What happened
During a mission to disperse diesel fuel over a scrub-covered ravine in the Omahina Valley near Waverley, a Fletcher aircraft experienced a critical mid-air emergency. Prior to the accident, the pilot had briefly operated the hopper jettison control to increase the deposit of diesel on thick vegetation. This action caused the cockpit to fill with dense, black smoke, revealing that diesel oil had coated the interior of the fuselage from the hopper back to the tail cone. Additionally, an oil film was present on the underside of the aircraft.
After the crew attempted to clean the oil and repair a leaking connection in a spray boom, several sorties were completed without incident. However, during the eighth sortie, as the aircraft was climbing out of the ravine toward a landing strip located approximately 300 to 400 feet above the valley floor, witnesses observed flames emitting from the underside of the fuselage.
As the aircraft leveled out and turned 90 degrees to the right, it disappeared behind a ridge. The plane subsequently struck trees on a steep slope before diving almost vertically toward the ground. The impact resulted in the detachment of the right wing and ignited fuel from broken lines. The fire was further fueled by diesel released from the hopper jettison system and petrol from the Kohler APU tank.
Findings
An investigation into the crash determined that an in-flight fire created an emergency situation that compromised the pilot's ability to maintain full control of the aircraft. The fire was most likely triggered by the ignition of diesel oil fumes and residue within the fuselage, with the heat from the APU exhaust pipe serving as the primary ignition source.