`Aviation aluminum crankcase weld repair dispute`

Recent (January 2014) consulting email from a family-owned engine-repair business in Oklahoma, one of the few FAA-approved shops for weld repair of Lycoming and TCM aircraft engine crankcases. The dispute: Canadian failure investigators criticized their use of 4043 filler (undermatching) on Aluminum Association 355 castings. Tom walks through the matching/undermatching/overmatching trade-off and the four classes of filler (4145 overmatching, 4009 matching, 4043 undermatching). Frames the case as a demonstration of how to give a client options without making the design decision yourself ("if an aircraft goes down...I don't want them coming back to me").

Before we go to Amber's [presentation], I think I have time to give you a case study. On Monday we'll start titanium, and probably finish up with titanium. So: a guy who's the engineer for a family-owned business out in Oklahoma sent me an email this past January. I've done some work with him. He basically does weld repair on aluminum cast engine blocks for aviation. If you've got a Lycoming or a Teledyne Continental engine, the aluminum case contains your crankshaft, and the piston heads bolt to this crankcase. The crankcase is just sort of there to keep the oil in the sump — you've got oil running through holes in the crankcase for the bearings, and then it comes spraying out. It's not really an engine block; the pistons are inside the piston heads, which are made out of aluminum but are all hot isostatic pressed. The case he's welding is basically a shroud to contain the oil that's spraying out of the crankshaft and connecting rods as it's running.