Accident Overview
On 22 December 2010 at 1520Z, a Cessna 172 (registration ZS-JXE) operated by a private pilot experienced an engine failure during a scenic flight. The aircraft had departed Kitty Hawk Aerodrome (FAKT) at approximately 1500Z for two circuits and a scenic flight. The pilot held a private pilot license and had a total flying experience of 503.3 hours, with 459.2 hours on type. The weather at the time included a surface wind from 340° at 20 knots and a temperature of 28°C.
Sequence of Events
After completing two circuits and landings, the pilot flew south-south-east of the aerodrome. At about 400 feet AGL and seven minutes from Kitty Hawk, the engine began running rough. The pilot increased throttle but engine revs decreased. The fuel pump was switched on with no effect. The pilot selected a forced landing area in a maize field with plants about 250 mm high. During the approach, the aircraft descended fast and touched down on wet ground—over 100 mm of rain had fallen in the previous three days. The wheels sank into the soft soil, the nose landing gear broke off, and the aircraft nosed over onto its back.
Injuries and Damage
The pilot sustained minor injuries. The aircraft was substantially damaged, including the propeller, wings, left-hand wing strut (bent), vertical stabilizer, and the nose wheel breaking off. The maize field also sustained damage.
Investigations
Examination of the magnetos revealed that both were earthed: the right magneto had a condenser lead in bad condition with wire touching the frame, and the left magneto had a similar issue. The engine was dismantled and found detonation on pistons No. 2 and No. 4, with melted aluminium heads causing oil filter blockage and subsequent seizure. The pilot stated that automotive fuel had been used for the last 23 hours of operation, and the aircraft lacked a supplemental type certificate for such fuel. However, the investigation concluded that the engine failure was caused by the magneto earthing, not the detonation.
Probable Cause
The probable cause was an unsuccessful forced landing due to engine failure because both magnetos were earthed via bad condenser leads.