What happened
On August 14, 2014, a Jet Airways ATR 72-500, registration VT-JCZ, was preparing for a scheduled flight from New Delhi to Bhopal. During the initial takeoff roll on runway 29, the flight crew received an engine fire warning for engine number one. The warning activated before the aircraft reached V1 speed, prompting the pilot to immediately take control and reject the takeoff.
The crew executed the "on ground engine fire or Severe Mechanical Damage" checklist and issued a MAY DAY call to Air Traffic Control, requesting the activation of all emergency services. To suppress the fire, the crew discharged the aircraft's fire extinguishing agents; the fire warning was successfully extinguished after the second agent was deployed. The aircraft was subsequently towed back to the bay, and all 65 passengers and the crew were disembarked safely without any injuries.
The investigation
AAIB India investigators examined the engine and the maintenance history of the aircraft. The investigation revealed that a scheduled replacement of fuel nozzles on engine number one had been performed during a night halt in Delhi the previous day. While the maintenance records indicated that wet motoring and ground runs had been completed with no leaks observed, subsequent inspections told a different story.
Post-incident examinations of the engine showed soot deposits and heat damage on the right-hand side of the engine, spanning from the #1 to the #7 fuel nozzle positions. Detailed inspections of the secondary fuel manifold revealed that the conical seals at several nozzle positions showed signs of scoring and deformation. Furthermore, nitrogen leak tests conducted during the investigation confirmed that several fuel nozzle B-nuts were under-torqued, specifically at positions #2, #4, and #5.
Findings
- The fire was caused by fuel leaking from the secondary fuel nozzles due to improperly torqued B-nuts.
- Maintenance performed the previous night failed to detect the leak during the initial ground runs.
- The fuel manifold and nozzle threads were found to be dry, suggesting a lack of appropriate anti-seize compound during the recent installation.
- The aircraft's airworthiness documentation, pilot licenses, and maintenance programs were all found to be valid and compliant at the time of the incident.