What happened
On 17 July 2012, an ATR 72-2 and12A, registration PK-WFK, operated by Wings Air, arrived at Adisutjipto International Airport from Surabaya. After landing and parking, the flight crew shut down the left engine while keeping the right engine running in hotel mode using a propeller brake. Shortly after, the crew received an engine overheat warning. Moments later, a fire warning for the right engine activated, and the crew heard shouts from outside the aircraft requesting fire extinguishers. The pilot deployed both fire extinguisher bottles to suppress the flames.
The investigation
The investigation focused on the engine nacelle, where engineers found soot on the lower cowling and evidence of fuel exposure on the nacelle floor. A subsequent inspection of the engine revealed that the fuel nozzle connector fitting at position 1 was wet. Data from the Flight Data Recorder (FDR) showed a growing discrepancy in fuel flow between the left and right engines in the flights leading up to the incident, suggesting a progressive leak.
Investigators determined that the fuel nozzle replacement, performed about a month prior, had been completed without using the manufacturer-specified special tool (PWC56616). This likely led to an improper installation that loosened due to engine vibration.
Findings
- The primary cause of the fire was the accumulation of fuel on the engine nacelle floor, which evaporated and reached auto-ignition temperatures due to the high heat within the nacelle.
- The fuel leak originated from a loose connector fitting on the position 1 fuel nozzle.
- The fuel nozzle had been improperly installed during a maintenance task because the required special tool was not utilized.
- High ambient temperatures and the lack of propeller airflow while in hotel mode allowed fuel vapors to reach an auto-igniting state.
Safety action
Following the incident, the operator updated its Engineering Authorization to mandate the use of the required manufacturer special tools for the periodic restoration of fuel nozzle adapters on their PW127M engines.