What happened
On 05 January 2016, a training flight departing from Groutville airfield experienced a sudden loss of power. The aircraft, an Aero trike Spirit II with registration ZU-CDU, was being operated by a flight instructor and a student pilot for training purposes. After approximately 35 minutes of flight, the engine began running roughly, followed by a significant decay in power.
The instructor took control of the aircraft, reducing the throttle to stabilize the engine while searching for a landing site. During the maneuver, the engine ceased functioning entirely. The instructor identified a gravel road on a nearby sugar cane farm as a potential landing spot. While attempting the forced landing, the aircraft pitched forward just before touchdown, causing the nose gear to strike the ground with significant force. The aircraft slid approximately 4/0 meters before coming to a halt. Both occupants sustained minor injuries.
The investigation
Following the incident, the aircraft was returned to Groutville airfield for a technical examination. Investigators and approved technicians inspected the engine, including the cooling fans, heat shrouds, and carburetor, all of which sustained impact damage during the landing.
While the oil system and various gaskets showed no signs of leakage or abnormality, the inspection of the engine internals revealed significant heat damage. Specifically, the rear piston and cylinder exhibited signs of seizure. The investigation established that the engine failure was triggered by detonation, a process where the fuel-air mixture explodes rather than burning smoothly. This combustion malfunction generated extreme temperatures, causing the piston rings to stick and the piston to seize against the cylinder wall.