In-flight breakup - PZL M18A Dromader, VH-IGT, 58 km south-west of Nyngan, New South Wales, on 29 December 2008

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.