What happened
On the morning of 15 January 2024, a Thrush S2R-H80 aircraft, registration ZS-ART, was conducting agricultural spraying operations near Glenside Aerodrome in KwaZulu-Natal. While flying under visual meteorological conditions, the pilot was approximately 30 minutes into a maize spraying mission when the engine revolutions per minute (RPM) suddenly dropped to idle. After a brief, eight-second period of regained power, the RPM decayed to idle once more.
In response to the power loss, the pilot initiated an emergency circuit, scanning the terrain for a suitable landing site. Between two options—a dam and a maize field—the pilot selected the field containing a center pivot. The aircraft was brought down in the field before airspeed was lost. During the landing roll, the aircraft swerve to the left and stopped approximately 75 meters from the touchdown point. There were no injuries and the aircraft sustained only minor surface scratches from the surrounding vegetation.
The investigation
SACAA AIID investigators analyzed data from the aircraft's MPV-50T engine monitoring system. The data confirmed that engine parameters, including gas generator speed and torque, dropped significantly during the incident. The pilot had attempted to use the emergency lever to recover power, which resulted in a temporary peak in engine parameters before the loss of power persisted.
Technical examinations were conducted on several critical components. The Fuel Control Unit (FCU) was sent to the original equipment manufacturer (OEM) for testing. While the unit passed functional tests, investigators noted corrosion on the main metering valve sleeve. Although this corrosion was on a non-functional surface and did not impede the unit's operation, it is a condition typically associated with the presence of water in the fuel system. The fuel pump also passed all functional tests without deviation.
Findings
- The primary cause of the incident was a sudden reduction in engine power, the exact mechanism of which could not be definitively determined.
- The presence of water in the fuel system remains a possible contributing factor, as evidenced by the corrosion found on the Fuel Control Unit's main metering valve.
- The pilot successfully executed a forced landing in a suitable location, preventing further damage or injury.