What happened
On 15 September 2014, an Air Tractor AT-802A, registration ZS-TBW, was engaged in aerial firefighting operations near the Mondi Vrede Farm in Mpumalanga Province. The aircraft was part of a coordinated effort involving multiple fire-bombing and spotter aircraft tasked with suppressing forest fires in the area.
During the 13th approach of the day's operations, the aircraft encountered a malfunction with its Fire Retardant Delivery System (FRDS), which prevented the release of the hopper load. While attempting to maneuver, the aircraft descended to approximately 50 feet above ground level. In a nose-up attitude, the aircraft struck a stand of pine trees, which severed the right wing. The impact caused the aircraft to roll into an inverted position and strike the ground at a steep 70-degree angle. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
SACAA AIID investigators examined the wreckage and the aircraft's maintenance and operational history. The investigation confirmed that the pilot was highly experienced, with over 19,000 total flying hours. The aircraft's documentation, including its Certificate of Airworthiness and maintenance logs, were all found to be valid and in order.
Investigators also reviewed the performance of the FRDS. While the pilot had reported a similar issue with the gatebox doors earlier that day, subsequent testing of the system revealed no mechanical anomalies or defects in the dumping mechanism. There was also no evidence that the pilot had successfully engaged the manual or emergency dump systems before the collision.
Findings
- The primary cause of the accident was the collision of the right wing with trees during a right-hand bank maneuver intended to avoid obstacles.
- The aircraft was operating at a low speed of approximately 125 mph, as required by the Aircraft Flight Manual (AFM).
- The terrain was hilly, and the aircraft's flight path involved navigating rising terrain.
- It is likely that the FRDS was activated before the system reached the necessary operating pressure of 3000 psi, which prevented the successful release of the fire retardant.
- The aircraft's flaps were set to 15 degrees, rather than the 10 degrees specified in the AFM procedures.