Development of load spectrum for full scale fatigue test of a trainer aircraft

Abstract

PZL-130 "Orlik" is a turbo-propeller engine trainer airplane, entirely designed and build in Poland. This plane is used in Polish Air Force mainly for primary training of polish military pilots. Current modernization of this airplane (which mainly consists of the engine and wings conversion) is enhanced by major change in the maintenance system. Maintenance system change program (SEWST) is carried through by EADS PZL-Okȩcie (manufacturer) and ITWL (Air Force Institute of Technology). One of the major program task is a Full Scale Fatigue Test of the airframe which will be conducted by VZLU in Czech Republic. This article will present the methodology which was used to prepare a characteristic load spectrum for this test. Following sections describe the whole process from statistical analysis of data recorded in the onboard flight recorders through strain gauge based flight load measurements to development of a fatigue load spectrum. As a result a characteristic flight load spectrum block was obtained representing equivalent 200 flight hours. This spectrum will be used in a Full Scale Fatigue Test which is designed to estimate fatigue life and critical points in the structure. After completion of all the above described steps the obtained spectrum was both statistically consistent and representative for characteristic flight program in Polish Air Force. This guaranteed that the fatigue test based on this load spectrum will estimate actual fatigue life for these aircrafts operated in Polish Air Force and determine critical points in which structural damage may occur during operation.