What happened
On 22 May 2015, an Air France Boeing 777-F, registered F-GUOC, was preparing for a cargo flight from Paris-Charles-de-Gaulle to Mexico City. During the pre-flight phase, the co-pilot calculated a preliminary take-off weight of 243 tonnes, which was actually 100 tonnes lower than the true weight of 343 tonnes. This erroneous value was entered into the On-board Performance Tool (OPT) by both the co-pilot and the captain.
As the crew entered the performance data into the Flight Management System (FMS), the aircraft's reference speeds were significantly lower than normal. Although the FMS displayed a message indicating it could not compute reference speeds, the crew did not recognize the discrepancy. The crew ultimately entered manual take-off speeds (V1 of 143 kt) based on the incorrect weight and a flap configuration of 5 degrees.
During takeoff from runway 26R, the aircraft reached the rotation speed of 154 kt. Immediately after rotation, the aircraft failed to climb and began to sink, triggering the Tailstrike Protection (TSP) system. The aircraft eventually cleared the opposite runway threshold at a height of approximately 170 feet. During the climb, the crew identified the 100-tonne weight error and continued the flight to the destination without further incident.
The investigation
The BEA examined the flight data, crew statements, and the aircraft's performance tools. The investigation focused on why the crew failed to detect the massive discrepancy between the calculated weight and the actual weight. Investigators also reviewed the airline's procedures regarding weight verification and the effectiveness of the aircraft's automated warnings during data entry.
Findings
- The primary cause was the use of an erroneous weight that was 100 tonnes lower than the actual weight.
- The crew's cross-check failed because both pilots used the same incorrect weight provided by the first pilot, eliminating any independent verification.
- The airline's procedures did not require independent weight inputs from multiple crew members.
- The aircraft's FMS provided a warning regarding unavailable reference speeds, but the crew did not understand its significance in the context of the weight error.
- The aircraft's systems did not provide a warning regarding the gross difference between the weight entered in the EFB and the weight calculated by the FMS.
- The crew's attention was divided during the preparation phase due to the presence of relief pilots and other tasks.
Safety action
The BEA issued several safety recommendations to Air France, the DGAC, Boeing, and EASA. These recommendations focus on improving data entry procedures, enhancing protections against the use of erroneous speeds on the Boeing 777, and developing technical systems to detect gross input errors on exposed aircraft types.