Incident Overview
On 21 October 2006, a Boeing 767-31K (registration G-DAJC) operated by a commercial air transport company was involved in an incident at Manchester Airport. The aircraft was on its first flight after maintenance that included replacement of the left engine. The flight crew reported burning smells and smoke in the cockpit, leading to an early return. There were no injuries among the 12 crew and 278 passengers, and no damage to the aircraft.
History of the Flight
The aircraft was scheduled to fly from Manchester to Palma, Majorca. After an uneventful engine start, the crew taxied toward Runway 24L. While crossing Runway 24R behind a landing Airbus A330, the commander (the handling pilot) advanced power for the first time that day. The pilots noticed a smell of burning rubber and were informed by the cabin supervisor of a similar odor in the cabin. Suspecting the smell came from the preceding aircraft, they delayed takeoff. After five minutes, the smell cleared and the commander decided to continue.
Takeoff commenced, but at approximately 80 kt the smell returned. The commander continued the takeoff, and after becoming airborne the odor intensified. Faint smoke appeared on the left side of the flight deck. The autopilot was engaged, and the pilots donned oxygen masks. The cabin supervisor reported fumes and smoke in the cabin. A 'mayday' was declared, requesting an immediate return. Radar vectors were provided for an approach to Runway 24R.
The commander made a passenger announcement with his oxygen mask on, but it was faint in the cabin. Later, as smoke dissipated, he repeated the announcement without the mask. The co-pilot completed the air conditioning smoke checklist and switched off the utility electrical busbar as a precaution. By finals, the fumes were less noticeable, and both pilots removed their masks. The aircraft landed safely on Runway 24R and cleared onto a taxiway, where the left engine was shut down. Total airborne time was about nine minutes.
Communications with fire services confirmed no external signs of smoke or fire. The aircraft taxied to a remote stand using the right engine and was shut down. Passengers disembarked via steps and were bused to the terminal. Fire service personnel noted a strong lingering odor of burning rubber and advised opening cabin doors.
Crew Debrief
After the incident, the crew were debriefed. The company medical adviser provided guidance on smoke inhalation and re-issued the operator's smoke inhalation policy. He advised the crew to refrain from flying duties for 24 hours. During debrief, it was revealed that smoke had activated the rear left toilet smoke detector, prompting cabin crew to prepare two fire extinguishers. The cabin crew had attempted to inform the flight crew via intercom but refrained from interrupting the emergency communication with ATC.
Engineering Issues
An engineer boarded after passenger disembarkation and informed the flight crew that the replacement left engine had not undergone high-power ground runs because it was supplied 'pre-tested'. The source of the smoke was suspected to be oil contamination associated with the replacement engine. The operator could not determine the exact source of contamination and sought advice from the aircraft and engine manufacturers.
The possibility of engine oil overfilling was considered but discounted by the engine manufacturer, as overfilling 'does not result in contamination of the compressor and engine bleed off-takes'. The manufacturer believed the most likely reason for oil smoke was contamination of the gas path during the engine's overhaul or installation. Additionally, although the engine had been test-run before installation, there was no test cell monitoring for smoke or smells from engine bleeds.
Four days later, another pilot report of an electrical burning smell was submitted, which was cleared by inspection of the cabin air re-circulation system.