What happened
On 25 October 2009, a Cessna F177RG Cardinal, registration G-AZVP, was conducting a private flight when the pilot attempted to land at Derby Aerodrome. During the approach, the pilot noticed that the green 'down-and-locked' light on the instrument panel failed to illuminate after the landing gear lever was moved to the down position. After cycling the gear lever twice with no change in the light indication, the pilot decided to use the emergency hydraulic hand pump to manually extend the landing gear.
The pilot operated the hand pump until firm resistance was felt, but then focused on the final approach. The landing itself was performed on the main wheels first and appeared normal; however, as the nosewheel made contact with the runway, the nose gear collapsed. The aircraft came to rest on the runway, resulting in a bent propeller and damage to the front cowling and landing gear doors. The pilot was uninjured during the event.
The investigation
An examination of the aircraft's landing gear system was conducted by a maintenance organisation. Investigators found that the nose landing gear had successfully moved into the locked position. However, the investigation revealed that the left main landing gear down-and-locked microswitch had moved out of its proper position. This misalignment prevented the electrical circuit from completing, which caused the green indicator light to remain extinguished.
Findings
- The lack of gear indication was caused by a misaligned microswitch on the left main landing gear.
- During the manual extension process, the pilot felt firm resistance in the hand pump but did not continue pumping to achieve the necessary 'clunk' or 'thud' that signifies the nose gear is fully locked.
- Insufficient hydraulic pressure was applied via the manual pump to fully lock the nose gear into position.