Perceived discomfort for tri-axial helicopters vibrations
* Presenting author
Vibrations are an important contributor to perceived discomfort in helicopters cabins. A test campaign was conducted in order to understand how discomfort varies for helicopter tri-axial excitations. Six experiments were conducted, which involved 30 participants. Subjects were seated on a six degree of freedom vibration table. They had to evaluate discomfort of several stimuli. The first three experiments investigated the influence of vibrations due to the blade passage frequency of the main rotor, to the tail boom modal behaviour and to a combination of these two sources. The impact of a phase shifted vibrations and of amplitude-modulated excitations were studied in a fourth and fifth experiments. Finally, the last experiment focused on real signals measured on several helicopters of Airbus fleet. Results showed that 1) vertical vibrations represent the major contributor to discomfort in helicopters; 2) for amplitude-modulated excitations, discomfort only depends on the amplitude of the modulation, not on the modulation frequency; 3) out of phase stimuli are perceived in the same way than phased stimuli; 4) helicopter frequency content above 30 Hz does not increase discomfort; 5) ISO2631-1 comfort index is a good predictor of discomfort evaluations.