What happened
On 14 April 2012, a Boeing 737-33A, registration G-ZAPZ, was performing a commercial passenger flight from Chambery Airport, France, to London Gatwick. During the takeoff roll, the flight crew experienced a slight vibration, which they initially attributed to turbulence. As the aircraft rotated, the pitch attitude increased rapidly, leading to a tailstrike on the runway.
The impact caused longitudinal scoring to the rear fuselage skin and damage to the rear heated drain mast. Despite the strike, the aircraft continued to accelerate and successfully achieved the required climb performance, landing safely at Gatwick with no fatalities and no injuries to the 131 passengers or 5 crew members.
The investigation
The AAIB investigation focused on the takeoff performance parameters and the use of the onboard Electronic Flight Bag (EFB). It was established that the commander used an EFB to calculate takeoff data but failed to enter the correct takeoff weight. Because the EFB had been placed in standby mode rather than being shut down, it retained the takeoff weight from the previous flight sector.
This resulted in the use of a takeoff weight approximately 6,600 kg lower than the actual weight. Consequently, the calculated takeoff speeds (V1, VR, and V2) were significantly lower than required. The investigation also examined the aircraft's mechanical condition, discovering a broken spring within the elevator feel and centering unit, which reduced control resistance and contributed to the excessive pitch attitude during rotation.
Findings
- The primary cause of the tailstrike was the use of incorrect takeoff weight data in the EFB performance calculation.
- The commander omitted to update the takeoff weight, leaving the EFB with the weight from the previous flight.
- The crew did not cross-check the EFB-calculated performance figures against the manual load sheet.
- A broken outer main spring in the elevator feel and centering unit reduced pitch resistance, contributing to the excessive pitch attitude.
- The EFB software design allowed the retention of data from previous sectors when placed in standby mode, creating a risk of using outdated information.
Safety action
Following the accident, the operator updated its Operations Manual to include more robust procedures for using the EFB. This included requirements to shut down and restart the software prior to takeoff calculations and instructions to compare calculated V2 speeds against tabulated values as a gross error check. The operator also implemented a training programme to refresh crew skills regarding aircraft performance calculations.