History of the Flight
The aircraft was cruising at FL100 en route from East Midlands Airport to Kristiansund, Norway, when a door warning light illuminated. The pilot observed that the P1 emergency exit main handle was slightly away from its locked position. As he reached to pull the door inward and the handle toward closed, the door "popped out with an extremely large amount of force" within one to two seconds. The door remained attached to the aircraft. The pilot declared a MAYDAY and returned to Newcastle without further incident.
Investigation
The operator conducted an investigation in collaboration with the aircraft manufacturer. The investigation concluded that the pilot may have inadvertently disturbed the emergency exit main handle while checking or operating a portable oxygen bottle. When the handle was nearly overcentre, vibration and a spring action in the mechanism caused it to move fully open, illuminating the door warning light. A secondary latch initially held the door closed, but due to low friction in its mechanism and lost motion from a migrated roll pin in its operating lever, it did not secure the door, allowing it to open into the slipstream.
Safety Actions
The operator implemented several safety actions:
- An email was sent to all crew to notify them of the event and emphasize correct door operation and security.
- A fleet check of aircraft with similar doors was conducted to verify correct operation of primary and secondary locks.
- Placarding of the secondary handle will be improved to clearly indicate the locked position.
- A strap will be fitted to the emergency exit main handle to reduce the likelihood of inadvertent disturbance.