Aerial Topdressing Accident at Orari Gorge Station (ZK-DZA)

Incident Overview and Operations Context On the day of the accident, aircraft ZK-DZA was conducting an aerial topdressing operation at Orari Gorge Station, located approximately 16 km north-northwest of Geraldine in Canterbury. The work began at 08:12, and by 16:30, the aircraft had completed about 100 sorties, distributing 100 tonnes of superphosphate fertilizer over the farm. The operations were generally uneventful, except for two instances of the engine stopping while idling on the ground. One stoppage occurred during start-up after the lunch break, and the other followed a pause at about 16:30 to attach a Transland spreader unit. The pilot was not concerned by these stoppages, noting that the engine had a tendency to do this in warm ambient temperatures and attributing it to “vapour lock.” ## Final Flight and Crash Sequence At about 16:55, the pilot took off again to spread a mixture of 575 kg of selenium pellets and between 100 and 150 kg of superphosphate over a higher area of the farm. The aircraft’s weight and centre of gravity were within permitted limits. About five minutes later, the loader driver heard “a thump” and saw the aircraft on the side of a hill about one kilometre northwest of his position. He immediately radioed base to inform the station manager that a crash had occurred. A farmer working about 4 km away was the only eyewitness to the accident. He saw the aircraft flying away from him and dropping a short trail of fertilizer before making “a funny move sideways” and then coming to a stop on the ground. He returned to his house and telephoned Orari Gorge Station to raise the alarm. Station personnel arrived at the crash scene by 4WD vehicle within ten to fifteen minutes. They found the aircraft wrecked and the pilot dead. No fire had occurred. ## Crash Site and Damage The crash site was on a steep grassy slope at 1,700 feet above mean sea level. The aircraft had contacted the ground in roughly a landing attitude, at a high rate of sink, and drifting to the left. It was severely damaged: the main undercarriage legs were separated, the nose leg was folded back under the fuselage, the engine was displaced, and the spreader was torn off. Of the rest of the airframe, only the tail section remained intact. Deceleration was rapid, and the ground slide covered a distance of sixteen metres. The accident was not survivable. ## Investigation Findings The weather was calm with only high cloud. Examination of the engine revealed no evidence that it may have lost power in flight. An autopsy on the pilot showed that he had received a broken neck and a ruptured heart in the impact. He was suffering from moderately severe coronary heart disease at the time of death. The crash investigator concluded that this very experienced pilot may have had a heart attack and been seriously incapacitated in flight, prompting him to attempt an immediate emergency landing on the hillside.