What happened
On 5 February 2006, a Bombardier Challenger 604, registration D-ABCD, was performing a non-scheduled commercial passenger flight from Geneva to London Luton Airport. During the final approach to Runway 26, the aircraft experienced an unexpected increase in engine thrust. While the approach was initially stable, the engine fan speed (N1) rose to 64% below 50 feet radio altitude.
As the aircraft approached the runway, the commander disconnected the autopilot. The subsequent flare resulted in a prolonged float along the runway surface. The aircraft eventually touched down approximately 800 metres before the end of the runway. Although the crew applied reverse thrust and braking, the aircraft continued to travel down the runway, eventually running off the paved surface and into the soft ground of the stopway. The aircraft travelled approximately 30 metres beyond the end of the paved area, where the nose and right main landing gear struck concrete lighting plinths, causing damage to the aircraft gear and the approach lighting system. There were no fatalities and no injuries to the three crew members or the single passenger on board.
The investigation
The AAIB investigation examined the aircraft's flight recorders, which showed the aircraft's pitch and thrust parameters. The investigation found that the engine thrust had increased significantly during the final stages of the approach. The investigators also reviewed the crew composition, noting that the pilot in the left seat was an experienced examiner providing instruction to the right seat pilot, who was the nominated commander for the flight.
Technical examinations of the Bombardier Challenger 6 and 04 revealed that the landing gear had sustained damage from the impact with the concrete bases. The investigation also looked into the design of the lighting plinths, finding that they did not meet the safety criteria specified in CAP 168, as they presented a vertical face to aircraft wheels in soft ground.
Findings
- The primary cause of the overrun was the unintended increase in engine thrust during the approach, which led to a prolonged float and a late touchdown.
- The pilot in the right seat lacked recent experience operating the aircraft from that position, which may have contributed to the failure to identify the thrust increase.
- The crew composition, with an examiner in the left seat and a trainee commander in the right seat, may have created a situation where the instructor was reluctant to intervene.
- The construction of the approach lighting plinths did not satisfy the requirement to be 'delethalised' to prevent damage during runway excursions.