On 29 December 2008, at about 1145 Eastern
Daylight-saving Time, a PZL-M18A Dromader (TPE331) aircraft,
registered VH-IGT, took off from a road on a property 58 km
south-west of Nyngan, New South Wales to conduct agricultural
spraying operations. About 10 minutes later, the aircraft was seen
flying back towards the road when a witness saw something fall off
the aircraft, and reported that the aircraft then rolled and
impacted the ground. The pilot, who was the sole occupant, was
fatally injured.
The investigation found that the outboard 1.8 m of
the right wing separated from the aircraft resulting in a loss of
control and subsequent impact with the terrain. The separation of
the right wing section could not be conclusively attributed to any
particular factor.
During the course of the investigation, it was
determined that a number of operators of the aircraft type were not
applying the appropriate service life factors to determine the
effective hours flown when their aircraft were operated at take-off
weights above 4,700 kg. The effect was to overestimate the
remaining service life of those aircraft.
It was also found that operators had an
interpretation of the Civil Aviation Safety Authority (CASA)
exemptions that, by their understanding, permitted operation at
weights in excess of the maximum take-off weight and allowed them
to operate at higher take-off weights without the need to account
for the additional limitation imposed by the manufacturer for
operation at those weights.
As a result of the accident, the following safety
action has been taken or proposed:
- The operator undertook a retrospective process of applying the
service life factors to its aircraft fleet during operations that
had involved take-off weights above 4,700 kg and will apply them to
all relevant future flights.
- CASA advised that they had contacted Certificate of
Registration holders of M18 Dromader aircraft to verify that they
had a procedure for recording and factoring aircraft hours that
included overweight operations. Further verification would also
occur as part of CASA's routine surveillance program. CASA also
advised that they will provide education to operators on the
intention of the exemptions and will be revising the exemptions to
ensure that the intended interpretation is clear.