What happened
On July 31, 2002, a Cessna 310, registered as V5-JTF, was conducting a domestic charter flight from Virginia Aerodrome toward Pilanesberg. Shortly after departure, the pilot encountered an issue where the aircraft's undercarriage failed to retract into the fuselage.
In an effort to resolve the issue, the pilot operated both the standard and emergency landing gear extension systems. However, the undercarriage unsafe warning light remained illuminated, indicating the gear was not properly locked. Following several unsuccessful attempts to clear the warning, the pilot elected to divert the flight to Lanseria Airport.
While performing a fly-past at Lanseria, Air Traffic Control notified the pilot that the right-hand main undercarriage appeared to be partially extended. In response to this information, the pilot decided to retract the gear, which led to a belly landing on Runway 06R. The impact caused damage to the underside of the aircraft and resulted in both propellers striking the runway surface. There were no injuries to the pilot.
The investigation
SACAA AIID investigators examined the mechanical state of the landing gear assembly to determine why the extension systems failed to lock the gear in place. The investigation focused on the structural integrity of the trunnion components and the securing mechanisms used to hold the undercarriage in position.
Findings
The investigation established that the failure was caused by the migration of the right-hand aft upper attachment pin of the main undercarriage trunnion. This movement occurred because the slotted securing pin, which was intended to hold the component in place, had succumbed to corrosion and subsequently broke away.