Aircraft Brake Dust Dispersion (Airwash) Testing

Prior industrial hygiene research involving wheel brake changing on a light general aviation aircraft has shown negligible potential for asbestos fiber exposure to mechanics that perform such work. This is despite the use of organic-style brake friction pads that contained asbestos. It has been otherwise established that chrysotile asbestos is largely degraded to a non-crystalline, amorphous substance by the heat and mechanical shear forces inherent to the braking process. However, trace (<1.0%) quantities of chrysotile have been found in brake wear dust. Disc-style brakes, the types used on aircraft, are of open design, such that wear dust is typically dispersed into the ambient air during and after brake application. For fixed-gear aircraft, the brake assemblies are also subject to substantial air velocities while the aircraft is in flight. This research was undertaken to measure and characterize the airflows experienced by aircraft wheel assemblies during takeoff, cruise, and landing maneuvers. No wear (brake) dust was observed at any point during the study.