What happened
On 31 July 2010, a Pioneer 300 Hawk, registration G-JDRD, was conducting a private flight from Dunkeswell Airfield in Devon. Shortly after takeoff, the pilot attempted to retract the tricycle landing gear. While the two main gears retracted normally, an 'unsafe' warning light indicated that the nose landing gear had not locked.
Following a second attempt to cycle the gear, the nose gear remained in an unsafe position. The pilot attempted to manually wind the gear down, but the indication persisted. Fearing that the nose of the aircraft might dig into the ground and cause an inversion, the pilot decided to perform a landing on the grass area parallel to Runway 2D. A pilot in a separate aircraft visually confirmed that the nose gear was indeed not locked. The subsequent wheels-up landing was successful, resulting in no injuries and only minor damage to the propeller and the area beneath the fuselage.
The investigation
Investigators examined the aircraft by extending all three landing gears and manually locking them into position. The inspection revealed that the nose gear was swinging freely because it was disconnected from the extension and retraction mechanism.
Technical analysis focused on the electrical landing gear actuator, which utilizes a gearbox to drive three shafts. The nose gear assembly features two universal joints on its actuating shaft. The investigation established that the universal joint located at the gearbox end of the shaft had failed due to an overload.
Findings
- The nose landing gear failed to lock down because the universal joint at the gearbox end of the nose gear shaft had failed in overload.
- This failure left the nose gear without any electrical or manual drive from the mechanism.
- The aircraft was fitted with a 10 amp circuit breaker, whereas the manufacturer originally specified a 7 amp breaker. It is unclear if a lower-rated breaker would have tripped and prevented the mechanical damage, though the use of a 10 amp breaker is noted as common.