Incident Overview
On 18 August 2005, a Boeing 757-200APF cargo aircraft, registration TF-FIE, experienced a smoke event in the cockpit shortly after taking off from London Stansted Airport. The aircraft was on a scheduled night cargo flight to Liege, Belgium, with two crew members on board and no passengers. The takeoff was uneventful until approximately 5-10 knots below V1, when the captain perceived possible smoke in the cockpit. At that moment, the first officer could not confirm the presence of smoke.
Flight Details
At around 500 feet above ground, the captain activated his reading light and stated that he could see smoke, which the first officer confirmed by smell. The crew contacted the control tower, explained the situation, and requested a turn-back and landing. The controller asked if they were declaring an emergency, but the captain declined, noting that the smoke had cleared; however, he preferred to return. The aircraft was given radar vectors to final approach and landed on Runway 23 without difficulty after an airborne time of 11 minutes. The Airport Fire Service attended but, after a brief inspection, the aircraft taxied back to the gate with everything appearing normal.
Findings
A technician from the maintenance provider attended the aircraft and agreed that an odor of hot oil was present, apparently emanating from the air conditioning system. Subsequent inspection revealed an oil leak, apparently from the No 1 bearing in the left engine, which had been ingested into the intermediate pressure compressor and then into the air conditioning bleed air. Initial actions included changing and inspecting the pressure and scavenge oil filters. The operator later opted to replace the left engine. After the replacement, the aircraft was released to service with no further reports of air contamination.
A subsequent strip examination of the engine showed that a cracked No 1 bearing front ring seal had been responsible for the oil leak. The crew reported no injuries, and the only damage noted was to the main bearing in the engine.
Probable Cause
A cracked No 1 bearing front ring seal had been responsible for the oil leak.