What happened
On 11 July 2018, a Piper PA-3 and200T Seneca II, registration G-FILE, was performing a private flight from Bristol Airport to Cotswold (Kemble) Airport. Upon arrival, the pilot intended to execute a touch-and-go landing on Runway 08.
During the landing sequence, the pilot observed three green landing gear indications in the cockpit. The aircraft touched down at approximately 90 knots. As the pilot retracted the flaps in preparation for the subsequent takeoff, the left wing suddenly dropped. The pilot attempted to correct the wing drop using the ailerons and aborted the takeoff attempt. However, the left main landing gear collapsed, causing the left propeller, aileron, and the underside of the left wing to strike the runway. The aircraft veered left and came to a halt on the grass area between the tarmac and grass runways. There were no injuries to the pilot or the two passengers on board.
The investigation
The investigation examined the aircraft's hydraulic and landing gear systems. The Piper PA-34-200T Seneca II utilizes a retractable hydraulic tricycle configuration where each leg is secured by a spring-loaded downlock hook.
Investigators found that during the recovery of the aircraft, the right main landing gear also collapsed. At the accident site, it was discovered that neither main landing gear downlock was engaged. Interestingly, the recovery team found that hydraulic pressure in the system was preventing the downlocks from re-engaging, a condition that was only resolved after the pilot operated the cockpit emergency landing gear release lever to depressurize the system.
Findings
- The investigation established that the main landing gears became unlocked at some point after the pilot had confirmed the gear was down via the cockpit indicators.
- It is possible that a brief application of hydraulic pressure to the retraction system occurred during the landing, which was sufficient to unlock the gears but not to retract them.
- No mechanical defects were found in the landing gear, linkages, or microswitches that could have caused the unlocking.
- The specific cause of the hydraulic pressure that triggered the unlocking could not be determined.