What happened
On 13 February 2008, an Alouette III helicopter, registration ZS-RJW, was conducting a local flight near the Overberg Fire & Rescue Station to test a newly installed rescue hoist. The flight was intended to verify the functionality of the hoist following recent maintenance work performed on-site by a visiting engineering team.
Shortly after departing at an altitude of approximately 400 feet, the hoist operator noticed an issue with the left aft cabin sliding door. Within moments, the unsecured door moved upward and collided with the main rotor blades. The impact caused severe in-flight vibrations, forcing the pilot to execute an emergency roll-on landing in an open field. During the landing, the damaged main rotor blades struck the tail boom and the tail rotor drive shaft. There were no injuries to the three occupants on board.
The investigation
SACAA AIID investigators examined the maintenance activities that preceded the flight. The investigation established that a maintenance engineer and his assistant had been performing non-scheduled repairs, including the replacement of the tail rotor head and the rescue hoist head. During these tasks, the assistant had moved the left cabin sliding door to access a lubrication bin in the baggage compartment.
Crucially, the floor hatch—which provides the lower guide rail for the door—had been left in the vertical down position to facilitate the hoist replacement. Because the floor hatch was not in its closed position, the door's lower brackets were not seated in their proper rail. The investigation found that the maintenance crew failed to verify that the door was correctly latched before departing the station.
Findings
- The primary cause of the accident was the failure of the maintenance crew to properly latch the door in its bottom rail.
- The maintenance engineer did not perform a sufficient post-maintenance inspection to ensure all components were secured.
- The pilot's pre-flight walk-around was limited to a visual inspection and failed to detect the unsecured door.
- The hoist operator's observation of the door issue occurred too late to prevent the impact.
- The visibility of the door's locking mechanism was compromised because the brackets were painted the same color as the aircraft fuselage.
- The floor hatch was left in the hoisting configuration, which removed the necessary support for the door's lower brackets.