What happened
On March 17, 2016, an ATR42-500, registration LY-DAT, was performing a scheduled domestic flight from Esbjerg (EKEB) to Billund (EKBI) under instrument flight rules. Shortly after takeoff, at an altitude of approximately 560 feet, the aircraft's right engine suffered an uncommanded flame-out. The aircraft's systems automatically increased power to the left engine and initiated the feathering of the right propeller.
During the subsequent single-engine approach to Billund, the left engine experienced three separate compressor stall events. These stalls produced visible flames from the exhaust, which the flight crew mistakenly identified as an engine fire. Due to the high workload, the crew deviated from standard operating procedures, including a lack of proper callouts during power adjustments. Upon landing, the crew shut down the left engine and evacuated the aircraft from the runway.
The investigation
The Danish Accident Investigation Board examined the aircraft's fuel system, engine condition, and maintenance history. Investigators focused on why the right engine lost power despite the cockpit instruments indicating sufficient fuel. The investigation also scrutinized the mechanical state of the left engine and the maintenance performed on the fuel probes several months prior to the incident.
Findings
- The right engine flame-out was caused by fuel starvation resulting from an empty right fuel tank.
- The fuel quantity indication system provided inaccurate readings, showing more than 500 kg of fuel remaining when the tank was actually empty.
- The error originated from a faulty connector on the third capacitance probe in the right tank, likely introduced during a heavy maintenance check between December 2015 and February 2016.
- At the time of the maintenance, there was no explicit requirement to verify the accuracy of the fuel quantity indication system after reinstalling the probes.
- The left engine's compressor stalls were caused by significant deterioration and damage within the engine's hot section, which reduced rotor speed efficiency.
- The flight crew's perception of an engine fire was driven by the visible flames during the compressor stalls.
- The operator lacked specific procedures for managing fuel calculations and did not have established limitations for fuel quantity inaccuracies that would necessitate manual verification.