What happened
On 21 July 2017, a Boeing 737-86J, registration C-FWGH, was preparing for a commercial passenger flight from Belfast International Airport to Corfu, Greece. During the takeoff roll on Runway 07, the crew noticed the aircraft was not accelerating at the expected rate. As the aircraft reached rotation speed, it lifted off with a shallow climb angle. Shortly after departing the runway, one of the aircraft's tyres struck a runway approach light located 29 metres beyond the end of the runway, causing damage to the light fitting.
There were no fatalities and no injuries among the 6 crew members or 179 passengers on board. The investigation revealed that the engines were set to an N1 of 81.5%, which was far below the required 93.3% calculated for the day's conditions.
The investigation
The AAIB investigation was delayed because the incident was not initially reported to them by the crew or the operator, though it was reported to Canadian authorities. The AAIB became aware of the event via a Mandatory Occurrence Report filed by airport air traffic control personnel. Due to this delay, the Flight Data Recorder and Cockpit Voice Recorder data had been overwritten by subsequent flights.
Investigators examined the Flight Management Computer (FMC) and the Electronic Flight Bag (EFB) data. They determined that the thrust error was likely caused by a manual data entry error. Specifically, the crew appears to have entered the expected top-of-climb outside air temperature (-52°C) into the N1 limit page instead of the actual ambient temperature (+16°C).
Simulations conducted by the AAIB indicated that while the aircraft could have stopped safely had the pilot aborted the takeoff, it likely would have lacked the performance to climb safely had the pilot chosen to continue the takeoff following an engine failure.