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Key points
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The in-flight break-up of an amateur (kit) built Acroduster aircraft reinforces to operators and maintainers of these aircraft the importance of conducting additional detailed inspections of areas that are critical for flight.
On 18 August 2021, an amateur-built Stolp Acroduster II SA-750 biplane broke-up during a flight from Caboolture airfield, north of Brisbane. The pilot, who was the sole occupant, was fatally injured.
As noted in its preliminary report, the Australian Transport Safety Bureau’s technical examination determined two eye bolts, and the left roll brace, used to secure the aircraft’s upper wings, had failed due to fatigue cracking, triggering the break-up sequence.
Coinciding with the release of its preliminary report, the ATSB issued a Safety Advisory Notice (SAN) to owners and maintainers of Stolp Acroduster SA-700-750 aircraft, notifying them of the fatigue cracking issue.
“In this accident, the fatigue cracks formed in an area of the eye bolts that were obscured by the securing nuts and threads of the eye bolts,” ATSB Director Transport Safety Kerri Hughes said.
“This meant the cracks would not have likely been readily identifiable during standard maintenance inspections, without disassembling the attachment points.
“Owners and maintainers of experimental amateur-built aircraft should consider conducting additional detailed inspections that exceed the minimum standards, in areas of the aircraft that are critical to the safety of flight.”
The initial finding of fatigue cracking on the aircraft’s eye bolts was immediately shared, in August 2021, with the Civil Aviation Safety Authority, as well as the National Transportation Safety Board and Federal Aviation Administration in the United States (as the aircraft’s state of design), and the US-based Experimental Aircraft Association.
The aircraft design owner, Aircraft Spruce, was also notified.
The Experimental Aircraft Association subsequently released a notice on its website informing members of the accident, and a link to the ATSB’s preliminary report and SAN.
The Federal Aviation Administration issued a notice to more than 280,000 web subscribers informing them of the wing attachment point fatigue cracks, and also provided a link to the ATSB’s material.
Additionally, Aircraft Spruce issued a safety advisory notice to every purchaser of Starduster and Acroduster design plans since 2003.
“The ATSB welcomes these safety actions by authorities and the manufacturer in response to this accident,” Ms Hughes concluded.
Read the report: In-flight break-up, Stolp Acroduster II SA-750, VH-YEL, 16 km north-east of Caboolture airfield, Queensland, on 18 August 2021