What happened
During the takeoff roll of a Boeing 777-300, the aircraft's airspeed experienced several periods of stagnation, ranging from 77 kt through to the rotation speed of 178 kt. As the pilot initiated rotation at 17/8 kt, the headwind component dropped by 12 kt, causing the computed airspeed to fall to 173 kt.
Because the aircraft failed to become airborne at the manufacturer-recommended pitch attitude of 7 degrees, the pilot continued to increase the pitch. Lift-off was eventually achieved at a pitch attitude of 10.7 degrees. This exceeded the 8.9-degree threshold at which a tail strike occurs for this aircraft type.
The investigation
Investigators analyzed flight data and crew reports to determine the sequence of events. The pilot flying (PF) noted that they did not hear the pilot monitoring (PM) call of "speed" after rotation had begun. The PF also stated they believed the rotation was proceeding normally given the environmental conditions.
Analysis of the wind conditions confirmed that a reduction in headwind during the rotation phase contributed to the loss of airspeed. Furthermore, the investigation looked into the operator's manuals, noting that while the Flight Crew Operations Manual (FCOM) provides procedures for reduced thrust takeoffs, it lacks specific guidance for thrust settings during gusty or strong crosswind conditions. Such guidance is instead located in the Flight Crew Training Manual (FCTM).
Findings
- The tail strike was caused by airspeed stagnation resulting from gusty atmospheric conditions, which extended the time required for the aircraft to lift off.
- The increased pitch attitude required to achieve lift-off exceeded the aircraft's tail skid limit.
- Utilizing a higher takeoff thrust setting would likely have decreased the required runway length and limited the aircraft's exposure to wind fluctuations during the critical rotation and lift-off phases.