CFM Schiller manufactures air spring system units for ground vibration tests (GVT); the design is adapted to the customer-specific loads.
The GVT air spring system units simulate the dynamic behavior of the aircraft under flight conditions, while the plane can remain on the ground. This allows the executions of a modal analysis of the aircraft. The GVT serves to prove and validate FEM calculations of the aircraft structure. Each air spring system unit is carried out as a welded framework, which comprises a hydraulic lifting mechanism, an adapter spindle with integrated load cell, air springs, and a pneumatic level control system.
The hydraulic lifting mechanism operates at the jacking points of the aircraft and lifts it until the landing gear loses contact to the ground. During the ground vibration test, the aircraft rests on the integrated air springs. The system features two possible natural frequencies: 1.6 Hz and 0.9 Hz. The lower natural frequency is achieved by connecting additional volumes to the air spring system. The air spring system units are flexibly movable on caster wheels and can thus be positioned exactly below the aircraft’s jacking points. The hydraulic actuators with the adapter spindles carry the entire load of the aircraft during lifting and testing.