High levels of vibration exist in helicopters and manufacturers are seeking to quantify vibration discomfort. They use the ISO 2631-1 standard, proposed for all types of transport. This study aimed to verify the validity of this index in the specific case of helicopters. Perception tests were carried out in the laboratory. Volunteers assessed the discomfort of vibratory stimuli on test benches generating vertical and triaxial vibrations. Foot, seat and backrest accelerations were measured for each participant according to each stimulus. The ISO 2631-1 comfort indices were then compared with the evaluations given by the participants. The results showed that the standard provided a good estimate of discomfort. However, it lacks precision in estimating the discomfort of stimuli which include amplitude modulations, as can happen in helicopters. A new discomfort index is proposed based on ISO 2631-1 and allows better prediction of subjective assessments.
Vibrations contribute to helicopter’s ride comfort. This study aimed to determine the relationship between main rotor vertical excitations and discomfort. Fifty-three participants, seated on a helicopter seat fixed to a vibration test bench, evaluated the discomfort of vertical sinusoidal vibrations using a magnitude estimation procedure. Stimuli had a frequency between 15 and 30 Hz and a level between 0.32 and 3.16 m/s2. The average discomfort was shown related to vibration velocity using Steven’s power law, without any frequency dependence. The exponent depended on velocity and was 1.18 for higher velocities (approx. above 0.008 m/s) and 0.65 for velocities below that limit.
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