Incident Overview
During an extended taxi, a single-engine airplane experienced a fire in the right brake assembly. The pilot, an airline transport pilot with 4,100 hours of flight experience, and his two passengers evacuated the aircraft without assistance. The fire was subsequently extinguished using large capacity fire extinguishers.
Engine Monitor Data
Data downloaded from the aircraft's engine monitor revealed that during the taxi, the engine operated at an average speed of 1,640 RPM. The aircraft reached speeds up to 29 mph, and data indicated that the pilot frequently reduced speed without correspondingly reducing engine RPM.
Pilot Operating Handbook Guidance
The Pilot Operating Handbook for the airplane includes the following instruction: "Taxi with minimum power needed for forward movement. Excessive braking may result in overheating or damaged brakes. Damage due to overheated brakes may result in brake system malfunction or failure."
Post-Incident Examination
An examination of both left and right brake assemblies was conducted. The O-rings on the left brake pistons were found to be soft and round in shape. In contrast, the O-rings on the right brake pistons were observed to be hard and brittle.
Probable Cause
No probable cause was stated in the source material.