What happened
On 26 February 2022, a Thunderbird MKVI aircraft, registration ZU-ECY, departed from New Tempe Aerodrome in the Free State for a return flight to Lindbergh Lodge in the North West province. The flight was being operated under visual flight rules by a pilot and one passenger.
While cruising approximately 17 nautical miles from the departure point, the pilot observed the engine temperature gauge rising to its maximum limit of 195°C. Due to the uncertainty regarding the cause of this abnormal reading, the pilot decided to perform a precautionary landing in an open field. During the landing maneuver, the right main landing gear detached, and the nose wheel struck a rock. This impact caused the aircraft to nose over, resulting in the propeller striking the ground. While the aircraft sustained substantial damage, there were 0 fatalities and no injuries to the occupants.
The investigation
SACAA AIID investigators examined the aircraft's maintenance history and the mechanical state of the engine. The investigation confirmed that the pilot held a valid National Pilot Licence and a current medical certificate. The aircraft's last annual inspection had been completed by a licensed maintenance organization only 0.35 flight hours prior to the accident.
Technical analysis of the engine, a Rotax 912 ULS, revealed that a water pipe responsible for supplying coolant to the radiator jacket had become loose. This disconnection caused a gradual loss of coolant, which triggered the overheating. The investigation determined that the damage to the airframe was a direct result of the impact forces from the rough landing terrain and the subsequent nose-over.
Findings
- The engine temperature reached its maximum threshold during the cruise phase because the water pipe disconnected during flight.
- A water pipe clamp was likely not properly secured following the most recent annual inspection, leading to the coolant leak.
- The aircraft's engine was found to be undamaged upon inspection after the pipe clamp was replaced.