Evaluation of Novel Seat Cushions to Mitigate Helicopter Aircrew Exposure to Vibration

Undesired vibration transmitted through the helicopter seats has been known to cause fatigue and discomfort to the aircrew in the short-term as well as neck strain and back pain injuries due to long-term exposure. This research study investigated the use of novel energy absorbing cushion materials integrated into helicopter seats to mitigate the aircrew whole-body exposure to high vibration levels. Replacing the cushion material on a helicopter seat was a low cost solution with less certification effort that provided a reduction in the vibration transmitted to the aircrew. Novel energy absorbing cushion material, namely, the Hybrid Air Cushioning System known as Mitigator and a viscoelastic polyurethane material known as Sorbothane, were evaluated using flight tests on the NRC Bell-412 helicopter. The test results confirmed that the aircrew vibration levels can be effectively reduced through proper optimization of the seat cushion impedance properties. In particular, integration of the Hybrid Air Cushioning System into the seat significantly reduced the 1/rev peak while marginally reducing the 4/rev peak that resulted in an overall reduction in the aircrew vibration.