Report of the Second Piloted Aircraft Flight Control System - Acgsc.org

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The desirability of the spring force gradient was partially off-set by the need for trimming this force after changing to a new flight condition. This configuration may not be important in fixed wing aircraft, but the helicopter is more apt to be operating over a variety of flight conditions and there will be more of a tendency for the pilot to forego the trim changes and cope with the bungee force in the trimned position. This does not mean he will not camplain about the difficulty of flylns in these conditions. In fact, complaints of a trimnable bungee on the rudder pedals of the S-5s type helicopter has resulted in the developnent of a paver control for the tail rudder even though it was not considered necessary after the initial flignt tests of tne helicopter. After flight testing the first rudder servo with no feel it was evident that the rudder pedals were entirely too light and they would still be too light even at'ter 10 or 50 hours of flying with them. A pneumatic cylinder was attached to the pedal control with a bleed across the piston so that temporary centering could be obtained, but after a time the pedal force was independent of pedal position. It must be remembered that there is an appreciable difference in pedal position between climb and descent because of Wxerences in rotor torque for these conditions, which have to be compensated for by the tail rotor. The rate feel of the prleumafic cylinder invokes no objections but the temporrry position feel did. As a result, the type of feel device proposed for this control was me which consisted of centering springs across the valve of the power control so that a given rate of servo travel would be produced by a given force from the pilot. - - -. .- THE OVERALL FLIGHT CONTROL SYSm The artit'icial feel device should be integrated in fhe overall control system to aid the pilot in flying the aircraft. It supplements the pilot's vision and should. not transmit any confusing signals. In fact it is believed that the feel requirements for any aircraft may vary considerably depending upon what is required to xly that aircraft most proficiently. In the case of a helicopter, assuming that good flying qualities at hi& speed have been obtained with properly designed aeromamic surfaces, hovering stability should be approved. At the present time it is a question &ether helicopters will become big enough to afford tne added weight of a suitable auto-pilot, or whether a sufficiently light weight auto-pilot can be developed to install in the present helicopters. SikorsQ Aircraft is engaged in a program to attempt the latter. As flight tests have not been made on the initial proposal it is difficult to say whether the auto-pilot will be successful; but it is of the differential input type so that the pilot may fly with the stabilizing effect of the auto-pilot always present. The system is integrated with the existing hydraulic power control units, which makes it possible to keep weight at a minimum. Several types of feel are being considered including a type where the actual gyro signals convey, by means of a force, what the auto-pilot considers a proper way to fly a helicopter. There is certainly mamy problems connected with such a device which pending flight tests will reveal and lead to hoped-for solutions.
FUGET RESEARCH ON FORCE WHEEL CONTROL by DUNSTAN GRAHAM, Lt., USAF RICHARD C. LATHROP, Capt., USAF of Wright Air Development Center, Wright-Patterson Air Force Base, Oio In order to sccomplirh precieion flying, etatic ad dpnaaio rtability of the sirplane'fi flight path ie required. The prorlrion of tbir rtability need not intorfore with the pilot 1 r control of tho flight path. Bbroe tranrdwrr connected to the pilot's cockpit oontrolr oan be wed to biar the referencor of the rtabiliring eyetem. This romultr in easy aontrol by the pilot of fliat whioh is artificially rtabilired and coor0inated. Tho practical mccerr of Neb a war demonrtrated on the All Weathu Branah's #ore@ Wheel B-17. Qpeeiment r were made in the atateerr llke a caras natural handliag q~ulitiet~ and nonlimar force gradient configurationr. All Woathor Branohla future rerearch plan8 oom&rire experiment8 with the C+ (dercribed in anothor pcqpor), and the application of force uhwd control to other airframe antomatic control combination in an atternpt to meet spcrcific operational requirmentr.
Page 1 and 2: -3-a'uo#Su!qs~~ MVN 3Hl 4 0 lN3WlIJ
Page 3 and 4: CONTENTS 1, Centering Charauteristi
Page 5 and 6: CENTERING CHARACTERISTICS OF POWER
Page 8: Since pilqt effort and s*face force
Page 14: The centering characteristics excep
Page 18: -mtla= etlq 30 pwdo o q m ~APA opl
Page 21 and 22: HELICOPTER POWERED CONTROL SYSTEM P
Page 23 and 24: Returning to the discussion of the
Page 25: loaded by-pass valve closes, and fr
Page 29 and 30: precisely. The fir at demonstration
Page 31 and 32: to hare thq coakpit controle comman
Page 33 and 34: conrtsnt speed). While this ryrtem
Page 35 and 36: I I SURFACE I AIRCRAFT DYNAMICS LOA
Page 37 and 38: AUTOMATIC PUT DYNAMICS a LOAD DISTU
Page 39 and 40: FORCE ME- SERVO. \ - = AMPLIFIER =
Page 41 and 42: The configuration described above r
Page 43: AN ANALYSIS OF FULLY-POWERED AIRCRA
Page 46 and 47: "W@J@tI pendm ao poqtmeard euofenfo
Page 48 and 49: Ooeo red em;Co* ey tg areqm - a d m
Page 50 and 51: Variation of Valve Flcnr with Press
Page 52 and 53: p - instantaneons density (mare per
Page 54 and 55: where %, , %+ , fi , and A r' are p
Page 57 and 58: The error equation (l), with XI * i
Page 61 and 62: C C U P m ZERO - (Bulk Modulus infi
Page 63 and 64: Canparing equation (32) vith eqatio
Page 66 and 67: EFFECT OF ADDRIG A SPEUNC IllbD AT
Page 70: The outtmt 4 is then -tion (a) may
Page 74 and 75: 71 It is of interest to anmine the
Page 77 and 78:
It w ill now be shrnm that the quad
Page 79:
tp = 4 1' ( 4 include. aU flaxibill
Page 83 and 84:
Frequancy Response of Another prore
Page 85 and 86:
or, ii the pinton s p w A, in f ~ t
Page 88 and 89:
$ - BZ~W~ pfY88WC)* - presstam on e
Page 90 and 91:
INTRODUCTION PARAMETERS FOR THE DES
Page 92 and 93:
to the piston. When the spool membe
Page 94 and 95:
Figure 2 shows an oscillographlc re
Page 96:
lication of equations. - The method
Page 99 and 100:
The solution to equation (11) , is
Page 101 and 102:
I RATIO OF PEAK TRANSIENT CYLINDER
Page 103 and 104:
Equations (21) and (22) are written
Page 105 and 106:
variation of this rise time with T
Page 107 and 108:
CHART ILLUSTRATING EFFECT OF INERTI
Page 109 and 110:
pa lo=$ $8 uoy$eyQd moy pamwam $ndq
Page 111 and 112:
IMPROVEMENT OF POWER SURFACE CONTRO
Page 113 and 114:
FIG. 2 INSTALLATION - POWER OPERATE
Page 115 and 116:
AMPLITUDE RATIO- DB I 0 I 0 I cn 0
Page 117 and 118:
The overall reaotien rpring rate ir
Page 119 and 120:
FIG.5 - SCHEMATIC -- BASIC TYPE POW
Page 122 and 123:
With theae substitutions into equat
Page 124:
Although only one type of power oon
Page 127 and 128:
0 AMPLITUDE RATIO- D8 I I I I rU rU
Page 129:
In the range ai airplane natural fr
Page 132 and 133:
Figure 1. anticipation of the targe
Page 134 and 135:
The constant k helped to improve th
Page 137 and 138:
to determine if there was behaviora
Page 139 and 140:
SYNTHESIS OF FLIGHT CONTROL SYSTEMS
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The hydraulic system itself is a hi
Page 147:
P :: 7 OT- a- ' 06- 09- . I
Page 150 and 151:
Zeros introduced by resonance of th
Page 152 and 153:
explicit set of specifications-or a
Page 155:
her@ is to lnake the push-rod as st
Page 160:
particular problem. We then choose
Page 164 and 165:
changing flight corditions. Idea-,
Page 166 and 167:
A,. Area of bydraullc jack giston.
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