What happened
On 29 August 2011, an Alpi Pioneer 400, registration G-CGVO, was performing a private flight from Shobdon Aerodrome in Herefordshire. As the aircraft was rotating into its takeoff attitude, the left-hand gull-wing door suddenly opened and became detached from the fuselage.
Following the door's release, the pilot performed a landing back on the runway from an altitude of approximately 5 feet. However, the touchdown occurred heavily on the nose landing gear. The impact was severe enough to cause the nosewheel to break off and the aircraft nose to contact the runway, resulting in damage to the propeller tips, the paintwork, and the detached left door.
There were no fatalities and no injuries to the pilot or the passenger on board.
The investigation
Investigators examined the aircraft's door mechanism, which utilized a system of three pins engaging holes in the door post and an override plate on the sill. The investigation found that the handle was in the closed position at the time of the accident.
An inspection by an LAA inspector highlighted several design concerns regarding the carbon fibre door. These included the limited depth of the pin engagement and the shallow nature of the front blind hole, which could lead to structural damage if the pin were to bottom out. Additionally, the inspector noted that the door hinge functioned more like a ball joint, lacking the rigidity of a conventional hinge.
Findings
- The primary cause of the accident was the insufficient engagement of the latching bolts with the door frame.
- The aircraft was loaded very close to its maximum all-up weight at the time of the flight.
- The design of the door hinge provided insufficient structural rigidity.
- The door latching mechanism featured a shallow engagement depth for the pins.