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Is it okay for plane to sit for a few weeks?

SwimmingDragonfly96

Well Known Member
Due to weather and travel, I don’t think I’ll be able to fly my new to me 7a for about 3 weeks total (one week in now). I know planes sit for months to years sometimes and their motor is fine, while others in similar conditions will develop problems.

I could go over to the hangar and ground taxi it for some minutes to get everything flowing, but I’ve heard this doesn’t do much to help the motor. What are your opinions? Should I let it sit or go taxi it for a bit?
 
Due to weather and travel, I don’t think I’ll be able to fly my new to me 7a for about 3 weeks total (one week in now). I know planes sit for months to years sometimes and their motor is fine, while others in similar conditions will develop problems.
I could go over to the hangar and ground taxi it for some minutes to get everything flowing, but I’ve heard this doesn’t do much to help the motor. What are your opinions? Should I let it sit or go taxi it for a bit?

If you can't fly it, don't start it or turn the prop. The cooling system is designed for flight. Ground running does not distribute the cooling air properly.
 
Especially in the winter here, airplanes sit for longer than that. In the hangar, I keep mine on a float charger and a crankcase dehydrator 24/7/365. No good data that that device has any contribution to making it to TBO, but think that the theory is sound, and I haven't has a single catastrophic engine failure in the two years I've been using it. ;)
 
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It's worse

Ground running (or any running) puts combustion byproducts including water into the oil. Short runs without getting oil temps up to operating temps make it worse so don't. Turning to prop by hand to a different cylinder (old logic) will spread out the bad effects of exposure to all cylinders. Now we've realized it takes any remaining oil film off of the cam so don't do that either.

You live in Fog City near the ocean. It's not Florida bad like me but it's bad enough.

If you don't use Camguard, I'd start.
If you can block (won't use the word seal) the exhaust and air intakes, I would.
If you have the energy to make or cash to buy an engine dehydrator, I'd consider it.

Lots of related threads here on VAF. You'll get lots of opinions. Protect this investment. It's not like the economy or markets are protecting your other ones these days.
 
Short answer is no it is not a good idea. Problem with sitting is it can turn into months. If it's in a hangar not to big deal.
A guy across the taxi way from me just replaced his 0-360 because it ate the cam up. Oh he flies quite a bit also.
I have personal experience with cam replacement, because of not flying a Lycoming and an IO-520 continental engine.
Life got in the way and rust got to the cams.
It was an expensive lesson, But I have learned and now I go forth with experience as my guide.
All that said, I bought an RV-6A 0-360 400 hours a few years ago that I knew has not been flying for God only knows how long off a ramp in Arlington Washington for a cheap enough price (to replace the engine)
I has been fine after 200 hours (oil testing clean)
Your luck may not be as good as mine. Art
 
Short answer is no it is not a good idea. Problem with sitting is it can turn into months. If it's in a hangar not to big deal.
A guy across the taxi way from me just replaced his 0-360 because it ate the cam up. Oh he flies quite a bit also.
I have personal experience with cam replacement, because of not flying a Lycoming and an IO-520 continental engine.
Life got in the way and rust got to the cams.
It was an expensive lesson, But I have learned and now I go forth with experience as my guide.
All that said, I bought an RV-6A 0-360 400 hours a few years ago that I knew has not been flying for God only knows how long off a ramp in Arlington Washington for a cheap enough price (to replace the engine)
I has been fine after 200 hours (oil testing clean)
Your luck may not be as good as mine. Art

Thanks for the advice. Definitely not sitting for more than a few weeks unless the weather doesn’t let up.
 
Cam

Local Cessna fatal with cam failure and broken rings in two cylinders. Pilot failed to perform the first item on the emergency checklist: FLY THE AIRPLANE.
Lycoming 360, had cam replaced and then sat for a LONG TIME.
 
Is there anything about aircraft pistol engines that make them any different than automobile engines in regards to corrosion while sitting? I’ve had cars and motorcycles sit around for quite some time and fire right up as long as the battery was charged (and carbs weren’t gummed up on motorcycles).

Another question, does 100LL prevent gumming up of gas that’s seen in carbs of motorcycles that use auto gas? I see a lot of posts about corrosion, but never see anyone posting about cleaning gummed up carbs, etc.

Thanks VAF brain trust.
 
Is there anything about aircraft pistol engines that make them any different than automobile engines in regards to corrosion while sitting? I’ve had cars and motorcycles sit around for quite some time and fire right up as long as the battery was charged (and carbs weren’t gummed up on motorcycles).

Another question, does 100LL prevent gumming up of gas that’s seen in carbs of motorcycles that use auto gas? I see a lot of posts about corrosion, but never see anyone posting about cleaning gummed up carbs, etc.

Thanks VAF brain trust.

100LL doesn’t seem to gum up.. I’ve ferried an airplane with years old gas and it started right up.. as for the rest of the engine, perhaps it’s the short exhaust pipes that let in moist air, or the metals used are more prone to corrosion, idk, but the cam on Lycoming engines sits on top and seems like the most likely thing to corrode. Continental engines have the cam below and they seem to corrode less..
 
Due to weather and travel, I don’t think I’ll be able to fly my new to me 7a for about 3 weeks total (one week in now). I know planes sit for months to years sometimes and their motor is fine, while others in similar conditions will develop problems.

I could go over to the hangar and ground taxi it for some minutes to get everything flowing, but I’ve heard this doesn’t do much to help the motor. What are your opinions? Should I let it sit or go taxi it for a bit?

Leave the keys with your buddies and let them fly it!!
 
Is there anything about aircraft pistol engines that make them any different than automobile engines in regards to corrosion while sitting?

Another question, does 100LL prevent gumming up of gas that’s seen in carbs of motorcycles that use auto gas?

Auto engines have the following that is different.

1. positive crankcase ventilation that pulls clean, filtered air through the crankcase. This keeps the water (a key product of combustion) out of the air so for cars that driver far enough to get up to operating temps, it keeps the air cleaner. The highest dew point is equal to ambient air. Aircraft start with a 180F dew point and condense water every shutdown.
2. Auto gas has about 20 times less sulfur than 100LL. Sulfur and water make acid in the crankcase.
3. Air/fuel controls on the auto engine substantially reduce excess raw fuel in the blow-by.
4. Since emissions drive reduced low by, there is less volume for the system to neutralize.

All of these reduce basic contributors to crankcase conditions that promote corrosion after 3 weeks. Camguard shows it can extend that time.

100lLL is very stable and has a low vapor pressure, auto gas is not.
 
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All of these reduce basic contributors to crankcase conditions that promote corrosion after 3 weeks. Camguard shows it can extend that time.

"Theoretically", so does an engine dehydrator by continuously keeping the dewpoint well below ambient humidity, as well as flushing any post-shutdown moisture-laden air, exchanging it for dry air. Cost me about $45 to build...can't see a downside.

I can't speak to Camguard...many people are convinced that it's a good addition. I use it on the premise that there's likely no downside, and a lot of smart people think that it might help.
 
"Theoretically", so does an engine dehydrator by continuously keeping the dewpoint well below ambient humidity, as well as flushing any post-shutdown moisture-laden air, exchanging it for dry air. Cost me about $45 to build...can't see a downside.

I can't speak to Camguard...many people are convinced that it's a good addition. I use it on the premise that there's likely no downside, and a lot of smart people think that it might help.

Mac, we are in complete agreement - the dryer is the most effective, but I was addressing the OP's question as to why cars don't have the same issues. Also he parked the plane and all the water and acids condensed already, so a dryer will have to work for a long time to get it cleared. That is why I adopted the 5 min purge while the engine is hot.

I have been using dehydrators for 10 yrs. I am working on a 4th generation with a Peltier device and electronic control to periodically stir the crankcase pot and measure humidity. ;)
 
Mac, we are in complete agreement - the dryer is the most effective, but I was addressing the OP's question as to why cars don't have the same issues. Also he parked the plane and all the water and acids condensed already, so a dryer will have to work for a long time to get it cleared. That is why I adopted the 5 min purge while the engine is hot.

I have been using dehydrators for 10 yrs. I am working on a 4th generation with a Peltier device and electronic control to periodically stir the crankcase pot and measure humidity. ;)

A more high volume purge is a good idea IMHO. Based on a post I saw on here a few years ago (might have been yours), I use a 12v pool toy inflator in through the dipstick tube for a few minutes after shutdown while I'm pushing the plane back into the hangar, then hook up the lower-volume dehydrator before I leave.

I agree with you about auto engines. No question that the dinosaur-era technology of most aircraft engines mandate some engine care considerations that we don't need to employ for our cars.

Regarding dehydrators, I opted for simplicity and a high volume of silica gel. I only measure the humidity in the silica chamber, which typically runs 10% - 12%.

I empirically trust the process, but won't know the real value for at least another 1500 tach hours. Hopefully not less.
 
Another step to consider in amongst all the other options, is opening the oil door and opening the dipstick after shutdown. If you unscrew your dipstick and just pull it out far enough to set the head off to one side and leave the tube open, you can watch a LOT of steam escape the chamber while it's still hot. It's a good way to remove a bunch of the moisture from the engine while it's still in vapour form.
 
Due to weather and travel, I don’t think I’ll be able to fly my new to me 7a for about 3 weeks total (one week in now).

Ohhhh my young Yedi California resident. First world problems. Try Moose Jaw, Sask in March!!!!

Its fine but don't ground run it. Oil needs to get up to temp to do any good otherwise you're just creating more moisture.
 
Is it bad for the engine? Depends on the surrounding circumstances, such as: is it hangared, or parked outside? Is it in a humid environment or a dry one? How often does it sit for 3 weeks straight? If it's an occasional thing, it's probably not the end of the world. The average privately owned light GA airplane flies something like 40-50 hours a year, so many of them do sit. But if it's sitting 3-4 weeks on a regular basis, I'd expect the possibility of some issues over the long term.

As others have said, if it's not going to fly, don't move the prop or ground run it, because you won't get it hot enough long enough to get rid of the moisture inside the engine.
 
I would think a fresh oil change and filter would drain a lot of moisture out of engine, then periodically ground run it for 20 seconds as not to get it hot, but lubricate the internals ,would be helpful keeping everything lubricated without any extra moisture forming. This is assuming it’s grounded for maintenance or prolonged weather, and your there to run it.
 
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The amount of water produced by ground running is astronomical - In the gallons range. However only a small portion of that makes it to the oil.
Water in the oil does not really hurt a sitting engine. The problem comes from the protective oil dripping off of the cam and cylinder walls exposing the bare metal to Humidity in the air. It takes several days for the bare metal to become exposed. You can extend that to weeks by using Aeroshell 20W/50 oil and by adding Camguard. This buys you a bit of a safety margin for letting the plane sit a little. – You never know when work/weather/maintenance issues/life will force your plane to sit for a while.
It is important to understand that the moisture we need to fear is the humidity in the air, not the water in the oil. That water tends to be entrapped in the oil.
The humidity inside the engine would be the same whether you have fresh oil, or 100% water in your sump. I know this is not actually true, but it is true from a practical standpoint. In my opinion the most important things you can do are:
1. Use Camguard
2. Remove the dipstick after running. (While an engine is cooling the
moisture in the sump is released into the air and will then condense in
the upper regions of the engine, like the cam)
3. Use an engine dehumidifier – requires significant work for a regular
flyer, so I don’t find them practical. If you know in advance that the
plane will sit, then they are wonderful.
 
3. Use an engine dehumidifier – requires significant work for a regular
flyer, so I don’t find them practical. If you know in advance that the
plane will sit, then they are wonderful.

It literally takes me 30 seconds or less to connect my dehydrator to my airplane...as much time as it takes to open the oil door and stick a rubber stopper into the dipstick tube.
 
Is it bad for the engine? Depends on the surrounding circumstances, such as: is it hangared, or parked outside? Is it in a humid environment or a dry one? How often does it sit for 3 weeks straight? If it's an occasional thing, it's probably not the end of the world. The average privately owned light GA airplane flies something like 40-50 hours a year, so many of them do sit. But if it's sitting 3-4 weeks on a regular basis, I'd expect the possibility of some issues over the long term.

As others have said, if it's not going to fly, don't move the prop or ground run it, because you won't get it hot enough long enough to get rid of the moisture inside the engine.

Just did an annual inspection on a pristine Piper Archer that's hangared in a well-insulated heated floor hanger that is temperature controlled year round. 22 hours on the airplane last year. Cylinders were full of rust. Its the acids and moisture in the oil that do harm. Not the environment.
 
Just did an annual inspection on a pristine Piper Archer that's hangared in a well-insulated heated floor hanger that is temperature controlled year round. 22 hours on the airplane last year. Cylinders were full of rust. Its the acids and moisture in the oil that do harm. Not the environment.

I read an article recently whereby they tested several dehumidifiers. They found all of them worked to lower humidity levels in the case. However, cylinder humidity remained unchanged. If you believe that article, dehumidifiers would do nothing to prevent cylinder corrosion.
I run Aeroshell 15/50 Semisynthetic in my airplanes. I believe a quantity oil with appropriate additives helps a great deal. Both of my airplanes have sat at one time or another for a few months for various reasons and I have never had any corrosion issues, at least in my cylinders.
 
See Lycoming service letter L180B

It says you can see rust as soon as 2 days,… but letter calls for maximum of 30 days (in reasonably dry environment) without taking further action


It calls for vapor phase corrosion inhibititor, etc. (called Vci in letter now called vcpi at spruce) If I know I will down for a while I put this in and fly before it sits for a while.
 
in the future

In the future, when we are all using unleaded avgas, is there a better engine oil one could use that would allow longer down time between flights?
 
Just did an annual inspection on a pristine Piper Archer that's hangared in a well-insulated heated floor hanger that is temperature controlled year round. 22 hours on the airplane last year. Cylinders were full of rust. It's the acids and moisture in the oil that do harm. Not the environment.

If you say so. I'm just a pilot, and about as far from an A&P as one can get.

I sometimes wonder if hours flown, by itself, always tell the whole story. Would flying 30 minutes every weekend have the same result as flying 22 hours the first month and then sitting for 11 continuous months?

Do airplane engines that live in Arizona suffer the same corrosion as those that live in coastal Florida, given the same amount and frequency of use?
 
Dehydration

I think engine dehydration is a valuable tool in preventing engine damage from moisture during sit times and even short term down time. Using a temperature and humidity data logger I documented the effect of dehydration on a Lycoming O-360. While this is relative to crankcase environment only, cylinder dehydration is a more difficult problem to solve. My data can be found here. I use dehydration between all flights not just for long term storage. EAA recently had a Webinar talking about dehydration that had some interesting information on the topic and can be found here.
 
My 9A was parked in a heated hangar for 5-1/2 months last year as I was down recovering from shoulder surgery. A good portion of that time the propeller was removed for tear down inspection. My mechanic told me that if my oil was fresh, it shouldn't be much of an issue - but don't start it unless you are going flying. When it was time to fly again, I made sure I'd topped off the battery and everything went fine.

3 weeks really isn't much of a break, in the cold Alberta winter, I'm often 3-4 weeks between flights. I'd be more concerned with pilot rust than engine issues.
 
I would think a fresh oil change and filter would drain a lot of moisture out of engine, then periodically ground run it for 20 seconds as not to get it hot, but lubricate the internals ,would be helpful keeping everything lubricated without any extra moisture forming.

20 seconds isn't enough to get any oil pressure built up to move oil around. But heating the air volume inside the engine *does* happen quickly, a 20 second "run" would then condense it's moisture on the cold surfaces of the engine where no new oil has been deposited, and you're worse off than if you just let it sit.

Don't start your engine unless you plan to run it for a good 20-30 minutes at cruise power settings... You need that to boil off the residual moisture in the oil left over from the last run. If you don't, you just add to it.
 
The point of a brief run of a cold engine is to coat all the surfaces with cold oil, which leaves a much thicker layer than does a shutdown hot. The thicker layer should be more resistant to being washed off by condensation. My direct observation is that the thick layer stays in place during five months of winter inactivity, with much more oil everywhere than is normally present the day after shutting down hot.

Whether this is actually better is a matter of opinion, of course. It assumes that the last flight got the oil hot enough long enough to boil off all the water, so the only moisture present is what is produced during the 45 - 60 second run cold. It also assumes nobody turns the prop to scrape the oil off the cam and cylinder walls.
 
20 seconds isn't enough to get any oil pressure built up to move oil around. But heating the air volume inside the engine *does* happen quickly, a 20 second "run" would then condense it's moisture on the cold surfaces of the engine where no new oil has been deposited, and you're worse off than if you just let it sit.

Don't start your engine unless you plan to run it for a good 20-30 minutes at cruise power settings... You need that to boil off the residual moisture in the oil left over from the last run. If you don't, you just add to it.

My oil pressure is up in 4 seconds, leaving 16 to coat internals. An old aircraft builder told me this works. Who knows?
 
Due to weather and travel, I don’t think I’ll be able to fly my new to me 7a for about 3 weeks total (one week in now). I know planes sit for months to years sometimes and their motor is fine, while others in similar conditions will develop problems.

I could go over to the hangar and ground taxi it for some minutes to get everything flowing, but I’ve heard this doesn’t do much to help the motor. What are your opinions? Should I let it sit or go taxi it for a bit?

I can’t imagine an engine having problems with sitting for 3 weeks. Lots of aircraft do that for different reasons. Use camguard if you are worried.
 
I can’t imagine an engine having problems with sitting for 3 weeks. Lots of aircraft do that for different reasons. Use camguard if you are worried.

I wonder what percent of engines make it to TBO. If it is the majority then there probably isn’t a need for some changes. I have never used one in the past but bought one today from rbaviation. If 40% humidity is the number to beat, humidity is always higher here in Michigan. For a small investment I hope to help me get closer to TBO than the average engine.
 
I can’t imagine an engine having problems with sitting for 3 weeks. Lots of aircraft do that for different reasons. Use camguard if you are worried.

To be honest, this is probably the best answer to the OP’s question I have seen in this thread. I’ve owned airplanes for 45 years, and while I fly a lot, I don’t get around to every plane every week. Heck, this winter we flew one of our planes once in January due to all the storms coming across the Sierra- and all the rest just sat!

Don’t let your airplane sit any longer than necessary, don’t try short little ground runs because you think it will help….and don’t let your airplane stop you from that once-in-a-lifetime month-long cruise to Antarctica!

The majority of homebuilders will never get anywhere close to enough hours on their plane/engine to worry about TBO….

Paul
 
It assumes that the last flight got the oil hot enough long enough to boil off all the water, so the only moisture present is what is produced during the 45 - 60 second run cold.

Every flight, no matter how long, will end with moisture condensing in the engine after shutdown. It isn't "dry" when you park it after a longer flight, it just has the minimum amount of moisture possible because it's boiled off all of the remnants from previous flights.

Any ground run that isn't long enough or hot enough to boil off that moisture, will have the moisture of the current run *added* to it at shutdown. Your 45-60 second run is adding moisture to a system that already has moisture, every time you do it... And it's not removing any because you're not running it long enough to boil anything off.
 
Getting rid of water emulsified in the oil takes at least 180 degrees for quite a long time. That's not the point of the cold run before storage.

Water that condenses on engine parts during storage doesn't get through the oil layer. Multiple cycles of pressure and temperature changes can deposit water continually over the winter and eventually wash off the oil layer. The cold run makes the layer much thicker, making it harder to wash off.

There's no reason to do multiple brief cold runs, as Snowflake suggested.

If water vapor from combustion condenses on the inside of the engine after the final flight of the year, that water will get mixed in with the oil during the brief run prior to storage. Whether that bit of water is more or less important than the continual deposition of water through the winter is one of those questions that probably will never be answered definitively.

Engines stored in dry conditions (eg. a heated hangar during the prairie winter, where relative humidity inside the hangar is usually below 30%) experience very little corrosion compared to engines stored outdoors in a humid climate. That suggests to me that the water vapor inside the engine due to combustion is less important than the continual deposition of water throughout the winter.
 
Skip to 3:20 in the video to hear what an actual engine rebuilder says about those short engine runs.

https://youtu.be/PSx2_vdozMg
:confused:

Yes, I am a strong opponent of short engine runs whether we're talking cars, boats, motorcycles, snowmobiles, four wheelers, tractors…or any other seasonal motorized equipment including airplanes. On the other hand I also acknowledge that getting an airplane engine up to operating temperature for one hour once a week is simply an impractical expectation for many airplane owners around the country.
 
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Building a dehydrator isn't that hard, nor is disconnecting it before flight and hooking it up afterwards. I'm sure i've seen plans for more than one here on VAF. It does require that you have power to run a small circulation fan, but that might even be achieved with a battery and/or solar panel if power isn't available.
 
I have a friend who places small incandescent light bulbs in exhaust pipes.

Better than nothing.

Yeah, there are two ways to keep the dew point below ambient temperature....increase the temperature or decrease the humidity. In the winter, I use a small heater with a fan and 80 watt heating element to keep the tightly-closed interior of my boat in storage from growing mold due to condensation. Doesn't take much.
 
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