HEARING DAMAGE BY COCKPIT NOISE IN MOTOR GLIDERS "From motor glider to hearing aid"

Abstract

Background: Over the past fifteen years touring motot gliders and gliders with retractable propulsion units have developed with incredible speed. More than 1/3 of the annual glider production is delivered by the manufacturers with retractable propulsion units. These glider constructions in particular are equipped with two stroke engines resulting high frequency sound emissions. Due to the requirements of the sound insulation regulations, all powered gliders are optimized to avoid sound emissions especially with regards to the anti-noise lobby living near airfields but they are not optimized to avoid noise in the cockpit. To find out the noise level in the cockpit of those powered gliders and how it affects the hearing of the pilots, the cockpit noise of 6 touring motor gliders and 8 gliders with retractable propulsion units were measured. Results: Both types of motor gliders are too loud for pilots and may become hazardous to their hearing if they are not equipped with personal noise protection. In extreme cases an exposure time of 20 seconds to the cockpit noise of a glider with retractable propulsion unit may cause permanent hearing damage. Conclusion: Pilots must be warned to not fly motor gliders without personal noise protection.