Occurrence
On 25 October 2024, at 0830Z, a Jabiru SK aircraft (registration ZU-BSA) departed from Springs Aerodrome (FASI) in Gauteng for a private flight to Brits Aerodrome (FABS) in North West province under visual meteorological conditions. Approximately 25 minutes into the flight, the pilot felt an engine vibration. She broadcast a Mayday call on the TIBA frequency 124.8 MHz and initiated a precautionary landing on an open field beside the N12 highway near Daveyton. During the landing, the right main gear struck a rock, damaging the wheel. The pilot shut down the aircraft, disembarked unassisted, and was uninjured. The aircraft sustained substantial damage to the wheel.
Engine Examination
The aircraft owner arranged for an approved person to perform an engine teardown. The inspection revealed that Cylinder No. 4's piston was completely shattered. The connecting rod on Cylinder No. 4 was severely deformed, bent, and twisted. The cylinder head of Cylinder No. 4 was pitted from the failed piston, but both intake and exhaust valves remained intact. Aluminum particles from the shattered piston were found in the oil sump. A loose circlip, which secures the piston pin, was also visible among the debris. The report concluded that a complete piston failure caused the destruction of Cylinder No. 4, not a valve failure. Two potential causes were noted: the loose circlip may have allowed the piston pin to move, hook onto the engine block, and break the piston; alternatively, a cracked piston may have failed spontaneously.
Findings
The pilot held a valid Private Pilot Licence and Class 2 medical certificate. She had flown 78.7 hours on this aircraft type. The aircraft's last annual inspection was on 22 October 2024 at 2028.5 airframe hours; the incident occurred 0.5 hours later. The engine had accumulated 1348.8 total hours, with 786.8 hours since its last overhaul. The engine overhaul interval is 1000 hours. The aircraft had a valid Authority-to-Fly certificate. Weather conditions were not considered contributory; wind was 280° at 10 knots.
Probable Cause
In-flight engine failure caused by the failure of the No. 4 piston and its connecting rod; the cause of this failure cannot be determined conclusively. The engine failure resulted in the successful precautionary landing.
Contributing Factor
Piston failure.