May 2009 Issue

First Word: 05/09

Ho-hum, another week another cylinder recall. Thatís a bit of an exaggeration, I guess, but not by much. Considering the number of recalls, ADs and service bulletins that zing by, you have to wonder if weíve forgotten how to make airplane parts in the is country. When I started flying in 1969, I only vaguely recall any parts call backs. Of course, I was too poor to own an airplane then and when youíre in the renter loop, you donít notice such things. And noticing or not noticing them may be part of the problem here. As I was researching the article on camshafts in this issue, I asked a couple of the engine shops I know if parts quality has gotten really bad lately or are we just noticing it more. They seemed to be of the universal opinion that things are worse than ever with regard to manufacturing shortfalls making it into the supply chain. Thatís not the same as saying quality control is worse than ever because quality is, by its major definition, consistency. My guess is that parts built today are more uniformly on spec than they were 30 years ago or even a decade ago. So why all these recalls? My theory is that statistical process control has something to do with it. This method of quality control works great in the kind of volumes that the auto industry does. I donít think itís quite so hot when the volumes sink to the dozens and hundreds that GA manufacturers typically do. Even though both Lycoming and Continental have largely converted to CNC equippage, thereís still far more handwork in airplane building than in carmaking.

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