Boeing A75N1 Stearman Broken Engine Mount Bolts Inspection of a recent engine installation uncovered a fractured engine-mount bolt. After informing the STC holder of the failure, we were told we should have re-torqued these bolts after 25 hours of operation. This information was not included in the STC. The submitter believes the STC is inadequate in ensuring continued airworthiness. Part Total Time: 100.0 hours. Cessna 170B Failed Tailwheel Assembly During an annual inspection, all parts inside the tailwheel unit were found extremely worn. Additionally, the tailwheel axle had been damaged and its end was partially ground off, 288
Untorqued, Delaminated
Inspection of a recent engine installation uncovered a fractured engine-mount bolt. After informing the STC holder of the failure, we were told we should have re-torqued these bolts after 25 hours of operation. This information was not included in the STC. The submitter believes the STC is inadequate in ensuring continued airworthiness.
Key Takeaways:
- Issues arose from inadequate maintenance instructions, as seen with fractured engine mount bolts on a Boeing Stearman due to missing re-torquing guidance in an STC.
- Several aircraft models experienced recurring structural integrity problems, including repeated cracking of Cessna 182S battery mounts and empennage damage on Cessna Corvalis models from extreme braking.
- Common component failures and extreme wear were observed, such as extensively worn Cessna 170B tailwheel assemblies and frequently disconnected Diamond DA40 alternate air control valve cables due to stripped threads.
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