Document
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON. D.C. 20546 REPLY TO GP ATTN OF:
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Attentions Mias Winnie M. Morgan
PROMs GP/Office of Assistant General Counsel for
Patent Matters
SUBJECTt Announcement of NASA-Owned U . S . patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U . S . Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided?
U-S. Patent No. : 3
Government or
Corporate Employee i //t QA #/£/)/??£fit
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Source (if applicable)
NASA patent Case No. s C^\C''"fO ¥
l
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
Yes / / No / * * . /
Pursuant to Section 305(a) of the National Aeronautics and
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an invention of ..."
Elizabeth A. Carter
Enclosure
Copy of patent cited above
NASA-HQ
[in 3,711,042
United States Patent
Rempfer et al. [45j Jan. 16,1973
154] AIRCRAFT CONTROL SYSTEM 3,482,805 12/1969 Knemeyer 244/77 D 3,575,362 4/1971 Hammond 244/77 D [75] Inventors: Paul S. Rempfer, Heath, Ohio; Alan 3,182,933 5/1965 Smithetal 244/77 D J. Robertson, Topsfield; Lloyd E.
3,095,169 6/1963 Osder 244/77 D •-*!'
Stevenson, Wakefield; Joseph S.
3,521,839 7/1970 Diani 244/77 D Koziol, Jr., Newtonville, all of Mass. 3,240,447 3/1966 Olshausen 244/77 D
I
[73] Assignee: The United States of America as Primary Examiner—Milton Buchler represented by the Administrator of Assistant Examiner—Stephen G. Kunin the National Aeronautics and Space Attorney—Herbert E. Farmer and John R. Manning Administration ABSTRACT [22] Filed: July 13,1970 [57] [21] Appl. No.: 54,271 An aircraft control system, particularly suited to ro- tary wing aircraft, in which longitudinal acceleration and course rate commands are derived from a manual [52] U.S, Cl 244/77 D, 244/17.13, 318/489 control stick to control translational velocity of the [51] Int.CI B64c 13/18 aircraft along a flight path. In the collective channel [58] Field of Search 244/77 D, 3.21, 77 A, 77 E, the manual controls provide vertical velocity com- 244/17.13; 318/489 mands. In the yaw channel the manual controls pro- vide sideslip or heading rate commands at high or low [56] References Cited airspeeds, respectively. The control system is particu- larly suited for rotary wing aircraft and permits pilots UNITED STATES PATENTS to fly along prescribed flight paths in'a precise manner 3,592,417 7/1971 Simon 244/77 D with relatively low work load.
3,584,814 6/1971 Murphy 244/77 D 3,287,724 11/1966 Zupanick 244/77 D 10 Claims, 3 Drawing Figures 88 90 YAW ROTOR ACTUATOR
PATENTED JAN 161973
3.711.042
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INTEGRAL PROPORTIONAL COMPENSATION FILTER
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INVENTORS PAUL S. REMPFER ALAN J. ROBERTSON LLOYD E STEVENSON JOSEPH S. KOZIOL, JR.
BY ATTORNEY
PATENTED JAH16 1973
3,711.042
SHEET 2 OF 2
3,711,042
AIRCRAFT CONTROL SYSTEM The collective channel for the helicopter control system is similar in construction to the lateral and lon- ORIGIN OF THE INVENTION gitudinal channels except that the collective stick com- mands a vertical velocity and the channel has an al- The invention described herein was made by em- 5 titude hold capability.
ployees of the United States Government and may be The yaw channel has two modes of operation for two manufactured and used by or for the Government for different airspeeds of the aircraft. In the low speed governmental purposes without the payment of any mode, the foot pedals command a yaw rate which is royalties thereon or therefor.
compared with a measured yaw rate. An integrated rate BACKGROUND OF THE INVENTION 10 signal is compared with a heading reference signal for a heading hold capability. The resulting error signal from 1. Field of the Invention the two comparisons controls the yaw channel actua- This invention relates to the field of aircraft and is tor. In the high speed mode, the foot pedals command more particularly related to aircraft flight controls for side-slip which is compared with a filtered, measured the guidance of aircraft.
15 sideslip signal to control the yaw channel actuator. In 2. Description of the Prior Art addition, in this mode a filtered roll signal from the The general task of an aircraft pilot is to control the lateral channel is cross coupled so that coordinated translational velocity of the aircraft so that the craft turns can be made by means of the lateral control stick.
flies along a prescribed flight path. In contemporary commercial aircraft, translational velocity is controlled DESCRIPTION OF THE DRAWINGS: indirectly by the pilot. The indirect control is particu- The novel aircraft control system will be better un- larly noticeable in rotary wing aircraft, where the vehi- derstood together with its numerous objects and ad- cle is generally unstable or, at most, includes an at- vantages by reference to the following drawings in titude stabilizing control system to assist the pilot.
which like reference numerals refer to like elements Although helicopters with such stabilizing systems de- throughout the several figures.
mand a high pilot work load, their utility under visual FIG. 1 is a diagramatic presentation of the longitu- flight rules has not been hampered and they have been dinal control channel of the aircraft control system.
used successfully. It is generally agreed, however, that FIG. 2 is a diagramatic presentation of both the an advanced control system is required before the full lateral control channel and the yaw control channel operational usefulness of the helicopter will be real- 30 which includes a cross coupling input from the lateral ized.
channel.
It is, accordingly, an object of the present invention FIG. 3 is a diagramatic presentation of the collective to disclose an aircraft control system which permits a control channel of the aircraft control system.
pilot to directly control ground velocity and vertical velocity over the entire flight regime of rotary wing air- 35 DESCRIPTION OF THE PREFERRED craft.
EMBODIMENTS: It is still a further object of the present invention to The novel aircraft control system is a four axis disclose a helicopter control system which can be system. The pilot directly controls the aircraft transla- operated by the pilot to direct the helicopter along its tional acceleration with respect to the ground, course flight control path without excessive work load.
rate, rate of descent, and, at high forward speeds, It is a further object of the present invention to dis- sideslip and at low forward speeds, heading rate.
close a helicopter control system in which the input Because the control system is particularly suited to ro- devices provide a commanded rate of change of vehicle tary wing aircraft, the invention is described in an em- course, rate of change of vehicle ground velocity and - bodiment particularly adapted to helicopters.
change in vehicle vertical velocity.
FIG. 1 discloses the longitudinal control channel generally designated 10. The longitudinal channel is an SUMMARY OF THE INVENTION acceleration command channel with velocity holding The novel aircraft control system incorporates a con- capability. The manual control member operated by trol member which introduces acceleration and course the pilot is the longitudinal center stick 12. When the rate commands in the pitch and roll channels, respec- center stick 12 is displaced from its central detent posi- tively, to directly control the translational ground tion, a translational acceleration command with velocity of a rotary wing aircraft. The acceleration respect to the ground is produced. The commanded ac- commands are integrated and compared with a ground celeration is converted by integrator 14.to a com- velocity signal measured along the longitudinal axis of manded ground speed. An inertia! measuring unit 16 is the aircraft. Similarly, the course rate commands are installed in the helicopter to provide a signal represen- integrated and compared with a course signal. In both tative of the aircraft longitudinal ground speed. The in- cases an error signal is produced by the comparison, ertial measuring unit 16 may be a stable platform on and control actuators are driven by the error signal to which integrating accelerometers are positioned to guide the aircraft along the desired flight path at a sense the movement of the aircraft along the longitu- desired ground velocity. In addition to the error signal dinal axis of the airframe. The signals from integrator developed from the integrated signal, the command 14 and inertial measuring unit 16 are compared in an signal itself is applied to the control actuators directly.
algebraic summing device or comparator 18 which Both the pitch and roll control channels include at- produces an output equal to the ground speed error.
titude stabilizing devices in the form of vertical gyros gr The error signal from comparator 18 passes through a and rate gyros. Integral plus proportional compensa- compensation network 20 to a summing network 22 tion is also employed to obtain a zero steady-state er- which also has a direct acceleration input from the lon- ror. gitudinal stick 12 through path 24.
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3 4
The compensation network 20 has both integrating 48 is a course error signal which is transmitted to com- and proportional circuits which generate an incremen- pensation network 52 and a summing network 54. The tal acceleration command proportional to the error in compensation network 52, as in the longitudinal chan- ground speed and the integral of the error. This type of nel, has both proportional and integrating charac- compensation serves as a trimming input which forces 5 teristics so that an incremental course command pro- the stead-state error in ground speed toward zero. The portional to the course error and its integral is incremental acceleration command is then summed produced. Again the integrated signal serves as a with the original acceleration command at the trimming input in the system.
summing network 22 to provide a pitch attitude com- ' The incremental course command is summed with ' mand signal. the original course command transmitted by path 55 at The pitch attitude command signal is translated summing network 54. The combined signals are a roll through another summing network 26, compensation attitude command proportional to the sum and are / network 28 to the pitch actuator 30 connected to the transmitted through summing network 56, compensa- helicopter rotor or rotors 32. A vertical gyro 34 pro- j twork 58 and roll actuators 60 to the rotor 32. A t on ne vides a stabilizing signal representative of the aircraft vertical gyro 62 which also may share a number of pitch attitude and a rate gyro 36 provides a damping components, such as a gimbal system and rotor, with signal representative of the aircraft pitching rate. Filter vertical gyro 34 in FIG. 1 delivers a stabilizing signal 38 associated with the rate signal of the gyro 36 serves representative of aircraft roll attitude to unit 56 and to smooth the signal. Both of the gyroscopically produces a roll rate signal transmitted 2Q rate gyro M produced pitch attitude and pitch rate signals are through a smoothing filter 66 to network 56. The rate added at summing network 26 to the pitch attitude tude signals are algebraically added to the roll and atti command from summing network 22. The summmg command to produce a lateral error signal. The attitude network 26 is an algebraic summation device similar to , ^^ compensation network 58 error signa passes comparator 18 and the output of the network 26 is a , integrating characteristics, 2J whkh has proportiona and pitch attitude error representing the difference of the agajn to sefve as a trimmi device The cornpensated pitch^attitude command and the sensed attitude and , error signa dfives actuatQr 6Q whjch in turn through ra * _ the conventional swashplate, controls lateral cyclic The compensation provided by network 28 also has ,.
pUch Qn rotQr 32 tQ duce aircraft rol moments integrating and proportional characteristics sim.lar to ^ ^^ . ^ ^^ 30 when centef sdck 42 g in Qf network 20. Again the compensation network 28 detenl Qn c ondi to zero course rat the serves as a trimming device. ... 7 ... /" . ,. . . . .. . .
_. . . . . . . . -„ helicopter maintains the course indicated at the output K r The error signal then drives the pitch actuator 30 , . ., „., . , .. , .
e r . . . . , , , ,. ,_ . ..., of integrator 46. When the helicopter ground speed which in turn controls the helicopter rotor 32. It will be . f . ., . . . , « • • , 'j j .u . u i. -.U ... m j .u signal from mertial measuring unit 16 is equal to or understood that between the pitch actuator 30 and the 35 . . , . , , . , . . . , 1 - 1 - I . 1 1 - 1 greater than t h e preselected value which opens t h e blades of rotor 32, conventional rotor control linkage f, - . _, . . . . , . . , „„ blockin filter the lateral m including a swashplate are provided in order to vary the S "' ™™ ™<* channel 40 erate as a co rse ra e Wlth angle of attack of the rotor blades and generate an air- °P ^ " ' coinmand system * course hold ca ablllt as craft pitching moment. P y described. When the ground s eed dr s below the When the longitudinal center stick 12 is in its central 40 P °P Prelected value, the roll ax 1S or detent position corresponding to zero acceleration becomes a course deviation command system with res ect to the course held b the out ut of command, the helicopter maintains the ground speed P ? P integrator present at the output of integrator 14.
The vaw The lateral control channel, indicated generally by control channel, indicated generally by the the reference numeral 40 in the lower portion of FIG. 45 numeral 70 at the upper portion of FIG. 2, is a sideslip 2, is a course rate command system with a course hold command system with coordinated turn capability capability. In a manner similar to the longitudinal chan- whenever the helicopter airspeed is equal to or greater than a nel, the pilot commands course rate by displacing his preselected value, for example 50 feet per lateral center stick 42 from its central detent position. second, and is a heading rate command system with In contrast to the longitudinal channel, however, the 50 heading hold capability whenever the airspeed is less than tne course rate signal is transmitted to a blocking filter 44 preselected value. The switching between the two before it reaches integrator 46. The filter is controlled modes of operation is automatic, with the by the inertial measuring unit 16 and acts as a gate to ganged mode switches 72 and 74 in position as block the course rate command from passing to in- « shown in FIG. 2, the yaw channel is in the sideslip tegrator 46 whenever the indicated ground speed from command mode. The mode switches 72 and 74 are ac- unit 16 is less than a preselected speed, for example, 10 tuated to the a position above the preselected airspeed feet per second. When the ground speed is equal to or by an airspeed sensor 75. Displacement of the pilot's greater than the preselected speed, the filter 44 permits pedals 76 from the central or detent position com- the course rate command to be passed to integrator 46 mands a sideslip. The sideslip sensor 78 is an air data which converts the course rate to a course command. sensor and produces a signal representative of the air- ; The course command from integrator 46 is compared craft sideslip. A filter 80 smooths the sideslip signal, by comparator 48 with a course signal from inertial The sideslip command from pedals 76 is compared with measuring unit 50. It will.be understood that the iner- the sensed sideslip at algebraic comparator 82 which tial measuring unit 50 may share several components produces a yaw rate command proportional to sideslip with inertial measuring unit 16, particularly a stabilized error. The sideslip error is transmitted through platform, if the velocity signals are generated by an in- summing network 84, switch 74, summing network 86 tegrating accelerometer. The output of the comparator and yaw actuator 88 to the helicopter tail rotor 90.
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It will be understood that the yaw actuator 88 may be respectively. The overall rate of descent command connected in certain helicopters having tandem rotors from summing network 120 is compared with the to the tandem rotors rather than a separate tail rotor to sensed rate of descent from unit 122 at the comparator generate the yawing moment. 124. The resulting error signal from comparator 124 is The roll attitude command is also cross coupled from 5 then supplied to power actuator 126 and the helicopter the lateral channel 40 through a smoothing filter 92 rotor 32. Power actuator 126 operates through a and is added to the sideslip error at summing network swashplate on the rotor blades collectively to affect the 84. This cross coupled roll signal permits the helicopter thrust of the helicopter rotor.
to execute coordinated turns by means of the lateral When collective stick 112 is in its centered position, center stick 42 while in the sideslip mode of operation. the pilot commands a zero rate of descent and the Any sideslip command is summed with the roll com- helicopter maintains the altitude indicated by the out- ut of mand at summing network 84 to generate a yaw error P integrator 114. Therefore, the collective stick signal. commands a velocity and the collective channel is A rate gyro 94 supplies a yaw rate damping signal capable of holding altitude whenever the collective stick is in its through smoothing filter 96 to the summing unit 86 centered position.
II is seen from the above that an where the damping signal is combined with the error aircraft control signal upstream of this summing junction. system is disclosed which employs acceleration corn- It will be noted that when the pilot's pedals 76 are in mands in the longitudinal channel and course rate com- mands in the lateral the central or detent position in the sideslip mode, the channel to control the translational round sideslip error at higher forward speeds should be zero « velocity of the aircraft. The yaw channel for the most part and coordinated turns may be accom- produces sideslip commands and allows coordinated turns In u er s eed ran es and plished by means of the lateral center stick 42. PP P 8 automatically converts to a When the helicopter airspeed drops below the hanging rate command system with heading hold ca abilit in the lower s eed ran es The preselected value, the airspeed sensor 75 automatically 25 P y P g - collective changes the flight mode switches 72 and 74 from the a channel produces rate of descent commands and has to the b position converting the yaw channel 70 to a altitude hold capabilities through the full flight regime alrcra heading rate command system with heading hold capa- f '• Whlle the novel alrcraft contro1 s stem has been bility. In this mode, a displacement of the pilot's pedals y desc bed WIth 76 from the central position commands a heading rate. 30 n P^cular instruments and control The commanded heading rate is converted by Integra- mechanisms, ,t should be understood that various tor 98 to a heading command and is transmitted to modifications and substitutions can be made without ,-- . . . ,. , ... , .. departing from the spirit of the invention. The manual comparator 1 0 0 where i t i s combined with a heading , . , . . . - , . . .
• , • ,ni -n. control members employed by the pilot may be side J f f reference signal from magnetic gyro compass 102. The „ , .", .. . . . .
. ,A . ... .lu j- 35 arm controllers. If a high quality mertial measuring unit f output of comparator 100 is the incremental heading . , , , C \ • • c • • f j , , .. _,.. is employed to produce the velocity information, it may rate command proportional t o heading error. This i u j - i c t . . - i j .. . , - , , • . 7 j. also be used in place of the vertical gyro and gyro corn- L heading error is summed with the original heading rate . . ., ,. .... •. , , ,. , .„, . , .«.. pass to supply the reference attitude and reference command ,n path 101 at summing network 104 to pro- ^ information. While the inertial measuring unit v,de a yaw rate signal proportional to the sunr The ^ g stable table, a strapped- 4Q & described as includin a transmissmn of the error signal through switch 74, ^ down m wkh ra{e Qs m be used tQ summing network 86, yaw actuator 88 to rotor 90 is as , .
required angu ar fate information with the stable ta described above. . . ble, the angular rate may be derived from the gimbal When the pilot s pedals 76 are in the central position , e information It is a|so ible that a radio gource in the heading rate mode, commanding a zero heading 45 such as an instrument landing system (ILS) with rate, the helicopter maintains the heading indicated by equipment (DME), a ground based distance measuring the output of integrator 98. approach radar with uplink or an airborne approach The vertical or collective control channel is m- g . d transponders may be available radar with round base dicated generally by the reference numeral 110 ,n FIG. , to provjde the ground ve ocity amj coufse information 3. The collective control channel is a rate of descent 0 j nction with body mounted accelerometers. In 5 in con u command system with altitude hold capability. The ^ , such a case verdca gyro and gyro compass may be positioning of the collective stick 112 commands a rate , vertical velocity can uti|ized for angu ar resolutjon and of descent or velocity. The rate of descent command is i ding the accelerometers with a be obtained by b en converted by the integrator 114 to an altitude com- barometric or radar altimeter. It will, therefore, be un- mand. An altimeter 118 provides a signal representa- 55 invention has been described derstood that the present live of the actual aircraft altitude and the commanded illustration rather than limitation, by way of altitude is compared with the sensed altitude signal in What is claimed is: comparator 116. The output of comparator 116 is an i A translational acceleration control system, with incremental rate of descent command proportional to velocity holding capability, for a rotor driven VTOL altitude error. The incremental command is summed aircraft comprising: with the original rate command transmitted by path means for providing a translational acceleration 119 from the collective stick 112 at summing network command signal; 120 to provide a net rate of descent command. means for integrating the translational acceleration An inertial measuring unit 122 provides a signal command signal to produce a commanded ground representative of the actual aircraft rate of descent. speed signal; The measuring unit 122 also may share a stable table means for providing a longitudinal ground speed with the measuring units 16 and 50 in FIGS. 1 and 2 signal;
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means for combining the commanded ground speed speeds greater than a preselected speed, thus per- signal with the longitudinal ground speed signal to mitting the use of the same means for providing produce a ground speed error signal; the heading rate command signal as provides the compensating means, connected to the output of the sideslip command signal.
combining means for producing said ground speed 5. A course deviation control system for a rotor- error signal, for producing a compensated incre- driven VTOL aircraft comprising: mental ground speed error signal proportional to means for providing a course deviation command the error in ground speed and the integral of the signal; error; means for providing a course signal; means for combining the compensated ground speed means for combining the course deviation command error signal produced by said compensating means signal with the course signal to produce a roll at- with the translational acceleration command titude command signal; signal to provide a pitch attitude command signal; means for providing a roll attitude signal; means for providing a pitch attitude signal; means for providing a roll rate signal; and means for providing a pitching rate signal; and means for combining the roll attitude command means for combining the pitch attitude command signal, roll attitude signal and roll rate signal to signal with the pitch attitude signal and with the produce a control signal for controlling the lateral pitching rate signal to produce a control signal for cyclic pitch of the rotors of the VTOL aircraft to controlling the angle of attack of the rotors of the control aircraft rolling moments, said system VTOL aircraft to thereby control the aircraft further comprising means for sensing the ground pitching moment.
speed of the VTOL aircraft and means responsive 2. A course .rate control system, with a course hold to said sensing means for converting the system to capability, for a rotor-driven VTOL aircraft compris- a course rate control system when the ground ing: 25 speed exceeds a predetermined value.
means for providing a course rate command signal; 6. An aircraft collective channel system for con- means for integrating the course rate command trolling rate of descent with altitude hold capability signal to produce a course command signal; comprising: means for providing a course signal; means for providing a rate of descent command means for combining the course command signal signal; with the course signal to produce a course error means for integrating the rate of descent command signal; signal to produce an altitude command signal; compensating means connected to the output of said means for providing an altitude signal; combining means for producing a compensated in- means for combining the altitude command signal cremental course command signal proportional to with the altitude signal to produce an altitude error the course error and the integral of course error; signal; means for combining the compensated course error means for combining the altitude error signal with signal produced by said compensating means with the rate of descent command signal to produce a the course rate command signal to provide a roll net rate of descent command signal; attitude command signal; means for providing a rate of descent signal; and means for providing a roll attitude signal; means for combining the net rate of descent com- means for providing a roll rate signal; and mand signal with the rate of descent signal to con- means for combining the roll attitude command trol the aircraft.
signal, the roll attitude signal and the roll rate 7. An aircraft course rate control system with a signal to produce a control signal for controlling course hold capability comprising: the lateral cyclic pitch of the rotors of the VTOL means for providing a course rate command signal; aircraft to control the aircraft rolling moments.
means for integrating the course rate command 3. An aircraft heading rate control system with head- signal to produce a course command signal; ing hold turn capability comprising: means for providing a course signal; means for providing a heading rate command signal; means for combining the course command signal means for integrating said heading rate command with the course signal to produce a course error signal to produce a heading command signal; signal; means for providing a heading reference signal; means for combining the course error signal with the means for combining the said heading reference course rate command signal to provide a roll at- signal with the heading command signal to titude command signal; produce a heading error signal; means for providing a roll attitude signal; means for providing a yaw rate damping signal; and means for providing a roll rate signal; and means for combining said yaw rate damping signal, means for combining the roll attitude command heading error signal and heading rate command signal to control the aircraft. signal, the roll attitude signal and the roll rate signal to control the aircraft; and 4. An aircraft control system as described by claim 3 including: means for automatically blocking the course rate means for providing an airspeed signal; and command signal input to the integrating means means for automatically selecting between a heading when ground speed is less than a preselected rate command signal based system for operation at speed, thus causing the means for providing the airspeeds less than a preselected speed or a sideslip course rate command signal to behave as a means command signal based system for operation at air- for providing a course deviation command signal
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and the control system to behave as a course means for providing a yaw rate damping signal; and deviation command system with respect to the means for combining said sideslip error signal, roll course held by the integrating means.
attitude command signal from the roll axis, and 8. An aircraft course rate control system with a yaw rate damping signal to provide coordinated course hold capability comprising: 5 turn capability for controlling the aircraft.
means for providing a course rate command signal; 9. An aircraft control system as described by claim 8 means for integrating the course rate command including: signal to produce a course command signal; means for filtering the roll attitude command signal means for providing a course signal; for the purpose of smoothing prior to crossfeeding means for combining the course command signal 10 said signal from the course rate command signal with the course signal to produce a course error based system to the sideslip command signal based signal; system.
means for combining the course error signal with the 10. An aircraft control system as described by claim course rate command signal to provide a roll at- 8 including: titude command signal; IS means for providing an airspeed signal; and means for providing a roll attitude signal; means for automatically selecting between a heading means for combining the roll attitude command rate command signal based system for operation at signal, the roll attitude signal and the roll rate airspeeds less that a preselected speed or a sideslip signal to control the aircraft, said system further command signal based system for operation at air- comprising means for providing a sideslip com- 20 speeds greater than a preselected speeds, thus per- mand signal; mitting the use of the same means for providing means for providing a sideslip signal; the heading rate command signal as provides the means for combining the said sideslip command sideslip command signal.
signal and sideslip signal to produce a sideslip error signal; 25