Safety analysis The circumstances associated with the accident involving VH-TZJ on 24 October 2013 are still being investigated. This analysis focuses only on the recorded aircraft hours for M18 aircraft operating at higher weights. A number of aircraft manufacturer supplements, Australian exemptions and national and overseas supplemental type certificates have allowed for operation of the PZL Mielec M18 Dromader aircraft at gross weights above the maximum stipulated by the aircraft manufacturer. A number of strategies to reduce accompanying risk have been used, including the progressive adjustment (or factoring) of actual flight hours to determine airframe life. The evidence to date shows that, in a number of cases, the application of adjustments to M18 aircraft flight hours in Australia has been inconsistent and/or unreliable. In particular, it would appear that in the period prior to 2009, such factors may not have been applied at all. In consequence, operators of such aircraft may not have assured themselves that their aircraft’s recorded flight hours truly reflect their aircraft’s airframe life. This raises the possibility that these aircraft might be close to or have exceeded their prescribed maintenance schedules or airframe life, increasing the risk of in-flight failure of aircraft structure(s), components and/or controls. The issue applies to turbine- or piston-engined Australian M18 aircraft approaching any of the 5,000, 6,000 or 10,000-hour service life limits, and which were flown at weights above 4,700 kg prior to 2009 without the appropriate service life factoring having been applied. The centre wing to outboard wing fittings on VH-TZJ, including the one that failed on 24 October 2013, were installed new in 2004. The ATSB estimated that, even if appropriate factoring had been applied, these fittings would not have exceeded the 10,000-hour limit at the time of the accident. However, it is likely that the aircraft would have accrued more than the permitted limit of 10,000 hours by the time of the accident and the airframe would have been required to be removed from service.
Safety analysis The circumstances associated with the accident involving VH-TZJ on 24 October 2013 are still being investigated. This analysis focuses only on the recorded aircraft hours for M18 aircraft operating at higher weights. A number of aircraft manufacturer supplements, Australian exemptions and national and overseas supplemental type certificates have allowed for operation of the PZL Mielec M18 Dromader aircraft at gross weights above the maximum stipulated by the aircraft manufacturer. A number of strategies to reduce accompanying risk have been used, including the progressive adjustment (or factoring) of actual flight hours to determine airframe life. The evidence to date shows that, in a number of cases, the application of adjustments to M18 aircraft flight hours in Australia has been inconsistent and/or unreliable. In particular, it would appear that in the period prior to 2009, such factors may not have been applied at all. In consequence, operators of such aircraft may not have assured themselves that their aircraft’s recorded flight hours truly reflect their aircraft’s airframe life. This raises the possibility that these aircraft might be close to or have exceeded their prescribed maintenance schedules or airframe life, increasing the risk of in-flight failure of aircraft structure(s), components and/or controls. The issue applies to turbine- or piston-engined Australian M18 aircraft approaching any of the 5,000, 6,000 or 10,000-hour service life limits, and which were flown at weights above 4,700 kg prior to 2009 without the appropriate service life factoring having been applied. The centre wing to outboard wing fittings on VH-TZJ, including the one that failed on 24 October 2013, were installed new in 2004. The ATSB estimated that, even if appropriate factoring had been applied, these fittings would not have exceeded the 10,000-hour limit at the time of the accident. However, it is likely that the aircraft would have accrued more than the permitted limit of 10,000 hours by the time of the accident and the airframe would have been required to be removed from service.
ao-2013-187_interim.docx