Airplane Owner Maintenance

A Maintenance Oriented Podcast For Airplane Owners, Pilots, and Mechanics

Month: November 2021

192 – We Always Knew He Had A Screw Loose!

November 20, 2021 /

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My good friend, Clark Trobaugh, flew into KSHD this past week, and while he was visiting with his family, I walked over to his airplane on the ramp and noted a few things that needed attention…

Here’s the one that prompted Clark’s brother Scott to send me a text that said, “Thanks for looking out for him. We always knew he had a screw loose and I’m glad you could fix it.” That made me laugh, for sure! These brothers have a lot of fun together.

It turned out the screw was the wrong one… it was a sheet metal screw and should have been a machine screw. Check it out:

And here’s the result after installing the correct screw:

I also discovered a panel chafing under the left horizontal stabilizer:

I removed the panel, cleaned the area, and reinstalled it:

Another item that needed attention was a shielding ground connection on the left alternator… check out this video:

And one more item I took care of for Clark was the left and right elevator trim tab connections… take a look at this:

Since there is a bushing in this location, the bolt should be tightened onto the bushing and the rotation happens around the bushing. I greased the bushing, reinstalled the bolt and nut, and installed a new cotter pin, for both trim tabs.

Here’s how the pieces look when taken apart:

And here’s the end result after reassembly:

Listen to the audio for this episode for more details on these items, as well as a tribute to Clark and Scott’s dad, Larry Trobaugh, who passed away in May of 2020. Larry was a great man, and I think so highly of him and his family.

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191 – A Tale of Two Exhaust Valves

November 13, 2021 / / 2 Comments

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In this episode, we are talking about two different exhaust valves, both of which showed signs of burning when we looked at them with the borescope.

One valve was in the beginning stages of burning, and the other was too far gone. Scroll down for more info and some photos.

We also talk a bit in this episode about Arthur St. Clair and his P35 Bonanza. I mentioned him in a previous episode, and recently he came back to Classic Aviation so we could borescope his cylinders and exhaust valves. Thankfully, all his valves were in good shape. Here’s a photo from that day:

Now for the two exhaust valves mentioned in the title for this episode…

Here’s a photo of the one that was too far gone, and the cylinder had to be removed and sent out for repair:

Notice the green edge from 11 o’clock to 2 o’clock on the valve… a badly burning area. The valve guide was also very worn, so we sent the cylinder out for repair.

I also cut the old rotocoil apart for this valve and it had a lot of black carbon bits in it, and the internal spring showed the classic flat spot that is many times seen when an exhaust valve has been burning. Here’s the rotocoil:

The other burning exhaust valve on this same engine was only in the beginning stages, and after lapping the valve and installing a new rotocoil and new valve springs, the compression was 72/80 after runup! What a fantastic result! Here’s what that one looked like:

The small area at 12 O’clock on the valve is starting to burn, but it was salvageable by lapping and installing a new rotocoil to ensure proper valve rotation and better sealing capability.

So the moral of the story is, borescope your exhaust valves at regular intervals, like 50 hours, and hopefully you can catch a burning valve before it’s too far gone and has to be removed.

Have a great week everyone!

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