The Flight
On 24 November 2002 at 0915 hours UTC, a Piper PA-28R-180 Cherokee Arrow, registration G-BAPW, departed from Runway 24 at Denham Aerodrome, Middlesex. The private pilot, aged 56 with 881 flying hours (750 on type), was performing a single circuit to check the aircraft after its Annual Inspection. The takeoff was uneventful and the landing gear retracted normally when selected up.
Landing Gear Malfunction
On the downwind leg, the pilot selected the landing gear down, but the three green gear down and locked lights failed to illuminate. Cycling the landing gear lever had no effect. The pilot then performed the emergency landing gear extension procedure, also without success. During a low pass over the control tower, he was advised that the landing gear appeared to be in the down position. He proceeded to land using full flap on final approach. After touchdown, the right main landing gear partially collapsed. The pilot shut down the engine and turned off the fuel. The left gear then also partially collapsed, causing the aircraft to slew off the left side of the runway. The nose gear remained extended. The aircraft came to rest about 40 metres from the runway edge. The pilot, who was uninjured, exited the aircraft without difficulty.
Investigation Findings
After recovery to a hangar, it was observed that the circuit breaker for the landing gear had tripped. The aircraft was jacked up and, after resetting the circuit breaker, the landing gear was cycled up and down. On the third cycle, the electric motor stopped running partway through the gear extension cycle. Further investigation revealed that the down solenoid for the landing gear motor was operating intermittently. When the solenoid was tapped, the motor started running again and the landing gear continued to extend and lock in the down position. The emergency lowering function was found to operate satisfactorily when tested in the hangar. It was concluded that the faulty landing gear down solenoid had interrupted the electrical supply to the motor during gear extension in flight, preventing the gear from fully extending. The tripped circuit breaker was believed to be associated with the faulty solenoid, probably as a result of an intermittent internal short in the solenoid.
Rectification
The landing gear down solenoid was replaced. The up solenoid was also replaced as a precaution. Since the rectification, the problem has not re-occurred.