What happened
On 17 January 2002, a Piper PA-3-200T, registration G-BFLH, was conducting a training flight from Bristol Airport to Oxford (Kidlington) Airport. The crew consisted of an instructor in the right-hand seat and a student pilot in the left-hand seat, with a second student passenger in the rear.
During a simulated engine failure maneuver following a go-around at Bristol, the instructor closed one throttle to mimic a failure. This action triggered the landing gear warning horn. Although the instructor later increased the manifold pressure to 14 inches to simulate a feathered propeller, the horn continued to sound. To mitigate the loud noise and allow for clearer communication with the student, the instructor pulled the landing gear warning circuit breaker.
Crucially, this specific circuit breaker also disables the hydraulic motor responsible for gear extension and retraction, as well as the gear position indicator lights. During the subsequent approach and circuit at Oxford, the instructor focused on coaching the student and monitoring traffic, failing to reset the circuit breaker. Consequently, the landing gear remained retracted. Both pilots failed to notice the gear status during their final landing checks, resulting in a wheels-up landing on the runway. The aircraft came to rest at the edge of the runway with damage to the propellers, fuselage, and flaps, but there were no injuries to the three occupants.
The investigation
The investigation examined the mechanics of the gear warning system and the actions taken by the crew. It was determined that the warning horn is triggered by a micro switch in the throttle quadrant that responds to throttle movement rather than manifold pressure. The investigation found that the micro switch can become misaligned, which explains why the horn persisted even when manifold pressure was increased.
Findings
- The instructor pulled the landing gear circuit breaker to silence the horn, which inadvertently disabled the hydraulic gear-operating motor and the cockpit position lights.
- The instructor failed to reset the circuit breaker during the flight.
- The crew failed to identify that the landing gear was not extended during the landing checklist.
- The warning horn's continued operation was likely due to a misaligned micro switch in the throttle quadrant, which responds to throttle position rather than manifold pressure.