Incident Details
On 19 November 2003, a Boeing 757-236 (registration G-CPES) operated an airline departed on a scheduled passenger flight from London Heathrow to Istanbul. As the aircraft rotated for takeoff, a strong smell of oil became apparent in the cockpit. After completing after-takeoff checks, the flight crew confirmed the smell persisted, albeit less intense. The Cabin Services Director was called to verify. The crew decided to return to London Heathrow, declared a PAN to air traffic control, and followed the Quick Reference Handbook procedure, including donning oxygen masks. The approach and landing were uneventful, with no injuries to the 9 crew and 63 passengers.
Engineering Investigation
Post-flight troubleshooting found no defects that could explain the oil smell. However, checks of engine oil quantities revealed they were above the operator's specified maximum fill level. In-service experience indicated that overfilling can cause oil to leak past the compressor front bearing seal, enter the gas path, and be drawn into the cabin/cockpit air supply. The operator had established an in-house maximum fill level of one litre below the 'FULL' graduation on the oil tank sight glass. Following this incident, the operator amended its oil servicing procedures to further reduce the likelihood of overfilling.
Subsequent Occurrence
On 7 September 2004, another Boeing 757 (G-CPER) operated by the same company experienced similar oil smells. The AAIB's investigation into that occurrence was ongoing at the time of this report.