Evaluation of Aircrew Whole-Body Vibration and Mitigation Solutions for Helicopter Flight Engineers

Flight testing has been performed on a Bell-205 helicopter to investigate aircrew whole-body vibration (WBV) exposure levels on a rag and tube Flight Engineer (FE) seat in accordance with ISO2631 and MIL-STD1472 standards. Results show that the helicopter cabin vibration is dominated by the N/rev harmonics of the two-bladed main rotor speed. The aircrew WBV levels vary significantly depending on the flight conditions; the highest WBV levels occur at high speed level flight conditions. With reference to the ISO2631 and MIL-STD-1472 guidelines, the aircrew WBV exposure level on the standard FE seat in the entire tested flight profile is qualitatively rated as "uncomfortable". Limiting the maximum duration of such missions to 1 hour would ensure compliance with the limit of ISO2631 vibration health and risk guideline "Caution Zone". It is also noted that the use of gunner seat insert cushion for combat missions can lead to a significant increase in the aircrew WBV levels. However, the use of selected carry-on cushion pads can provide an effective WBV mitigation to the aircrew in the majority of flight conditions. Further occupant WBV tests on a human rated mechanical shaker table also verified that selected carryon seat cushion pads are also effective in the mitigation of occupant WBV levels on the Bell-412 helicopter.