History of Flight
On 15 February 2017 at 0210Z, the pilot of a Cessna T188C, registration ZS-ALB, departed from a private airstrip at Kwaggasbult, Dendron, Limpopo Province, for a crop-spraying operation. The pilot had refuelled the aircraft with 30 US gallons of fuel. The intended spray field was located approximately 15 nautical miles north-west of the departure point.
About ten minutes into the flight, the engine RPM began to drop, and the aircraft could not maintain its altitude of 600 feet above ground level. The pilot increased throttle and lowered flaps in an attempt to maintain height, but these actions were unsuccessful. The pilot then dumped the crop-spraying load and selected an open field near a residential area to perform a forced landing.
During the landing roll, the aircraft's undercarriage struck rocks on the selected field and broke off. The propeller and engine cowling were also damaged. The pilot was not injured. The accident occurred at 0220Z at coordinates S23° 18' 38.7" E029° 14' 34", elevation 3,452 feet, approximately 6.4 nautical miles north-east of Dendron. Meteorological conditions were wind light and variable, temperature 18°C, with few clouds at 6,500 feet.
Damage
The undercarriage was separated from the aircraft after impacting rocks. The propeller and engine cowling sustained damage. The engine did not stop during the accident sequence.
Investigation Findings
The investigation revealed that the pilot was appropriately rated and licensed for the agricultural operation. The aircraft had completed a maintenance inspection at 4,777.9 hours and was released to service following a test flight on 7 February 2017; it was serviceable at the time of the accident.
The engine lost RPM but never stopped. The pilot executed a forced landing that was unsuccessful due to the undercarriage colliding with rocks. Post-accident engine testing found the engine operated normally. The terrain selected for the forced landing was unsuitable because rocks covered by grass contributed to the fuselage damage.
Probable Cause
The probable cause was determined as: aircraft lost engine RPM, as a result the pilot executed a forced landing during which the undercarriage collided with a rock and broke off. The cause of the engine RPM drop was undetermined.