What happened
On 18 August 2005, a Boeing 757-200APF, registration TF-FIE, was performing a cargo flight from London Stansted Airport to Liege, Belgium. During the takeoff roll on Runway 23, the captain noted what appeared to be smoke in the cockpit at approximately 5 to 10 knots below V1 speed. Although the first officer could not visually confirm the smoke, both crew members detected an odor of hot oil, which seemed to be coming from the air conditioning system.
The handling pilot requested a return to Stansted. While the air traffic controller inquired if an emergency was being declared, the captain declined, noting that the visible smoke had dissipated, though the desire to land was maintained. The aircraft landed safely without difficulty after a total flight time of 11 minutes. Following the landing, the Airport Fire Service inspected the aircraft but found no immediate issues, allowing the plane to taxi back to the gate.
The investigation
The AAIB investigation focused on the source of the oil odor and smoke. A maintenance technician inspected the aircraft and confirmed the presence of a hot oil smell. While initial maintenance steps involved inspecting the pressure and scavenge oil filters, the operator ultimately decided to replace the left engine. A detailed strip examination of the engine was performed, which identified the specific mechanical failure.
Findings
- An oil leak from the No 1 bearing in the left engine had occurred.
- The leaking oil was ingested into the intermediate pressure compressor.
- The oil then entered the air conditioning bleed air system, causing the odor and smoke in the cockpit.
- The leak was caused by a cracked No 1 bearing front ring seal.