What happened
On 22 October 2013, a Boeing 757-200, registered N605AA, was operating a commercial passenger flight en route to Miami when smoke began to accumulate within the cockpit. The aircraft was positioned approximately 100 nm south-east of Providenciales, Turks and Caicos Islands, at the time of the incident.
Upon detecting the smoke, the flight crew donned oxygen masks and goggles and initiated the required emergency descent procedures. The crew requested an emergency descent from Miami Air Traffic Control and diverted the aircraft toward Providenciales. During the descent, a flight attendant reported that fluid was leaking from the left engine, though no fire was visible. The crew performed the 'Smoke, Fumes and Fire' and 'Smoke Removal' checklists. As the aircraft descended through 10,000 ft, the smoke density decreased sufficiently for the crew to remove their protective gear. The aircraft subsequently landed at Providenciales Airport without further incident. There were no injuries to the 6 crew members or 169 passengers on board.
The investigation
Investigators examined the left engine following the landing. The inspection revealed a low oil level and a distinct smell of fuel within the oil system. Significant debris was identified on the magnetic chip detectors, specifically within the high-speed gearbox detector.
Further analysis established that a seal within the Low Pressure (LP) fuel pump had failed. This failure allowed fuel to leak into the high-speed gearbox and subsequently into the oil system. The investigation traced the path of the smoke from the main bearing seal in the Intermediate Pressure (SD) compressor section into the HP2 port, which then carried the smoke into the left air conditioning pack and associated ducts. The fuel pump in question had reached 11,600 hours of operation, approaching its recommended 12,000-hour maintenance interval.
Findings
- A heavily damaged seal in the Low Pressure fuel pump allowed fuel to contaminate the oil system.
- Fuel entered the oil system via a failed pump seal, providing a pathway for smoke to enter the engine pneumatic bleed air system.
- The smoke traveled from the IP compressor section through the HP2 port into the aircraft's air conditioning ducts.
- This specific engine type had previously experienced four other instances of fuel pump faults resulting in smoke entering the bleed air system.