What happened
On 5 October 2007, a Fletcher FU24-950M aircraft, registration PK-PNZ, was performing aerial agriculture spraying over the Rokan Estate in Riau, Indonesia. The flight was part of a second daily session of fertilization activities. After taking off from a private airstrip using runway 18, the pilot initiated a left turn toward the plantation area. During the climb, the aircraft encountered a strong wind from the right. This sudden force caused the aircraft to descend, leading the left wing to strike the tops of nearby palm trees. The impact resulted in the loss of the wing tip, making the aircraft uncontrollable and causing it to crash into the plantation approximately 238 meters beyond the runway end. The pilot sustained minor injuries, but the aircraft suffered substantial damage.
The investigation
The investigation focused on the flight technique, environmental conditions, and pilot training. Investigators found that the aircraft was airworthy and had no mechanical malfunctions. The airstrip, located within a palm plantation, functioned much like a tunnel, with trees flanking the runway. Crucially, the windsock at the site was positioned lower than the surrounding tree canopy, making it invisible to the pilot during the pre-takeoff phase. This prevented the pilot from detecting the crosswind conditions. Furthermore, while the pilot held a valid commercial license and type rating, there was no evidence of specific training for the complexities of agricultural flight operations.
Findings
- The pilot lacked specific training and experience regarding the unique demands of agricultural flight operations.
- The aircraft encountered a downdraft or strong crosswind that caused it to sink at a low altitude and low airspeed.
- The windsock was obscured by palm leaves, preventing the pilot from observing wind direction and speed before takeoff.
- The airstrip's configuration, surrounded by 15-meter-tall trees, created a "tunnel effect" that masked environmental changes.
- The operator lacked a formal training syllabus for pilots not already experienced in agricultural maneuvers.
Safety action
Following the accident, the operator implemented new Standard Operating Procedures for agricultural flights and updated the airstrip by widening the runway area and moving the windsock to a position higher than the trees. The Directorate General Civil Aviation subsequently published new regulations specifically for agricultural aircraft operations (CASR Part 137) to standardize safety requirements in the industry.