History of the Flight
On 18 December 2002, a Piper PA-28RT-201 Cherokee Arrow IV (registration G-GHRW) was operated on a Commercial Pilot's Licence training flight from Cranfield Airport, Bedfordshire. The aircraft had been under investigation for an intermittent problem where the 'gear unsafe' light remained illuminated after gear retraction, though no specific defect was found by maintenance.
After a normal pre-flight check, the aircraft was taxied for departure on Runway 04 with the student handling. The takeoff was normal, but upon retracting the landing gear, the red 'gear unsafe' light remained on. When the instructor moved the gear lever down, the left main gear failed to indicate locked down. The instructor cycled the gear lever several times, but each time the same abnormal indications occurred: the gear unsafe light stayed on after gear up, and only two green lights (nose and right main) illuminated after gear down selection.
On the downwind leg, the instructor attempted to lower the gear using the alternate system, but the left main gear still did not indicate locked down. A flypast of the tower was made, and air traffic control reported that the landing gear appeared down and locked. On a subsequent downwind leg, the instructor interchanged the gear indicator bulbs, but the abnormal indications persisted.
The instructor assumed control for the landing from a normal approach, believing the issue was likely an indication fault. After touchdown, the aircraft settled with the left wing slightly low. As it slowed, the left main gear gradually collapsed. The engine was shut down during the landing roll, and the left wing contacted the runway at a speed between 20 and 30 knots, causing the aircraft to slowly depart the left side of the runway. No injuries were reported. Damage comprised the left wing, wing tip, pitot probe, aileron, and flap.
Engineering Investigation
After the left wing was lifted during recovery, the left main gear could be pulled into the down-and-locked position by hand, though with some difficulty. Subsequent landing gear retractions performed in the hangar showed no problems. When the left main landing gear linkages were disconnected for inspection, some joints were found to be stiff, but no specific reason was identified for the failure to lock down. During repairs, the left main gear was removed and various bushes were replaced as a precaution.
Following reinstallation of the left main gear, the aircraft was flight-tested, and the landing gear operated satisfactorily, including the alternate lowering system. No further problems with the landing gear were reported.