What happened
On 22 December 2010, a Cessna 172, registration ZS-JXE, was conducting a private scenic flight after completing two circuits at Kitty Hawk Aerodrome (FAKT). While flying approximately seven minutes away from the aerodrome at an altitude of 400 feet, the engine began running roughly. Despite the pilot increasing the throttle and engaging the fuel pump, the engine power continued to decline.
Seeking an emergency landing site, the pilot identified a maize field east of Pretoria near Welbekend. During the approach, the pilot attempted to maneuver around a mound separating two fields, but the aircraft descended rapidly during a turn. The ground was notably soft and wet following heavy rainfall in the preceding days. Upon touchdown, the wheels sank into the earth, causing the nose landing gear to detach. The aircraft subsequently nosed into the ground and overturned.
The investigation
SACAA AIID investigators examined the wreckage and the engine components to determine the cause of the power loss. The investigation focused on the magneto's condition and the fuel used in the aircraft. Technical inspections of the magnetos revealed that the condenser leads on both the left and right units were in poor condition. Specifically, the wiring was touching the magneto frames, which effectively earthed the components and prevented the production of sparks.
Furthermore, the investigation found evidence of detonation in the second and fourth pistons. Analysis of the fuel records indicated that the aircraft had been operating on automotive fuel for approximately 23 hours prior to the accident, despite the lack of a Supplemental Type Certificate (STC) for such use. While the engine sustained significant damage from this detonation, investigators determined that the primary cause of the immediate engine failure was electrical.
Findings
- The engine failure was caused by both magnetos being earthed due to faulty condenser leads.
- The improper installation of the magnetos by the maintenance organization led to the chafing of the earthwires.
- The aircraft had been using automotive fuel for the previous 23 hours without authorization.
- The pilot was properly licensed and rated for the operation.
- The landing was unsuccessful due to the soft, saturated ground conditions and the loss of engine power.