And more importantly, could you service the strut safely?
If you’ve ever had a low strut, you know it can be very frustrating.
Sometimes it can be challenging to sort through all the maintenance manual information, your POH information, your local A&P’s instructions, and your fellow aviators’ opinions, about shock struts and how they should be maintained.
What if there was a simple and clear way to learn about shock strut servicing?
Very soon, there will be a way!
The video training course for “Servicing Landing Gear Shock Struts” will be available in the near future.
Be watching for more details.
Also in this episode, we talk about “FEVA” or “Failiing Exhaust Valve Analytics,” a concept being developed by Mike Busch and his team at Savvy Aviation. If you’d like to learn more, here’s a very interesting article.
This discussion was prompted by an email I received that said, “Dean, what do you think of Mike Busch and his Savvy Aviator columns?” I answered that question in today’s podcast episode.
I received an email recently from Spence, the owner of an S35 Bonanza with a Turbo-Normalized IO-520 engine. He included a picture of his #2 cylinder exhaust valve. Here’s what it looked like:
At first glance, my reaction was something like, “Oooh, that’s ugly!”
The most concerning area is the spot at the 10 o’clock position. There’s also a little concerning area at the 2:30 position as well, but not as much as the 10 o’clock position. The normal deposits seen on the top and bottom edges of the valve have been burned away over at the 10 o’clock position. The small red spot is concerning, but not as concerning as if it was green. As it says in the excellent exhaust valve poster “Anatomy of a Valve Failure,” produced by AOPA, “Green means stop!” This is because the color green has been seen on valve edges that are imminently in danger of a piece breaking off.
For sure, Spence’s borescope photo is a classic visual presentation of a burning exhaust valve. Perhaps you’re wondering, “What does “burning” mean?” And that’s a great question. It means there’s an area that is not sealing well between the edge of the valve and the valve seat when the valve is closed. This condition allows very hot exhaust gases to rush through a small gap between the valve and seat at just the wrong time when those gases are the hottest, and over time if left uncorrected, the edge of the valve can suffer extreme heat damage and finally be in danger of a piece of the valve breaking off.
Not something you want to risk while you’re flying along in your Turbo-Normalized Bonanza! (Or any airplane for that matter.) But an airplane with a turbocharger is especially vulnerable because even a small piece of an exhaust valve would be enough to completely trash the turbocharger.
The next question might be, “How would you know if an exhaust valve was burning?” This is also a great question. You might see a drop in compression, but the best way by far to find a burning exhaust valve is with a borescope. With some training in what to look for, a burning exhaust valve is very noticeable, as in the photo above.
Spence did a great thing when he found this burning valve. Finding it was one thing, but deciding what to do about it was the next big question. In his email, Spence asked, “Do you believe this is a candidate for lapping in place and is it something you would be able to do for me?”
Spence was very interested in a less-invasive way to remedy his burning exhaust valve, especially since he has had other cylinders fail this way over the years, and this particular cylinder had only 368 hours on it (he actually paid a reputable engine shop to take the new Superior cylinder, check the exhaust valve tolerances, and perform a 3-angle cut before installing the cylinder.) He was understandably weary of changing cylinders.
I agreed to give the lapping procedure a try, with a couple conditions. One, we would not want the exhaust valve guide to be significantly worn. And two, the edge of the valve and valve seat must be in reasonably good condition.
On the agreed upon morning, Spence showed up at Classic Aviation at KSHD, and we got to work. We got things opened up and before removing the valve springs, we did a cold compression check and could not get more than 30/80 psi, with significant leakage past the exhaust valve. A healthy cylinder should be a lot more than 30/80, even with a cold compression check.
We got some borescope photos of the valve edge and seat, and aside from the normal spotty appearance, things looked quite good.
After removing the valve springs, our second condition was also met, in that the valve guide did not have a substantial amount of wear. I checked this by wiggling the valve stem up and down and side to side, in various positions.
Now it was time to perform the lapping procedure. “Lapping an exhaust valve” involves removing the rocker cover, exhaust rocker arm, and valve springs. This allows you to carefully push the valve into the cylinder far enough to see the edge down through the top spark plug hole. In this position, you can carefully apply valve grinding compound on the seating area of the valve, rotating the valve as needed to lightly coat the full 360 degrees of seating area. At this point, pull the valve back against the seat and rotate it back and forth using whatever method you decide, in order to restore a good smooth seal between the valve and the seat. I use a wood dowel rod chucked in a cordless drill, with a piece of thick vinyl tubing clamped between the dowel rod and the valve stem, which acts as a shock absorber and works very well. It may take several rounds of applying the compound and lapping the valve, and rinsing it off with solvent in between times, letting it run out the bottom spark plug hole onto a shop towel.
It’s important to rinse the valve edge off each time in order to examine the progress. My biggest regret from this particular lapping job, is that I did not take incremental photos along the way. It was by far the best result I’ve ever seen. After the first round of lapping, there was a nice smooth even band most of the way around the valve, with a distinct darker uneven area for about 30 or 40 degrees of rotation… corresponding to the burning side of the valve. After the second round, the bad area was noticeably smaller, and after the third round, even smaller still. We did a fourth round of applying the coarse grit compound for good measure (the bad area was pretty much completely gone at this point,) and finished it off with one round of lapping with fine grit compound.
The result was nothing short of spectacular:
This is about as perfect of an exhaust valve edge as you could hope for! Needless to say we were thrilled.
We washed the cylinder out with some Av Gas in a squeeze bottle, blew it out with compressed air, and repeated that process a second time. Then we sprayed some LPS-2 in the cylinder for some lubrication so the cylinder walls would not be dry for starting.
We put everything back together and installed a new rotocoil assembly P/N SA629117-1 on the exhaust valve, and a new rocker cover gasket.
Spence did a short ground run so we could check for leaks, and then he did a test flight to check engine operation and get it hot so we could do another compression test.
While Spence was out flying, I cut the old rotocoil apart, and was SHOCKED at what I found: (I had heard of this happening, but had never seen it myself.)
The spring inside the rotocoil should be one long continuous spring. This one was in many pieces, clearly making this part non-functional. The rotocoil serves a very important purpose. It causes a small and incremental rotation of the valve every time the rocker arm presses against the valve stem, and helps to maintain a good seal between the valve and valve seat. When an exhaust valve stops rotating, there is a much greater possibility for a hot spot to develop. It’s important to stop a hot spot as soon as possible. If not, cylinder removal may be inevitable.
We are very hopeful this cylinder has been rescued from premature removal. Not only did the lapping process restore an excellent seating area on the valve, but the compression came up dramatically as well… after the test flight, we got an amazing 70/80!
Thank you Spence, for the opportunity to work with you on your cylinder! Of all the valve lapping projects I’ve done, this one is a favorite for sure.
The result was absolutely amazing, and I have a few takeaways as I think about the whole valve lapping process:
Even low-time cylinders can develop exhaust valve problems.
ALWAYS do a borescope inspection along with every compression test (preferably with every oil change.)
Take action immediately when you notice a burning exhaust valve (lapping is often a good solution if caught early.)
ALWAYS install a new rotocoil assembly when lapping a Continental exhaust valve, to help ensure the valve will rotate properly and consistently.
If you do remove a cylinder for repair, be sure a new rotocoil is installed as part of the repair process (sometimes they are reused unless you specify otherwise.)
If you’d like to see or hear more info on this topic, be sure to check out episode 109 of the Airplane Owner Maintenance Podcast. It’s called “Exhaust Valve Problems – Could Lapping Be A Good Option?” Apparently airplane owners want to learn about this topic… episode 109 is the 4th highest downloaded episode of all time, do date.
I got an email from Michael this past week. He owns a Mooney M20J, and something strange happened with cylinder #1’s EGT and CHT recently. Michael agreed to let me share the story, so that’s the main feature in this episode. The picture above is one Michael took with his borescope while looking for any obvious problems with the cylinder.
Before we get to that story, here are a few items I included in this episode:
How I microwaved a fork, and nothing bad happened 🙂
How I’ve been fighting the mice at Classic Aviation.
The great people this week who either stopped by the shop to say hi, or who sent me an email or voice message:
Mike, and his Cirrus SR22.
Steve and Janet, and their Twin Comanche.
Rudy and his Mooney M20J.
Michael and his Mooney M20J. (This is the featured story in this episode.)
A little follow up from the Piper Saratoga story I talked about in the last episode
… and here’s the little basil plant that has become more interesting than I ever thought it would:
Here are a couple more samples from the excellent photos Michael took of cylinder #1 with his borescope:
Finally, for those of you who love great books, especially books that use good aviation stories to teach life lessons, I have a good one to recommend.
John Ramstead has a new book coming out real soon called “On Purpose With Purpose.” From his days as an F-14 Tomcat pilot, to a near-fatal horse-riding accident, to his transition to a podcaster, speaker, and coach, John’s book is absolutely inspiring. I’ve already pre-ordered my copy, and I’ve been reading the digital version… it’s excellent!
12/80! That’s a terrible compression test result. And unlike some cylinders, this one did not show any obvious reasons for the low compression… take a look at the valves after the cylinder was removed:
Unless I’m missing something, I don’t see anything that would explain such a low compression number. The cylinder has been shipped to Tim Barnes at Skyline Cylinders for repair, so I’m hoping he will be able to give me more information about it. You can listen to the audio for more thoughts about this whole experience, and maybe I’ll give an update on it in a future episode.
I also mentioned in this episode my latest project in the shop at Classic Aviation – an annual inspection on a nice E33A Bonanza:
It’s a great airplane, with a great owner – now that’s a good combination!
The post “172 – A Perplexing Low Cylinder Compression on a Piper Saratoga” appeared first at AirplaneOwnerMaintenance.com
Can you see the problem with this exhaust muffler?
Maybe a closer look will help: (The cracked area was just inside the shroud that collects heat for the cabin.)
Thankfully Matt, the owner of a nice Cessna 170, had a carbon monoxide detector in his airplane that picked up the small amount of “bad gas in the cockpit.” Check out his panel:
I discovered Matt’s CO detector is available at Aircraft Spruce for $99. He’s been happy with this detector, and I would think it’s FAR BETTER than the little “spot detectors” that are often used in airplanes.
Here’s a link for the CO detector in the above photo:
On another note, I mentioned in this episode that I got to meet General Chuck Boyd yesterday as he was getting ready to depart SHD in his beautiful T34 airplane. It was such a pleasure to meet him, and I want to say “Thank you Sir, for your service in the Air Force!”
I had a surprise call this morning… my friend Eddie called and wondered if he could borrow a borescope. One of the cylinders in his Sonex’s Jabiru engine had zero compression, and he wanted to take a look inside the cylinder, especially at the exhaust valve.
Since I’m always looking for a good story, it didn’t take me long to say, “This sounds interesting… I’ll grab my borescope and drive right over to the airport.”
We got the borescope set up and quickly noticed the exhaust valve appeared to be open a tiny bit when it should have been fully closed. There was just enough leakage past the valve to keep the compression at zero.
We’re still not totally sure about that area at about the 8 o’clock position, but we didn’t see anything alarming when we looked at the valve edge with it open.
Thankfully, Eddie had done some research online and quickly got some feedback about the importance of regularly adjusting the valves in the Jabiru engine.
Sure enough, the exhaust valve had no clearance between the valve stem and the rocker arm (it should be .010)
After adjusting both valves on that cylinder, Eddie did another compression test, and we were pleasantly surprised… 70/80! And it was even a cold compression test!
It’s always great when there’s a simple solution!
Well done Eddie! And thanks for the good story we can all learn from!
In this week’s episode, we also talk about Lycoming SI 1418, a rarely used procedure for cleaning cylinders on the engine using some special equipment and ground up walnut shells.
Listen to this concept and let me know your thoughts… hit that button over to the right and tell me if you think it’s a crazy idea, or a great idea… I’m curious about it.
Reminder: I offer a service to evaluate your borescope photos. If you are not sure what your pictures mean, send them to me and I’ll evaluate them and send you a report within two days.
Our guest for today’s episode is Autumn Duntz, an aviation interior designer and refurbishment expert… welcome Autumn!
After observing some poor quality elements in a newly refurbished Beechcraft A36 Bonanza interior, I wondered how this type of thing could be avoided. After a little online research, I found Autumn’s website, AutumnElizabethDesign.com. I quickly realized she would be a great guest for the podcast.
I was curious about what airplane owners can do to avoid typical pitfalls and make the whole interior refurbishment process more fun and less stressful, while also achieving the desired results.
Autumn Duntz stands out in the industry, providing a refreshing and very personalized alternative to the big companies you might typically think of when it comes to airplane interiors.
Here are some samples of Autumn’s design work:
Although Autumn mostly works with larger airplanes and business jets, she has a wealth of wisdom to share with us that also applies to small airplanes.
In this episode, we covered topics from maintenance friendly designs, to regulations, to taking care of leather… and my favorite tip: “Provide maintenance covers for the seats and interior of your airplane when you take it to the shop!” I loved that tip.
If you need some help with designing YOUR airplane’s interior, I highly recommend having a conversation with Autumn to see if you’d like to work with her.
I’m confident if you choose to work with Autumn in designing an interior, or a paint scheme, you’ll experience the following results:
She will be easy to work with and make the process much less stressful.
There will be excellent communication throughout the process.
You’ll love the results, both of the work, and of working with her.
Here’s how you can learn more about Autumn’s services, and get in touch with her:
If so, would your passengers know how to operate them?
Here’s an emergency exit window where the instructions were hardly readable:
Thankfully, the lettering was etched into the panels, and a fine point Sharpie did the trick:
Imagine trying to remove that window if you were completely unfamiliar… these placards are important!
Find out in today’s episode why the placards were unreadable, and also hear about the other squawks that were discovered on an A36 Bonanza during annual inspection.
If you have a crazy story of something you discovered after a new interior was installed in your airplane, please let me know… I may do an episode in the future about airplane interiors, and things to be aware of.
In a previous episode, I shared the story about how I accidentally left a shop towel in an engine…
I got some great feedback from that episode, including the picture above… a flight student found a shop towel during preflight… in a place you would not expect.
It’s one more reminder to be extra-diligent during maintenance, and to have another person look over your work before installing the cowling.
In this week’s episode, I’m sharing the feedback I got from the story of the shop towel in the engine. (If you missed that story, you can find it in episode 165.)
There are some really good lessons to be learned… I want to say a big “thank you” to everyone who sent me feedback and helpful stories.
I’ve been receiving messages from airplane owners who are performing borescope inspections on their engine cylinders and exhaust valves… I always love to hear those stories, because I’m convinced borescoping can make flying safer by detecting failing exhaust valves before they come apart in flight.
Do you have pictures of your exhaust valves, but you’re not sure what they mean?
I can help with that, for sure.
I offer a service to evaluate borescope pictures for airplane owners.
It’s very easy to work with me, and here’s the process:
Go to this link, and make the appropriate payment:
Send me an email with your borescope pictures (dean{at}airplaneownermaintenance{dot}com)
Within 48 hours, I’ll send you a report with evaluations of your borescope pictures to help you understand what the pictures are saying, and things to be aware of.
Lieutenant Commander (LCDR) James Cox, a member of the Navy’s Blue Angels Team, is our guest today on the podcast! He exceeded my expectations in so many ways in our conversation, and I’m thrilled to share this interview with you. You’ll definitely want to listen to this one!
Although the Blue Angels do a lot of traveling, Jim is also a dedicated family man, and we talked about how he stays connected with his wife and kids while serving with the Blue Angels. Jim said, “Communication is key.” That’s a good word for all of us, in all kinds of life situations!
Throughout our conversation, Jim was quick to say, “This is not about me. This is about the team, and I’m grateful to be a part of it. As a team, we have the great privilege and responsibility to serve and inspire people and communities all over the country with a message of teamwork, professionalism, and excellence, in order to motivate individuals to reach their greatest potential in life.” (My paraphrase.)
Here’s the team:
In our conversation, Jim said so many things worth remembering, and here are a few noteworthy quotes:
“I always had an eye for the sky.”
“I’m proof that hard work alone can get you anywhere.”
“The flying is utterly amazing, but the community outreach portion of what we do is definitely the highlight.”
“I couldn’t be where I am today without my mom and dad.”
“The best thing you can absolutely do as a 16 year old in high school is to be the BEST 16 year old you can possibly be.”
“You start with the end in mind, but the PROCESS is so important!”
“The only way that we can fly the way we do is because of trust.”
“Everything we do is predicated on safety. Safety is absolutely first and foremost number one in everything.”
You can learn more about the Blue Angels at the website: BlueAngels.Navy.Mil
Jim, I am absolutely grateful for the opportunity to speak with you. Thank you Sir, and your family, and the whole Blue Angels team, for representing our country so well. We appreciate you!
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