System Simulation in Aircraft Landing Gear and Tire Development.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
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Main gear load vs. time is predicted for an F-4E aircraft through the use of subsystem modeling and analog computation. Subsystems modeled are the aerodynamics, engine dynamics, vertical strut dynamics, fore-aft strut dynamics, tirewheel dynamics, brake dynamics, and antiskid dynamics. The problem is restricted to a landing sequence with three degrees of freedom permitted for the aircraft. Aerodynamics are based on constant coefficients of lift, drag, and pitching moment. A drag chute is also employed. Engine dynamics are based on a linear thrust vs. velocity schedule. The strut dynamics are modeled by a mass-spring-damper system. The tirewheel dynamics subsystem applies Newtons Second Law to derive the wheel slip ratio and ground-tire coefficient of friction. Brake dynamics are based on a schedule of brake torque vs. brake pressure. Antiskid dynamics model the Hytrol Mark II antiskid system. Stopping distances from simulation are compared to flight test data to verify the model. Results from the simulation agree with flight test data. A schedule of main gear load vs. velocity is proposed as an alternative to current tire testing practice. Author
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