Should one leave the Tanis plugged in for winter?

[Marauder]

Do you have these same concerns when the OAT is 70 degrees?  If the engine is held at a relatively constant temperature (including the surrounding air in the engine compartment) how would the outcome be different?

I do and that is why I fly frequently. The difference is that we are talking about planes most likely sitting like this during the winter for extended periods of time and not flying as much.

As a side note, as a scientist by training, all of these topics are speculation. Until someone produces a controlled study showing scientific evidence to this, it is all guess work. This goes for the LOP/ROP, Camguard, José’s Pee Venturi, etc.


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[Yetti]

If you are in a winter dry climate, I would propose that the 60-80 degree heat with 4000 percent humidity we have in our lovely subtropical environment down south will let more moisture in the engine, than your dry environment with the artificial heat.

[steingar]

4 hours ago, Marauder said:

As a side note, as a scientist by training, all of these topics are speculation. Until someone produces a controlled study showing scientific evidence to this, it is all guess work. This goes for the LOP/ROP, Camguard, José’s Pee Venturi, etc.

 

Since there is no data it is speculation indeed.  Thus in the absence of actionable data the most logical course of action is to do what makes flying easiest, since if flying is easy one will do it more often, which is better for the engine and aircraft in cold wx.  Thus the reason I say to keep it warm.

[pwnel]

16 minutes ago, steingar said:

Since there is no data it is speculation indeed.  Thus in the absence of actionable data the most logical course of action is to do what makes flying easiest, since if flying is easy one will do it more often, which is better for the engine and aircraft in cold wx.  Thus the reason I say to keep it warm.

I like your argument, but lets assume then there is NO flying going to happen.  I.e., out of the country for three months.  I will pickle the engine as per Continental's instructions (pickle oil, dessicant spark plugs, dessicant bags in exhaust and sealing it etc).  Given that I really respect Mike Busch and his way of thinking, I haven't heard too strong an argument for NOT leaving the Tanis on, hence my approach right now is to pickle and leave the Tanis on Dec - Feb as the best thing to do for the engine.  You can do up to 10 hours on the pickle oil, so if a chance presents itself, I'll go do a run around the patch for an hour whenever I can.

Edited November 13, 2018 by pwnel

[DXB]

7 hours ago, Marauder said:

 

My concern would be that keeping it warm all the time without finding a way to dispose of the moisture would lead to a green house effect. Just opening the oil dip tube and hoping the engine vent would be enough to allow moisture out is wishful thinking. If they said, “used with a desiccant flow system”, I’d be more prone to think that will be a good approach.

And keeping the engine warm all the time and not flying it still leaves the concern of oil migrating off of the cam and other parts.




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I have the same heater you do, and leaving on all the time in cooler temps seems to put my oil and cylinders in the realm of summer ambient temps - 70s-90s. So I'd think oil loss of the cam would be no worse than in the summer, though I guess it might become an issue if it got left on during an unseasonably warm winter day. 

Whether  the heater keeps  moisture out of the engine seems like a complicated question that I don't really have my head around.  I'd think actual measurements in real world conditions wouldn't be too hard to accomplish, though apparently it's not trivial because this debate persists.  

[carusoam]

There is plenty written up by MSers that have used desicants and air pumps to supply dry air to their engines for extended periods of time.

Lets not confuse the three devices...

1) Heaters are great for warming the engine to avoid really cold starts with really thick oil...

2) Dehumidifiers are For keeping moisture away from corrodable surfaces...

3) Pre oilers are the things that put the oil back on all the surfaces after time and temperature have allowed the oil to drip and drain back to the oil pan...

4) We get some confusion by heating air, where the RH has a tendency to drop.  Winter cold air has a pretty low moisture content, and warming it up drives the RH even lower...

5) The problem with this thought process is... the air inside our engines is not following these simple rules... it is high humidity air in a pretty tight container... and some parts are open to the outside through the air intake, others are open to the exhaust, a few parts are open to the case vent

If you are not going to fly for a few months... dehumidifiers work, pickling is fine, leaving the engine open is almost good...

but leaving part of the engine with moisture still in it at 70°F is likely to increase the rate of oxidation...

So why heat the engine up?

Mike Busch is really smart, and writes pretty well... rarely has left us uninformed...

Tanis is really smart, and writes in a commercially acceptable manner...

Taking either of them out of context is a bit dangerous, for your wallet...

They may be saying leaving the heat on is harmless.... as in it won’t damage things by overheating or lighting a fire....

But they are not outwardly saying it will do what you want it to do... “heat your engine to prevent internal corrosion...”

That is what I would need to see to believe this could work, then I would be looking for an MSer that has done this before... preferably a mechanic that sees multiple engines frequently....

Call the fine folks at Tanis and ask directly their thoughts... They must have had several people each year have the same idea.

They aren’t trying to sell something for the wrong reason, just to make a buck... that technique usually has a high failure rate... in this case an expensive failure rate....

If it did work that way, i’d Leave the heat on....

Got Time to make a call?

we need a contest... MSer with the most responses from different vendors.... @wcbis pretty good at this!

PP thoughts only, my steam tables are printed on paper...

Best regards,

-a-

[pwnel]

1 hour ago, carusoam said:

Mike Busch is really smart, and writes pretty well... rarely has left us uninformed...

Tanis is really smart, and writes in a commercially acceptable manner...

Taking either of them out of context is a bit dangerous, for your wallet...

They may be saying leaving the heat on is harmless.... as in it won’t damage things by overheating or lighting a fire....

But they are not outwardly saying it will do what you want it to do... “heat your engine to prevent internal corrosion...”

Well it seems to be exactly what Mike is saying. Not that Mike is the final word on all things aviation - which is why I'm asking my respected MS'ers opinions too.  I guess it's fair use to simply paste his statement here exactly (from his recent book "Engines").

[larryb]

You want data? I have data. Here is my most recent real time monitoring report.

 

I have done numerous tests at different temps, oil cap open vs closed, etc. I find 90 degrees is a good temp for RH less than 30%. Oil cap open did not make a huge difference in my previous lycoming. I have not tested the oil cap in my current continental. I do leave the cap open because that is where the probe goes. I never saw condensation on the underside of my Lyc oil cap but I have seen it on my Conti cap. Not sure why the difference.

 

 

 

[carusoam]

Pwnel,

Circle the last line below the highlighting...

The article contains the context necessary to make use of the idea...

Using a heater that doesn’t do what the last sentence says, won’t do what the OP is asking for...

Of course in much of the country, the dry winter air takes care of the rust issue pretty well on its own... most of the time...

I like Larry’s approach... more relevant data is better...

i’m Leaning a lot on my mechanic’s experience on this... 

He also pays the electric bill... could be a conflict of interest involved with his opinion... 

What I didn’t like from my own experience... the amount of moisture drops that collect on the oil cap’s inner surface

So give the cap a look next time... expect a lot of moisture to be available after shut-down...

Find a way to allow the moisture to get out...

I waiver on leaving the oil cap off... Fear of forgetting it some how... or something getting dropped in...   unfounded fear mostly...

Best regards,

-a-

[Marauder]

I have the same heater you do, and leaving on all the time in cooler temps seems to put my oil and cylinders in the realm of summer ambient temps - 70s-90s. So I'd think oil loss of the cam would be no worse than in the summer, though I guess it might become an issue if it got left on during an unseasonably warm winter day. 
Whether  the heater keeps  moisture out of the engine seems like a complicated question that I don't really have my head around.  I'd think actual measurements in real world conditions wouldn't be too hard to accomplish, though apparently it's not trivial because this debate persists.  

If you fly regularly, I agree that keeping the oil flowing will do more to protect the engine during short periods of non use. The question is if you heat up the engine in the winter to 60 to 80 degrees are you introducing moisture in the engine and then not flying enough or at all.

Since I know of no real data showing what is really going on inside of an engine managed this way, who knows what we are doing to our engines.


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[larryb]

Heating or cooling the engine will not introduce moisture. It is just there. A warmer temperature will hold more of that water as vapor and therefore not available to cause corrosion.

Immediately after a flight I see RH climb as the engine cools. It peaks around 12 hours post flight and then gradually reduces over the next 2 days.

I have seen 100 % RH after taxiing only when I didn’t turn on the heater. I turned the heat on and after a day it dropped to 30%. Taxiing without flying is definitely a bad thing.

[carusoam]

Just For fun...

Take a look at the picture from Mike’s book above...

The caption doesn’t represent the picture!

If I follow what the picture is doing.  My crank shaft is going to be really chilly in the middle of my 70° engine... the prop will behave like a giant aluminum heat sink attached to the shaft.

The caption clearly notes...   insulated engine and propellor covers...

maybe they meant cabin cover...?

Maybe that is a clear insulation on that there Cessna prop...?  

This is why technical products have applications engineers to support them...

Find out who the applications engineer is at Tanis and give him a call...

See if you have what Mike referred to as a multi-point engine heater...

Most engine heaters at entry level only heat the oil sump (single point heater).  The next level adds a second block heater. The third level adds cylinder heaters for each cylinder...

Hard to follow the instructions and get all the details right... I think Mike Busch has an engineering degree to go with his aviation and writing skills...

Writing for people’s consumption, and publishing it to be printed... a simple omission or mix-up lasts forever in print... trying to find somebody that can proof read at the tech level that Mike uses is not easy to come by...

It looks from the picture that the expensive prop cover isn’t needed. People use prop covers to keep snow and ice from sticking to the prop... 

The caption clearly states insulated prop cover.  Which technically makes a lot of sense...

Can’t go halfway and expect that will be good enough...

Now it’s a phone call or email to Mike Busch to ask if he really meant insulated prop cover.

See the hangar heater that Clarence just installed in his Canadian hangar... That might be a lower cost solution and more effective too....

Best regards,

-a-

[Marauder]

You want data? I have data. Here is my most recent real time monitoring report.
 
I have done numerous tests at different temps, oil cap open vs closed, etc. I find 90 degrees is a good temp for RH less than 30%. Oil cap open did not make a huge difference in my previous lycoming. I have not tested the oil cap in my current continental. I do leave the cap open because that is where the probe goes. I never saw condensation on the underside of my Lyc oil cap but I have seen it on my Conti cap. Not sure why the difference.
 
 

 

Can you explain how this data was taken? Where was the humidity for the engine monitored? If inside the engine, where?


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[larryb]

6 hours ago, Marauder said:

Can you explain how this data was taken? Where was the humidity for the engine monitored? If inside the engine, where?


 

The temp/humidity sensor chip is mounted in the end of an aluminum tube inserted into the oil fill tube. It goes as deep as I can get it. In the Lycoming IO360 in my J it went to about 2" above the oil, using the dipstick as the reference. In my current Continental TSIO-360 it's about 6" below the top of the oil fill due to blockages in the path. I was able to get much closer to the top of the oil in my J but the readings are similar between both engines.

 

 

 

[Marauder]

1 hour ago, larryb said:

 

The temp/humidity sensor chip is mounted in the end of an aluminum tube inserted into the oil fill tube. It goes as deep as I can get it. In the Lycoming IO360 in my J it went to about 2" above the oil, using the dipstick as the reference. In my current Continental TSIO-360 it's about 6" below the top of the oil fill due to blockages in the path. I was able to get much closer to the top of the oil in my J but the readings are similar between both engines.

 

 

 

Can it measure from within the top end of the engine? If moisture is going to accumulate, I would think it would be at the top of the engine where the heat may be a few degrees warmer.

[larryb]

Can it measure from within the top end of the engine? If moisture is going to accumulate, I would think it would be at the top of the engine where the heat may be a few degrees warmer.

In the case of my current engine, it is at top. The oil cap is at the top left rear in the continental engine, and the probe is maybe 6" down from the top of it. I'll take a picture next time I fly, hopefully tomorrow. 

 

 

[larryb]

Here is one recent graph. Yesterday I taxied up to the avionics shop for a GTN software upgrade, and taxied back without flying. You can see the RH climb as the engine cools, up to about 90%. At 90 degrees the heater starts up, and you can see the humidity drop overnight down to 27% this morning. I draw two conclusions from this graph:

1. The heat does help drive out the humidity.

2. Running the engine without flying really drives up the humidity. I have seem 100% in this case, and it will stay there if I leave the heater off.

 

[larryb]

Here is a different graph. I returned home after a 1.5 hour flight. Because my power strip was switched off and I did not realize it, there is no heat and no data for 24 hours after landing. The graphs and heat both start 24 hours after landing. We start out at about 55% RH and drop to 22% after 24 hours at 90 degrees F.

 

[mooniac15u]

4 hours ago, larryb said:

Here is one recent graph. Yesterday I taxied up to the avionics shop for a GTN software upgrade, and taxied back without flying. You can see the RH climb as the engine cools, up to about 90%. At 90 degrees the heater starts up, and you can see the humidity drop overnight down to 27% this morning. I draw two conclusions from this graph:

1. The heat does help drive out the humidity.

2. Running the engine without flying really drives up the humidity. I have seem 100% in this case, and it will stay there if I leave the heater off.

 

Given a constant amount of moisture in the air, increasing air temperature will decrease the relative humidity because warm air is capable of holding more moisture.

[carusoam]

Great data, Larry!

Some things for people to Keep in mind...

1) warming the engine may not (probably doesn’t) drive the moisture out...

2) it increases the (relative) amount of moisture that the same air can hold...

3) the sensor will read the rh, but not the moisture content...

4) So, the RH does decrease, but the moisture probably didn’t go anywhere...

5) To drive the moisture out, warm it significantly and allow it to vent...

6) if able... don’t allow the moisture to stay in the engine, or cool or condense...

7) Make sure the engine is seeing the same temps all over, not just warm near the sensor and cold at the other end of the case...

There is probably some guidance for corrosion risk... ?

RH below...

• 90%
• 50%
• 30%
• 10%

When you are living in an area below 10% you know things are pretty dry.... dry nasal cavity, eye crusties, flaky itchy skin

Above 50% is pretty comfortable. Probably not good for metal surfaces...

Best regards,

-a-

[larryb]

The reason I say the heat drives out the moisture is the fact that the RH drops over time at a constant temperature. I suspect there is some amount of air flow through the open oil filler cap and the oil vent tube. The heat causes the moisture to evaporate to the air, and the air movement transports it out of the engine. Perhaps the warm engine encourages some convective air flow, but that would be a guess.

 

Some internet research on humidity and corrosion I did a few years ago found a study that shows RH < 30% has little to no corrosion. Between 30 and 60% some minor corrosion, and accelerating corrosion > 60%. This is from memory, and I do not have a reference handy.

 

Here is the key point: If the moisture is suspended as water vapor in the air it is not available to cause corrosion. For the moisture to cause corrosion, it must be present on the surface of the metal. 

Larry

[mooniac15u]

5 hours ago, larryb said:

Here is a different graph. I returned home after a 1.5 hour flight. Because my power strip was switched off and I did not realize it, there is no heat and no data for 24 hours after landing. The graphs and heat both start 24 hours after landing. We start out at about 55% RH and drop to 22% after 24 hours at 90 degrees F.

 

In your data it looks like you roughly went from 10 deg C (50 deg F) to 30 deg C (90 deg F) and the RH went from about 50% to 25%.  If you look at the graph below you can see 50% RH on the green line which corresponds to about 5g of water per kg of air at 10 deg C.  Holding that amount of water constant and moving straight across the graph to 30 deg C you can see that it corresponds to less than 25% RH.

Your measurements track pretty closely to the expected change in RH with a constant amount of water.  I don't think you are driving any moisture off with your heater.

[Marauder]

In your data it looks like you roughly went from 10 deg C (50 deg F) to 30 deg C (90 deg F) and the RH went from about 50% to 25%.  If you look at the graph below you can see 50% RH on the green line which corresponds to about 5g of water per kg of air at 10 deg C.  Holding that amount of water constant and moving straight across the graph to 30 deg C you can see that it corresponds to less than 25% RH.
Your measurements track pretty closely to the expected change in RH with a constant amount of water.  I don't think you are driving any moisture off with your heater.

I was wondering about that correlation. I think adding a desiccator to the system would pull the moisture out. The question comes down to Larry’s findings that at a 25% humidity level, no corrosion would occur.

I also wonder if the humidity remains constant throughout the engine area. I think that is why Mike B speaks about really insulating the entire engine and prop. Any cold areas would be a magnet for condensation.


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[NJMac]

Isn’t the safest bet twofold. Fly weekly or pickle it?


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[pwnel]

28 minutes ago, NJMac said:

Isn’t the safest bet twofold. Fly weekly or pickle it?


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During winter in the North East you just don't know what weather will do.  Given that I fly only on weekends, weather may very well stop one from flying for several consecutive weekends. You won't know beforehand that the plane might go unflown for several weeks.  Best I can do is keep the Tanis on under the insulated engine blanket while in the hangar. That way it's at least ready should good weather and my schedule coincide. The added benefit is that this seams to be the best engine preservation strategy too.

If you DO pickle the engine properly, that means minimally taking out the dessicant spark plugs and reconnecting ignition every single time you fly.  Facing that hassle is going to prevent you from flying in the first place.  (you can at least fly 10 hours on the pickle oil)

This winter I have an extra shenanigan in that I may be away for 3 months.  In which case I WILL of course pickle, but I will also keep the Tanis on under the insulated engine cover.  (The preponderance of evidence and opinions so far in this thread seems to indicate that is the best idea)

 

Edited November 21, 2018 by pwnel