What happened
On the afternoon of 30 October 2024, a Cessna 172E with registration ZS-DVY was being ferried from Cape Winelands Airport (FAWN) to Cape Town International Airport (FACT) following a periodic maintenance inspection. The flight was being operated under private (Part 91) regulations in visual meteorological conditions.
While orbiting in the vicinity of Cape Town International Airport to allow other traffic to pass, the engine experienced a sudden drop in power, falling from 2300 RPM to 1000 RPM before ceasing entirely. The pilot declared a Mayday and, realizing the aircraft could not reach the runway, opted to perform a forced landing in an open field near the Symphony Nature Reserve. During the landing on the uneven, grass-covered terrain, the landing gear collapsed and the propeller struck the ground, resulting in substantial damage to the aircraft. The pilot escaped the wreckage without injury.
The investigation
SACAA AIID investigators examined the aircraft's maintenance history and the meteorological conditions at the time of the incident. The aircraft had recently undergone a mandatory periodic inspection (MPI) on the same day as the flight. Post-accident inspections of the fuel tanks revealed approximately 60 litres of Avgas 100LL remained, which was sufficient for the intended flight duration.
Engineers conducted a test run of the engine at a maintenance facility, which met all required operational parameters. While the maintenance organization could not definitively prove the exact cause of the power loss, investigators analyzed the atmospheric data, noting a temperature of 22°C and a dew point of 13°C.
Findings
- The pilot held a valid Commercial Pilot Licence and a Class 1 medical certificate.
- The aircraft's maintenance and airworthiness documentation were up to date.
- Based on the recorded temperature and dew point depression, the carburettor icing probability chart indicated a risk of moderate icing at cruise power or serious icing at descent power.
- It is probable that carburettor icing caused the engine to lose power and stop while the aircraft was orbiting.