What happened
On 16 August 2004, a Socata TB2 and0 Trinidad, registration G-FIFI, was conducting a private local flight from Kemble Airfield. Following a routine takeoff, the pilot noticed that while the main landing gear lights indicated a locked position, the 'transit/unlocked' light for the nosewheel remained illuminated.
After performing a visual inspection near the control tower, air traffic control confirmed that the nosewheel appeared to be stuck at an angle of approximately 45 degrees from the vertical. The pilot climbed to 2,000 feet to consult the operating handbook and attempt emergency checklists, but the gear could not be secured. After declaring an emergency, the pilot opted to land on the asphalt runway. During the landing, the pilot attempted to keep the nosewheel off the ground for as long as possible; however, shortly after touchdown, the nosewheel collapsed, causing the aircraft to skid 130 metres. There were no injuries to the pilot or the passenger.
The investigation
The investigation focused on the failure of the landing gear to lock and the subsequent collapse. Engineers examined the hydraulic system, which relies on a motor-driven generator, and the secondary emergency system which uses compressed gas struts to lock the nosewheel.
It was determined that the compressed gas struts lacked sufficient pressure to fully lock the gear. Additionally, the investigation found that the brushes on the hydraulic generator were excessively worn, likely rendering the primary hydraulic system inoperable. Although the aircraft had recently undergone an annual inspection, the generator brushes had not been checked. The maintenance organisation had omitted this task because they believed it was not required under the Light Aircraft Maintenance Schedule (LAMS).
Findings
- The emergency compressed gas struts lacked the necessary pressure to ensure the nosewheel locked in the down position.
- The hydraulic generator brushes were worn to a point that likely prevented the hydraulic system from functioning.
- The hydraulic generator brushes had not been inspected because the maintenance provider believed the inspection was not mandatory under the generic LAMS guidelines, despite the manufacturer's manual recommending checks every 1,000 hours.