ACAP Crashworthiness Analysis by KRASH

The KRASH Computer Program was used to analyze the crashworthiness of the Army/Sikorsky Advanced Composite Airframe Program (ACAP) helicopter. A mathematical model of the ACAP airframe, landing gear, and crushable fuselage understructure was constructed, consisting of masses, beams, and springs. Crash impacts of this model at the two design level impact velocities and several roll and pitch angles were simulated. A typical sequence of events, including landing gear stroking, fuselage contact, and subsequent understructure crushing that occur as the crash impact energy is dissipated, is described. The results of these simulated impacts, including the maximum load factors, the landing gear honeycomb strut and fuselage understructure crushing, and the stroking of the seats are summarized. The use of the predicted load factors in subsequent NASTRAN analyses of the airframe structure is described. It was shown that the ACAP structure meets the crashworthiness requirement of maintaining living space and, with the crashworthy seats, protects the occupants from injurious headward accelerations.