What happened
On 5 April 1998, a Boeing 747-400, registration 9M-MPC, was preparing for a scheduled passenger flight from London Heathrow to Kuala Lumpur. The flight crew, which included a commander and a first officer acting as the handling pilot, had planned a takeoff using full thrust to comply with local noise abatement procedures.
During the takeoff roll on Runway 2tL, the commander observed fluctuations in the airspeed indications around 100 kt. As the aircraft reached rotation speed, the commander applied an additional rearward input to the control column to assist the first officer in maintaining the target climb speed. This maneuver caused the aircraft to pitch up at an accelerated rate. Consequently, the tail of the aircraft struck the runway as it lifted off.
Following the impact, the aircraft continued its climb, but air traffic control notified the crew that debris was falling from the tail section. An APU fire warning subsequently activated. The crew followed emergency procedures, which included depressurizing the aircraft and jettisoning 74,000 kg of fuel. The aircraft returned to Heathrow and landed safely on Runway 27R. There were no fatalities and no injuries to the 314 passengers or 22 crew members on board.
The investigation
The investigation focused on the cause of the excessive pitch rate and the resulting structural damage. Investigators examined the aircraft's loading, confirming that the weight and center of gravity calculations were accurate. Analysis of the Digital Flight Data Recorder (DFDR) revealed that the aircraft's response to control inputs was correct and that the elevator trim setting was appropriate for the takeoff conditions.
Physical examination of the aircraft identified significant damage to the rear fuselage frames and the APU firewalls. The impact had caused the APU access doors to disengage; one door was recovered near Wraysbury, while the other was found near Byfleet. The investigation also looked into the cause of the intermittent APU fire warning, which was linked to broken fire detection loops trailing against the fuselage skin.
Findings
- The aircraft achieved a pitch rate of approximately 5.5°/sec during the additional rearward control input, significantly exceeding the manufacturer's recommended rate of 2 to 3 degrees per second.
- The tail strike occurred at a pitch attitude of 12.5 degrees.
- The primary cause of the tail strike was the excessive pitch rate induced by the additional rearward control column input applied by the commander.
- Local atmospheric disturbances, such as windshear or gusts associated with nearby rain showers, likely caused the airspeed fluctuations observed during rotation.
- The loss of the APU access doors and the subsequent fire warning were direct results of the structural damage sustained during the runway contact.