What happened
On 28 September 2017, a Boeing 737-8K5, registration G-FDZJ, was performing a commercial passenger charter flight from Malta International Airport to Manchester. The aircraft was carrying 136 passengers and 6 crew members. During the takeoff roll from runway 1s, the pilot flying attempted to rotate the aircraft at the calculated speed. However, the aircraft failed to respond to the standard control column input. The pilot was forced to apply significantly more rearward elevator deflection than usual to initiate rotation. The aircraft eventually became airborne, but with only approximately 300 metres of runway remaining. Once the aircraft had established a climb, the crew applied rearward trim to compensate for the control forces.
The investigation
Investigators examined the flight data recorder, which revealed that the elevator deflection required for rotation was 10.9 degrees, compared to a typical 8.3 degrees observed on previous flights. The investigation focused on the discrepancy between the calculated takeoff weight and the actual aircraft configuration. It was determined that the stabilizer trim had been set to 4.5 units based on a load sheet that incorrectly reported a Mean Aerodynamic Chord Takeoff Weight (MACTOW) of 23.4%.
Further inquiry into the ground handling process revealed that because the passengers had been checked in by a cruise ship operator rather than the airport handling agent, the agent lacked specific data regarding seat assignments. The handling agent proceeded under the assumption that passengers were distributed evenly across the cabin. However, the actual passenger loading was heavily biased toward the front of the aircraft, resulting in a true MACTOW of only 17%.
Findings
- The aircraft was out of trim for takeoff because the load sheet contained an incorrect MACTOW value.
- The error originated because the actual seating positions of the passengers were not communicated to the handling agent.
- The handling agent used an assumed even distribution of passengers to generate the electronic load sheet, which did not reflect the actual forward-heavy loading.
- The flight crew's performance calculations and FMC entries were consistent with the erroneous information provided on the official load sheet.
Safety action
Following the investigation, the operator committed to updating procedures to ensure that for any flight where check-in is not managed by the handling agent, the position of empty seats is communicated to the load controller. Additionally, the operator will ensure that all handling agents have a reliable method for determining actual passenger seating positions on partially loaded flights to ensure accurate load sheet production.