What happened
On 26 March 2018, a Beechcraft B200, registration ZS-KGW, was conducting a private charter flight from Wonderboom Airport (FAWB) to pick up passengers at OR Tambo International Airport (FAOR). During the approach to FAOR, the crew attempted to extend the landing gear but heard a loud noise emanating from the nose wheel well. Following the gear selection, the cockpit failed to show the required three green lights, indicating the gear was not properly locked.
The crew attempted to orbit the airport to troubleshoot the issue and tried to use the manual emergency extension mechanism. However, the pumping lever handle became stuck, rendering the manual extension unsuccessful. After confirming the gear remained retracted, the crew decided to return to FAWB for an emergency landing. Prior to touchdown, the crew shut down the engines and feathered the propellers. The aircraft performed a wheels-up landing on runway 29, skidding for approximately 450 meters. While the aircraft sustained damage to the propeller blades, landing gear doors, and the under-cargo compartment, there were no injuries to the two crew members.
The investigation
SACAA AIID examined the mechanical components of the nose landing gear retraction and extension mechanism. The investigation focused on why the gear failed to extend despite the crew's efforts. Investigators reviewed maintenance records, which showed the aircraft had been maintained by a regulated organization in accordance with manufacturer procedures, and that all mandatory periodic inspections had been completed.
Findings
- The primary cause of the undercarriage failure was the failure of the actuator sleeve within the nose landing gear assembly.
- This sleeve, which acts as a spacer to maintain the actuator's position, egressed from the bearing plate during operation.
- The loss of the sleeve allowed the actuator to shift from its assembly bracket, causing a misalignment of the actuator drive shaft and the chain drive.
- This misalignment forced the driving chain to jump from the sprocket and become jammed against an assembly bracket, preventing the gear from extending through either normal or emergency procedures.
- The investigation noted that the design of the sleeve lacks a specific securing mechanism, which may have allowed it to migrate out of position during flight operations.