What happened
On 6 February 2009, a Boeing 737-3L9, registration G-OGBE, was preparing for a commercial passenger flight from Birmingham Airport to Edinburgh. Due to deteriorating weather conditions involving snow and freezing temperatures, the aircraft underwent de-icing procedures prior to departure.
During the takeoff roll, the aircraft reached a speed of 155 kt. At the rotation speed (VR), the first officer attempted to pull the control column back to lift the nose, but the aircraft failed to rotate. The pilot then applied significantly more physical effort, but the nose failed to rise. Concerned that ice accretion might have compromised the flight controls, the captain made the decision to reject the takeoff. The aircraft was able to stop within the remaining runway, and the crew subsequently identified that the stabiliser trim had been incorrectly set.
The investigation
The AAIB investigation examined the flight data recorder and the circumstances surrounding the pre-flight preparations. It was established that the aircraft had been left overnight with the stabiliser in a full nose-down position. While the crew had performed de-icing, the sequence of standard pre-flight checks was disrupted.
Investigators found that the crew's attention was divided between managing the de-icing holdover time and managing the aircraft's configuration, as they had left the flaps in the up position to accommodate the slushy conditions. The investigation also included a simulator trial by the operator, which demonstrated that while a more forceful pull was required due to the trim setting, the aircraft could have safely climbed away if the takeoff had continued.
Findings
- The primary cause of the failed rotation was that the stabiliser trim was set to an incorrect position (2.3 units instead of the required 4.5 units).
- The crew was distracted by several factors, including the need to meet a revised takeoff time dictated by the de-icing holdover limit and the unusual requirement to taxi with flaps up.
- The incorrect trim setting did not trigger the cockpit warning horn because the setting remained within the permissible 'green band' range (1.0 to 6.3 units).
- The captain's decision to reject the takeoff above V1 was influenced by concerns regarding potential ice accumulation on the control surfaces.