What happened
On 10 March 2006, a Boeing 757-236, registration G-CPET, was preparing for a passenger flight at London Heathrow Airport. Following the start of both Rolls-Royce RB211 engines, the co-pilot noted an unusual odour within the flight deck. As the aircraft began taxiing, the co-pilot reported feeling light-headed, euphoric, and unwell; the commander subsequently experienced similar symptoms.
As the aircraft moved, the co-pilot began using an oxygen mask. Due to the physical symptoms experienced by the crew, the aircraft was stopped on the taxiway. The commander determined that the crew was no longer fit to continue the taxiing process, and the aircraft was subsequently towed back to its stand. There were no injuries to the 7 crew members or 149 passengers, and the aircraft sustained no damage.
The investigation
The investigation focused on identifying the source of the fumes that affected the flight crew. A review of the aircraft's technical logs revealed a previous entry from 4 March 2006, which noted an occasional brief smell of oil on the flight deck, though no smell had been detected in the cabin at that time. An earlier engineering check following that incident had found no traces of oil, and the aircraft had been cleared for service.
During the inspection of G-CPET following the 10 March event, investigators identified staining on the oil feed tubes that supply the front bearing of the left engine. This staining suggested a potential leak of oil into the gas path.
Findings
- The flight crew experienced symptoms of light-headedness and euphoria due to an unusual odour in the cockpit.
- Staining on the oil feed tubes for the left engine's front bearing indicated a possible oil leak into the gas path, which may have been the source of the fumes.
- It could not be definitively proven that this specific leak was the sole cause of the odour.