History of the Flight
The aircraft, a Beech 76 Duchess (registration G-OADY), was conducting a training flight for a Commercial Pilot's Licence. The exercises included stall recovery in the landing configuration. After completing the exercise, the aircraft returned to Leeds Bradford Airport. On joining the downwind leg, the pilot-under-instruction noted the airspeed was 5 to 10 kt lower than expected. The instructor checked the power and flap settings, observing that the landing gear was down with three green lights illuminated. Earlier, after the last stall recovery, the instructor heard the student call "gear up" and saw him reach for the landing gear selector lever, but the action was not completed. Both pilots considered this an inadvertent error.
During the landing roll, about 100 to 150 meters after touchdown, the nose landing gear collapsed, and the aircraft stopped abruptly. Before evacuating, the pilots saw the landing gear lever in the UP position. They were certain the lever was not selected UP during the roll and theorized it might have been accidentally knocked up by the student's knee, but later determined that the lever requires a pull-out action before moving, so it could not have been knocked inadvertently unless it had already been pulled out.
Discussion
The aircraft's landing gear interlock is controlled by an airspeed switch active between 59 and 63 kt, with no weight-on-wheels switch. If the gear is selected UP above that speed, it retracts. After the incident, the switch on G-OADY was tested and found to operate within the specified range. Tests on similar aircraft raised on jacks showed that after the gear is locked down, moving the selector lever a small distance upward can break the hydraulic lock, though this requires pulling the lever out first. The three green lights can remain on even when the gear is not fully locked.
Safety Action
The operator's standard procedures required flaps to be selected UP after vacating the runway. Following the accident, the operator added a requirement for a physical check of the landing gear lever position in addition to a visual check of the three green lights when confirming the gear is down.