Yetti Posted October 3, 2018 Report Share Posted October 3, 2018 Or stated another way. This is an effect. The cause has not been identified. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted October 5, 2018 Report Share Posted October 5, 2018 The damaged threads look like they were pulled apart... from one side... So... the assembly, under extreme compression, started to bend... at the threads and groove... inherently weekest area... the inside of the bend goes under compresion... The outside of the bend fails under extension... be looking for what made the control rod assembly run out of space... where bending was its method of relieving the stress... is the heim bearing still functional? if it is seized, that would add stress where it didn’t belong... Also look at the other end of the control rod... a failure at the other end may have caused / contributed to the known broken part... look all the way back to the actuator, where the motion starts... the grooved and threaded parts are all known for their strengths and weaknesses ... and get sized appropriately... to include these issues... of course, in the past... Mooney has spec’d one thing and received something else in its place... like a heat treatment step that got muffed... Huck bolts on tails should be a reminder... (long bodies) heat treatment on springs... (electric gear) Any insight to what made these 80 or so airframes the focus of the one SB? was it a single lot of bad bearings needing to be replaced... after they were installed... Or do the SNs coincide with all O2s or something like that? having two different parts share the same part number is very unlikely. At one end, it is expensive laziness that costs a ton in the end... In the case of GM ignition switches... it was criminal intent, intentionally hiding that a better part was available and being used... the known deadly part was hiding and not taken out of service for decades... the dash followed by a version number is all it takes... they didn’t invent block chain technology for this basic issue... but when it comes to track and trace... every nut, bolt, and heim joint can be followed... Stuff that keeps Quality Engineers awake... Hope that adds to the MS knowledge base... PP thoughts only, not a QA/QC guy... best regards, -a- Quote Link to comment Share on other sites More sharing options...
jackn Posted October 9, 2018 Report Share Posted October 9, 2018 So, for us non structural engineering types. Are you saying the rod end was in too far, therefore the wheel was being stopped by the top of the wheel well. That maybe the tire was providing a little give, but eventually the rod end failed? Quote Link to comment Share on other sites More sharing options...
Warren Posted October 13, 2018 Report Share Posted October 13, 2018 As I read through this it is still hard to understand. I question the failure mode. If it failed in tension it would have broken while retracting the gear. How does a failed link then properly extend and lock the gear? Buckling failure seems far more likely under the compression load. It seems like the gear extended fully and the force caused the threaded section to buckle and fail after full extension. I can see a slightly buckled joint still fully extending the gear then getting pulled in tension during retraction and continually cycled until failure. However, this should cause cracking and an obvious pattern in the failed part. It sounds like this is not supported by the failure analysis but it is hard to believe that a full tension failure would allow the gear to extend. If a partial tension failure with necking was followed by a buckling failure on extension, there should be obvious signs of bending prior to full failure. Just random thoughts from my failure analysis experience. Still hard to understand based on the failure analysis vs. the description of the operation during failure. 1 Quote Link to comment Share on other sites More sharing options...
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