After arriving at the property strip, the pilot was briefed on the spray area by the property owner. In the meantime, the aircraft was loaded with 1,500 litres of spray solution. The pilot subsequently boarded the aircraft and was observed to secure his safety harness, and don gloves and a helmet, before departing for the task.
The spray area was about 800 m from the strip. Witnesses at the strip observed the aircraft as it began spraying and noted that the procedure turns at the end of each run were conducted at a consistent height. The turns were flown initially to the left to offset the aircraft from the previous run, and then reversed to align the aircraft for the next run. About 30 minutes after spraying had commenced, one of the witnesses observed the aircraft rolling right during a turn reversal in a procedure turn. The aircraft continued rolling until it was in an inverted attitude, and then descended into the ground where it immediately caught fire.
The aircraft was fitted with a Pratt and Whitney PT6A-45R turbine engine driving a five-bladed metal Hartzell reversible-pitch propeller. This engine-propeller combination provided the aircraft with a significantly higher performance than other models of the aircraft type that were powered by piston engines.
The pilot was appropriately qualified to undertake the flight. Of his total flying experience, about 9,500 hours was in agricultural flying. However, he had flown only about 80 hours on turbine-powered Air Tractor aircraft, the bulk of his flying experience being on piston engine models.
Examination at the accident site revealed that the aircraft had struck the ground inverted and in a level attitude. Ground marks indicated that the aircraft was yawing right and at low forward speed at impact.
The fire destroyed the airframe. The destruction of some components of the flight control system, particularly the aileron system, precluded determination of their serviceability prior to impact.
Three blades of the propeller had failed in overload against the direction of engine rotation. The position of failure was about 200 mm from the propeller hub. The failure surfaces indicated that the blades were at a coarse pitch angle at the time of failure.
The metal end fittings of the pilot's safety harness were found in the wreckage. Each was separated from the other with the latch on the locking buckle stowed in its housing, as it would be if the harness was locked. Examination of the end fittings revealed no discernible deformation on any load carrying part of the fittings, suggesting that the harness was not secured at impact.
The witness description of the aircraft's behaviour, along with the evidence at the impact site, indicated that the aircraft probably stalled aerodynamically as the pilot reversed the direction of the procedure turn. It is likely that the aircraft was in a nose-high attitude at the time. This would explain the apparent low forward speed of the aircraft at impact. Assuming that the pilot was conducting the turns at typical altitudes, it is unlikely that there would have been sufficient height available for the pilot to recover the aircraft to normal flight. The pilot's low experience level on turbine powered Air Tractor aircraft compared with piston engine powered models may have contributed to the loss of control.
Details obtained during the investigation did not allow any conclusions to be drawn concerning the security of the pilot's safety harness at impact.
|Date:||18 September 1997||Investigation status:||Completed|
|Time:||1400 hours EST|
|Location:||15 km S Nyngan|
|State:||New South Wales||Occurrence type:||Collision with terrain|
|Release date:||01 March 1999||Occurrence category:||Accident|
|Report status:||Final||Highest injury level:||Fatal|
|Aircraft manufacturer||Air Tractor Inc|
|Type of operation||Aerial Work|
|Damage to aircraft||Destroyed|
|Departure point||'Montrose', Nyngan NSW|
|Departure time||1330 hours EST|
|Role||Class of licence||Hours on type||Hours total|