XV-15 litho - NASA's History Office

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Figure 40. Proprotor response to cockpit control input. 46 Flight Controls One of the more difficult technical challenges in the development of the XV-15 TRRA was the design of the flight control system. The XV-3 had revealed various degrees of flying qualities, handling qualities, and pilot work load deficiencies in nearly all flight modes. It was the job of the engineers to address these problems and produce a flight control system that could meet existing and pending handling qualities and stability and control requirements from military and Federal Aviation Administration (FAA) standards. While normal operations would be conducted by a crew of two, the XV-15 control system was designed to permit a single pilot to perform all normal and emergency procedures from either seat. The controls effort was divided into four categories: Primary Flight Controls, Secondary Flight Controls, Thrust/Power Management System, and Automatic Flight Controls. Because the tilt rotor aircraft combines the flight characteristics of a conventional helicopter and those of a fixed-wing airplane, its flight control system had to blend the basic elements of these two vehicle types. The flight deck of the TRRA was configured so that each pilot station had complete controls for pitch, roll, yaw, and thrust in all modes of flight. They consisted of control sticks, rudder pedals with brakes, and power levers (for proprotor collective pitch and engine throttle functions). A single set of airplanetype throttles, rpm governor, flap, and landing gear controls were located in the center console. Collective Lateral Cyclic Longitudinal Cyclic Directional In the helicopter mode, the controls apply collective or cyclic blade pitch changes to the rotors to produce control moments and forces. Fore and aft cyclic pitch (produced by moving the center control stick fore and aft) provides longitudinal control, and differential cyclic pitch (in response to rudder pedal motion) produces directional control. Collective pitch commanded by collective lever input is used for vertical control, and differential collective pitch, resulting from center stick
lateral input, controls roll. Figure 40 illustrates the helicopter mode control functions and the resulting proprotor forces that control aircraft motion. Conversion or reconversion can be made within a corridor having a wide range of airspeeds, conversion angles, and fuselage attitudes. While the fixed-wing control surfaces (ailerons, elevator, and rudder) remain active in all flight configurations, the rotor controls are automatically phased out in two “mixing boxes,” as the nacelles are tilted toward the airplane configuration. This system is designed so that the need for control inputs during conversion is minimized, the primary requirement being a longitudinal input to maintain attitude as the large mass of the nacelles is tilted. The phasing of the controls through conversion is smooth and not apparent to the pilot and the process effortless. In the area of automatic flight controls a stability and control augmentation system (SCAS) was incorporated in the aircraft design. It consisted of actuators which were connected to the longitudinal, lateral, and directional fixed control linkages in the fuselage. The SCAS makes automatic control inputs with these actuators to effect rate damping, control augmentation, and pitch and roll attitude retention. SCAS actuator motions are in series with the pilot’s control inputs. Force-feel system (FFS) actuators prevent SCAS actuator motions from feeding back motions or forces into the control stick or pedals. These actuators are installed in parallel to the longitudinal, lateral, and directional control linkages and are effective in all flight modes. The SCAS and FFS control laws (i.e. the equations built into the automatic control system) are hard-wired on circuit cards which can be changed to alter the control characteristics of the aircraft. This feature would later be used for tilt rotor aircraft flight controls research. Another unique and flight-critical element of the TRRA was the conversion system. This electro/hydraulic/mechanical system was designed by Bell with functional redundancies to provide fail-operate and fail-safe features. After extensive testing using production hardware, all operational and performance goals were met and the system was qualified for flight. Emergency Egress System The safety goal of the TRRA project stated that two simultaneous failures should not result in the loss of life. However, in the event of a catastrophic situation, emergency protection for the crew was to be provided with the installation of ejection seats. This was possible because the tilt rotor aircraft, unlike conventional helicopters, provides a clear crew ejection path without the need to remove the proprotor blades. The Government-furnished LW-3B seats were developed by North American Aviation (later Rockwell International) of Columbus, Ohio, for the OV-10 aircraft used by the Marines and the Air Force. These seats, termed “zero-zero” seats, were designed to be capable of ejecting a crew member and deploying the parachute for a safe landing with the aircraft in a normal attitude while on the ground and at zero airspeed. These seats were propelled out of the 47
Page 1:
The History of The XV-15 Tilt Rotor
Page 5:
Contents Prologue . . . . . . . . .
Page 9:
Dedication The story of the success
Page 13:
Foreword The development of tilt ro
Page 17 and 18:
List of Figures Figure 1 Leonardo d
Page 19 and 20:
Figure 41 Simultaneous static test
Page 21 and 22: Figure A-2 Transcendental Model 2 t
Page 23 and 24: List of Acronyms AARL Army Aeronaut
Page 25: TRENDS Tilt Rotor Engineering Datab
Page 28 and 29: Figure 2. Illustration of vertical
Page 30 and 31: Figure 4. McDonnell XV-1 compound h
Page 32 and 33: Figure 7. Henry Berliner tiltpropel
Page 34 and 35: Top: Figure 9. The Baynes Heliplane
Page 36 and 37: Figure 13. Illustration from the Ha
Page 38 and 39: Figure 17. Bob Lichten, extreme lef
Page 40 and 41: Figure 20. Tiedown tests of the XV-
Page 42 and 43: 16 Research and Engineering), obtai
Page 44 and 45: 18 management continued to show int
Page 46 and 47: 20 Building the Technology Base Aer
Page 48 and 49: Figure 25. Bell 25-ft. diameter pro
Page 50 and 51: Figure 28. Performance tests of 5-f
Page 52 and 53: Figure 31. Bell 25-ft. diameter pro
Page 54 and 55: 28 Tilt Rotor Research Aircraft Pro
Page 56 and 57: 30 During the late 1960s and early
Page 58 and 59: 32 range of loading conditions and
Page 60 and 61: 34 The initial projected cost of $4
Page 62 and 63: Figure 35. Illustration of the Boei
Page 64 and 65: Figure 36. 1/5 scale XV-15 model in
Page 66 and 67: 40 under the contract. To accomplis
Page 68 and 69: 42 Aircraft Development The primary
Page 70 and 71: 44 Test stand angle box Test stand
Page 74 and 75: Figure 41. Simultaneous static test
Page 76 and 77: 50 helicopters. For the conversion
Page 78 and 79: 52 Prior to the start of flight ope
Page 80 and 81: Figure 44. Initial Bell tiedown sho
Page 82 and 83: 56 degrees 25 and a brief assessmen
Page 84 and 85: Figure 45. XV-15 in the Ames Resear
Page 86 and 87: 60 NAVAIR managers as a means of de
Page 88 and 89: Figure 46. Government and Bell pers
Page 90 and 91: Figure 49. Tiedown test facility at
Page 92 and 93: 66 Wheel height Top: Figure 51. Met
Page 94 and 95: 68 Symmetric beam mode Antisymmetri
Page 96 and 97: Figure 55. XV-15 during short takeo
Page 98 and 99: Top: Figure 56. Flow visualization
Page 100 and 101: 74 during “degraded” flight con
Page 102 and 103: Figure 59. Hover acoustics tests du
Page 104 and 105: 78 Nose weight Top: Figure 61. Typi
Page 106 and 107: 80 Following the completion of cont
Page 108 and 109: 82 After the proprotors stopped, th
Page 110 and 111: 84 sudden stoppage of the right eng
Page 112 and 113: 86 A reconversion to the helicopter
Page 114 and 115: 88 Paris Air Show By early 1981, th
Page 116 and 117: 90 enroute from Farnborough to Fran
Page 118 and 119: Top: Figure 66. Senator Goldwater i
Page 120 and 121: Figure 69. Shipboard evaluations of
Page 122 and 123:
Figure 71. XV-15 at the New York Po
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98 Crash (October 16 and 17, 1991).
Page 126 and 127:
100 The End of an Era By the mid 19
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Top: Figure 73. XV-15 at the Dallas
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104 management system was very effe
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106 could make use of the same flig
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Figure 76. The Bell tilt rotor eagl
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110 demonstrations two years earlie
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112 Future Tilt Rotor Aircraft By t
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114 tiltrotor aircraft program. Thi
Page 142 and 143:
116 Model 1-G Characteristics Power
Page 144 and 145:
Figure A-3. Transcendental Model 2
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Figure A-4. XV-3 three-view drawing
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Figure A-5. XV-3 inboard drawing, s
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Nacelle angle (degrees) 124 120 90
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Figure A-8. General layout and majo
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Figure A-9. Side view inboard profi
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Figure A-11. XV-15 height-velocity
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132 Weight Design . . . . . . . . .
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134 WBS LEVEL: Bell Army/NASA I II
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136 US Army Air Mobility Research a
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138 Army/NASA (continued) Staff (19
Page 166 and 167:
140 Appendix C—Chronology 1452-15
Page 168 and 169:
142 1968 Boeing Vertol awarded cont
Page 170 and 171:
144 November, Initial piloted simul
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146 24 March 1982 XV-15 demonstrate
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148 30 July 1987 FAA/NASA/DOD Tilt
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150 21 August 1990 V-22 reached 340
Page 178 and 179:
152 14 June 1993 The Department of
Page 180 and 181:
154 Appendix D—Awards and Records
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Figure D-1. Jean Tinsley, first wom
Page 184 and 185:
Figure E-3. XV-15 flying by the Sta
Page 186 and 187:
Figure E-7. Bell test pilots Roy Ho
Page 188 and 189:
Figure E-11. Ken Wernicke, Bell til
Page 190 and 191:
164 Appendix F—Bibliography Tilt
Page 192 and 193:
166 Ball, J. C. “XV-15 Shipboard
Page 194 and 195:
168 Churchill, G. B.; Dugan, D. C.
Page 196 and 197:
170 Edenborough, H. K. “Investiga
Page 198 and 199:
172 Harendra, P. B.; Joglekar, M. J
Page 200 and 201:
174 Kvaternik, Raymond G. “Studie
Page 202 and 203:
176 Magee, J. P.; Pruyn, R. “Pred
Page 204 and 205:
178 Martin, Stanley, Jr.; Erb, Lee
Page 206 and 207:
180 Rutledge, Charles K.; George, A
Page 208 and 209:
182 Tischler, M. B.; Leung, J. G. M
Page 210 and 211:
184 Whitaker, H. L.; Cheng, Yi. “
Page 212 and 213:
186 Daniel C. Dugan Daniel Dugan gr
Page 214 and 215:
188 Carnet, 88 Carpenter, Ron, 91 C
Page 216 and 217:
190 Moffett Airfield, Moffett Field
Page 219 and 220:
Monographs in Aerospace History Lau
Page 222:
National Aeronautics and Space Admi
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