HIGH-PERFORMANCE UH-1 COMPOUND HELICOPTER MANEUVER FLIGHT TEST PROGRAM
BELL HELICOPTER TEXTRON INC FORT WORTH TX
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The report presents the results of flight tests conducted with the USAAVLABS-Bell High Performance Compound Helicopter to extend its flight envelope. Particularly with respect to maneuvers. Rotors with standard UH-1B and tapered tip blades were evaluated. With the tapered tip blades, the compound helicopter was flown to a true air-speed of 221 knots and the rise in power required and rotor controls load associated with compressibility was delayed by about .05 Mach number. Approximately 55 maneuvers, encompassing a velocity- normal acceleration envelope exceeding 2gs at 190 knots, were accomplished. The distribution of lift between the wing and rotor is defined and it is shown that the rotor provides the largest increase of normal load factor during the maneuver. Normal maneuver and structural limited rotor thrust coefficients are defined as a function of advance ratio and rotor propulsive force. Although rotor system dynamics, blade twist, planform, airfoil, etc., will influence these values of limiting thrust coefficients, it is believed that with proper interpretation the limits shown are generally applicable to all rotorcraft.