A FATIGUE TEST ON A SAILPLANE WING

Abstract

In 1976-1977 a full-scale fatigue test on a sailplane wing was carried out in the Laboratory of Light Structures of Helsinki University of Technology. The wing was of glass fibre construction, with carbon fibre reinforced wing spar caps. The fatigue test progran consisted of portions representing ground loads due to ground runs, ground- air-ground cycles in launching and landing, and gust loads due to atmospheric turbulence in ffight. Gust loads due to atmospheric turbulence were calculated by using a power spectral method according to the mission analysis criterion. The mission profile consisted of parts representing launching, circling in thermals, flight over start and finish lines, and various types of cross-country flight. In calculating the response of the aircraft to gusts, the elasticity of the aircraft was taken into account by using an unsteady aeroelastic calculation method. The fatigue testing progran covered a flight time of 4000 hours with a safety factor four. The fatigue test was divided into 40 blocks, each block representing 400 hours of flight.