Research shake test on an Airbus helicopter technology demonstrator

ifasd2024 Tracking Number 49

This abstract comprises the work of the research shake test on an AIRBUS Helicopter full scale technology demonstrator. The test on the entire helicopter was performed by the vibration test team of the DLR-Institute of Aeroelasticity within three weeks in March/April 2023 at AIRBUS Helicopters Deutschland GmbH (AHD) in Donauwörth, Germany. In addition to the shake test, a ground resonance test with the landing skid on ground was also carried out in parallel for each main test configuration. For the shake test the helicopter was soft suspended at the main rotor hub in a dedicated test rig with a pneumatic spring system (Figure 1). The existing helicopter test rig of DLR with the associated pneumatic air suspension was further developed and completely redesigned for this test. These modifications were designed to enable fast changes between different test boundary conditions, i.e. helicopter suspended for shake test and landing skid on the ground for ground resonance test. The rotor blades were removed for the test and the main rotor head was replaced by a mechanical adapter with rotor cross to introduce force and moment excitation from electro dynamic shakers installed on vibration isolation in the test rig. The purpose of the shake test was to test new methods, hardware and to provide the necessary experimental data to achieve permit to fly of the helicopter demonstrator and to adjust the numerical models of the structure. The results of the shake test therefore mainly comprise experimental modal parameters and frequency response functions for equivalent excitation on main rotor hub and on tail rotor. For the first time in such a test, the equivalent force and moments on the main rotor hub were calculated online from a real-time controller and were recorded together with the other response signals. An equivalent modal substitute model was identified from the shake test consisting of 55 unique modes. This modal model was established with a dedicated software and database which can be used for visualization and correlation of modal analysis results, but also for the analysis of scatter and nonlinear trends in modal analysis results. The paper will focus on the tools and procedures applied during the tests, whereas the test results are subject to confidentiality and cannot be presented in detail.