What happened
On 21 October 2006, a Boeing 767-31K, registration G-DAJC, was prepared for a commercial passenger flight from Manchester Airport to Palma, Majorca. This flight was the first operation of the aircraft following maintenance work that included the replacement of the left engine.
During taxiing behind another aircraft, the flight crew noticed a smell of burning rubber. The crew initially suspected the odor was due to the aircraft's recent movement behind a landing Airbus A330 and decided to delay takeoff to see if the smell would dissipate. After five minutes, the odor had cleared from both the flight deck and the cabin, leading the commander to proceed with the departure.
As the aircraft accelerated through approximately 80 knots, the smell returned. As the aircraft became airborne, faint traces of smoke appeared on the left side of the flight deck, and the cabin supervisor reported fumes and smoke in the passenger cabin. The crew declared a ‘mayday’ and requested an immediate return to Manchester. As a precaution, the crew donned oxygen masks and the co-pilot deactivated the air conditioning smoke and utility electrical busbar. Following an ILS approach, the aircraft landed safely.
The investigation
The investigation focused on the source of the smoke and the recent maintenance performed on the left engine. The aircraft was taxied to a remote stand using the right engine, after which the left engine was shut down. Following the landing, passengers disembarked via bus.
An engineer inspected the aircraft and noted that the replacement left engine had not undergone high-power ground runs because it had been provided as a "pre-tested" unit. The investigation sought to determine if oil contamination was present. While the possibility of an engine overfill was considered, the manufacturer stated that overfilling does not cause oil to contaminate the compressor or engine bleed off-takes.
Findings
- The smoke and burning smell were likely caused by oil contamination within the engine gas path, which may have occurred during the engine overhaul or during its installation into the aircraft.
- The replacement engine had not been subjected to high-power ground testing prior to installation.
- The crew successfully managed the emergency, returning the aircraft to Manchester without injuries to the 278 passengers or 12 crew members.