XV-15 litho - NASA's History Office

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44 Test stand angle box Test stand low-speed gearbox Figure 39. Bell test apparatus used for transmission qualification testing. Torque converter XV-15 Center gearbox XV-15 Main transmission Extensive qualification test operations were then conducted on the Bell transmission test rig illustrated in figure 39. This apparatus placed the transmission elements in a continuous drive linkage that simulated the engine-input and the proprotor drive-output shafts flight loads. The test apparatus drive system was assembled so that a prescribed torque was applied to the XV-15 TRRA transmission which was then operated for a specified number of hours at a selected RPM. During these qualification tests a range of torque levels and RPM’s was applied to the left and right main transmissions, the engine coupling gearboxes, and the center gearbox. Over the next two years the qualification test program revealed problems that required modification of gear designs, gear and shaft welding processes, bearing designs, and lubrication and cooling arrangements. The transmission ground tests also included an evaluation and calibration of the output torque sensing system which was to provide the input to the torque indicator on the instrument panel. This sensing system consisted of concentric cylindrical shafts affixed to each other at one end. The inside shaft transmitted the torque while the outside shaft remained unloaded. The torque was measured by determining the magnitude of the deflection of the loaded (inside) shaft and comparing it to the undeflected, un-torqued (outside) shaft. This torque sensing device, however, did not provide output data of sufficient accuracy for a primary flight instrument. After considerable effort to correct the problem, Bell suggested a rather unusual approach. This was to make an exception to a standing XV-15 TRRA Project Office and Bell policy and allow the use of research instrumentation system data for primary flight instrument data. The Project Office agreed and the transmission output torque indication in the cockpit was now to be obtained from research instrumentation strain gages mounted on the proprotor drive shaft (called the proprotor mast). The research instrumented proprotor mast had a calibration resolution of two to three percent, sufficient for the management of the aircraft. Despite concerns by Bell and Government engineers about the reliability and durability of this instrumentation-based torque indication system, it served the XV-15 well during many years of flight operations. Fuel Cells Hydraulic drive Proprotor mast Test stand high-speed gearbox Torque converter During the formulation of the TRRA Program Plan, a prime focus of many discussions among members of the Government Project Office was the need
to build “safety” into the design. In the 1960s, the Army and civil rotorcraft operators were experiencing loss of life and property due to post-crash fires. Studies that examined the statistics from these crashes showed that injuries and fatalities were significantly reduced when rupture and tear resistant fuel cells were installed. The fuel cells, basically flexible rubberized fabric bladders that held the fuel, were less likely to burst and release fuel upon impact with the ground than rigid metal tanks or fuel-containing wing structures that did not include the bladders. By the early 1970s, the use of fuel cells, in particular in Army helicopters, had dramatically reduced the incidence of postcrash, fuel-fed fires. The original Bell Model 300 design (predecessor to the XV-15) incorporated a “wet wing,” which used the volume within the wing to hold the fuel. While crashworthy fuel bladders would significantly increase the cost and weight of the fuel system and would reduce the available fuel volume by about five percent, the potential safety benefits were believed to be high enough to accept penalties, and the fuel cells were made part of the XV-15 design. Bell then contracted with Uniroyal Inc., of Mishawaka, Indiana, the manufacturers of fuel cells for Army helicopters and Air Force fixed-wing fighters, to fabricate the cells for the XV-15 TRRA. With no background in the design of fuel cells for a research aircraft, a method for the selection of the thickness of the rubberized fabric (i.e. the number of the rubberized fabric laminates used in the bladder material) had to be defined. Thinner fabric would be lighter and easier to install in the wing (through small openings in the aft wing spar) but it would be more susceptible to impact damage than the thicker-wall material. To resolve the issue, a standard test was conducted at the Uniroyal facility on December 3, 1974. Two test bladders, in the shape of cubes measuring three feet on each side were fabricated, one with a light gage material and one with a thick wall material. The bladders were filled with water and dropped from a height of 65 feet onto a concrete surface. The lighter-gage material bladder ruptured on impact, while the thicker-walled bladder material did not. This not-so-scientific method, along with the previously qualified seam and fitting designs and validation of acceptable tear and puncture material characteristics, provided the basis for the qualification of the thicker-wall fuel cells for use in the XV-15. In addition to the fuel bladders intended to provide fuel containment in the event of damage to the wing structure, the interconnecting fuel lines between adjoining cells (there are two cells in each wing) were provided with breakaway fittings which sealed in fuel when the lines were broken on impact. The fuel system, like all other critical XV-15 TRRA systems, was designed with adequate redundancies (such as dual fuel pumps with the capability to feed both engines) so that a single failure would not result in the requirement to terminate the flight. 45
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 72 and 73: Figure 40. Proprotor response to co
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
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Figure 71. XV-15 at the New York Po
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98 Crash (October 16 and 17, 1991).
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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
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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
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140 Appendix C—Chronology 1452-15
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142 1968 Boeing Vertol awarded cont
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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
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152 14 June 1993 The Department of
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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
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Figure E-7. Bell test pilots Roy Ho
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Figure E-11. Ken Wernicke, Bell til
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164 Appendix F—Bibliography Tilt
Page 192 and 193:
166 Ball, J. C. “XV-15 Shipboard
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168 Churchill, G. B.; Dugan, D. C.
Page 196 and 197:
170 Edenborough, H. K. “Investiga
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172 Harendra, P. B.; Joglekar, M. J
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174 Kvaternik, Raymond G. “Studie
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176 Magee, J. P.; Pruyn, R. “Pred
Page 204 and 205:
178 Martin, Stanley, Jr.; Erb, Lee
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180 Rutledge, Charles K.; George, A
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182 Tischler, M. B.; Leung, J. G. M
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184 Whitaker, H. L.; Cheng, Yi. “
Page 212 and 213:
186 Daniel C. Dugan Daniel Dugan gr
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188 Carnet, 88 Carpenter, Ron, 91 C
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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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