What's the truth about ground running?

[RobertE]

Well, it's Saturday evening and I'm too lazy to go to the airport for what is my usual hour or so flight to nowhere as a minimum each week to keep the rust off the airplane and me.  Which got me thinking about rust.

We've all heard of the dangers of ground running (moisture and acids absorbed into the oil without the necessary time or temperature to boil it off).  But something just seems wrong about that thinking so I wonder if there is someone who can describe the thought process that can get me there?  Let's agree that, with our Lycomings at least, there are two threats of corrosion - the forementioned water/acids but also a cam that has been idle so long that the oil has departed it (which is what camguard is designed to address).  Surely, if the goal is to recoat the cam, there is some short interval for which the benefits of a fresh coat of oil exceed the penalty of a little moisture in the oil, no?  And speaking of moisture in the oil not being cooked off, don't we all find ourselves running the engine for 10 minutes or so at the end of every flight - particularly in the winter - during which the oil is often well below the 180 degrees deemed required?  If a few minutes of the engine operating with cool oil really did damage wouldn't we all be putting our engines at risk with every winter flight?

Can someone make a good argument why I shouldn't run my engine for, say, 2 minutes to recoat my cam if I'm not able to go flying for an extended period of time?

Thanks.

 

 

 

 

 

 

 

 

 

[ArtVandelay]

My oil after 5 mins of taxiing is still 180, I also open the oil fill to allow water vapor to escape after a flight. Don't know it if it helps.

I think the cam gets coated after a few seconds, personally I think having clean oil when you store the plane is more important

[DonMuncy]

15 minutes ago, RobertE said:

Well, it's Saturday evening and I'm too lazy to go to the airport for what is my usual hour or so flight to nowhere as a minimum each week to keep the rust off the airplane and me.  Which got me thinking about rust.

We've all heard of the dangers of ground running (moisture and acids absorbed into the oil without the necessary time or temperature to boil it off).  But something just seems wrong about that thinking so I wonder if there is someone who can describe the thought process that can get me there?  Let's agree that, with our Lycomings at least, there are two threats of corrosion - the forementioned water/acids but also a cam that has been idle so long that the oil has departed it (which is what camguard is designed to address).  Surely, if the goal is to recoat the cam, there is some short interval for which the benefits of a fresh coat of oil exceed the penalty of a little moisture in the oil, no?  And speaking of moisture in the oil not being cooked off, don't we all find ourselves running the engine for 10 minutes or so at the end of every flight - particularly in the winter - during which the oil is often well below the 180 degrees deemed required?  If a few minutes of the engine operating with cool oil really did damage wouldn't we all be putting our engines at risk with every winter flight?

Can someone make a good argument why I shouldn't run my engine for, say, 2 minutes to recoat my cam if I'm not able to go flying for an extended period of time?

Thanks.

It would seem to me that your answers are going to be of two types. First are theories of why it is OK or bad. And second are accounts of how "my friend did it and it either lasted 4x TBO or required OH within 400 hours". Unless someone did some super serious testing or data analysis, I would not be betting my life on the answer. I think you pick the theory that makes  the most sense to you, and go with it.

[Hank]

If you're already at the airport, with the plane out of the hangar or untied & uncovered, sitting inside with the engine running, just taxi to the end of the runway and go around the pattern a couple of times.

My occasional 3 full stops at night takes a whole half hour or so from engine on to engine off. How much time will you save on the whole trip to the airport by not flying? 

[N601RX]

I've saw some people our airport crank their plane up and taxi 2 minutes up to the MX shop for work. The valve covers were removed 10 minutes later and everything had droplets of water on it.

[jetdriven]

I think you an get by with ~20 seconds of running but no longer than that.  And only just once. 

[Yetti]

Doesn't the Lycoming engine have a breather tube?

[larryb]

I have a limited amount of data. This graph shows almost 100% humidity after taxi back from avionics shop. I was horrified when I saw that and immediately turned on the heat to 80 degrees and that brought it down over the next day.

Next is a similar graph but after a flight.

My conclusion is a ground run is bad.

[PTK]

Robert, here is an article which may help you shed some light into answering your question and provide you with another option.

http://www.reiffpreheat.com/Article-Sutton.pdf

If you're not able to fly the engine for a month or so there are things you can do to control the relative humidity inside the engine. The focus needs to shift from recoating with oil to actually controlling humidity. If engine environment is bone dry by moving the condensation point as far away from the engine as possible, it makes it extremely difficult for it to corrode. Even without oil coating. (According to this article up to a month or so. Beyond this, although the author doesn't address it as it's not the focus of the article, other things may need to be done, i.e. pickling.)

Simply running it on the ground will recoat with oil but will also give it a fresh and healthy bolus of dihydrogen monoxide! Not a good thing, imo.

[aviatoreb]

I have been thinking about this lately - I am usually very good about flying the airplane every week or so at least.  I make a point of it.

I March I am heading to Florida for a paint job.  They say "35 days or so".  I am a little buggered that I cannot do anything about corrosion during that period.  I wonder if I should look into pickling during that painting period - if I can even get that done?

[Piloto]

I think the whole issue about corrosion is overstated. If you keep the plane in a metal hangar humidity will stay outside the hangar. Condensation happens on the outside of the walls. I have a lot of steel tools in the hangar and they don't even rust. Running the engine on the ground helps if you keep the plane outside. Just check with boat owners at the marina. They run the engine and A/C generators at least every two weeks to keep them from rusting. And they are cooled by sea water thru the heat exchanger.

José

[carusoam]

The reasons for a two minute ground run on the odd weeks vs. letting the engine sit....

1) there is no discernible difference in letting an engine sit for one extra week in the year.

2) a two minute ground run does generate moisture by combustion.

3) the two minute ground run does not heat the whole engine enough to drive out moisture that collected.

4) if the ground run is long enough, like 15 minutes, the other concerns start to become important.

5) a flight around the pattern takes how long?

 

Letting an engine sit for a month.... Check with the engine manufacturer's guidelines regarding pickling.  It may be worth performing the process just to say it was done.  Special oil and moisture adsorbing parts...

Best regards,

-a-

[Bob - S50]

I'm with Hank.  Unless you live with the airplane, how long do you spend getting to the airport, pulling the plane out, putting it back, and driving home?  For me, that would be about 1.5 to 2 hours depending on traffic.  Does running the engine for 2 minutes vs flying 5 minutes away from the airport and 5 minutes back to the airport ( saving you 8 minutes) really make that much difference?  If so, you are way too busy.

[1964-M20E]

Once you are at the airport go up for 15 to 20 minutes it don't hurt and it keeps you VFR current as well at least one landing just ground running doe not get you current.

[Jeff_S]

The OP is from St. Helena, CA, which Google Maps tells me is in the mountains north of Napa Valley.  My guess is that the general humidity in that area is usually pretty low, but correct me if I'm wrong on that.  With a generally low-humidity environment to begin with, it seems to me that just flying like normal, every couple of weeks or so, would be all the protection you need.  I do believe that limited ground running would actually put more condensation into the engine, so that could potentially generate more potential for corrosion.

Don't get me wrong...I think that the generally reduced flight hours and age of the GA fleet OVERALL is creating a potential for corrosion, but I also think the CamGuard guys have done a good job creating a market for their product.  If you live in a fairly arid environment (read: not very near the ocean) and fly it at least a few times a month, then I don't believe corrosion is really going to be a big deal.

[M20F]

Flying a plane does more than just exercise the engine.  Running it around a bit gets all the parts moving around not bolted to the engine as well which I think is important.

[jetdriven]

On December 20, 2015 at 9:27 AM, Piloto said:

I think the whole issue about corrosion is overstated. If you keep the plane in a metal hangar humidity will stay outside the hangar. Condensation happens on the outside of the walls. I have a lot of steel tools in the hangar and they don't even rust. Running the engine on the ground helps if you keep the plane outside. Just check with boat owners at the marina. They run the engine and A/C generators at least every two weeks to keep them from rusting. And they are cooled by sea water thru the heat exchanger.

José

No way.  My plane is frequently covered in water condensation in the mornings and its inside a metal hangar.  The humidity makes its way in there, and when the temp cools to the dew point it condenses out on the metal airplane skin. And the engine case.  And the inside of the engine. 

I can't remember the last time I saw a bad cam in a boat or car.  And I can't remember a week that goes by I don't hear of a lycoming with a bad one.  

[Piloto]

5 minutes ago, jetdriven said:

No way.  My plane is frequently covered in water condensation in the mornings and its inside a metal hangar.  The humidity makes its way in there, and when the temp cools to the dew point it condenses out on the metal airplane skin. And the engine case.  And the inside of the engine. 

I can't remember the last time I saw a bad cam in a boat or car.  And I can't remember a week that goes by I don't hear of a lycoming with a bad one.  

Woow!! Texas is much more humid than Florida. In 30 years in a hangar in Florida I have never seen condensation inside the hangar. Maybe your roof is leaking.

José

[ArtVandelay]

My mechanic has a 78J with original engine, 37 years in south Florida, his cam is still good. Hangared of course and replaces oil after 25 hours.

[Marauder]

On December 20, 2015 at 9:27 AM, Piloto said: I think the whole issue about corrosion is overstated. If you keep the plane in a metal hangar humidity will stay outside the hangar. Condensation happens on the outside of the walls. I have a lot of steel tools in the hangar and they don't even rust. Running the engine on the ground helps if you keep the plane outside. Just check with boat owners at the marina. They run the engine and A/C generators at least every two weeks to keep them from rusting. And they are cooled by sea water thru the heat exchanger.

José

No way.  My plane is frequently covered in water condensation in the mornings and its inside a metal hangar.  The humidity makes its way in there, and when the temp cools to the dew point it condenses out on the metal airplane skin. And the engine case.  And the inside of the engine. 

I can't remember the last time I saw a bad cam in a boat or car.  And I can't remember a week that goes by I don't hear of a lycoming with a bad one.  

5 minutes ago, jetdriven said: No way.  My plane is frequently covered in water condensation in the mornings and its inside a metal hangar.  The humidity makes its way in there, and when the temp cools to the dew point it condenses out on the metal airplane skin. And the engine case.  And the inside of the engine. 

I can't remember the last time I saw a bad cam in a boat or car.  And I can't remember a week that goes by I don't hear of a lycoming with a bad one.  

Woow!! Texas is much more humid than Florida. In 30 years in a hangar in Florida I have never seen condensation inside the hangar. Maybe your roof is leaking.

José

I think a lot depends on the hangar construction. On a cold damp day, my plane is covered like Byron says with condensation in my current hangar. The floors are blacktop and there are gaps and openings around the door tracks.

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[Shadrach]

10 hours ago, jetdriven said:

No way.  My plane is frequently covered in water condensation in the mornings and its inside a metal hangar.  The humidity makes its way in there, and when the temp cools to the dew point it condenses out on the metal airplane skin. And the engine case.  And the inside of the engine. 

I can't remember the last time I saw a bad cam in a boat or car.  And I can't remember a week that goes by I don't hear of a lycoming with a bad one.  

Whoa! Really? I live in the mid-Atlantic and I've never come to the airport and found condensation on the plane, whether morning, noon or night. 

[mike_elliott]

17 minutes ago, bluehighwayflyer said:

Neither have I, and I base my plane in the Florida panhandle, although 50 miles inland from the Gulf and in a very nice, new, and "high and dry" private box hangar.  I do believe the corrosion threat is very real, but manageable, however, and a quality hangar is the most important line of defense. 

Guys, you are trying to dispel the concept that  planes based in Florida are complete junk once they overnight here and should never be considered for purchase! Lets keep these well kept planes as our secret and let the rest of the believers continue to shop for their planes above Latitude 50 for extra corrosion protection.

[pinerunner]

The issue is this. Do you really recoat the camshaft with oil if you just idle it? What I've read from Deakins and Bush is that there is only "windage" getting oil onto the camshaft lobes during regular usage. That's an oily fog inside the engine when its running that gets a little oil on everything. It's why a little blow-by turns into oil on your belly coming out the vent. No little holes pumping oil onto the lobes.

A good oil with the right additives leaves a very thin film that sticks to the cam lobes even after most of the oil has drained slowly off and if you let it sit a long time that's all you have on first startup. Just turning it over by hand will wipe that off and undo that protection without generating any windage to get a new layer on so the "turn it by hand" routine may be OK for everything except the camshaft lobes. Running it at idle presumably doesn't generate good enough windage to oil the camshaft lobes well. I suppose it does generate some windage but is it enough? Lycomings have their camshaft on the top so it might be expected to be the last thing to get windage oil on it. Running it up to speed without flying gives poor cooling. So the best advice as far as I can tell is to either fly it frequently or pickle it properly and leave it alone.

Its hard to prove these things since the camshaft is hard to get at and examine. Who's going to run it in different ways and then open it up to check the camshaft?  

[larryb]

If you have condensation inside your hanger try a fan running continuously. I had some condensation infrequently. I read about this solution on beech talk. So far so good.

[DXB]

54 minutes ago, pinerunner said:

Its hard to prove these things since the camshaft is hard to get at and examine. Who's going to run it in different ways and then open it up to check the camshaft?  

In the medical world there are excellent resolution distal chip cameras on long flexible scopes that could snake down the dipstick tube and turn up to look up at the cam.  They could even sample material that is on the cam lobe.  I imagine similar quality stuff has made it into industrial use in recent years? Someone should answer this question once and for all to define optimal ground run conditions, if any exist.  I believe that ground run can't get rid of combustion-generated moisture, but but with modern anti-corrosive additives, I'd think re-coating the lobes with oil might still have value.