What happened
On 14 January 2014, a Piper PA-28RT-201T Turbo Cherokee Arrow IV, registration G-OPJD, was conducting a private flight from Alderney to Thruxton Airfield. While on final approach to Runway 25, the pilot observed that the green indication light for the right main landing gear was not illuminated.
In an attempt to rectify the issue, the pilot performed a go-around and attempted to recycle the gear several times. During subsequent circuits, the pilot requested visual confirmation of the gear status from the control tower but did not receive a definitive response. After approximately 45 minutes of attempting to extend the gear, including the use of the manual free-fall release lever, the pilot proceeded with an emergency landing. The aircraft's fuel was cut prior to touchdown; however, the right main landing gear collapsed during the landing roll. There were no fatalities and no injuries to the pilot or the two passengers. The aircraft sustained damage to the right wingtip, flap, right entry step, right landing gear, and the underside of the aerial.
The investigation
The investigation focused on the failure of the landing gear to extend and lock. Examination of the aircraft revealed that the downlock hook had failed to engage with its pin. This mechanism was found to be stiff due to a buildup of dirt and light corrosion, which prevented the hook from engaging properly during gravity-driven extensions.
Furthermore, the investigation found that the landing gear could not be retracted using either the electric pump or the manual hand pump. Upon removing and inspecting the Automatic Gear Down and Emergency Free Fall Gear Valve, investigators discovered that a broken seal had released fragments that were obstructing the normal gear down port. This blockage prevented hydraulic pressure from properly extending the gear.
Findings
- The right main landing gear failed to lock because the downlock hook mechanism was stiff due to corrosion and dirt.
- A broken seal within the Automatic Gear Down valve caused debris to block the hydraulic port, preventing normal powered extension.
- Because of the valve blockage, the landing gear was actually extending via free-fall rather than through hydraulic power during the initial attempts.
- The increased friction in the downlock hook mechanism prevented the gear from successfully engaging the pin during these gravity-based extensions.