Continuous pre-heat

[Dan Thomas]

The flight school I went to most times handed me a hair dryer and instructed me to put it in the cowl with cowl plugs installed. Drag a extension cord out to the plane on the ramp. Sometimes they would plug them in to engine heaters but 9 times out of 10 I used the hair dryer. Couple times I walked back into the school after plugging in the dryer and the instructor said "you ready to go" as soon as I walked in. The hair dryer may have run for 5-10 minutes max. They ran the engines to at least 3000 hrs.

Bad habits die hard as I use a hair dryer on my own plane in the hangar in conjunction with a oil pan heater. I do fly my plane multiple times a week so hopefully I won't have much corrosion to deal with.

Hair dryers typically have cheap little brush-type motors in them. Brushes make sparks constantly, and those motors aren't sealed. Any fuel leakage getting together with that sparking is going to immolate the airplane.

We used car warmer heaters. Watch for the ones that use shaded-pole fan motors. They have no brushes, although they still have a thermostatic temperature control switch that will make a spark. I took one apart once and disabled that switch, bypassing it so the heater just ran all the time. I just didn't leave it unattended for any great length of time.

 

[Pinecone]

Hair dryer is OK, as long as the inlet is in clean air. Don't stick the whole hair dryer inside the cowl.

 

[Dan Thomas]

Hair dryer is OK, as long as the inlet is in clean air. Don't stick the whole hair dryer inside the cowl.

At temps well below freezing it will never warm that engine like that. Take one outside in the cold and try it against your hand. Next to nothing. They can only increase the temp so much in one pass, so they need to be drawing previously-heated air to get anything done.

 

[Pinecone]

Then how are people using small electric heaters to heat engines?

 

[Dan Thomas]

Then how are people using small electric heaters to heat engines?

Up inside the cowling. Here in cold Canada we even have legal guidance on it: https://tc.canada.ca/en/aviation/re...orthiness-notices-b037-edition-1-4-april-1997

At the flight school we had loose heaters that we just tucked into the air outlet of the cowling, setting the heater on the lower cowl so it blew the warmed air forward. The cowls were covered with fitted insulated cowl covers that trapped the warmed air inside.

 

[Pinecone]

Many online pictures of people with small heater sitting on the ground with a duct for the hot air into the cowl.

Canada is special. You idea of a brisk cold is Americans idea of frozen solid.

 

[Magman]

Radial Engines typically have a Oil Tank Drain that is checked periodically.

Since most light aircraft have a sump quick—drain would it be wise to check once in awhile?

My presumption that it is seldom done and the water on the bottom of the sump

is spread around the interior of the engine during operation.

 

[bluerooster]

Hair dryers typically have cheap little brush-type motors in them. Brushes make sparks constantly, and those motors aren't sealed. Any fuel leakage getting together with that sparking is going to immolate the airplane.

We used car warmer heaters. Watch for the ones that use shaded-pole fan motors. They have no brushes, although they still have a thermostatic temperature control switch that will make a spark. I took one apart once and disabled that switch, bypassing it so the heater just ran all the time. I just didn't leave it unattended for any great length of time.

You don't need to go flying if you have a fuel leak. A hair dryer will point out that leak if you don't know about it, so it can be repaired prior to flight.

 

[Dan Thomas]

Radial Engines typically have a Oil Tank Drain that is checked periodically.

Since most light aircraft have a sump quick—drain would it be wise to check once in awhile?

My presumption that it is seldom done and the water on the bottom of the sump

is spread around the interior of the engine during operation.

When the engine runs, the water gets emulsified into the oil. That's why the oil on the dipstick when you check it after shutdown after a brief run on a cold day has that mocha color to it. The water takes time to settle out to the bottom of the sump. Lots of time.

 

[Magman]

That’s my point.

Drain the water so it’s not there to be emulsified and spread internally.

Not after flight!

 

[Pinecone]

1) Are you SURE that the drain is at the absolute bottom? I am not sure on aircraft engines, but on car engines, it is NOT. A MityVac actually gets more oil out of a car engine.

2) Spreading in through the engine is what gets it evaporated. See the post by Engineer Ted. In parts of the engine, the oil is heated to over 212F, so the water boils out.

3) Emulsions do not settle out over a very long time.

 

[Dan Thomas]

2) Spreading in through the engine is what gets it evaporated. See the post by Engineer Ted. In parts of the engine, the oil is heated to over 212F, so the water boils out.

3) Emulsions do not settle out over a very long time.

You don't actually need to boil the water. Its vapor pressure rises with temperature and it evaporates much faster at 180°F than it does at 50°F.

Emulsions of water and oil do settle out. Just takes a bit of time. The oil is not dissolved in the water. It's not in solution. It will separate.

 

[Magman]

Many people only change oil once a year. If you disburse the water by operating

the engine you will also be producing more water in that time. Sort of like

walking up the DOWN escalator.


Access to the Oil Quick Drain is easier on some aircraft than others. It may be

beneficial to drain a cup out when convenient.

Dan’s illustration is a good reason why.

 

[Dan Thomas]

Many online pictures of people with small heater sitting on the ground with a duct for the hot air into the cowl.

Canada is special. You idea of a brisk cold is Americans idea of frozen solid.

Yeah. Some Americans are preheating on what we would consider pleasant days. We just use multigrades and a bit of good judgement. A small electric heater ducting air into the cowl on a -10°F day would be a waste of time and electricity. The serious guys use combustion heaters. Or they have a hangar and use an in-cowl heater.

 

[Pinecone]

Many people only change oil once a year. If you disburse the water by operating

the engine you will also be producing more water in that time. Sort of like

walking up the DOWN escalator.


Access to the Oil Quick Drain is easier on some aircraft than others. It may be

beneficial to drain a cup out when convenient.

Dan’s illustration is a good reason why.

But the amount of water stays the same, IF the engine is run at a high enough temp for long enough.

If you just run it up, you pump more moister in the engine without evaporating the water that is there. So when the engine cools, the new water in the engine condenses and adds to water in the oil. Rinse, repeat, add more water.

With the engine flown and hot for an hour, the amount of water in the engine is only the amount of vapor in the engine at shutdown.

 

[Magman]

How do we know a 1 hour flight is sufficient to boil off the water?

 

[Checkout_my_Six]

How do we know a 1 hour flight is sufficient to boil off the water?

well....it's at least three hours. Cause after three hours I gotta pee.

 

[Dan Thomas]

How do we know a 1 hour flight is sufficient to boil off the water?

Because our flight school airplanes typically flew for an hour at a time, even in cold weather, and crankcase moisture was no problem in most of them. Shorter flights would give us that mocha-colored oil on the dipstick. An hour or more and the dipstick oil was free of emulsion. The Lycoming O-235 was the only engine that gave us hassles, and those engines are known to run cooler. I blocked off the oil cooler and eventually left that cover on year-round. Couldn't get the oil temp up otherwise, and we had water issues in those engines if the temp was allowed to stay low.

But we didn't spend a lot of time taxiing. In some places, extended idling could really introduce much more moisture that takes longer to drive off.

Ram engines recommend an hour's flight, at least, with the oil reaching at least 180°F. Lycoming has a similar recommendation.

 

[Dan Thomas]

well....it's at least three hours. Cause after three hours I gotta pee.

Or you might end up with undesirable moisture somewhere else, too.

 

[Magman]

So 1 hour is fine for the flight school aircraft . ( Cessnas ? 152? )

It seems Cherokees tend to run cold which is not good and theoretically

would result in more corrosion issues.

I wonder if there is any data on this issue comparing aircraft type, frequency and

type of flight, type oil, oil temp, oil change interval, pre-heat and additives?

 

[Pinecone]

Too many variables.

1 hour is a good rule of thumb.

The real number is 53 minutes 26.33434566 seconds to drive off the excess water.

 

[Snowmass]

I have found that if you can start an engine on AVGAS there is no need to preheat which is down to about 5 degrees but be sure to catch on the first try if below freezing or risk of plug frosting. Air cooled Porsche 911s are not preheated and they also aircraft engines. Preheating is easy on the battery and starter but not necessary.