Incident Overview
During taxi for takeoff, air traffic control notified the flight crew of a fire on the right side of the airplane. The fire had occurred earlier while the crew was using the auxiliary power unit (APU) to start a main engine. The main engine start was aborted when the APU failed to provide sufficient bleed air pressure.
Post-Incident Inspection
A subsequent inspection of the APU revealed a liberated turbine exducer blade. This blade caused an imbalance in the turbine wheel, which allowed smoke and flames to escape from the APU exhaust located atop the right wing root.
Prior Reports
Over the past five years, there have been seven service difficulty reports and four accidents or incidents associated with exducer failures in this model APU.