What happened
On May 2, 2012, an ATR-72-212A, registration B-22810, operated by China Airlines (TransAsia Airways) as flight GE515, departed Taipei Songshan Airport for Magong, Penghu. The aircraft was carrying 72 passengers and 4 crew members. During the climb, the flight crew received a primary warning, followed by an "ENG 1 FIRE" alert. The crew responded by moving the left engine throttle to flight idle and requested radar vectors for a return to Songshan Airport.
While executing the return, the crew performed engine fire extinguishing procedures, discharging two fire bottles into the left engine. During the descent and approach, the aircraft's Enhanced Ground Proximity Warning System (EGPWS) activated multiple times. The aircraft struggled to intercept the ILS localizer for Runway 10, and the crew's attempt to maneuver for terrain avoidance at low altitudes resulted in several stall warnings. Despite the turbulence and technical challenges, the aircraft landed safely at Songshan Airport with no injuries.
The investigation
The investigation focused on the mechanical failure of the engine and the subsequent flight maneuvers. Investigators examined the left engine's turbine section and analyzed the flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the sequence of EGPWS and stall warnings. The investigation also reviewed the crew's management of the emergency and the air traffic control (ATC) communications during the approach.
Findings
- The primary cause of the engine fire was a material shrinkage defect in the casting of a first-stage power turbine rotor blade. This defect led to a fatigue crack, causing the blade to fracture and break away.
- The broken blade struck other components within the turbine stage, damaging the shroud and low-pressure turbine casing.
- The resulting imbalance caused vibrations that ruptured the number 6 and 7 bearing oil lines, spraying hot oil onto the engine exhaust, which ignited the fire.
- The crew's flight management during the emergency was noted as a contributing factor; specifically, the crew did not declare an emergency or explicitly notify ATC of the engine fire, which hindered the controller's ability to plan effectively.
- The crew's execution of EGPWS Mode 2 recovery procedures—involving high pitch angles at low speeds—led to multiple stall warnings.
- The aircraft encountered moderate to severe turbulence and localized wind shear during the approach.