What happened
On 15 February 2017, a Cessna T188C, registration ZS-ALB, departed from a private airstrip at Kwaggasbult Dendron in the Limpopo Province to perform agricultural spraying duties. The pilot had recently refueled the aircraft with 30 US gallons of fuel and intended to spray a field located approximately 15nm to the northwest.
Roughly ten minutes into the flight, the pilot experienced a sudden drop in engine RPM. Despite attempts to increase throttle and deploy flaps to maintain altitude, the aircraft could not sustain its 600-foot AGL flight path and began to descend. To mitigate the risks of the descending aircraft, the pilot dumped the chemical load before selecting an open field near a residential area for an emergency landing. During the landing roll, the aircraft's undercarriage struck rocks hidden beneath the grass, causing the gear to break off. The impact also resulted in damage to the propeller and engine cowling. The pilot escaped the incident without injury.
The investigation
SACAA AIID investigators confirmed that the pilot was appropriately licensed for the type of operation being conducted. The aircraft had recently undergone a maintenance inspection and a successful test flight on 7 February 2017, and was considered airworthy at the time of the event.
While the engine experienced a loss of RPM, investigators noted that the engine did not actually stop during the sequence. Post-accident testing of the engine revealed that it was operating normally, leaving the specific reason for the initial RPM drop unidentified.