What happened
On the morning of 11 January 2023, an Air Tractor AT-402A, registration ZS-THH, departed from the unlicensed Leeukop Aerodrome near Deneysville, Free State, for an agricultural spraying mission. The aircraft was carrying 1,000 litres of herbicide and 400 litres of fuel.
During the takeoff roll on Runway 26, the pilot experienced a sudden gust of wind from the right, causing the tail wheel to settle back onto the grass surface. In an attempt to regain lift and reduce weight, the pilot dumped the hopper load. However, the aircraft failed to reach sufficient rotational speed. The left main landing gear struck a fence post and support pole at the end of the runway, and the left wing collided with a gate. This impact caused the aircraft to spin 180 degrees before coming to rest in an adjacent maize field. The pilot escaped the 0 fatalities accident without assistance, though the aircraft sustained substantial damage.
The investigation
SACAA AIID investigators examined the aircraft's weight and performance parameters. They determined that the aircraft's takeoff weight was approximately 3,378 kg, which exceeded the maximum takeoff weight (MTOW) of 3,175 kg by about 6%.
Analysis of the airfield conditions revealed that the 980-metre grass runway featured an uphill slope for the chosen takeoff direction. Based on the aircraft's configuration and the high density altitude of 6,461 feet, the required runway distance to clear a 50ft obstacle was estimated at 1,334 metres for a paved surface, implying even greater requirements for the unpaved, sloping strip.
Findings
- The pilot failed to perform a weight and balance calculation or consult the Aircraft Flight Manual (AFM) regarding required takeoff distance prior to the flight.
- The aircraft exceeded its maximum takeoff weight, directly impairing takeoff and climb performance.
- The available runway length was insufficient for the aircraft's heavy configuration and the uphill terrain.
- High density altitude may have further degraded engine performance during the critical takeoff phase.
- At the time of the accident, the aircraft was not yet officially endorsed on the operator's Air Operating Certificate (AOC).