What happened
On 12 December 2011, a Xi’ An MA60, registration PK-MZG, operated by PT. Merpati Nusantara Airlines, experienced an engine fire during a scheduled passenger flight. The aircraft was performing the second leg of its route, departing from Sultan Muhammad Salahuddin Airport in Bima, Nusa Tenggara Barat, bound for Denpasar, Bali.
During the climb, passing approximately 6,000 feet, the flight crew received an engine fire warning. The cockpit voice recorder indicated a period of confusion between the pilots as the warning light flickered. After a delay of nearly two minutes, the crew decided to shut down the engine. The pilot flying proceeded to feather the propeller and discharge the fire extinguisher bottle, though the fuel shut-off was not performed until 59 seconds later. The crew subsequently returned to Bima and landed safely. There were no injuries among the 42 people on board.
The investigation
The KNKT investigation focused on the origin of the fire and the crew's response to the emergency. Investigators examined the engine components and found that the fire was triggered by a fuel leak at a fitting on the fuel flow transmitter. This specific fitting had been improperly tightened during the initial engine integration by the aircraft manufacturer and had remained untouched since.
Furthermore, the investigation scrutinized the crew's performance during the emergency. Analysis of the cockpit voice recorder revealed that the pilots engaged in lengthy, non-essential discussions after the warning activated, which delayed critical emergency actions. The investigation also noted that the sequence of actions—specifically discharging the extinguisher before cutting off the fuel—did not align with standard procedures.
Findings
- The primary cause of the fire was a fuel leak originating from a loose fitting on the fuel flow transmitter.
- The fitting was found to be improperly tightened, despite the presence of a locking wire.
- Crew coordination was suboptimal, characterized by a lack of a "check and recheck" philosophy and ineffective communication.
- The flight crew's response sequence was incorrect, as the fire extinguisher was deployed before the fuel supply was shut off.
- The delay in executing emergency procedures increased the risk of the fire spreading.
Safety action
Following the incident, PT. Merpati Nusantara Airlines conducted inspections of its MA60 fleet to check for similar fuel leaks. The Xi’ An aircraft manufacturer issued Service Bulletins (MA60-73-SB293 and MA60-73-SB302) instructing operators to inspect engine nacelle fuel and oil lines and to ensure proper torque is applied when replacing fuel flow meters.