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

[Flying Canuck]

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.

[thiggins]

https://youtu.be/PSx2_vdozMg

[MacCool]

Originally Posted by thiggins

https://youtu.be/PSx2_vdozMg

Some good points regarding the value of compression testing, ongoing oil analysis, and inspection of filter pleats.

[Snowflake]

Originally Posted by tracy

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.

[wil780]

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.

[tracy]

Originally Posted by Snowflake

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?

[robert@jonesrv10.net]

Originally Posted by SwimmingDragonfly96

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.

[rockwoodrv9]

Originally Posted by robert@jonesrv10.net

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.

[Ironflight]

Originally Posted by robert@jonesrv10.net

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

[Snowflake]

Originally Posted by wil780

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.