What happened
On 16 November 2011, a King Air 200, registration ZS-ACS, was conducting a routine training flight from Wonderboom Aerodrome (FAWB) in Gauteng. While performing maneuvers within the General Flying Area, the flight crew discovered that the right main landing gear had failed to extend.
In an attempt to rectify the issue, the crew performed emergency checklist procedures, utilizing both the normal electrical system and the manual extension method. Despite these efforts, the gear remained retracted. The pilot notified Air Traffic Control of the emergency, and the aircraft was permitted to orbit at 5/5000 feet AGL to burn off fuel while the crew continued troubleshooting. The aircraft subsequently executed an emergency landing on Runway 11 with the right main gear still up. Upon touchdown, the aircraft veered left and slid 1200 meters along the runway before exiting onto the grass. There were no injuries to the two crew members and one passenger, though the aircraft suffered substantial damage to its flaps and belly.
The investigation
SACAA AIID investigators examined the aircraft at a maintenance facility, where retraction tests were performed. The investigation focused on the mechanical integrity of the landing gear system. The inquiry established that the right main landing gear actuator had suffered an internal failure.
Metallurgical analysis of the actuator revealed that the bevel gears within the unit exhibited extensive wear, including missing teeth. It was determined that fragments from the worn teeth had become trapped between the gears, causing the undercarriage drive motor to trip on overload and preventing any extension attempts. Additionally, the investigation found that one of the three support structure sections used to secure the actuator to the wing was fractured and heavily deformed.
Findings
- The primary cause of the incident was the mechanical failure of the right main landing gear actuator due to internal gear wear and tooth breakage.
- The failure of this specific component created a lock-up condition that rendered both the normal and emergency extension systems ineffective.
- The flight crew was properly licensed and followed appropriate emergency procedures and troubleshooting protocols.
- Weather conditions at the time of the incident were clear (CAVOK) and did not contribute to the event.
- The aircraft was being operated by an accredited training organization and maintained by an approved maintenance organization.