What happened
On 14 September 1999, a REIMS F406, registration ZS-OEE, was conducting a commercial flight from Eros, Namibia, to Rand Airport. Approximately 50 nautical miles from the destination, the pilot observed the door unsafe annunciation light illuminate. While a visual inspection of the front and rear cabin doors revealed no obvious defects, the upper rear door unexpectedly opened later in the flight. In response, the pilot decreased the airspeed to 120 knots to stabilize the aircraft.
As the aircraft transitioned to the left base leg for runway 35 at Rand Airport, it encountered turbulence. This atmospheric disturbance caused the lower rear door to open fully. The door subsequently detached from its hinges and began flapping against the fuselage. The stay cable, which was the final connection to the airframe, eventually failed, causing the door to fall into a residential street below. Despite the loss of the door, the pilot successfully completed the approach and landed the aircraft safely.
The investigation
SACAA AIID investigators examined the door closing mechanism to determine why the door failed. The inquiry focused on the mechanical integrity of the locking system and the physical state of the door hardware. The investigation established that the door could be closed even when the mechanism was not in the required over-center condition.
Findings
- The door closing system was found to be operating outside of specified tolerances.
- Evidence of wear and tear was identified within the door mechanism.
- The investigation could not definitively conclude whether the door was improperly secured by the pilot or if the degraded state of the mechanism allowed it to unlatch during flight.