Vibration Tests on the Helicopter BK117-C2

Abstract

Vibration tests were performed on a new prototype helicopter, the BK 117-C2. The tests were performed at the test laboratory of the DLR Institute of Aeroelasticity in Göttingen.The goal of the tests was to analyse the dynamic behaviour of the helicopter, to investigate the effect of different vibration absorbers, and to identify the modal parameters. During the tests the helicopter was suspended with an air spring in a special vibration test rig. Dynamic excitation forces were introduced at the rotor hub and the acceleration respones were measured at 128 structural points. In addition to the response measurements, the classical Phase Resonance Method was applied for the identification of important eigenmodes. After the termination of the tests the FRF measured during hub excitation were used for the identification of additional modes. The results are presented and discussed. The measurements of the test campaign delivered a comprehensive data base for rational selection of effective means for vibration reduction and control.