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

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power operated syetem and that of the airplane made pilot operation difficult and operation with the automatic pilot unsatiefactoxy. An analyeis of the problem indicated that the difficulty could be attributed primarily to the reaction epring rates of the sgsten. The structure of the reaction vetem had been deaignqd for strength in accordance wlth anticipated loads and not for rigidity and thus accounted for a large portion of the elasticity. The compressibility of the oil along with mansion of the power cylinder, I~~Iraulic tubing ard other components also contributed to the low overall spring rate of the qstem. Bending of a m and linkage8 in the feedback system ad entrained air in hydraulic oil were recognised as other factors involved. 1t was also found that the original ralw, although providing required gain at higher amplitudes, caused too high gain at low amplitudes resulting in instability. Other probleuw included backlaeh uxl play in the system which was attributed primarily to bearings and the movenent of the power cylillder piston "0" ring In its Nstardardm groove. Various changes to the syetem were made in an effort to improve performance. These included the design of a control valve whose gain varied as the square of valve displacement, use of close tolerance bearings ad bolte throughout, and use of more rigid feedback ad control linkages. The reaction structure was also etrengthened locally, but it was found that a large portion of the fin contributed to the spring rate. Althaugh some improvement was realited from this effort, it was apparent tMt the performance was still less than desired. Figura 3 shows the frequency response curves of amplitude ratio ad phaee of the sgstem with these inprovements. The natural frequency of the airplane upon which this control system was being used is shown by the dashed vertical line on figure 3. .It can be eeen that the pawered surface control eyetam phse lag wae 70° for 11/4 degree eurface amplitude. For smaller surface amplitude8 the phase lag increased rapidly. In this rmga of unplitndes the combined phaee lag of the control syetsm and tht of the airplane approached a value so high that mfflcient phaee lead could not be realised from m automatic pilot to keep the closed loop sgstem stable. To be on the safe side the powered control system should ham less than kS degrees phase lag, for q amplitude at which the rudder is effectiw, at a frequency 5 times that of the airplane natural frequency.
AMPLITUDE RATIO- DB I 0 I 0 I cn 0 cn 0 E l I 0 (0 O G 0 0 0 0 PHASE ANGLE 0
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-3-a'uo#Su!qs~~ MVN 3Hl 4 0 lN3WlIJ
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CONTENTS 1, Centering Charauteristi
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CENTERING CHARACTERISTICS OF POWER
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Since pilqt effort and s*face force
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The centering characteristics excep
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-mtla= etlq 30 pwdo o q m ~APA opl
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HELICOPTER POWERED CONTROL SYSTEM P
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Returning to the discussion of the
Page 25 and 26:
loaded by-pass valve closes, and fr
Page 27 and 28:
FUGET RESEARCH ON FORCE WHEEL CONTR
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precisely. The fir at demonstration
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to hare thq coakpit controle comman
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conrtsnt speed). While this ryrtem
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I I SURFACE I AIRCRAFT DYNAMICS LOA
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AUTOMATIC PUT DYNAMICS a LOAD DISTU
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FORCE ME- SERVO. \ - = AMPLIFIER =
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The configuration described above r
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AN ANALYSIS OF FULLY-POWERED AIRCRA
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"W@J@tI pendm ao poqtmeard euofenfo
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Ooeo red em;Co* ey tg areqm - a d m
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Variation of Valve Flcnr with Press
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p - instantaneons density (mare per
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where %, , %+ , fi , and A r' are p
Page 57 and 58:
The error equation (l), with XI * i
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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: FIG. 2 INSTALLATION - POWER OPERATE
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
Page 145 and 146: 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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