Smith SD. Cockpit seat and pilot helmet vibration during flight operations on aircraft carriers. Aviat Space Environ Med 2004; 75:247–254. Introduction: Human vibration exposure data relative to military tactical and strategic aircraft operations are required for assessing the potential health risks and performance consequences when using helmet-mounted equipment. The objective of this study was to characterize cockpit seat and pilot helmet vibration in a jet aircraft during aircraft carrier flight operations. Methods: The Remote Vibration Environment Recorder (REVER) was used to measure triaxial accelerations at the seat base, seat pan, seat back, and helmet in the F/A-18C (Hornet) jet aircraft. Data were collected during flight operations on 2 aircraft carriers for a total of 11 catapult launches (CATs), 9 touch-and-goes (TGs), and 4 arrested landings (TRAPs). Helmet pitch acceleration and displacement were estimated from the helmet translational acceleration data. Results: Of particular interest was the substantial low frequency seat and helmet vibration observed during the catapult launch. During the stroke period, seat and helmet vertical (Z) accelerations reached 6 and 8 g peak-to-peak, respectively, and occurred in the frequency range of 3–3.5 Hz. The associated helmet pitch reached peak-to-peak displacements ranging between 9° and 18°. Discussion: The large helmet rotations may be associated with helmet slippage that can cause partial or complete loss of the projected image on a helmet-mounted display (HMD) (vignetting). This is highly undesirable when using the HMD as the primary flight reference. The aircraft operational vibration can be regenerated in the laboratory for investigating this specific concern. The goal is to develop helmet-mounted equipment design guidelines that consider hostile vibratory environments.
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