What happened
On 18 April 2018, a TL Ultralight TL-2000 STING, registration ZU-JEO, was conducting a ferry flight from Kuruman Airfield to Tedderfield Airfield. While joining the arrival circuit at the destination, the pilot attempted to deploy the landing gear but discovered the nose wheel failed to indicate a locked position. This was accompanied by a low voltage warning light. After unsuccessful attempts to manually extend the gear, the pilot diverted to Rand Aerodrome to utilize available emergency services.
Upon arrival at Rand Aerodrome, the pilot declared an emergency and was cleared to land on runway 29. In an effort to mitigate the impact, the pilot shut off the engine during the flare. However, the undercarriage collapsed upon touchdown, causing the aircraft to skid on its belly. While the pilot escaped no injuries, the aircraft suffered substantial damage to the underbelly and the landing gear components.
The investigation
SACAA AIID investigators examined the mechanical state of the aircraft and the maintenance history of the nose gear assembly. The inquiry established that the nose gear actuator tube had bent, preventing the gear from extending. This mechanical failure caused the actuators to draw excessive current, triggering the low voltage warning.
Further inspection by a maintenance organization revealed that the nose gear had been previously repaired using non-aviation standard components. Specifically, the assembly utilized a non-aviation grade aluminum hollow tube and a bullet cartridge to house a clevis bolt, rather than the part number recommended by the manufacturer. There were also no records in the airframe logbook documenting this specific installation.
Findings
- The primary cause of the undercarriage failure was the use of a non-aviation standard part on the nose gear actuator extension and retraction tube.
- The improvised modification, consisting of a fabricated aluminum tube and a bullet casing, lacked the structural integrity to withstand the forces required to move the nose gear.
- The bending of the actuator tube caused the nose gear to jam, which subsequently prevented the main gear from fully extending and led to the collapse of the main gear actuator during landing.
- At the time of the accident, the pilot's commercial license and medical certificate had expired.