductors 454 and 453. The Winding' of rotor R2 of this magnetic resolver is connected in series with» the winding 451| of the «motion> ratio of 4 to L vThe input wheel of colui-ter LOC., graduated (l to 59 minutes, moves 50 master generator MG so that a potential Eo‘ is applied across the winding of the' rotor which continuously making one revolution for each de varies with the air speed of the flight and, since gree of longitude. The other wheels are ad the rotor winding is oriented in accordance with vanced by decimal Geneva movements in the the true compass bearing angle CN of the flight, usual manner to register the units, tens and hun a potential is> derived from the horizontal wind dreds of the degrees of longitude. ing 440 of this resolver which has a value En When a flight is being conducted in the east sin CN anda potential is derived from the ver ern hemisphere the driving gear 43S is meshed gears ¿ist and 431 which introduce a further re with the gear 431 as disclosed and the counter LoC Will increase its reading as the ñight pro tical winding 44| which has a value Eo cos CN. The magnetic resolver MRI previously-referred ceeds eastward and will decrease its reading if 60 to, the rotor RI of which is driven 'from the shaft 4 I ß of the latitude counter LC, has its rotor wind the flight proceeds _westwardly~ This counter may ing energized by potential impressed thereon read 000 degreesv 00 minutes to 999 degrees 59 minutes but the maximum useful range is, of course, 060 degrees 00 minutes toA 180 degrees (l0 from the stator winding 428 of the 'feedback the flight proceeds into the Western hemisphere. former is bridged across the winding of poten In order therefore that the counter may increase tiometer P4. generator FGZ and has two windings of its Y minutes east or west. When the reference me 65 connected stator connected by conductors 454 and 455 with the primary winding' of trans ridian is crossed a reading 000 degrees 00 minutes formcr TI, the> secondary winding of which trans would be followed by 999 degrees 59 minutes as its reading through 00o degrees ol minute, etc., 70 means is provided whereby the navigator or pilotV may reverse the rotation of the counter as the flight crosses the reference meridian, This r¿leans is similar to that associated with the latitude . Potentials impressed upon the windings of po tentiometers PI and P3 are added and impressed upont'he primary winding of input transformer T2 of amplifier circuit AMPI over a circuit which mayl ire-traced from the lower terminal of the counter and comprises the reversing gears 442 75 primary winding of transfonner T2, over the 2,406,836 brush and the upper portion of the winding of potentiometer P3, over the brush and upper por tion of the winding of potentiometer PI to the upper terminal of the primary winding of trans former TZ. Similarly the potentials impressed upon the windings of potentiometers P2 and P3 are added and impressed upon the primary wind ing of input transformer TIZ of ampliñer circuit AMP2 over a circuit which may be traced from from bus-bar 504 through resistances 5I0 and 520 to the right grids of tubes VTI and VTI I. Potential from the 26-volt, 40o-cycle source AC is also supplied to the primary winding of step up transformer T3 which steps up the potential to 200 volts. The mid-point of the secondary winding of switching control transformer T3 is connected to the battery bus-bar 504, one end terminal is connected through resistance-s to the the lower terminal of the primary winding of 10 cathode of the left unit of the rectifier tube VTZ transformer TI2 over the brush and upper por and to the anode of the right unit of rectifier tion of the winding of potentiometer P4 and over tube VT3 and the other end terminal is connected the brush and upper portion of the winding of through resistances to the anode of the right unit potentiometer P2 to the upper terminal ofthe of rectiiier tube VT2 and to the cathode of the primary winding of transformer TI2. The po 15 left unit of rectifier tube VTS. A potential of tentiometers PI to P4 may be of the screwdriver 200 volts is similarly applied through the switch-V adjustable type to secure suitable adjustments of ing control transformer TIS to the cathodes and the feedback and signal potentials and to take anodes of tubes VTI2 and VTI 3. up any variations in the ratio of the transform Relays ARI, ARZ, ARM and ARIZ are prefer ers T2 and TIZ to the generators FGI and FG2. 20 ably of the high speed, glass sealed, merctu‘y con The amplifiers AMPI and AMP2 may be of the tact reed type disclosed in the application of C, E. type disclosed in the application of R. W. Ketch Pollard, Serial No. 487,999, ñled May 22, 1943. ledge, Serial No. 473,083, filed January 21, 1943. In case the output power from the air mileage The potential impressed upon the primary unit I is not sufficient to drive the tachometer winding of the'input transformer T2 of ampliñer 25 generator Which in turn drives the tachometer circuit AMPi is amplified by the dual ampliñer motor TM, output power from the unit I may be tube VTI and under the control of the dual diode applied over conductor 450 through resistance tubes VT2 and VT3 serving as full Wave rectiiiers 52! to the control grid of the dual rectiiier tube the output from tube VTI is applied to the grids VTI:` which in response to the signal ampliñes of the dual triode tube VT4 to operate one or 30 such signal to operate the anode relay ARS which the other of the relays ARI or ARE which control in turn applies power from the battery bus-bar the application of direct current from the source B` to the rotor circuit of the direct current mo tor LM. The potential impressed upon the pri mary winding of input transformer TI 2 of the amplifier AMP2 is ampliñed by the dual ampliiier tube VTII and under the control of the dual `diode tubes VTIZ and VTI3 serving as full wave rectiñers the output from tube VTI I is applied to the grids of the dual triode tube VTI@ to oper ate one or the other of the relays ARE I or ARAB which control the application of direct current from the source B to the rotor circuit of the di rect current motor LOM. Potential from the source AC of 26-volt 400 cycle is stepped up to 250 volts by the transformer T4, is rectified by the dual diode tube VT5 and the rectified current is ñltered by the ñlter cir cuit F and applied as a Z50-volt direct current 50d over conductor 451 to the unit I to drive the motor therein which in turn drives a tachometer generator to furnish the power for driving the tachometer motor TM. Anode potential is sup plied to the tube VTS from the Z50-volt bus-bar ñûû‘through the winding of anode relay ARS, cathode potential is supplied from the battery bus bar 504 and grid potential is supplied from the ground bus-bar 500 through resistance 522. In order that the air position indicator may be made sufficiently compact to be mounted in an instrument mounting space on the usual in strument panel of an airplane, an indicator of 45 the type disclosed at 5’ in Fig. 6 is provided. This indicator includes two two-directional stepping devices of the type STP shown schematically to the right of the indicator -and a single directional stepping device. One of the two-directional potential to the anode bus-bar 500. From this 50 stepping devices is capable of advancing the pointer of the latitude minutes indicator LCm bus-bar anode potential is applied through the in either direction of rotation and to rotate the windings of relays ARI and AR2 to the anodcs input shaft of the latitude degrees counter LCd of tube VT4, through the windings of relays ARI I one revolution for each degree of latitude. The and ARI 2 to the anodes of tube VTM, through other wheel of this counter is advanced by a deci -resistance 50i and resistances '502 and 503 in mal Geneva movement in the usual manner. series to the anodes of tube VTI and through re The other of the two-directional stepping devices sistance 5I I and resistances 5I2 and 5i3 in series is capable of advancing the pointer of the longi to the anodes of tube VTII. Filament heating tude indicator LoCM in either direction of rota current is supplied from the direct current source tion and to rotate the input shaft of the longi B, over the 26-volt bus-bar 504 through resist tude degrees counter LoCd one revolution for each ance 505 and the filaments of tubes VTS, VTZ degree of longitude. The other Wheels of this and VTI in series to the ground bus-bar 506, from counter are advanced yby decimal Geneva move bus-bar 504 through resistance 5I5 and the lila ments in the usual manner. The single direc ments of tube VTí‘ä, VTI 2 and VTII in series. 65 tional stepping device drives the input shaft of to the ground bus-bar 505 and from the bus-bar the air- miles counter AMC the input wheel of 504 through the filaments of tubes VTM, VT4, which makes one revolution for each ten nautical VT6 and VT5 in series to the ground bus-bar 50B. miles and the other wheels of which are advanced Potential from the battery bus-bar 504 is also by decimal Geneva movements in the usual man applied through the grid biasing resistances 501 70 ner. and 5I'I in parallel with the secondary windings of input transformers T2 and TIZ to the input grids of tubes VTI and VTI I, respectively, from bus-bar 504 through resistances 508, 509, 5I8 and 5I|9 to the cathodes of tubes VTI and VTII and> The indicator is provided with a reset knob E20 'for resetting the latitude counter and a reset knob 646 for resetting the longitude counter to indicate the latitude and longitude of a point the latitude and longitude of which are known. A aeoasae ' ~ 11 switch-button t2# is also provided for reversing the connection of the control conductors E22 and 623 to the windings of the stepping device which controls the latitude minutes indicator 12 'l5-I5 with the upper contact GHS associated there withponce during each revolution of the output shaft of the gear box 613 when the output shaft is rotated by the motor LlVI' in one direction, for examplefwhen a flight is being conducted LCm and the latitude degrees counter LC‘d so northerly in the northern `hemisphere and to that they may be operated in the reverse direc engage the spring Giâ with the lower contact E ll tion when a flight is being conducted `in the associated therewith once during each revolution southern. hemisphere and a similar button 646 is of the output shaft of the gear box 653 when provided for reversing the connection of the con trol conductors 5&2 and 5&3 to the windings of 10 the output shaft is rotated'by the motor LM’ in the opposite direction, for example, when a flight the stepping device which controls the longitude is being conducted southerly in the northern minutes indicator LoCm and the longitude de hemisphere. The engagement of spring 5 i5' with grees counter LoCd. contact SI5 completes a circuit over conductor Three motor-generator sets for controlling the air position indicator are provided, these sets .15 622 for one stepping magnet of the stepping device (not shown) which controls the latitude corresponding in general to the similar sets dis minutes indicator LCm and the latitude degrees closed in Fig. Ll. They, however, are installed counter LCd, and the engagement ofV spring 665 in an rassemblì-f separated from the indicator. with contact @il completes a circuit over con The motor-generator assembly for operating the air miles counter AMC of the indicator comprises 20 ductor 523 for the other stepping magnet of such stepping device. ' a motor TM’ which, through gearing EN! The motor-generator set for controlling the having a speed-up ratio of l to 4, drives the stepping device associated with the longitude master generator MG’ at four times the speed minutes indicator LoCm and the longitude de of the motor TM’ or, for example, at 729i) revo- lutions per minute when the motor TM’ is oper ating at a speed of 1800 revolutions per minute. The master generator MG’ is a two-phase, 400 cycle induction motor functioning as an induc grees counter LoCd comprises a split ñeld series across the control phase 60| of this generator and has the same frequency as the Li90-cycle, ZfS-volt supply AC of alternating current which is con nected to its iixed phase winding 6&2. The gen erator may be considered as a transformer, whose ratio is dependent on the rotational speed. The motor TM' through the gearing 5E!! and the re duction gear box 6&3 having a reduction gear ratio of i440 to i, rotates the cam '5&4 which once connected to the source AC of 40G-cycle current and its other phase winding 628 connected across the Winding of rotor RI ' of the magnetic resolver MRM’. One brush of motor LOM’ is connected over battery bus-bar 564 to the positive terminal of battery B` and the other brush of the motor connected direct current motor' LOM’ coupled directly with the rotor of the feedback generator FGQ’. This feedback generator is a two-phase, 40G-cycle induction motor functioning as a gen tion generator. A potential whose amplitude is proportional to the rotational speed appears 30 erator and has one of its phase windings 621 per revolution establishes a circuit over conduc- ~ is connected through the two field windings 63! and 632, respectively and over conductors §29 and 430 with the armatures of relays ARH and ARIZ located in the output side of the amplifier circuit AMPZ of Fig. 5. The rotor shaft of motor tor 52! and through the winding of the stepping LOM’ is also connected to the input shaft of the magnet (not shown) which advances the input reduction gear box 633 which has a reduction shaft of the air miles counter AMC. gear ration of 360 to 1 and on whose output shaft The motor-generator set for controlling the stepping device associated with the latitude min 45 the’cam 634 is mounted. Cam 634 is arranged to engage the spring 635 with the upper contact 636 utes indicator I_«Cm and latitude degrees counter associated therewith once during each revolution L-Cd comprises a split field series-connected direct of the output shaft of the gear box 533 when current motor LM' coupled directly with the the output shaft is rotated by the motor LOM’ rotor of the feedback generator FG! '. This feed back generator is a two-phase, 40G-cycle induc .50 in one direction, for example, when a night is being conducted easterly of a reference meridian tion motor functioning as a generator and has one and to engage the spring 635 with the lower con of its phase windings 535 connected to the source tact 531 associated therewith once during each AC of 40G-cycle current and its other phase wind revolution of the output shaft of gear box 633 ing 69d connected over conductors 401 and £08 with the winding of the potentiometer P3 asso A55 when the output shaft is rotated by the motor LOM’ in the opposite direction, for example when ciated with the input side of the amplifier .unit a flight is being conducted westerly in the east AMP! of Fig. 5. One brush of the motor LM’ ern hemisphere. The engagement of spring 635 is connected over battery bus-bar 504 to the posi with contact B35 completes a circuit over con tive terminal of battery B and the other brush of the motor is connected through the two field 60 ductor 642 for one stepping magnet of the step ping device (not shown) which controls the lon windings (5i i and 6 i2, respectively, and over con gitude minutes indicator LoCm and the longitude ductors ¿its and ¿Iii with the armatures of relays degrees counter LoCd and the engagement of AR! and ARZ located in the output side of the spring 635 with contact B31 completes a circuit amplifier circuit AMPI of Fig. 5. In this con nection it is to be noted that when the amplifier 65 over conductor E43 for the other stepping magnet of such stepping device. Y circuits of Fig. 5 are used with the modified The master generator MG' and the two feed form of apparatus disclosed in Fig. 6, the front »back generators FGI' and FGZ’ are enclosed in contacts of relays ARI, ARE, ARI l and ARIZ are a common housing 650 which closely embraces connected to ground and the back contacts are them whereby they are all similariy subjected left unconnected. ` to the same magnetic influences. The rotor shaft of motor LM’ is also connected Since a synchro-receiver such as is shown at to the input shaft of the reduction gear box SIS SR in Fig. 4 may not have sufñcient torque to on the output shaft of which cam 6M is mounted. operate a magnetic resolver, vsuch as MR2 also The gear box @i3 has a reduction ratio of 1440 to 4, a compass servo device indi 1. The cam 6M is arranged to engage spring` 75 shown in 2,408,836 13 14 cated by the box CS in Fig. 6, may be provided which may in the well-known manner be con openings in the face of the indicator unit 5. It will also be assumed that previous to the con trolled by a synchro-transformer coupled with templated night the airplane has been flown a synchro-generator driven by either a mag netic or earth inductor type compass control. The compass servo in turn `drives the synchro miles counter AMC. It will be assumed that a night is made in transmitter which is coupled with the synchro the direction indicated by the line FA in Fig. 3 15,865 nautical air miles as indicated by the air receiver associated with the course indicator CI. with a true compass course of CN degrees and at rI‘his course indicator is mounted on the instru such a true air speed that the distance traversed ment panel of the airplane. The compass servo 10 at the time an observation is to be made, may be also rotates the rotor R2’ of the magnetic re indicated by the vector FA. The latitude distance solver MR2’. component FB of the vector FA is therefore FA The horizontal stator winding 64B of the mag cos CN and the distance BA or p along the latitude netic resolver IWRZ’ is connected in series with parallel through the point A is therefore FA sin the winding of potentiometer P2 in Fig. 6 over 15 CN. The air speed is measured by the air mileage conductors 45| and 452 and the vertical stator winding'GiH is connected in series with the wind ing of potentiometer PI over conductors 45| and 453. The winding of the rotor R2’ of this magnetic resolver is connected in series with 20 the winding 60| of the master generator MG' so that a potential E0 is applied across the Winding of the rotor which varies with the air speed of the night and since the rotor winding is oriented. by the compass servo CS in accordance with the 25 true compass bearing angle CN of the night, a potential is derived from the horizontal winding B455 of this resolver which has a value of E0 sin CN and a potential is derived from the vertical wind ing 64| which has a value Eo cos CN. The magnetic resolver MRI', previously re unit | which operates the tachometer motor TM to drive the master generator MG at an angular velocity wo commensurate with the air speed or wo=KuV¢ where the true airspeed is expressed as Vt. As the night progresses from the point of take-olf F along the vector direction FA, the air miles counter AMC is driven through the reduc tion gear box 403 and the reduction gears 464 to >add the nautical air miles which the airplane nies to the record on the counter at the point of take oiî. The pilot noting the reading of the counter at any time and by subtracting therefrom the initial reading may ascertain the number of air miles 30 ferred to, has a rotor RI ’ which is rotated by the flown. ’ « Y If desired the counter AMC could be provided with a means for disconnecting the counter from its connection with the reduction gear box 493 and with means for resetting the counter to zero, similar to the means associated with the latitude two-directional stepper STP under the control of contacts operated by a cam (not shown) on the input shaft of the latitude degrees counter 35 counter LC, so that the air miles flown on any LCd of the air position indicator 5’. The wind night could be ascertained directly from the ing of this rotor is energized by potential im counter without the necessity of making a cal pressed thereon from the stator winding €523 or". the feedback generator FGZ’. Two windings of culation. ‘I‘he generator MG in operating generates a .its Y-connected stator are connected across the 40 potential in the circuit extending through the input of the amplifier AMP?, which in the well vertical stator winding 40|, the vertical stator windings of feedback generators FGI and FGZ known manner serves to amplify the output po tential of the magnetic resolver MRl’ and to and the winding of rotor R2 of the magnetic apply such amplified potential across the primary winding of transformer Tl of Fig. 5, the sec ondary winding of which transformer is bridged speed. across the winding of potentiometer P4. receiver SR in response to the true compass bear resolver MR2 which is a measure of the air Since the rotor R2 of the magnetic re solver is angularly positioned by the synchro The output potential from the stator winding ing of the night as determined by the flux gate SEI of the master generator MG’ is also impressed compass unit 8 or the auxiliary compass control across the input side of amplifier AMPA which in 50 unit I2, the rotor winding will assume a position the well-known manner serves to amplify this with respect to the stator windings of the mag potential and to apply such amplified potential netic resolver commensurate with the true course across the primary windings of transformers T3 angle CN (no compensation being made for the and T|3 of Fig. 5. eifect of wind). Since the potential impressed The apparatus employed in embodying the in 55 upon the rotor winding is in accordance with the vention having now been described, the manner air speed Vt of the night in the vector direction in which the apparatus functions and particu FA, which may be expressed KlwozEo, the po larly the apparatus disclosed in Figs. 4 and 5 will tential derived from the stator winding 44|, which nrst be described. It wil be assumed that the airplane in which the air position indicator isA 60 installed starts a flight from a position of 00 degrees 00 minutes latitude and 095 degrees 30 minutes longitude in the eastern hemisphere and that the flight is to proceed in the easter-n and northern hemispheres. The pilot knows the lati 65 tude and longitude of the position of take-off and therefore sets the latitude and longitude counters LC and LOC by the operation of the reset knobs 426 and 448 in the manner previously described so that they indicate this position as disclosed in 70 Fig. 4. He also sets the knobs 424 and 444 so that the counters will be operated in the proper direction for the contemplated night, the posi tion in which the knobs are set appearing as N and E on the shutters as viewed through the v75 may be identified as E1, may be expressed as E1=E0 cos CN and the potential derived from the stator winding 440, which may be identified as Ez, may be expressed as E2=Eo sin CN. If now the vector FA of Fig. 3 be considered the dis tance vector of the flight it may be expressed as having a potential Eat. Then the distance vector FB of the night position A will be FB=L=E1t=E0t cos CN or L=Eot cos CN and the vector BA or p of the night position A will be p=E2t=Eot sin CN. The potential from the stator Winding 44D, having the value E1 or En cos CN, is impressed across the winding of potentiometer PI and a potential derived therefrom is impressed through the transformer T2 upon the input circuit of amplifier tube VTI, is amplined by such tube and is impressed through condenser 521 and thence .2,406,836 .16 tiometer P13, lower than the signal potential through resistances 528 and 5729 in series to the v whereupon the ampl-iiìer AllEPI‘v/ill again func upper grid of tube VT4 and in a parallel path through resistances 530 and 524 to the lower grid of tube VT4. The output of tube VTI is shunted by two bridge circuits. The dual diode tube VT2 together with the two halves of the secondary winding of transformer '1T-_3 form one bridge and the dual diode tube VTS and the two halves of tion to operate relay ARE to again establish the circuit of the motor Ll l. The motor LM will again bring generator FGQ up to a speed atwhich the feedback potential applied across the wind„ ing of potentiometer P3 again balances the signal potential Eo cos CN. In this manner the motor attains a substantially constant speed at which the secondary winding of transformer vT3 .form the other bridge. The imnedances of vthese 10 the :feedback generator FGI has an output poten tial, herein designated E’r, which equalsthe po~ bridges are controlled by the 40G-.cycle current of _a reference phase obtained through thewind te tial Eo cos CN. Since the motor LM drives the tude counter LC as previously described, the counter will be advanced at such a speed w1 that The impedance of the ñrst bridge is connected between the junction of «resistances 52,8 and 52e 1.5 after the time t required `for the airplane to ily from the point F’ to the point A or a latitude dis and the mid-point of the secondary Winding of tance Erb or Eef; cos Cn, it will indicate in degrees transformer T3 which is connected through the and minutes the latitude distance L of the posi iilanient battery B to ground. The impedance of tion A of the airplane. the second bridge is connected between the junc It is a well-known rule of geography that the tion of resistances 530 and 524 and the midfpoint ing of transformer T3 from the source AC. ' of the secondary winding of transformer `T3 and the potential drops' due to the incoming sig nal current in these impedances are applied to the unser and lower gridsrespectively of tube VT4. Due to the noline of the diodes VTZ and VTS of. the. bridges, the bridges are conducting on change in longitude equivalent to a given depar turev varies in accordance with the secant of the average latitude. The basis for this'ass'ertion will be apparent from the following discussion con no ‘en alternate half cycles Of the reference frequency. sidered in connection with the diagram of Fig. 3. It will be assumed that the longitude of point A with respect to point F is to be determined. BA .and FE’are similar arcs of two circles and are ' proportional to the radii of the circles. There During the non-conducting half cycles the signal potential drop in either bridge is very small com 30 fore, if BA be designated p and FE be `designated llc or the longitude of the point A, then pared with the value during the conducting half cycles, When the ñrst bridge is conducting the L e signal on the upper grid of tube VT4 will be either positive or negative depending on whether the signal is in phase or phase opposition to the ref erence frequency. VIn other words the grid re ceives either the positive or the negative pulses of the signal depending on the phase of the sig nal with respect to the reference frequency. Sim ilarly, when the second bridge is conducting, that is,2 during, the alternate half cycles of the refer ence frequency, the lower grid of tube VT4 re Now the latitude of the point A is the angle BOF which is equal to the angle AOE», but angle vA0E is equal >to the angle OAC of the right angle triangle OAC. If now the angle OAC be desig nated A we have in the triangle OAC AC r AC=A0 cos À or cos À-ÃÖ-E (2) Substituting Equation 2 in Equation 1 we have ceives either the negative or the positive signal pulses according to the phase of the signal. p=Lo cos À or LQ= _p__ or Lor-.p sec À (3) cos )\ `If it be assumed that the incoming signal and the reference frequency are so phased that the A is the latitude angle so it follows that loWCl‘ unit of tube VT4 becomes conducting relay AR? operates in a circuit from battery on the bus Lo or Lo=p sec L bar .599 through the winding of relay ARZ, over 50 the anode-cathode path through the lower unit In the circuits under discussion the value of p of tube VT4, to the positive side of the ñlament in terms of potential is determined by the poten battery and thence to the ground bus-bar 506. tial derived frorn the horizontal stator winding lïtelaj.7 upon operating establishes a circuit for of the magnetic resolver MR2 and has a value asn sumed to be E2 or Eo sin CN and therefore the po 55 through resistance 5245, over the front contact of ~ tential value of p may be expressed Eo sin CN. The the motor LM which may be traced from battery B relay ARZ, `Cimductor ¿m9, through the rotor circuit of motor LM, over the normal contacts of limit switch LFS, conductor 4Ill, and over the back contact of relay ARI to the ground terminal of battery B. potential value of the latitude L has already been determined as E’r or Eo cos CN where E’1 is the output potential of the feedback generator FGI when such generator is operating at a speed w1 Motor LM is thus operated to drive Y 60 such as to satisfy the latitude vector L. As a the _feed back generator FGI. consequence the rotor RI has been positioned through the latitude angle A. Therefore in terms the generator FG! is running at such a speed that of potential and considering the output potential the potential output from its stator winding 40B 6.5 of the feedback generator FG2 to be E’z when yliyirlffror applied across the winding of potenti such generator is operating at a- speed such as to ometer P3 balances the signal potential E1 or En satisfy the longitude Vector Lo, Equation 3 may cos CN applied from the vertical stator winding be Written in terms of potential as ft'lI of the magnetic resolver MR2 across the wind E() Sin CN ing of potentiometer P i, at which time the ampli ' ~ The motor LM will quickly pick up speed until fier AMP-I will receive no vsignal potential and _re- ‘ lay ARÈ will cease operating to open the circuit ci in otor LM. (4) Referring now to Figs.V 4 and 5, potential from The motor will then tend to slow clown whereupon the generator FGI Will apply a tbe stator winding 411D having the value E12 or Eo feedback potential across the winding of poten tiometer P2 and a potential derived therefrom is sin CN is impressed across the winding of poten 17 2,406,836` impressed through the transformer TI2 upon the input side of amplifier tube VTI I, is amplified by 18 such potential E’2 across the rotor winding of the magnetic resolver MRI. It will be recalled that suchtube and is impressed through condenser 531 and thence through resistances 538 and 539 in the rotor R1 of this magnetic resolver is rotated in response to the operation of the latitude mo series upon the upper grid of tube VTM and in a tor LM. The angle through which the rotor RI parallel path through resistances 540 and 534 is turned is then equal to the angle subtended upon the lower grid of tube VTM. It will be as by the arc of latitude as appears by reference to sumed that the incoming signal potential for a Fig. 3 in which the angle of latitude is designated flight toward the east is in phase with the poten as li; Consequently, a potential is derived from tial impressed upon the left portion of the sec 10 the stator windings of the magnetic resolver MRI ondary winding of transformer TIS but out of which has a value E’2 cos A. This potential is phase with the potential impressed upon the right then impressed from the stator windings of mag portion of the secondary winding of such trans netic resolver MRI, over conductors 454- and 455 former. upon the primary winding of transformer TI , the The output of tube VTII is shunted by' two 15 secondary winding of which transformer is con bridge circuits, the dual diode tube VTI 2 together with the two halves of thesecondary winding of transformer T53 form one bridge and the dual nected in series with the winding of potentiome ter P4. Thus a potential equal to E’z cos A is impressed upon the winding of potentiometer P4 which is opposite in phase to the potential equal diode tube VTI3 and the two halves of the sec ondary winding of transformer TI3 form the 20 to Eo sin CN impressed upon the winding of po other bridge. The impedances of these bridges tentiometer P2. These potentials tend to balance are controlled by the 40G-cycle current of a ref each other and when the feedback generator erence phase obtained through the windings of . FG2 reaches a speed such that its output poten transformer TI 3 from the source AC'. tial E’z is of such a value that E’s cos >`=Eo sin CN The impedance of the first bridge is connected then the amplifier circuit AMPZ receives no input potential and relay ARI2 releases to open the between the junction of resistances 538 and '539 circuit of motor LoM. and the mid-point of the secondary winding of Motor LOM will then tend to slow down where transformer TI3 which is connected through the filament battery B to ground. The impedance of upon the generator FGZ will apply a feedback the second bridge is connected between the junc- » potential across the winding of potentiometer P4 lower than the signal potential Et sin CN Where tion of resistances 540 and 534 and the mid-point upon the amplifier AMPZ will again function to of the secondary winding of transformer TI3 and operate relay ARI2 to again establish the circuit the potential drops due to the incoming signal of motor LoM. The motor LOM will again bring currents in these impedances are applied to the upper and lower grids, respectively, of tube VTM. - the generator FG?. up to a speed at which the feedback potential applied across the winding of Due to the poling of the diodes VTIZ and VTI3 potentiometer P4 again balances the signal po of the bridges, the bridges are conducting on al tential Eo sin CN. In this manner the motor ternate half cycles of the reference frequency. attains a substantially constant speed at which During the non-conducting half cycles the signal the feedback potential 12’2 cos A is generated. potential drop in either bridge is very small com Since the motor LoM also drives the longitude pared with the value during the conducting half counter LoC as previously described, the counter cycles. When the first bridge is conducting the will be advanced at such a speed that after the `signal on the upper grid of tube VTM will be time t required for the airplane to fly from the either positive or negative depending on whether the signal is in phase or in phase opposition to 45 point F to the point A or a longitude distance the reference frequency. In other words the grid receives either the positive or the negative pulses of the signal depending on the phase of the signal with respect to the reference frequency. Simi or the longitude distance Lo, it will indicate in larly, when the second bridge is conducting, that 50 degrees and minutes the longitude of the position is, during the alternate half cycles of the refer A of the airplane. ence frequency, the lower grid of tube VTM re The modiñed form of air position indicator dis ceives either the negative or the positive signal closed in Figs. 5 and 6 functions in substantially impulses according to the phase of the signal. the same manner as the indicator just described. If it be assumed that the incoming signal and 55 The chief difference between the two indicators the reference frequency are so phased that the is ‘that the air miles, latitude and longitude counters of the air position indicator disclosed in lower unit of tube VTM becomes conducting, re Fig. 6 are remotely controlled from the motor lay ARIZ operates in a circuit from battery over generator sets by stepping impulses transmitted the bus-bar 50B, through the winding of relay ARI2, over the anode-cathode path through the 60 to the indicator whereby it becomes possible to locate the indicator on the instrument panel and lower unit of tube VTM, to the positive side of the to locate the motor-generator sets in any conven filament battery and thence to the ground bus-bar ient place in the airplane. While in the form of 505. 1Relay ARIZ upon operating establishes a the invention disclosed in Fig. 6 split field series circuit for the“ motor LoM which may be traced from battery B through resistance 536 over the 65 connected direct current generators have been indicated it will be evident that magneto type front contact of relay ARI2, conductor 43B, generators such as are disclosed in Fig. 4 could through the rotor circuit of motor LOM, over con be` used. ductor 429 and the back contact of relay ARII to It is also to be noted that the horizontal stator the ground terminal of battery B. Motor LOM is thus operated to drive the feedback generator 70 windings 685 and 621 of the feedback generators FGI' and FGZ’ are energized from the 400-cycle FGZ The motor LoM quickly picks up speed where source AC rather than from the potential derived from the stator windings of the master generator upon Vthe generator FG2 develops an output potential E’z in its stator winding 428 propor as disclosed in Fig. 4. In this modification, how tional to the air speed potential Eb and applies 75 ever, a potential generated by the master gen 2,406,836 19 erator MG', which varies in accordance with the ' air speed is made effective to determine that the feedback generators FGI? and FGZ’ shall gen erate the same potential as the master generator 20 the sine and cosine of the course angle, means controlled by said cosine potential for operating said latitude indicator, a magnetic resolver hav ing a rotatable rotor Winding rotatable by said when they run at the same speed as the master latter means for deriving a potential which generator by the application’of the output po tential from the master generator, through the amplifier AMPÁ’., to the speed control amplifier circuits AlVlIPi and AMP2 through the windings of the switching control transformers T3 and TIS. What is claimed is: varies in accordance with the cosine of the lati l. In an air position indicator for an aircraft, an indicator for indicating the instant number of tude angle, and means controll'edjointly by said latter potential and by said sine potential for op erating said longitude indicator. 4. In an air position indicator for an aircraft, an indicator for indicating the instant number of air miles fiown, and indicator for indicating the instant longitude position of said aircraft, an in dicator for indicating the instant longitude posi-v air miles ijoyvn, an indicator for indicating the instant latitude position of said aircraft, anindi 157 tion of said aircraft," means for operating said first` indicatorfin accordance with the air speed cator for indicating the instant longitude posi- Y tion of said aircraft, means" for operating said first` indicator in accordance with the air speed of the aircraft, means for generating a potential commensurate with the air speed of said air craft, means controlled in accordance with the true compass course of the flight for deriving of said aircraft, means for generating a potential commensurate witlrthe air speed of said air craft, means controlled in accordance with the true compass course of th'e flight for'resolving said potential into potentials which vary with the sine and cosine of the true course angle, a motor for driving said latitude indicator, a feedback generator driven thereby, a speed control de values of said potential which vary in accordance with the sine and cosine lof, the course angle, means controlled by said cosine potential for op 25 vice responsive to the output potential of said generator and to the cosine component of said erating said latitude indicator, means controlled air speed potentialfor causing said motor to drive . by said latter means for generating a potential said latitude indicator to continuously indicate which varies in accordance with the cosine of the the latitude position of said aircraft, a motor for latitude angle, and means controlled jointly by -said latter potential and by said sine potentialA 30 Vdriving said longitude indicator, a feedback gen erator driven by said latter motor, a magnetic for operating said longitude indicator. resolver having a rotor Winding >energizable by 2. In an air position indicator for an aircraft, the output potential from said latter generator an'indicator for indicating the instant number and rotatable by said first motor for deriving a of air miles flown, an indicator for indicating the potential from the output potential of said latter instant latitude position of said aircraft, an in generator Which varies in accordance with the dicator for indicating th'e instant longitude posi cosine of the latitude angle, and a second speed tion of said aircraft, means for operating- said control device responsive to said latter potential first indicator in accordance with the air speed and to the sine component of said air speed po of said aircraft, means for generating a potential tential for causing said latter motor to drive said commensurate with the air speed of said aircraft, 40 longitude indicator to continuously indicate the means controlled in accordance With the true longitude position’of said aircraft. compass »course of the flight for resolving said 5. In an air position indicator'for an aircraft, potential into potentials which vary with the an indicator kfor indicating the instant number Sine. and cosine of the true compass angle, a mo of air miles flown, an indicator for indicating the tor for driving said latitude indicator, a feed 45 instant latitude position of said aircraft, an in back generator driven thereby, a speed control dicator for indicating the instant longitude posi device responsive to the output potential of said generator and to the cosine component of said air speed potential for causing said motor to drive said latitude indicator to continuously indi cate the latitude position ofl said aircraft, a mo tor for driving said longitude indicator, a feed back generator driven by said latter motor, means operable by said first motor for deriving a poten tial from the output potential of said second gen erator which varies in accordance with the cosine of the angle of latitude, and a speed control de vice responsive to said derived potential and to the sine component of said air speed potential tion of said aircraft, means'for operating said first indicator in accordance with the air speed 50.. of said aircraft, means for generating a potential commensurateV with the air Vspeed of said air craft, means controlled in accordance with the true compass course of the flight for resolving said potential into potentials which vary with the sine and cosine of the true course angle, a mo tor for driving said latitude indicator, a feedback generator driven thereby, a thermionic speed control circuit responsive to the feedback poten tial of said generator and to the cosine compo for causing said latter motor to drive said longi 60 nent of said air speed potential for causing said . motor to drive said latitude indicator to contin tude indicator to continuously indicate the lon uously indicate the latitude position of said air gitude position of said aircraft. craft, a motor> for driving; said longitude indi 3. In an air position indicator for an aircraft, cator, a feedback generator driven by said latter an indicator for indicating the instant number motor, means operative by said iirst motor for of air miles ñovïn, an indicator for indicating the deriving a potential from the output> potential of instant latitude position of said aircraft, an in said second> generator which varies in accordance dicator for indicating the instant longitude posi with the angle of latitude, anda second thermi tion of said aircraft, means for operating said onic speed control circuit responsive to said de first indicator in accordance with the air speed rived potential and to the sine component of said of said aircraft, means for generating a potential air speed potential for causing said latter motor commensurate with the air speed of said air to drive said longitude indicator to Vcontinuously craft, means operative in accordance with the indicate the longitude position of said aircraft. true flight course of the iiight for deriving values WILLIAM H. T. HOLDEN. of said potential which varf,r in accordance with'