Ok,
So I'm nearing my third annual condition inspection next month and I'm trying to get all the bits and pieces in place beforehand this time (new air filter, spark plug gaskets, etc) and I've been reading a lot on the value of borescope inspections of the cylinders.
I'm not sure about replacing compression testing entirely, but I did get a good quality Wi-Fi borescope (depstech model wf010 with a 90 degree mirror attachment) from Amazon for $49

Other than a few articles,

https://www.aopa.org/news-and-media/all-news/2016/november/04/aircr...

http://www.aviationpros.com/article/10387051/borescope-inspections-...

Does anyone know of other resources I can read to learn about the procedure and what to look for?

Brad Cohen
N969BC
Tampa

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Comment by David J. Beaulieu on November 4, 2017 at 5:35pm

Brad, timely post!  I have the borescope John linked in his comment.  At the first 15 hr maintenance on my engine (UL Power 350iS) I just had to look in the cylinders to see what was going on.  I was somewhat clueless about interpreting what the heck I was looking at as "good or bad"  but I wanted a baseline reference.  There is a EAA webinar with Mike Busch on this very subject which I think is well worth watching.  Look it up in the archives.  Anyway, I ended up having an experienced mechanic for UL and the factory guys look at about a dozen pics I snapped and sent to them.  Their collective response was no concerns noted.  Here is a sample of what you can see with this scope.  John hit the nail on the head with his response!

Good Luck!

Comment by John Austin on November 2, 2017 at 1:48pm

Brad,

Speaking from experience with flexible scopes and rigid scopes, if I were you, I would return that scope if you are primarily expecting to do cylinder inspections.  The semi-rigid scope you bought will require a mirror to look laterally and you'll find a mirror quite frustrating to use. You'll also discover you really can't manipulate that scope once inside a cylinder to look back 180 degrees to fully visualize the valves.  HOWEVER, a semi-rigid like you bought is excellent for peaking around in nooks and crannies in the fuselage, wings, etc. and since it was only $49, you might want to keep it for that purpose.

A much better scope for cylinder inspections is the Vividea Ablescope VA400 Articulating Borescope.  Yes, it costs a lot more (actually, it's cheap relative to anything previously available), but it is truly useful and practical for cylinder inspections.  Since the tip articulates 180 degrees, you can fully visualize the valves and the cylinder head.  It is much easier to use than a mirror and your field-of-vision will be much greater.  I've had one for quite some time and really like it.  Mike Busch, the AOPA maintenance guru, recommended it in a recent article - and he was previously using scopes that cost thousands of dollars!

AOPA has an article, Anatomy of a Valve Failure, that is excellent and has a downloadable poster link to illustrate normal and abnormal valves.

The best way to learn to use the scope is to simply start routinely borescoping your engine every time you change the plugs or at annual, etc.  Since hopefully most of the valves will be normal, you'll get an idea of what normal looks like and then can give extra scrutiny to valves that look different.  The borescope was never meant to replace compression testing, it's complementary - it hopefully will provide clues to a failing valve before compression problems are an issue, and in a cylinder with poor compression, it sometimes makes it obvious it is a valve and not a ring problem.

Hope this helps!

John

N750A

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