What happened
During the early morning hours of the incident, a Sky Lease Cargo Boeing 747-412F, registered N908AR, was arriving at Halifax/Stanfield International Airport from Chicago/O’Hare International Airport. The flight was carrying three crew members and one passenger, with no cargo on board. While performing an instrument landing system approach to Runway 14, the crew identified a tailwind but did not update their performance calculations due to time constraints.
Upon touchdown at approximately 0506 Atlantic Standard to standard time, the aircraft experienced a firm landing. During the rollout, the No. 1 engine thrust lever moved forward of the idle position, which triggered the retraction of speed brakes and the disengagement of the autobrake system. A combination of a right crab angle, crosswinds, and asymmetric reverse thrust caused the aircraft to drift right of the runway centerline.
As the aircraft continued down the runway, the pilot monitoring was preoccupied with the lateral drift, leading to a lack of necessary callouts regarding deceleration. Although manual braking was initiated 8 seconds after touchdown, full braking pressure was not applied until the aircraft was only 800 feet from the runway end. Consequently, the aircraft exited the runway at 77 knots, traveling 270 m past the threshold. The aircraft struck approach light stanchions and a localizer antenna array, causing the No. 2 engine to detach from its pylon and resulting in a fire in the tail section. The aircraft eventually crossed a 2.8 m drop and was destroyed. The 3 crew members sustained minor injuries, while the passenger remained uninjured.
The investigation
The TSB examined the mechanical and operational factors contributing to the overrun, including the movement of the thrust lever and the delay in braking application. The investigation also included a fatigue analysis, which determined that the crew's performance was likely degraded by two specific risk factors: the timing of the flight and a lack of restorative sleep in the 24 hours preceding the accident.
Findings
- An unexpected tailwind increased the required landing distance.
- The movement of the No. 1 engine thrust lever forward of idle caused the speed brakes to retract and the autobrakes to disengage.
- The crew failed to recalculate performance data following the discovery of the tailwind.
- The delay in applying maximum braking effort prevented the aircraft from stopping within the available runway length.
- Crew fatigue, driven by flight timing and insufficient sleep, contributed to degraded performance.