What happened
On 20 July 2012, a Cessna T210M Turbo Centurion, registration G-BEYV, was conducting a private flight from Thurrock, Essex, to Nottingham. During the approach to Nottingham, the pilot noticed that the 'down and locked' indication for the main landing gear failed to appear. Recognizing the risk of the aircraft tipping during landing, the pilot diverted to North Weald Airfield.
Prior to landing, the pilot performed fuel burning to make the aircraft left-wing heavy, and the passenger moved his seat to the rear to ensure the right-hand door could be used for an easy evacuation. While flying over the airfield, ground observers noted that the nose gear appeared down and locked, but the main gear doors were open while the gear remained retracted.
Upon landing at North Weald, the aircraft initially touched down on the tie-down hook of the rear fuselage. The pilot then lowered the nosewheel to the ground. As the aircraft decelerated, it tilted to the left, causing the left wing tip, aileron, and left horizontal stabilizer to strike the runway. The nosewheel then castered to the right, causing the aircraft to rotate 180 degrees before coming to a stop. There were no injuries to the two occupants.
The investigation
Investigators examined the hydraulic system and found that the pilot and passenger had attempted to use the manual back-up pump, but it provided no resistance, suggesting a total lack of hydraulic pressure. The investigation focused on the possibility of an in-flight loss of hydraulic fluid or an internal failure of the hydraulic pump.
Post-accident inspections revealed that the piston of the left main landing gear door hydraulic actuator had been pushed out of the actuator body. This defect provided a path for hydraulic fluid to escape, which would prevent the pressure required to operate the uplock actuators from being maintained.
Findings
- The main landing gear remained retracted because the hydraulic pressure was insufficient to release the uplocks.
- A failure in the left main landing gear door hydraulic actuator allowed hydraulic fluid to escape the system.
- The lack of resistance felt during manual pumping indicated that the system was unable to generate or maintain pressure.
- The aircraft's movement on the runway was caused by the initial touchdown on the fuselage tie-down hook and the subsequent tilting of the aircraft.