What happened
On May 3, 2006, an Airbus A320, registration EC-HUK, operated by Iberia, arrived at Dublin Airport on a scheduled public transport flight from Barcelona. After the aircraft had landed, the crew attempted to start the aircraft's Honeywell 131-9A Auxiliary Power Unit (APU). While the first start attempt reached normal operating speed, the system detected an overtemperature condition, triggering an automatic shutdown.
During two subsequent attempts to restart the unit, the crew was unable to achieve stable operation, as the APU protection system terminated each sequence. During these maneuvers, air traffic control observed smoke and flames exiting the APU exhaust. The tower notified the flight crew and dispatched airport fire services. The aircraft was brought to a halt on Taxiway B3.
As emergency responders approached the aircraft from the rear, debris was noted on the taxiway. The fire, which was localized to the APU exhaust pipe, was successfully suppressed using foam. Following the confirmation of the fire, the captain ordered an emergency evacuation via the forward doors and over-wing exits. All 97 passengers and 6 crew members evacuated the aircraft safely with no injuries.
The investigation
Investigators examined the aircraft and the debris found on the taxiway. The investigation established that the fire remained contained within the APU exhaust pipe and did not spread to the rest of the aircraft. The debris recovered from the taxiway was identified as parts of the APU rear bearing assembly.
Following the incident, the APU, along with the Flight Data Recorder and Cockpit Voice Recorder, was removed for analysis. A specialized examination of the unit conducted at a facility in Germany revealed that the APU rear bearing had seized, causing significant damage to the rear bearing support assembly. The investigation also found that the central tie shaft had become grossly distorted and had disconnected from the load compressor.
Findings
- The fire was limited to the APU exhaust area and was contained by the aircraft's design.
- The primary cause of the mechanical failure was the seizure of the APU rear bearing.
- This seizure resulted in the structural disruption of the bearing support assembly and the distortion of the central tie shaft.