Airplane GEEK

Aviation News from around the world

Engine Health

By Vic Syracuse, EAA Lifetime 180848

This piece originally ran in Vic’s Checkpoints column in the May 2021 issue of EAA Sport Aviation magazine.

It is amazing to me how many airplanes changed hands in just the last year, especially in the middle of a pandemic. It takes more than a pandemic to keep some aviators from enjoying their passion. The converse side is that not all airplanes get exercised as much as they should, for lots of reasons. Sometimes it’s the weather, but oftentimes it can be bigger events, like the pandemic, financial issues, life-changing health concerns, or even the death of the aircraft owner. The unfortunate impact of these is that the aircraft engine’s health could also be impacted if proper care wasn’t exercised during the downtime. In the last year, we have seen increasing cases of engines with bad health, so I thought I would share some of them with you. The entire topic could probably fill up a book, so I am only going to cover some of the highlights and warning signs in this column.

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Here’s a great view of a cylinder with lots of rust in it caused by a long period of inactivity.

Since 90 percent of my annual activities are focused on Van’s Aircraft RVs, which are primarily powered by Lycoming engines, all of what you see here will be relevant to Lycomings, even though some of the recommendations could be pertinent to other piston aircraft engines.

I am going to start with this statement, and probably repeat it multiple times, because I want you to remember it: Inactivity is the mortal enemy of a piston aircraft engine.

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Here’s an eye-opener. The rusted magneto drive was removed from an airplane that was regularly run on the ground rather than flying. It is shown compared to one that sat on the bench in an Atlanta hangar for two years! You can visually see the difference between corrosive blowby gases circulating in a crankcase that has not been allowed to reach operating temperature for the proper length of time.

For those of you who are building airplanes, try to wait as long as possible toward the end of the project to procure the engine. It is common practice for the new ones from the factory to be pickled, so that will give you some leeway. Just be sure to leave it in the box and don’t break the seal. I’ve seen engines last many years if stored this way without any adverse problems. Once you do break the seal in order to mount the engine and do the cowl work, try not to move the crankshaft any more than necessary. Do not drain the oil out of the cylinders until you are ready for that first engine start.

If you found a really good deal on a used engine while building your airplane, consider filling the crankcase and cylinders with oil and storing it upside down. For Lycoming engines, this will keep the camshaft submerged in the oil and protect it.

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If the engine oil starts to look dark like this soon after an oil change, there’s a good chance that you need some cylinder work. A healthy engine should have oil that looks like the picture on the left, which was taken after 35 hours of operation from an IO-540 with 700 engine hours.

For those of you who happen to hit a period of inactivity that grounds the aircraft — whether due to weather, maintenance, or health — please do not just start the engine periodically and let it run on the ground. It is one of the worst things you can do to an aircraft engine. One of the byproducts of combustion is water, and you can see this if you look at any automobile’s tailpipe on a cold day. There’s a nice cloud of vapor billowing out of it after startup — and sometimes even longer if it is cold enough outside. You can’t see this as much on an airplane due to the propeller slipstream blowing it all away, but it’s there. Not only that, due to the larger cylinder-to-piston wall clearances in the aircraft engine, there is quite a bit of blowby from combustion that goes directly into the crankcase. Plus, it’s not just clean water vapor. It’s loaded with corrosive combustion byproducts.

It takes about 20-30 minutes of actual flight time at engine operating temperatures to get all of the harmful blowby gases to a true state of evaporation so that they are not condensing inside a cold engine upon shutdown. Running the engine on the ground will never achieve the temps needed to protect the inside of the engine. Take a look at the picture of a magneto taken from an airplane that was operated only on the ground for over a year compared to a magneto that sat on a bench in the shop for two years. It is quite an eye-opener.

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Here’s a good view of the camshaft in a Lycoming engine, which can only be viewed by removing a cylinder. This one looks good, with no scoring, so the engine only required a top overhaul.

For those of you looking for excuses to fly your airplane, feel free to quote me on this statement: Inactivity is the mortal enemy of a piston aircraft engine. The best thing would be to fly it every day, just like flight schools, where they can run their engines to TBO without major problems. It’s like the engines have a human side to them. They like to be fed every day, not just once a week or monthly. If daily or weekly exercise is good for human bodies, it might be just as good for anything mechanical as well.

I’m sure you’ve noticed how sometimes you feel stiff if you haven’t exercised or if you missed a workout, but things seem to loosen up once you get going again? Those of us who are older notice creaking joints when we first get up in the morning. Jumping out of bed isn’t the same as it used to be. Well, piston aircraft engines behave in the same way. You’ve probably noticed that as well if you’ve been paying attention. Outside of sitting for any length of time, the next abusive event to the engine is the startup. If it’s been flown regularly, the startup is probably easy. Oil pressure should come right up into the green, and it should be running smoothly rather quickly if you used the proper starting procedure. If it’s been inactive a while, sometimes there’s even a special ritual required to get all of the cylinders firing and hoping the oil pressure rises to the occasion. If only we could hear the engine, I’m sure it moans and grunts as much as we do!

Once the engine has been started, be careful not to exceed certain power settings until some of the engine temps have achieved the recommended values. While Lycoming manuals state that the engine is ready when power can be added without the engine stumbling, I have a different approach with mine since I am the one funding the engine. I wait until cylinder head temperatures are more than 200 degrees Fahrenheit and oil temperature is more than 80 degrees Fahrenheit before applying runup power. I know there is guidance out there that the engines should be preheated when the temperature is less than 20 degrees Fahrenheit, but I preheat mine when it’s less than 40. Why not? When preheated, the oil is usually already at 95-100 degrees when I start the engine, so it turns over faster, which is less draining on the battery and the starter. Plus, I know oil is moving faster through all of those small orifices inside the engine. By using an oil sump heater, in conjunction with cowl inlet covers and a blanket over the cowling, the whole engine compartment is warmed to a constant temperature. We don’t have some of the extreme cold temps in Atlanta that some of you have elsewhere, but preheating your engine is well worth the time and expense. There are lots of creative ways to preheat an engine, which would probably suffice for another column in itself.

The First Signs of Trouble

By now, you are probably wondering how you will know if your engine has been damaged from either inactivity or abuse. There are some indicators that you can discover on a prebuy or during routine maintenance.

One of the first signs of cylinder problems will be a darkening of the oil sooner than usual, which indicates a higher-than-normal blowby. Most aviation oil used in aircraft engines running leaded avgas will have a slight green tint to it when it is drained after 35-50 hours. A sure sign of a problem is if the oil starts to look black in the first 5-10 hours after an oil change. Recently, we had an engine in which the oil turned black as coal after 45 minutes of flight following a fresh oil and filter change. Another indication of a problem is that one or more of your spark plugs are wet with oil, especially the bottom ones.

The cylinder barrels are usually steel. When they sit for a while, they can begin to rust, especially in humid environments. Running the engine will scrape away the rust, but it can also leave pits in the cylinder walls, which allows the oil to escape past them. These pits and score marks can easily be seen by using a borescope to peer inside the cylinder.

The fix for bad cylinders is not all that difficult. They can be replaced individually or all at once. This is usually referred to as a top overhaul. When the cylinders are pulled off the crankcase, it is only then that you can get a view of a critical component called the camshaft. The camshaft gets the worst abuse at startup, especially on an engine without roller lifters. There are lobes on the camshaft whose purpose is to actuate lifters, which in turn move pushrods to open and close the intake and exhaust valves. At startup, this is done before any oil pressure, which means initially there is no lubrication.

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Oily spark plugs can be an early sign of cylinder problems, once break-in is completed. Engines that are run regularly and at proper operating temperatures should have dry plugs with a light gray color to them when using avgas.

So, now you can understand the potential for damage if the engine has sat for any length of time or has been abused by not preheating. Unfortunately, the only way to fix a worn camshaft is by tearing the engine completely down, which is a major expense.

Camshafts do not often fail catastrophically. Usually, there is just a gradual decrease in power. However, sometimes one lobe can fail such that the decrease in power on that cylinder is a real emergency. If you suspect camshaft wear, you can remove the rocker covers and measure the lift of the valve/rocker arms to see that they meet specs and all are equal, but the only surefire inspection is a visual one and requires removing a cylinder. My experience has been that within five to six months of flying an engine that has been inactive without pickling or proper storage, the camshaft will begin to fail. I’ve called this on at least six engines in the last 18 months.

For those of you who are buying an aircraft, take the time to understand the history of the engine relative to any periods of inactivity, cold weather operations, and oil change intervals. It could save you some serious costs.

For those of you who aren’t flying as often as you would like, be sure to add CamGuard or Lycoming LW-16702 at each oil change or use oil with the Lycoming additive already in it. Do change the oil every four months even if you don’t have many hours on it. However, do not use the CamGuard or Lycoming additive until break-in is achieved on new cylinders, or they will never break in.

Taking care of your engine will help to keep the fun factor alive. Of course, flying regularly is even more fun. Hopefully, I’ve convinced you of that.

Vic Syracuse, EAA Lifetime 180848 and chair of EAA’s Homebuilt Aircraft Council, is a commercial pilot, A&P/IA, DAR, and EAA flight advisor and technical counselor. He has built 11 aircraft and has logged more 9,500 hours in 72 different types. Vic also founded Base Leg Aviation and volunteers as a Young Eagles pilot and an Angel Flight pilot.

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