This is a suggestion brought about by a problem I found on my plane and the recent LML series on cowling fasteners.  When deciding how to build something, like the cowl fastenings, coming up with some really slick method is fine; as long as it doesn't make it a hassle to remove pieces for maintenance access and inspection.  In my experience if the cowl, or some access panel, is a pain to remove people tend not to remove it unless they really have to; like the required yearly inspections.  If it's simple to remove inspections are likely to happen more often.

Case in point.  I currently fly a Rockwell Commander 112.  (Apparently I'm trying to find out just how long you can make a Legacy project last, but that's another story.)  A couple of months ago my A&P and I replaced all four cylinder assemblies on the 112; high oil consumption.  (Another long story.  I've got a lot of them.)  The 112's cowl is fiberglass and the upper half is a snap to remove.  I can do it by myself less than 60 seconds.  With the top cowl removed you can inspect pretty much everything with a flashlight and mirror.  For the first few hours after replacing the cylinders I removed the upper cowl after every flight and did a visual inspection.  After that I removed the cowl every 2 to 3 hours for visual inspection up to about 15 or 16 hours.  The only problem found was during the inspection after the first flight.  One of the nuts on a fuel injection line wasn't tightened properly and we found a small amount of blue stain from the 100LL on the injector line.  Easy fix.

After 15+ hours with no more problems I figured everything was fine, but at a little over 20 hours I popped the cowl anyway and took a look around, and found a large oil patch on the bottom cowl.  The oily area was about the size of a dinner plate and since the inside of the 112's cowl is rough fiberglass it meant there was a pretty serious leak; one that wasn't there at 15-16 hours.  A little flashlight and mirror work traced the source to a fitting on the #4 cylinder oil return line where it goes into the cylinder head.  I was able to tighten the fitting's compression nut almost a full turn with just my thumb and one finger!  I don't like to think about what might have happened if I'd put off the inspection a few more hours.  (And yes, the other nuts were all tight.)

Bottom line, frequent inspections are a good thing.  Finding a problem in the hanger is much better than finding one in flight.  Build safe.

Tom Gourley


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