Cold weather starting

JOhnH said:
Ok. When I spoke about cold weather, I was talking about the Smokies. You are talking about the Rockies. I don't think I would ever attempt to start or fly in that weather.
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I'm looking at the beginnings of my 52nd winter in Alaska. Lots of good memories and looking forward to more.
 
James331 said:
With the CAP? maybe before rigor sets in?
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In Alaska pilots generally dress like they'll be walking home. Depending on a heater is a recipe for pain.

As to 406 rescue? It depends where you live. In Alaska the Air Guard sends C-130s with parajumpers or Pave hawks, depending on the situation. CAP isn't the first responder.
 
Stewartb said:
In Alaska pilots generally dress like they'll be walking home. Depending on a heater is a recipe for pain.

As to 406 rescue? It depends where you live. In Alaska the Air Guard sends C-130s with parajumpers or Pave hawks, depending on the situation. CAP isn't the first responder.
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The US needs more Alaska and less NYC/CA
 
AlleyCat67 said:
Wow. You managed to work your anti-government politics into a thread on engine preheating. Quite some mental gymnastics there.
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How so?

So you’d praise your government and pray to them as the mighty CAP 182 flew mindlessly overhead as you and your loved one died?
 
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Groundpounder said:
Anyone use RV antifreeze as a defrosting agent?
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From my post on page 1!

I use a metal garden sprayer with RV anti freeze. The key to making it work is getting it warm so I put the metal tank on the stove for a few minutes. Works great. Stays warm for quite a while so driving to the plane is no big deal. No pink stains like you'll hear about from guys who've never used it. ;)
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JOhnH said:
I swear by pulling the prop through, in the opposite direction of normal rotation for a cold start. I have never had it fail to start when I did that. But I have only had to do it when visiting up north. It never gets that cold in Daytona and besides, when I'm home, it is in a hangar.

Now HOT starts, they give me the willies.
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Why backwards? Seems bad on a vacuum pump?
 
While pulling my prop through backward on my right engine, I get a strange 'geared' sound that the left one does not make. I am thinking this is a vacuum pump.
Anyway, I don't like the sound, so it doesn't get pulled backward.
I rarely pull the props though, but in the cold weather she is a b***h to start, so I am going to try pulling the props through to see if it improves cold weather starting. It will be interesting to see if it makes a difference.
These are O-470's with the pressure carbs
 
The only time pulling the prop through is beneficial is if the engine isn't preheated (and needs to be) and when priming needs to be distributed ahead of hand starting.
 
mwagg737 said:
While pulling my prop through backward on my right engine, I get a strange 'geared' sound that the left one does not make. I am thinking this is a vacuum pump.
Anyway, I don't like the sound, so it doesn't get pulled backward.
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It's your starter.
 
Skymac said:
Why backwards? Seems bad on a vacuum pump?
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Because that is what the POH says. (At least that's the way I read it. Correct me if I'm wrong)
From the "Cold Weather Operation" section:
ENGINE
Use engine oil in accordance with Consumable Materials in the HANDLING, SERVICING AND MAINTENANCE Section.
WARNING
Ascertain that magneto switch and battery master switch are off before moving propeller by hand.
Always pull the propeller through by hand, opposite the direction of rotation, several times to clear the engine and "limber up" the cold, heavy oil before using the starter. This will also lessen the load on the battery if external power is not used.
January 1982 4-19
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Groundpounder said:
Anyone use RV antifreeze as a defrosting agent?
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I tried it, and I think t left stains in the paint. It looked like acid rain type marks, paint still had shine but I think that stuff did something. However, the RV waterline antifreeze (the pink stuff) did an excellent job removing frost.
 
GMascelli said:
I tried it, and I think t left stains in the paint. It looked like acid rain type marks, paint still had shine but I think that stuff did something. However, the RV waterline antifreeze (the pink stuff) did an excellent job removing frost.
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That's what I was referring to, the pink stuff. Looks like some is made with propylene glycol and some with ethylene. Propylene is what is used in aircraft deicing fluid, so I'm going to try to find some with that in it. Supposedly the Wal Mart branded RV antifreeze is propylene
 
What is the physics involved in the recommendation to pull the prop through? IOW, by what mechanism does it make the oil “limber up”?

I did not see that recommendation in the Continental document quoted above. I think dragging metal parts over one another in the absence of oil pressure is generally frowned upon, leading to the recommendation to just start the darn thing.
 
FastEddieB said:
What is the physics involved in the recommendation to pull the prop through? IOW, by what mechanism does it make the oil “limber up”?

I did not see that recommendation in the Continental document quoted above. I think dragging metal parts over one another in the absence of oil pressure is generally frowned upon, leading to the recommendation to just start the darn thing.
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Of course dragging metal parts across each other sans oil would be bad, but I think doing it at high, starting speeds would be worse. But in answer to your question, I don't know how it limbers up the oil. But between the POH and POA, I'll take the POH (almost) every time. Of course though, my POH is 51 yrs old and the physics may have changed since then. ;)
 
JOhnH said:
Of course though, my POH is 51 yrs old and the physics may have changed since then. ;)
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But...

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I think the idea is to get oil pressure up as soon as feasible, and the most efficient way to accomplish that is to start the engine.
 
Proposed experiment:

On a cold morning, take a fish scale and at a certain station on the prop see how many pounds of pull it takes to get the prop moving. Then, pull it through a few times and try it again and note the difference, if any. I predict the very first nudge may take a few extra pounds of pull to overcome “stiction”, but no appreciable difference beyond that.

Right now, most of my dealings are with my ROTAX 912. I do routinely pull the prop through one revolution prior to starting, but that’s just to get each prop blade within reach with my top-mounted engine. Others pull ROTAX’s through many blades to “burp” them for a good oil level reading before flight, but I tend to do that after each flight instead.

Speaking of which, the ROTAX is not fundamentally different from a car or motorcycle engine, and those routinely get started down to very low temps with no thought of “limbering them up”. So not sure any special techniques are called for in cold temps.
 
FastEddieB said:
What is the physics involved in the recommendation to pull the prop through? IOW, by what mechanism does it make the oil “limber up”?
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My only guess would be to overcome the static friction that has persisted. The longer two similar materials sit touching one another in a close proximity, the more molecular interaction they will have (See Cold Welding). Perhaps pulling the prop through breaks this and allows for a smaller coefficient of static friction when initially starting? If this were the case you wouldn't have to "pull the prop through" as much as just move it a smidge.

FWIW I don't do this.
 
Here’s an idea. Move someplace cold and park outside. Learn a little about what you’re talking about. Continental says there’s no need to preheat above 20*F. On a 20- something day go crank the motor to life and pay attention to how it works. The next day try it again after pulling the prop through a few times. There’s no question the starter will spin the engine faster after pulling it through, and there’s no question that the engine will fire off better with a faster rotation speed. The bottom line is I want to maximize the chances the engine will start the first time I turn the key. Pulling it through is a no-brainer. If you’ve had time to do a thorough preheat it makes no difference, but there are lots of times preheating in marginal temps isn’t practical.

What does it do? I suspect it scrapes down thick oil and frost on the cylinder walls and clears the path for the pistons and rings. What guys who actually do it will notice is how rigid the prop is on the first half revolution and how the effort reduces the more you pull it through. Start a big bore engine using a battery the size of a box of Pop Tarts for a few winters and you’ll learn what works!

Another good trick in borderline starting temps is to prime it first and then pull it through. Free it up and distribute your prime at the same time. Maybe hand prop your engine for a winter to test that one out.
 
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Stewartb said:
Here’s an idea. Move someplace cold and park outside. Learn a little about what you’re talking about. Continental says there’s no need to preheat above 20*F. On a 20- something day go crank the motor to life and pay attention to how it works. The next day try it again after pulling the prop through a few times. There’s no question the starter will spin the engine faster after pulling it through, and there’s no question that the engine will fire off better with a faster rotation speed. The bottom line is I want to maximize the chances the engine will start the first time I turn the key. Pulling it through is a no-brainer. If you’ve had time to do a thorough preheat it makes no difference, but there are lots of times preheating in marginal temps isn’t practical.

What does it do? I suspect it scrapes down thick oil and frost on the cylinder walls and clears the path for the pistons and rings. What guys who actually do it will notice is how rigid the prop is on the first half revolution and how the effort reduces the more you pull it through. Start a big bore engine using a battery the sixe of a box of Pop Tarts for a few winters and you’ll learn what works!

Another good trick in borderline starting temps is to prime it first and then pull it through. Free it up and distribute your prime at the same time. Maybe hand prop your engine for a winter to test that one out.
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Also learning to do like a rebound start, watch the prop come back just to compression and hit it with the starter again, not ideal but if your battery got zapped by winter it can help.

Or to ooooold school and bring your battery and oil inside the cabin with you after you shut down
 
Odyssey battery performance in cold temps is light years ahead of flooded batteries. EarthX is better yet. The problem is we use small batteries. They don’t have the amps to push a stiff engine. Simple solution. Limber up the engine.

No need to consider the old polar bear hunter thing about taking the oil inside if you use multi viscosity oil. No matter, the thing that’ll keep the engine from starting is frosted plugs, and the chances of that are really good below 20*.
 
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Cub Crafters is gonna be angry when they catch whoever stole their very special lightning bolt. ;)
 
Dan Thomas said:
Thick oil surely does keep the metal surfaces apart, up until the engine starts and runs and isn't getting oil into the galleries because it's too thick to be sucked up the oil pickup tube into the pump. I've seen engines damaged that way.

Generalizations can bite.
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I simply do not believe this. If it were true it would apply to auto engines too but these are started all the time without preheat at much lower temps (because MOGAS vaporizes much better in winter) . The lubrication systems are the same. An oil pressure is NOT required for lubrication. Are you aware that Chevrolet 6 engines had NO oil pressure to the rods in to the 1940s? I start my airport car with 15-40 oil many times at ten below.
 
Skymac said:
Why backwards? Seems bad on a vacuum pump?
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Myth. If you rotate the prop backwards and your vacuum fails because of it, than it was already about to go bad anyway. Mags don’t fire going backward, so rotating the prop opposite to its direction of rotation is the safest way to move the prop by hand for storage or what not.
 
Snowmass said:
Engine damage from cold WX starting down to around zero F is pure BS. I have started repeatedly in the high Rockies at temps a little above zero with no engine damage. Since I major my own engines I would have seen any such damage; there was none. Porsche 911s are aircooled engines very similar to aircraft engines and Porsche says nothing about a need to preheat. The main winter problem is getting the low vapor pressure AVGAS to fire without frosting the plugs. Thick oil is MORE protective of surfaces. Worry about high temps not cold temps.
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So what do you think about the fact that the colder the temp is, the smaller the clearance between the bearing shells and the crankshaft are? If there’s not enough clearance, then there’s no room for the oil, regardless how high the oil pressure reads. The chances of metal to metal contact are much higher at this point. Go out and try to rotate the prop in cold weather and you’ll notice how hard it is to do. It’s obviously not because of running thick oil, (if you’re using a multi-grade), it’s because that clearance between the crankshaft and bearings are tighter than normal.
 
A deep preheat to me means my entire engine is warmed... not just it’s oil thinned... and I insist on deep preheating of my girl...
 
Some people do tend to worry about it too much.
I don't even order my vehicles with a block heater. Run 5w30 oil, just start them up, let idle for a minute, and drive off.
 
Ryanb said:
So what do you think about the fact that the colder the temp is, the smaller the clearance between the bearing shells and the crankshaft are? If there’s not enough clearance, then there’s no room for the oil, regardless how high the oil pressure reads. The chances of metal to metal contact are much higher at this point. Go out and try to rotate the prop in cold weather and you’ll notice how hard it is to do. It’s obviously not because of running thick oil, (if you’re using a multi-grade), it’s because that clearance between the crankshaft and bearings are tighter than normal.
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Is this true? I thought heat expanded while cold temps resulted in shrinkage.
 
Snowmass said:
I simply do not believe this. If it were true it would apply to auto engines too but these are started all the time without preheat at much lower temps (because MOGAS vaporizes much better in winter) . The lubrication systems are the same. An oil pressure is NOT required for lubrication. Are you aware that Chevrolet 6 engines had NO oil pressure to the rods in to the 1940s? I start my airport car with 15-40 oil many times at ten below.
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And your car doesn't have SAE 40 or 50 oil in it (15W40 is an SAE 15 at low temps), nor do the bearings take nearly as much low-speed load as the aircraft engine does. There is something called the PV factor, the pressure times the bearing's surface velocity, that is higher in the aircraft engine due to the propeller's load always being there even at idle. Your car doesn't suffer such loading right from startup.

As far as lubrication systems, most aircraft engines have their oil pumps well above the oil sump. They're in the accessory housing and have to lift the oil sometimes six inches or more, and heavy oil resists that due to the drag in the pickup tube. The car's oil pump is down low, immediately above the oil level, and its lifting requirement is much lower. Even then I had oil pressure failure in my F150 one winter, using 15W30, when the temp was about -30°C (-22°F).

And old engines did indeed often have no oil pumps. They had splash lubrication, with small scoops on the rod caps to scoop oil into a hole to the bearing surface, and oil was flung off the rod onto the cylinder walls and camshaft lobes exactly as we still do with pumped systems. It was a poor system and engine life was short and RPM had to be limited.

Your experience with auto engines has few parallels with aircraft engines. They are different in many ways.
 
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