02-15-2016, 02:15 PM
FINAL REPORT - In-flight breakup involving PZL Mielec M18A Dromader aircraft, VH-TZJ, 37 km west of Ulladulla, NSW on 24 October 2013
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Quote:What happenedSafety Issues:
On 24 October 2013, the pilot of a modified PZL Mielec M18A Dromader, registered VH-TZJ, was conducting a firebombing mission about 37 km west of Ulladulla, New South Wales. On approach to the target point, the left wing separated. The aircraft immediately rolled left and descended, impacting terrain. The aircraft was destroyed and the pilot was fatally injured.
What the ATSB found
The ATSB found that the left wing separated because it had been weakened by a fatigue crack in the left wing lower attachment fitting. The fatigue crack originated at small corrosion pits in the attachment fitting. These pits formed stress concentrations that accelerated the initiation of fatigue cracks.
The ATSB also found that, although required to be removed by the aircraft manufacturer’s instructions, the corrosion pits were not completely removed during previous maintenance. During that maintenance, the wing fittings were inspected using an eddy current inspection method. This inspection method was not approved for that particular inspection and may not have been effective at detecting the crack.
Data from a series of previous flights indicated that the manner in which the aircraft was flown during its life probably accelerated the initiation and growth of the fatigue crack.
Finally, the ATSB also found a number of other factors which, although they did not contribute to the accident, had potential to reduce the safety of operation of PZL M18 and other aircraft. These included the incorrect calculation of the flight time of M18 aircraft and a lack of robust procedures for the approval of non-destructive inspection procedures.
What's been done as a result
The Civil Aviation Safety Authority (CASA) revised the airworthiness directive for inspection of the wing attachment fittings to ensure that they were inspected using the magnetic particle inspection method. CASA also made, or plans to make, a number of changes to their systems and procedures to address issues identified in this report.
Separately, the ATSB reminded operators of M18 aircraft of the importance of the correct application of service life factors when operating at weights above the original maximum take-off weight. In addition, PZL Mielec plans to release additional maintenance documentation clarifying the need for removal of the wings for proper inspection of the wing attachment fittings. Finally, at the request of the owner, the supplemental type certificate for operation of the modified M18 Dromader at take-off weights up to 6,600 kg has been suspended by CASA.
Safety message
This accident shows that even when flying within operational limits, the ‘harder’ and faster an aircraft is flown the more rapidly the structure will fatigue.
To help ensure that maintenance objectives are consistently met, the ATSB reminds aircraft maintenance personnel of the importance of only using properly-approved maintenance instructions. This accident confirms the importance of referring directly to those maintenance instructions when conducting maintenance.
Quote:Removal of wings to complete service bulletin actions
Although wing removal was necessary to provide adequate access for effective visual and magnetic particle inspections of M18 wing attachment fittings, the aircraft manufacturer’s service bulletin E/02.170/2000 allowed the wings to remain attached during these inspections.
Issue number:
AO-2013-187-SI-02
Who it affects:
Maintainers of M18 aircraft completing CASA AD/PZL/5 and PZL Mielec service bulletin E/02.170/2000
Status:
Safety action pending
M18 Dromader airframe life factoring
Operators of some Australian M18 Dromaders, particularly those fitted with turbine engines and enlarged hoppers and those operating under Australian supplemental type certificate (STC) SVA521, have probably conducted flights at weights for which airframe life factoring was required but not applied. The result is that some of these aircraft could be close to or have exceeded their prescribed airframe life, increasing the risk of an in-flight failure of the aircraft’s structure.
Issue number:
AO-2013-187-SI-01
Who it affects:
Operators of PZL M18 aircraft
Status:
Adequately addressed
Spectrum of flight loads
Operation of M18 aircraft with a more severe flight load spectrum results in greater fatigue damage than anticipated by the manufacturer when determining the service life of the M18. If not properly accounted for, the existing service life limit, and particular inspection intervals, may not provide the intended level of safety.
Issue number:
AO-2013-187-SI-04
Who it affects:
All operators of M18 aircraft
Status:
Adequately addressed
Use of eddy current inspection for airworthiness directive AD/PZL/5
The eddy current inspection used on VH-TZJ, and other M18 aircraft, had not been approved by the Civil Aviation Safety Authority as an alternate means of compliance to airworthiness directive AD/PZL/5. This exposed those aircraft to an inspection method that was potentially ineffective at detecting cracks in the wing attachment fittings.
Issue number:
AO-2013-187-SI-03
Who it affects:
All operators of M18 aircraft that have had their M18s inspected using the eddy current procedure QP.00.36 (EC)
Status:
Adequately addressed
Adequacy of the eddy current inspection procedure
The documented procedure for eddy current inspection of M18 wing attachment fittings did not assure repeatable, reliable inspections.
Issue number:
AO-2013-187-SI-06
Who it affects:
All operators of M18 aircraft that have had their M18s inspected using eddy current procedure QP.00.36 (EC)
Status:
Adequately addressed
Civil Aviation Safety Authority records
Important information relating to Civil Aviation Safety Authority (CASA) airworthiness directive AD/PZL/5 was not contained in CASA’s airworthiness directive file, but on other CASA files with no cross-referencing between those files. This impacted CASA’s future ability to reliably discover that information and make appropriately‑informed decisions regarding the airworthiness directive.
Issue number:
AO-2013-187-SI-07
Who it affects:
All aircraft operators in Australia
Status:
Adequately addressed
Assessment of NDT procedures
The Civil Aviation Safety Authority did not have a defined process for a robust, systematic approach to the assessment and approval of alternative non-destructive inspection procedures to ensure that the proposed method provided an equivalent, or better, level of safety than the original procedure.
Issue number:
AO-2013-187-SI-08
Who it affects:
All aircraft operators in Australia
Status:
Safety action pending
Australian supplemental type certificate SVA521
The engineering justification supporting Australian supplemental type certificate SVA521 did not contain consideration of the effect an increase in the average operating speed could have on the rate of fatigue damage accumulation.
Issue number:
AO-2013-187-SI-09
Who it affects:
All aircraft operators of the M18 aircraft in Australia operating under STC SVA521
Status:
Adequately addressed
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