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 extending through the cotter-pin hole used to secure the nut on the end of the axle. The entire Scott 3200 tailwheel assembly was replaced with a serviceable unit. Part Total Time: (unknown) Cessna 182S Cracked Battery Mount Structure Both aircraft battery-shelf support brackets were found cracked in their forward and aft ends (four cracks total). Each crack started at the end of the support in the 90-degree bend radius, propagating toward the center of the part. This is the fourth 182S/T model we have found to be cracked in this manner, each requiring replacement supports (p/n 0712059-1). One previously repaired aircraft has already cracked the replacement parts. Part Total Time: (unknown) Cessna Corvalis 300/350/400 Models Failed Empennage Structure Four reports dating back to 2006 detail structural damage to the empennage after extreme braking. Extensive structural damage-including gaps in the structure and de-bonding of the composite fuselage-have been identified. These extreme braking maneuvers consist of prolonged periods of heavy braking and tire skidding, resulting in large oscillatory motions known as “gear walk.” Cessna reportedly is developing an advisory to communicate information about the proper use of brakes as noted in the POH. Part Total Time: (various) Diamond DA40 Failed Alternate Air Control Valve A shop maintaining a fleet of 20 Diamond DA-40s is finding the alternate air valve body control cable (p/n DAI-9076-00-04) loose or completely disconnected. When reinstalling the cable, they find stripped threads on the alternate air valve body. This problem has now occurred on 14 different aircraft at between 147 and 350 hours TIS. Part Total Time: (various)
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:
- Various aircraft models are experiencing recurring issues, including fractured engine mount bolts, cracked battery mount structures, severely worn tailwheel assemblies, empennage structural damage, and failed alternate air control valves.
- Many of these problems stem from either inadequate or incomplete documentation, such as a Supplemental Type Certificate (STC) lacking critical re-torqueing instructions for engine mounts.
- Other recurring failures, like cracked Cessna 182S battery mounts and stripped Diamond DA40 alternate air valve threads, suggest potential design weaknesses, while operational factors like extreme braking can lead to significant structural damage.
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