Preheating

How to keep the Cessna 170 flying and airworthy.

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Bruce Fenstermacher
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Re: Preheating

Post by Bruce Fenstermacher »

Folks,

We have a pretty serious aircraft heating problem at work here in eastern PA. How to keep the inside of a EC-145 EMS helicopter warm enough that, one the drugs inside don't freeze and two the computers and screens work when we turn them on.
Selfy with EC-145
Selfy with EC-145
We do this with one or two ceramic heaters. Our current choice is a very industrial Broan NuTone Heat Heater 6201.
http://www.amazon.com/Broan-6201-Broan- ... oan+heater
Broan NuTone Heat Heater 6201
Broan NuTone Heat Heater 6201
As you can see the EC-145 has a lot of plexigass. They sit outside except through ice and snow storms, ready to go 24/7. The heaters are used almost 24/7 from the time the temp dips close to freezing.

The crews are not kind to them. The plugs are ripped out of the sockets when unplugged and they get pushed and shoved into storage without ceremony for every flight. They have a high and low range and are thermostatically controlled and have a mercury tip switch. I like these units.

We don't use them to preheat the engine of course but they could easily be adapted to the purpose. They are just under $50 at Amazon. Of course you will be drawing 12.5 amps using the 1500W setting and with all heaters of this type a 14 gauge extension cord is a must which will cost as much as the heater.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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gfeher
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Re: Preheating

Post by gfeher »

I went to this thread to look up the preheaters recommended by pdb above for a friend and noticed that at least the napaonline link no longer goes to the recommended heater and no one specifically identified the heaters. So I looked them up and here's the info on the two heaters recommended:

The napaonline heater: KAT'S part no. 37100 900W/120V Automotive Interior Heater (KAT'S Heaters/Five Star Manufacturing Group, Inc., W. Springfield, TN)

The oreillyauto heater: Zerostart & Temro Model 2600900 900W/120V Interior Car Warmer (Phillips and Temro Industries, Eden Prarie, MN)

Both are made in the US and are still available from various sources, including Amazon (although currently the KAT'S is called an engine heater on Amazon). The KAT'S is a little smaller and less expensive, currently about $75 on Amazon vs about $100 for the Zerostart & Temro on Amazon), but is still a good unit (I have one).
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
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Re: Preheating

Post by hilltop170 »

One other tip for reducing condensation buildup inside the engine after shutdown and during preheat operations is to remove the oil filler cap. Moisture is trapped inside the engine with the cap on. Leave it off after shutdown until the next flight and the case will continuously vent itself. Moist air is less dense than dry, as we all know from our primary weather training, and will exit the open filler neck while dry-er air enters thru the case vent. You always check oil before each flight, right? So just put the cap back on when you check/add oil. In very cold weather you can see steam coming from the filler neck when the cap is removed after a flight. Placing a single layer of red shop rag over the filler neck will prevent any foreign matter from entering the case if that is a concern.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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GAHorn
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Re: Preheating

Post by GAHorn »

The moist air is also warm and will tend to rise due to that as well.... the problem is, in our engines, the oil filler cap sources it's air from the low SUMP, while the crankcase vent is at the TOP of the engine. Warm, moist air will rise to the top of the crankcase and fill the overboard breather-tube and sink as it cools, pulling (presumeably dry) air into the engine thru the oil filler cap to replace it. (Lycomings are different in this matter.)

The Beech folks (with IO470/520/550 engines) promote the idea of ventilating the engine after flight. I don't like the idea for the simple reason it introduces a great way to get into trouble in the short-term while the benefits (if any) are only in the long-term ...and even then, only if the engine is not frequently flown.

I'd like to remind everyone that Continental advises against continuously heating an engine as they say it promotes corrosion. I have a long article they issued regarding their engine and how to treat it and I'll find it and post it asap.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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cessna170bdriver
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Re: Preheating

Post by cessna170bdriver »

gahorn wrote: [snip]... I'd like to remind everyone that Continental advises against continuously heating an engine as they say it promotes corrosion. I have a long article they issued regarding their engine and how to treat it and I'll find it and post it asap.
I’ve seen this written before and I seem to remember it making sense at the time, but now I fail to see the difference between continuous preheat, and storing the airplane in a heated hangar?
Miles

“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
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DaveF
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Re: Preheating

Post by DaveF »

I think it depends on how you preheat, and whether you cause any engine internals to be colder than the dew point. That could happen if you ran a full-time sump heater, heating the oil and humidifying the air inside the engine, but leaving crank and cam cold. On the other hand, if you used an air heater you'd be more likely to get an isothermal engine. Another possible consideration is the increase in chemical reaction rates vs. temperature.
iowa
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Re: Preheating

Post by iowa »

do they make a little heater that would shoot warm air out of a top vent?
dave
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1951 170A 1468D SN 20051
1942 L-4B 2764C USAAC 43-572 (9433)
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pdb
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Re: Preheating

Post by pdb »

EA48073A-57E0-422A-AA1A-6124559E433E.jpeg
In addition to my electric heater in my cowl, I have this little heater on the floor of the cockpit. I angle it upward to blow air towards the panel. Not only do the instruments warm but but the canopy and interior warm up as well. It works very well and I especially enjoy the warmth on the interior. After about two hours (when it’s really cold), the plane feels like it’s been in a hangar.

Once the plane is warm, its cabin heater can usually keep it comfortable.
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
http://farm3.staticflickr.com/2366/2527 ... 4e43_b.jpg
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GAHorn
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Re: Preheating

Post by GAHorn »

cessna170bdriver wrote:
gahorn wrote: [snip]... I'd like to remind everyone that Continental advises against continuously heating an engine as they say it promotes corrosion. I have a long article they issued regarding their engine and how to treat it and I'll find it and post it asap.
I’ve seen this written before and I seem to remember it making sense at the time, but now I fail to see the difference between continuous preheat, and storing the airplane in a heated hangar?
It had to do with the accelerated chemical reactions which occur at higher temps and the cycling of thermostats expanding/contracting the air inside the engine, expelling then reintroducing potentially moist air.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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170C
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Re: Preheating

Post by 170C »

I have a engine heater I made from a 1500 (max) watt space heater purchased at Lowe’s along with some metal ductwork. It blows warm air up under my cowling near the firewall on the opposite side from my gascalator. I cover my cowling with a movers blanket including covering the front of the cowling. It warms the oil temperature to just over 100 degrees.
OLE POKEY
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GAHorn
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Re: Preheating

Post by GAHorn »

The Continental bulletin I mentioned in an earlier post I’ve not been able to locate yet (another victim of my computer losses earlier this year) but the following link also contains Continental’s warning against continuous engine heat: http://www.reiffpreheat.com/Continental ... %20Ops.pdf
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
hilltop170
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Re: Preheating

Post by hilltop170 »

No matter how you preheat an engine, if started from a cold-soaked condition less than 30°F, preheat must be used long enough to thoroughly heat the engine core and to thoroughly heat the oil in the sump. This is a lengthly process. The colder the temperature, the longer preheat is required to properly warm the engine.

Fast heat will warm the cylinders rapidly enough to make them warm to the touch, and they will easily start, but will leave the oil and engine core in arctic conditions. If the oil isn’t warm, it will not flow properly and engine wear will be accelerated until the oil circulates properly. Engine sleeve bearings; main, rod, cam, etc are designed to run fully suspended in oil film which requires proper pressure and should never run with metal-to-metal contact due to lack of pressure which will wipe them out rapidly. Cold engine core temperature and cold oil temperature will inhibit pressure from coming up to spec in all areas of the engine, and if cold enough, metal-to-metal damage can occur.

“Get-home-itis” can alter rational thinking whether rushing preheat or pushing weather. It’s all a judgement call and it’s up to the pilot to determine when enough is enough. Let your pocketbook be your guide. Preheat is a lot cheaper than an overhaul.
Last edited by hilltop170 on Thu Dec 19, 2019 6:23 am, edited 1 time in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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GAHorn
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Re: Preheating

Post by GAHorn »

Very Good Words, Richard. If one thinks about that crankshaft and camshaft and gears which are buried in the engine, it would take several hours to warm the engine “core” up, probably 4 hours or more with a hot-air heater and several more than that with any other type. I suspect a hand or thermometer placed upon the prop-blade near the hub would be give a clue as to the crankshaft temperature. (That prop is a HUGE heat-sink and will suck heat out of an engine and dissipate it to atmosphere. Any serious cold outdoors will require a sheath to cover the prop also to reduce that tendency. A foam-sleeve might help. An engine-cowl cover is also a good idea. Some guys use an old sleeping bag (or one from their survival-kit in the bag compartment.) :wink:
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
hilltop170
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Re: Preheating

Post by hilltop170 »

You are correct George, the prop conducts a lot of heat out of the engine and should be covered as well as the spinner. I would consider 4 hours, if cold-soaked, would be minimum preheat time with a 20,000 BTU heater. Overnight is the minimum I use with a small 5000 BTU catalytic or 1500W electric car interior heater.

Condensation using any kind of direct fired combustion heater must be considered. When a direct fired combustion heater such as a salamander or catalytic heater is used on a cold-soaked engine, condensation will quickly coat the entire heated area, engine, cowl, everything. The heat should be continued until the entire engine is warm and the condensation is gone. It should go without saying that an open flame direct fired heater should NEVER be left unattended. Catalytic heaters are safe to leave unattended.

If a plane is operated in cold weather and left outside, complete covers should be used for frost protection as well as engine preheating. At least an insulated engine cover should be used in an unheated hangar. A 100W drop light will keep an engine warm with good insulated covers if used immediately after landing while the engine is still warm but won’t properly preheat an engine from cold-soaked unless left on for days. I would not be concerned with leaving a 100W drop light on all the time with an insulated engine cover but would hesitate to continuously use a heater that would cycle on and off.

Always preheat if engine temp cools below 30°F. Most folks don’t have fitted covers so anything is better than nothing. Moving blankets or sleeping bags work fairly well if there is no wind. In wind, fitted covers are necessary. However, in wind, there is usually no frost and a windshield cover flapping in the wind will damage/scratch the windshield so should be left off.
Complete airplane winter covers
Complete airplane winter covers
Insulated engine and spinner covers with 1/4” neoprene prop covers
Insulated engine and spinner covers with 1/4” neoprene prop covers
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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GAHorn
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Re: Preheating

Post by GAHorn »

hilltop170 wrote:.... A 100W drop light will keep an engine warm ....
If anyone still has 100W incandescent lamps. (I squirreled-away a few before they were “outlawed”...but the church talked me out of them to keep a water-line in an equipment-room from freezing.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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