A wind-tunnel investigation of helicopter directional control in rearward flight in ground effect
Robert J. Huston, Charles E. K. Morris, United States. National Aeronautics and Space Administration, Langley Research Center
National Aeronautics and Space Administration, 1971 - Transportation - 38 pages
An investigation was conducted in the Langley full-scale tunnel to study the aerodynamics that produce directional-control problems for a helicopter with a tail rotor in low-speed rearward flight in ground effect. A helicopter model mounted close to the tunnel floor was tested in tail winds from 0 to 25 knots.
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25 knots abrupt change adverse effects adverse fin force Aerodynamic characteristics angle of attack APPENDIX basic data center of pressure cnots collective pitch required constant tail-rotor thrust cross-plotted Effect of main-rotor Figure l6 fin center flight in ground flight-test forces and moments free-stream flow diminishes ground board ground effect ground vortex high tail-rotor hysteresis increase in rearward increase in tail-rotor knots Figure Langley full-scale tunnel Langley Research Center low-speed rearward flight main-rotor lift main-rotor power required main-rotor shaft main-rotor torque main-rotor wake measurements meters feet NASA TN newton-meters foot-pounds force newtons pounds force percent produce directional-control problems rearward velocity rotor and fin rotor thrust tail rotor operates tail wind tail-rotor collective pitch tail-rotor collective-pitch settings tail-rotor thrust coefficient tail-rotor thrust required tail-rotor torque coefficient tail-rotor torque required tested in tail thrust and torque torque-balance factor U.S. Customary Units unsteadiness V/STOL vehicle torque vertical fin vortex and carries wind-tunnel investigation