What happened
On 16 December 2011, an Air Tractor AT-602, registration ZS-NZW, was engaged in commercial crop-spraying operations at Farm Theunissen in Parys, Free State. After taking off from a private gravel runway with a significant fuel load, the pilot began transferring fuel from the left wing tank to the right wing tank while performing a left turn. During this maneuver, the engine stalled at an altitude of approximately 200 feet.
To mitigate the impact, the pilot dumped the remaining agricultural chemicals from the hopper before executing a forced landing in a nearby ploughed cornfield. While the aircraft initially began to roll to a stop, the landing gear wheels sank into a furrow in the soft ground. This caused the aircraft to nose forward, resulting in a propeller strike. The pilot escaped the incident without any injuries.
The investigation
SACAA AIID examined the circumstances surrounding the engine failure and the subsequent impact. The investigation confirmed that the pilot held valid commercial and agricultural ratings, and the aircraft possessed a valid certificate of airworthiness. Meteorological conditions at the time of the incident were clear with light winds, and weather was not a contributing factor.
Investigators noted that the aircraft had been maintained by an approved organization and had undergone a maintenance inspection shortly before the event. The investigation also reviewed the pilot's awareness of manufacturer communications regarding fuel management in this aircraft type.
Findings
- The engine failure was caused by fuel starvation during the fuel transfer process.
- The aircraft sustained minor damage to the engine and bent propeller blades due to the ground strike.
- The pilot was aware of Air Tractor Service Letter #178, which addresses fuel imbalance and the risks of uncoordinated flight leading to starvation.
- The forced landing was unsuccessful in preventing ground contact damage because the landing gear sank into a furrow in the field.
Safety action
- It is recommended that all Air Tractor operators be notified to ensure awareness of Service Letter #178 regarding fuel starvation risks.