Digital Simulation of Flexible Aircraft Response to Symmetrical and Asymmetrical Runway Roughness

Abstract : A method has been developed for determining the dynamic response of a flexible aircraft to runway roughness during takeoff or constant speed taxi. The equations that formulate the mathematical model have been programmed for a CDC 6600 digital computer and uses a Calcomp plotter for part of the program output. Three sets of runway elevation data are input to provide a forcing function at each landing gear. Three runway profiles measured at Washington National Airport, runway 36, were used to represent a typical commercial asymmetric profile. Three lines of profile were analytically generated to represent traversing a 1-cos dip at a 45 degree angle of approach. Several aircraft have been simulated with this program, each during a takeoff and a constant speed taxi. The data used to simulate the airplanes (McDonnell Douglas C-9A, Boeing 727-100, and an AMST) and the runway profile data used, are included in the appendix of this paper. Comparison of simulated results to limited experimental data was good. Peak vertical acceleration levels at the pilot's station were within 14%. The effect of the asymmetry of a profile on pilot's station vertical acceleration was significant providing the asymmetry of the profile was significant.