Background
The aircraft was on final approach with the pilot under check in control. A 5-knot downwind component was present. The autopilot was unserviceable, requiring the pilot under check to fly manually for most of the four flight legs. Due to a schedule change, the pilot under check had slept only two and a half hours before commencing duty. The check-pilot had been on duty for over twelve hours by the time of the accident.
Sequence of Events
During the last leg, the check-pilot simulated two engine failures. The second simulation occurred on final approach at about 7 DME, with power reinstated shortly after. The approach continued normally until the aircraft neared the threshold. The pilot under check began the flare higher than normal, and airspeed decreased below the optimum. The check-pilot prompted a corrective action, but the pilot under check did not react. At approximately 20 feet, the pilot under check retarded the throttles. The aircraft struck the runway heavily in a left wing low attitude, causing the left main landing gear and nose landing gear to be torn off.
Contributing Factors
The official investigation noted several factors: the schedule change, the unserviceable autopilot, fatigue in both pilots, unresolved command responsibility (the check-pilot believed his role was only as a safety pilot), and the pilot under check misjudging the flare, with the check-pilot not taking over in time to recover control. Additionally, the source mentions that overseas research has demonstrated that stress can induce subtle errors in visual perception, potentially causing a pilot on final approach to perceive the runway as being at a higher plane than it actually is. In this case, the simulated engine failure on approach during a long, fatiguing night operation may have caused a stress reaction in the pilot under check, leading to an incorrect perception of flare height.
Probable Cause
According to the official findings, the probable cause includes the schedule change, the unserviceable autopilot, fatigue in both pilots, unresolved command responsibility, the pilot under check misjudging the flare, and the check-pilot not taking over in time to recover control. A possible factor is visual perception errors resulting from stress induced by the pilot's reaction to the simulated engine failure.