What happened
On 23 September 2007, a Boeing 737-3Q8, registration G-THOF, was conducting a scheduled night passenger flight from Faro, Portugal, to Bournemouth Airport. During the instrument landing system approach to Runway 26, the aircraft's autothrottle system disengaged without any command from the flight crew. Crucially, the thrust levers remained in the idle position, and the crew did not immediately recognize that the automation had disconnected.
As the aircraft continued the approach with engines at idle, the airspeed decayed rapidly, eventually dropping 20 knots below the target reference speed. The commander took manual control and initiated a go-around procedure. However, during the transition to climb, the aircraft experienced a severe pitch excursion, reaching a maximum nose-up attitude of 44 degrees. The airspeed plummeted to 82 knots, resulting in a stall. Despite the crew's efforts to reduce the pitch, the combination of high thrust and the existing stabilizer trim position made the aircraft difficult to control. The crew eventually managed to recover the aircraft and completed a subsequent landing safely.
The investigation
The AAIB investigation examined the aircraft's flight data from the Quick Access Recorder (QAR) and interviewed the flight crew. The investigation focused on the mechanics of the autothrotle disengagement and the aerodynamic factors that prevented effective pitch recovery during the go-around. The investigators also reviewed the aircraft's maintenance history and the manufacturer's recommended upset recovery procedures.