History of the Flight
On 22 June 2004 at 0145 hours UTC, a Piper PA-28R-201T Turbo Cherokee Arrow, registration G-DNCS, was conducting solo stop-and-go circuits on Runway 27 at Liverpool Airport as part of a night qualification exercise. Earlier that night, the pilot had completed three circuits, a one-hour dual navigation exercise, and a full-stop landing with an instructor. The instructor noted the pilot performed checks consistently and competently. After refuelling and a brief briefing, the pilot was cleared for solo flight.
During the second solo circuit, the pilot completed downwind checks, selected landing gear down, and confirmed three green lights indicating gear down and locked. After receiving clearance for a stop-and-go, he completed finals checks and confirmed the green lights remained illuminated. The aircraft crossed the threshold at approximately 75 knots and flared normally. On touchdown, the landing gear collapsed. The pilot confirmed the gear selector was still down and the gear indication showed three greens before vacating the aircraft without assistance.
Landing Gear System
The aircraft is equipped with a retractable tricycle landing gear activated by an electrically powered hydraulic pump. The pump is controlled by a selector switch or a backup gear extender that lowers the gear regardless of selector position, depending on airspeed and engine power. Gear extension occurs below approximately 90 kt with power off, even if the selector is up. The backup extender uses differential air pressure across a diaphragm linked to a hydraulic valve and electrical switch. The system can be manually overridden by an emergency lever. A yellow light flashes when the override is engaged.
Two microswitches in the throttle quadrant activate a warning horn and red 'gear up' light under certain conditions, including gear up with power reduced below approximately 14 inches manifold pressure. During a normal approach, these conditions may not be met until just before touchdown, making automatic extension unlikely if gear is not selected earlier.
Engineering Inspection
Post-accident inspection at a maintenance facility found the landing gear selector in the DOWN position and the backup extender override lever in NORMAL. The nose gear doors had been forced open against the underside of the engine cowling, and the left main wheel hub was abraded on its outboard edge, consistent with gear extension commencing shortly before touchdown. When the aircraft was lifted and the battery master switch selected ON, the landing gear moved to down and locked without further intervention.
The backup extender actuating diaphragm was found to be leaking, and the system failed to lower the gear at simulated airspeeds below 90 kt. With the gear retracted and throttle closed, the landing gear warning horn did not sound unless the throttle lever was held hard against the left side of the throttle quadrant, a condition not encountered in normal operation. It was not possible to determine whether the landing gear had been activated manually or automatically during the final approach. No pre-existing condition was found that would have prevented full gear extension if selected down earlier.