What happened
On the evening of 8 March 2017, a Beechcraft King Air 90, registration ZS-MHM, was being repositioned from Lanseria Aerodrome to Rand Aerodrome for hangar storage. During the initial approach to runway 11, the pilot received a landing gear unsafe warning. After attempting to troubleshoot the issue and performing a low-level fly-past for air traffic control to visually verify the gear position, the pilot was unable to confirm the gear was down and locked.
Following an unsuccessful attempt to manually extend the gear using the emergency procedure, the pilot elected to land on the longer runway 29. To mitigate risk, the pilot shut down both engines and feathered the propellers to glide the aircraft in. Upon touchdown, the landing gear collapsed as the nose wheel made contact with the runway. The aircraft lost directional control and veered off the runway surface to the left, striking two runway lights in the process.
The investigation
SACAA AIID investigators examined the mechanical state of the aircraft and the cockpit systems. The investigation revealed that the landing gear motor had suffered an internal failure when a commutator end bearing collapsed. This failure caused excessive current flow, which subsequently tripped a circuit breaker. Notably, this circuit breaker was located beneath the floor structure, making it inaccessible to the pilot during the flight.
Furthermore, the investigation looked into the manual extension process. It was discovered that a loose cover plate, caused by a missing screw, was obstructing the movement of the manual extension hand crank. This mechanical interference likely prevented the pilot from applying sufficient pressure to fully lock the gear in place.
Findings
- The primary cause of the incident was the inability to secure the landing gear in the down and locked position via either the normal or emergency systems.
- An internal bearing failure in the landing gear motor led to an electrical overload.
- The deactivated circuit breaker was positioned under the floor panel, out of the pilot's sight and reach.
- A loose securing plate near the manual extension mechanism restricted the travel of the hand crank, which may have misled the pilot into believing the gear was properly extended.
- The aircraft sustained damage to the lower fuselage, landing gear doors, flaps, propellers, and engine nacelles, with no injuries reported to the pilot.