What happened
On 12 January 2013, an ATR 72-212A, registration F-OIQN, operated by Air Tahiti, was performing a scheduled passenger flight from Tahiti Faa’a Airport to Raiatea. During the takeoff roll, the engine number 2 showed abnormal interstage turbine temperature (ITT) and fuel flow values. Although the ITT exceeded 765 °C and torque fluctuated, the crew did not detect these anomalies and continued the takeoff.
At 500 feet, an engine oil warning appeared. As the aircraft climbed to 750 feet, an engine fire warning was triggered. The crew executed the emergency procedure, shutting down the engine and pulling the fire handle. Despite discharging both fire extinguishers, the fire remained uncontrolled, and cabin crew confirmed seeing flames. The captain declared an emergency and returned to the airport, opting to land on the runway rather than continuing a single-engine flight. After the aircraft came to a stop, the crew shut down the remaining engine and ordered an emergency evacuation. All 58 persons on board evacuated without injury, though engine number 2 sustained significant damage.
The investigation
The BEA examined the flight data recorder, cockpit voice recorder, and aircraft components. Technical examinations of engine number 2 revealed that blades on two stages of the power turbines (PT1 and PT2) had failed, causing the destruction of the turbine assembly, including shafts and bearings. This failure induced severe vibrations that compromised the lubrication system, spraying oil onto hot engine parts and igniting the fire. Investigators also found that at least one fire detection loop was in an open circuit following the incident.
Findings
- The primary cause of the fire was the failure of a power turbine blade, which led to a loss of lubrication and subsequent ignition of engine oil.
- The crew did not identify the engine parameter anomalies during the takeoff roll, partly because the operator's takeoff procedure did not specifically require a check of the ITT.
- The brevity of the ITT amber warning light during the takeoff roll contributed to the crew's failure to notice the overheating.
- The engine involved had not yet undergone the specific inspection recommended by Service Bulletin n° 21823, which aimed to identify manufacturing defects (shrinkage porosity) in certain turbine blades.