Airplane Owner Maintenance

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

Month: July 2023

231 – Piper Comanche Weird Electrical Problem and Seeping Oil Drain Valve

July 31, 2023 /

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In this week’s podcast episode, you’ll hear about:

  • King Air flying.
  • Listener feedback from the last episode on “Phantom Cylinder Cracks.”
  • The latest annual inspection I’m involved in.
  • … and a few other things!

I’m in the midst of an annual inspection on a Piper Comanche. I might talk more about this one in a future episode, but for now, I mentioned two strange things about this airplane in this week’s podcast:

The first strange thing was the oil quick drain kept seeping after I drained the oil and closed the drain valve.

I was perplexed when oil was collecting on the bottom cowling and seeping down over the nose tire.

Finally, I had to cut the safety wire and remove the Saf-Air P5000 drain valve to take a look.

Here’s what I found:

I removed the drain valve and put a temporary plug in the oil sump to prevent any further seepage. If you look closely, you can see a portion of the black o-ring holding the valve slightly open.

Here’s a closer view:

After opening the valve, I noticed the top o-ring had been pushed up off the valve, and it was the second o-ring that was holding the valve open. (Don’t worry, the other o-ring fell out of the hole when I removed the valve, so it’s not stuck somewhere in the oil sump.)

We will install new O-rings on the valve before reinstalling it in the oil sump. It actually has 3 total o-rings… the top 2 keep the oil from draining out of the sump, and the lower o-ring (that you can’t see in the photo) is slightly larger and it keeps oil from seeping out around the drain nipple during the oil draining process. McFarlane sells a kit that includes the three new o-rings and a new snap ring.

You can listen to the audio to hear more about this story.

… and hopefully, in a future episode, I’ll be able to update you on the weird electrical problem on this same airplane.

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230 “Phantom Cracks” in Airplane Engine Cylinders

July 17, 2023 /

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Do you think these really are cracks between the spark plug bosses and the fuel injector bosses? (Cirrus SR22 Continental engine.)

The owner of a Cirrus SR22 was told by a service center he had 4 cracked cylinders on his engine.

However, after taking a closer look and bringing their most experienced technicians together to thoroughly clean and examine the cylinders, it was discovered they were not cracked after all.

The service center was very professional with their communications and the process they used to evaluate the cylinders.

This whole scenario was such a great example of healthy collaboration between an aircraft maintenance service center and an airplane owner.

Listen to the audio of this week’s podcast to hear the full story, and some email communications I had with the airplane owner.

After thinking about the situation, here are some thoughts:

  • If an airplane engine cylinder is truly cracked, it needs immediate attention.
  • Sometimes, what appears to be a crack, is not a crack after all.
  • Thorough cleaning and precise evaluation are required.
  • Sometimes a second and third expert opinion are helpful.
  • Excellent communication between airplane owners and service centers is key.

Have a great week everyone!

The post, 230 “Phantom Cracks” in Airplane Engine Cylinders appeared first at AirplaneOwnerMaintenance.com

229 – Cessna 206 Alternator Not Working

July 8, 2023 /

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The charging system was not working, but why?

There was normal voltage at the alternator field terminal.

The field circuit resistance seemed normal as well.

But the alternator was not producing the normal 28 volts during operation.

Occasionally, it would produce a small amount of output voltage, like 25 or 26 volts, and then drop back down to battery voltage.

Clearly there was a problem.

After troubleshooting and seeking advice from a Cessna service center, we replaced the battery contactor and the alternator contactor in the MCU (master control unit) on the firewall. (The MCU is the electrical control box for the airplane. It’s located on the forward left side of the firewall.)

Replacing the contactors did not fix the problem.

After more troubleshooting and some calls to Hartzell Engine Technologies to speak with two different people, and after talking things over with the owner, we decided to order an overhauled alternator and a new ACU (alternator control unit.)

They arrived the next day, I installed them, and the system worked perfectly.

The alternator was back to producing its normal 28 volts. (I just wish I had taken the old alternator apart to see if I could determine the problem… I’m guessing one or both of the brushes were severely worn.)

The following photo shows what’s inside the MCU. The alternator contactor is the one in the top of the photo, slightly left of center. And the alternator control unit the the device to the left of the contactor that says “Lamar” on the side.

When replacing anything in this box, it’s very helpful to take photos first in order to put everything back in its place during reassembly!

Listen to the audio podcast for this episode to get the full story.

This episode also includes some of the email responses I received after asking if listeners wanted to continue receiving stories about exhaust valves.

Thank you to all who responded!

In a nutshell, everyone wanted to continue hearing about exhaust valves and the stories about lapping them and saving them, especially the stories that are instructive and educational.

Have a great week everyone!

The post, “229 – Cessna 206 Alternator Not Working” appeared first at AirplaneOwnerMaintenance.com

228 – Saving a Cylinder on Dan & Jeanne’s Bonanza

July 1, 2023 /

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Dan and Jeanne are some of the nicest people you will ever meet, so it’s always a privilege to work on their airplane.

It was annual inspection time, and the compression test on cylinder #1 was 25/80. The borescope showed a corresponding reason for the low compression… the exhaust valve had an uneven appearance, indicating it was not sealing well against the valve seat, and there was air leakage around the edge, causing that edge to get extra hot and burn… this is the reason for the uneven color pattern at 10 to 11 o’clock in the photo:

I discussed the situation with Dan, and we decided it was worth a try to lap the valve in place without removing the cylinder, in hopes we could save the cylinder from premature removal.

I lapped the valve and installed a new rotocoil to help ensure the valve was rotating properly during operation.

After reassembling everything and running the engine, we got a fantastic result… the compression was now 75/80!

When the annual inspection was completed, I sent the airplane out the door with great confidence the engine would perform well… and it did.

Not long after that, Dan and Jeanne flew the Bonanza to Montana to visit family and then later made the journey back home.

At the time of the annul inspection, Dan had agreed it would be a good idea to inspect the #1 exhaust valve at the next oil change to make sure all was well.

After having flown about 37 hours since the annual and since lapping the #1 exhaust valve, Dan returned to have things checked out.

The oil and filter change were completely normal; the compression in cylinder #1 was 77/80; and the borescope revealed the #1 exhaust valve had returned to normal!

Check it out: the circular patterns on the valve are now nice and concentric.

I’m hopeful Dan will get many more hours of reliable service out of this cylinder since we stopped the harmful trajectory of a burning exhaust valve.

On another note, I discussed a couple things in this episode that I noticed this past week while flying.

  • One was related to NOTAMs and the importance of being aware of them (along with something I discovered about NOTAMS, approach plates, and ForeFlight.)
  • The other one was a tip about starting PT-6 engines when they are still hot after a quick stop to drop off passengers and refuel.

In my research, I discovered an online course about NOTAMs, and I wanted to pass this link along for anyone who might be interested:

notamsmadeeasy.com

This is a course by Sarah Fritts. I do not know Sarah, and I do not receive any compensation from this course, but it seems like a good training resource, and I like to help promote those when I see them.

You can also learn more about Sarah over at her website:

ThinkAviation.net

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