Trust Your Hunches

The slightly dark coloration between the two visible Camlock screw heads was something new.

I’ve been spending enough time around the GlaStar lately—and taking every moment of good weather here in Oregon to actually fly it—that subtle changes stand out. Just the other day, I noticed a slight staining of the fuselage just behind the cowling line. I hadn’t noticed any bad smells and I didn’t have any leaks, but the stain was something I hadn’t noticed before.

So it was worth the 5 minutes to remove the top cowling and have a closer look. There wasn’t anything hugely obvious at first glance, though I did notice some grayish residue on the inner surface of the bottom cowl, on the same side of the airplane as the exterior stain. A minute or two later with a flashlight and mirror revealed the likely source: One nut on the left-front cylinder’s exhaust stack was gone. Not loose, gone.

Hmm. Nut, washer and lockwasher have left the building.

Now it was time to abort the planned afternoon flight, remove the lower cowling and have a closer look. Nothing else seemed amiss, and the other seven exhaust nuts were tight. I sometimes get ribbed for having two of everything on hand, so I enjoyed a moment of I-told-you-so as I pulled another exhaust nut, washer and lockwasher out of inventory. (I now have three left, time to reorder!)

While I was in there, I took a moment to check the hardware on the other parts of the exhaust system and give the entire lower half of the engine a good touch-feel-wiggle. All good.

The interesting thing is that the exhaust flange was still tight to the head, with little to no obvious leakage. I’ve seen breached exhaust gaskets and they can make a mess in relatively little time. I had no mess here. Whatever had happened to cause the exterior staining might or might not have been related to the exhaust leak—though I can’t think of what else it could be—but it was enough to cause me to have a closer look. I’m glad my curiosity got the better of me—this time.

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Marc Cook
Marc Cook is a veteran special-interest journalist who started as a staffer at AOPA Pilot in the late 1980s. Marc has built two airplanes, an Aero Designs Pulsar XP and a Glasair Aviation Sportsman, and now owns a 180-hp, steam-gauge-adjacent GlaStar based in western Oregon. Marc has 5000 hours spread over 200-plus types and four decades of flying.


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