For the RV-7's third annual inspection, I figured it would be a good time to see how the inside of the engine is holding up after almost 500 hrs. The differential pressure check passed with flying colors, and a friend had a good borescope he was willing to bring by the hangar. So we took some pictures and sent them off Bart at AeroSPort Power and Allen and BPA, who both said everything looks fine. I'm glad, because I have no clue what to look for other than obvious defects.
Anyway, the pictures were interesting and thought others might want to see. To me, they looked very different than what you might expect just seeing a piston or valve out in the open. The pictures below are from different cylinders.
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Marc Ausman
RV-7 980 hours, IO-390, VP-X (sold)
RV-8 (flying a friend's)
Thinking about low and slow backcountry build.
VAF Advertiser - Aircraft Wiring Guide
Book to help with experimental aircraft wiring.
On where your looking..Wear on a cylinder usually starts on the thrust side of the bore..I.e because of the position of the crank on the power the piston wants to rock towards the leading side as it gets driven down the bore.
If we were looking at the other side then yes I would expect to see the cross hatch....
Was the cross hatching visible all the way round the cylinder?..if so thats pretty good for supposedly 25% thru the life of the engine.
Thanks! Other than helping pull the cylinders off our tow plane when I was flying gliders, I'm new to aircraft engines. I have pulled bike engines down and saw one that still had the cross hatching even after 60k miles (and an NHRA championship). I don't know what the bore surface is on a lycoming but the cylinder plating used in bikes and cars these days seems pretty extraordinary!
Borescope Pics at 500hrs (Lycoming IO-390)
Linear Mode
