During the takeoff phase, the captain heard a loud thump coming from under the plane. Thinking a tyre had burst, he abandoned takeoff and activated the thrust reversers. Taking care in applying gradual braking, the plane was steered onto a taxiway off to the right of the runway and into a slight prevailing wind. As the Boeing 737 stopped, the crew discovered that the No. 1 engine was on fire.
By this time, fuel spilling from the port wing combined with the light wind had fanned the fire into a giant blaze. Fire quickly found its way into the passenger cabin, creating toxic smoke and causing the deaths of 53 passengers and two cabin crew, 48 of them from smoke inhalation. 78 passengers and 4 crew escaped, with 15 people sustaining serious injuries.
The subsequent investigation into the incident revealed that the No. 9 combustor can on the port engine had developed a crack due to thermal fatigue. This allowed the can to move out of alignment, and instead of directing the hot combustion gases out of the back of the engine, they now hit the combustion chamber casing. Eventually this led to a catastrophic explosive failure of the casing.
Following on from this, the forward section of the can was ejected from the engine, fracturing a fuel tank access panel and allowing jet fuel to flow out onto the hot engine exhaust. Combined with the fuel being fed to the now damaged engine, this ultimately sparked the blaze that engulfed the aircraft.
Records showed the engine in question, a Pratt & Whitney JT8D-15, had experienced previous cracks to the No. 9 combustor can that had been repaired. However, the AAIB found these repairs by welding were unsatisfactory in ensuring safe operation. Therefore, they likely contributed to the final severe cracking which led to the accident.
The procedures that were in place at the time also contributed to making matters worse. Thinking a tyre had burst and following standard operating procedure at that time, the flight crew braked slowly and cleared the runway. The slow braking of the aircraft allowed the fire to spread and shortened evacuation time. Since this incident, all flight crew now check wind direction before making their decision which direction to turn.
The surviving cabin crew (Arthur Bradbury and Joanna Toff) and two members of the Manchester Airport Fire Service were awarded the Queen's Gallantry Medal for their individual bravery, the two flight attendants who died in the incident (Sharon Ford and Jacqui Ubanski) were also awarded the same honour posthumously for their devotion to duty and bravery.
The swift incursion of the fire into the fuselage and the layout of the aircraft impaired passengers' ability to evacuate, with areas such as the forward galley area becoming a particular bottle-neck for escaping passengers, of those unable to escape 48 died as a result of incapacitating and subsequently lethal toxic gas and smoke, some very close to the exits with 6 dying through burns.
A large amount of dynamic research into evacuation and cabin and seating layouts was carried at Cranfield Institute to try and measure what makes a good evacuation route which led to the seat layout by Overwing exits being changed by mandate and the examination of evacuation requirements relating to the design of galley areas.
The use of smoke hoods or misting systems were also examined although both were rejected.