What happened
On the morning of 1 March 2025, a pilot operating a Storm RG aircraft, registration ZU-EOA, departed from the Aloe Bush Game Lodge Airstrip in Mpumalanga for a private flight. The flight was being conducted under Part 94 regulations in clear visual meteorological conditions.
After approximately 35 minutes of stable flight, the engine began running roughly and began emitting white smoke from the engine compartment. Shortly after these symptoms appeared, the engine ceased operation entirely. Despite the pilot's attempts to restart the engine, the power loss persisted, necessitating an emergency forced landing on the R3/Vaalfontein Road. During the landing roll, the pilot lost control of the aircraft, causing it to veer off the road and collide with a perimeter fence. The pilot escaped the wreckage without injury, but the aircraft sustained substantial damage to its engine, wings, landing gear, propeller, and canopy.
The investigation
Following the accident, the engine was transported to an approved maintenance organization for a technical teardown. Investigators and engineers examined the internal components of the engine to identify the source of the smoke and subsequent power loss. The examination focused on the cylinder assembly and the mechanical integrity of the valve train.
Findings
Technical analysis revealed that the exhaust valve spring retainer had fractured. This failure was the primary driver of the accident, as the broken retainer compromised the structural integrity of the exhaust valve assembly. This allowed the valve and piston assembly to shift out of their intended alignment, forcing internal components into the combustion chamber. This mechanical interference caused the abnormal combustion, visible as smoke, and ultimately led to the total engine stoppage. The investigation also confirmed that the weather conditions were favorable and not a contributing factor to the event.