What happened
On 27 December 2019, a Beechcraft Bonanza A36, registration ZS-KAJ, was conducting a private flight from Grand Central Aerodrome to Louis Trichardt Aerodrome. The flight proceeded normally through the takeoff and cruise phases under visual flight rules. However, as the pilot was turning onto final approach and had received landing clearance, the engine power dropped to idle.
Despite the pilot's attempts to troubleshoot the issue, the throttle remained stuck at full power while the engine failed to produce thrust. The pilot was forced to glide the aircraft over a line of trees. During this maneuver, the main landing gear struck treetops, and the right wing subsequently clipped a tall tree, causing the aircraft to veer 45 degrees from its original path. The aircraft eventually impacted the ground short of Runway 10, causing the left main wheel to collapse and the aircraft to spin before coming to a halt. All six people on board escaped the zero fatalities incident without injury.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's maintenance history. Upon inspecting the engine cowling after the landing, the pilot discovered that critical hardware was missing from the fuel control unit. The investigation focused on the connection between the fuel throttle rod end and the fuel control unit arm. Records showed that while the engine and fuel control unit had been installed in 2011, they had not been removed for overhaul since that time. The investigation also reviewed the most recent 100-hour maintenance inspection conducted in July 2019.
Findings
- The engine lost power because the bolt connecting the fuel throttle rod end to the fuel control unit arm separated from the nut.
- The hardware—specifically the bolt, nut, and pin—was not recovered from the site.
- The investigation determined that the bolt was not properly secured with a safety pin, which allowed it to loosen due to engine vibration over time.
- The aircraft had sufficient fuel reserves for the intended flight.
- The pilot held a valid commercial license and appropriate type ratings.
Safety action
- It is recommended that aircraft maintenance organisations ensure all maintenance personnel strictly adhere to manufacturer instructions and implement necessary dual inspections to prevent improper hardware installation.