What happened
On 1 June 2017, a Reims Cessna F406 Caravan II, registration G-RVLX, was performing a commercial cargo flight from East Midlands Airport to Kristiansund, Norway. While the aircraft was cruising at 10,000 feet, a warning light indicated that a door was unsecure. Upon inspecting the P1 emergency exit, the pilot observed that the main handle was not fully in the locked position.
In an attempt to secure the door, the pilot tried to pull the door inward and move the handle back to the closed position. This action caused the door to suddenly release with significant force, popping outward into the slipstream. Although the door remained attached to the airframe, the pilot immediately declared a MAYDAY and diverted the flight to Newcastle, where the aircraft landed without further incident. There were no injuries to the crew.
The investigation
An investigation involving the operator and the aircraft manufacturer examined the mechanical failure of the door assembly. It was determined that the pilot may have accidentally moved the emergency exit main handle while handling a portable oxygen bottle. As the handle reached the overcentre position, mechanical vibrations and spring tension caused it to move into the fully open position, triggering the warning light.
While a secondary latch was intended to keep the door closed, it failed to perform its function. The investigation found that the mechanism suffered from low friction and excessive lost motion, which was caused by a migrated roll pin within the operating lever. This prevented the secondary latch from properly securing the door against the aerodynamic forces of the slipstream.
Findings
- The primary cause of the door opening was the inadvertent disturbance of the emergency exit main handle during cockpit activities.
- A secondary safety latch failed to hold the door closed due to a migrated roll pin and low friction in the mechanism.
- The door sustained damage to the frame, the exit door itself, and the surrounding structure.