The International Cessna^® 170 Association

Has anyone used one of those portable kerosene shop heaters as a preheater? You know, the ones that look like a small jet engine mounted on top of the fuel tank? I need to get one for my shop anyway, and was thinking of making it do double duty as a preheater if I could find some ducting.....ha just hit me, I can use chimney flu sections to make an adapter that will channel the air right up into the engine bay I'd still have to get AC out to the tiedown spot, but at least it would not have to support a big electric heater, but only a small circulation fan. Thoughts and ideas

That's a lot of flame and heat to put up your airplane's cowl.

I use a drop light with the bulb guard removed,and some bailing wire formed into a hook to hang it off the throttle cable so it shines up at the oil sump. A friend recommended using a 100W bulb,but that didn't seem to do much,so I replaced it with a 125W (not 250W!) heat lamp bulb. Keeps things toasty with an old blanket thrown over the top cowl.Total cost should be around 15 or 20 bucks.
I've been doing this for a couple years now,don't seem to have any trouble with condensation in the upper part of the engine,but I just started leaving off the oil filler cap so that any moisture vapor can vent out that way. I throw on the blanket & hang my heat lamp in there pretty shortly after shutting the engine down,so the upper part of the engine never does get cold--therefore,no moisture should be condensing there.
I also put a lttle ceramic space heater (with thermostat) in the cabin to keep it warm & dry. It cost me about 20 bucks at Walmart . When it's too crummy to fly and too cold in the hangar to just hang out,I can sit in the airplane and read or whatever.

Eric

The ceramic heater I just bought is actually small enough to put up inside the lower cowl from below. I've thought about using it for an engine heater,but decided to stick with the heat bulb arrangement. I don't know if the thermostat inside the heater might possibly spark,if there were any gasoline fumes in the engine room that might be a real bummer.

Eric

I installed a "Safe Heat" pad that adheres on the bottom of the oil sump. Plug it in and wait a while--45 minutes when 25 degrees F. or so. I have a carburetor temperature gage and it will register an increase in temperature fairly soon after plugging in. I'm not sure if the cylinders get nice and toasty, but they do get some heat. Bought from McFarlane in Baldwin City, KS.

Yes I've used one. In fact it wasn't a small one. Mine is 180,000 BTU. Used it on my Cherokee once. Had it on the back of my pickup which put it at the right height to blow right in the front of the cowl from about a foot away with no duct work. Dam near melted the fiberglass nose bowl off the plane. Engine was nice and warm in about 5 minutes though.

If you use a smaller heater I'd use about 6 feet of pipe and direct the heat up through the bottom of the cowl. With an old blanket over the cowl blocking the front inlets, you will have a toasty engine in no time. The 6 feet of duct should keep the flame away from any combustables in the engine compartment as well.

I now use a propane fired heater with about 3 feet of duct to carry the heat to the front of the cowl. I also throw an old blanket over the top of the cowl. The fan on the heater runs on a 12 volt battery. The propane tank, heater and battery are mounted on a cart. Problem with this sytem is if the battery gets run down (I use an old battery) and the fan slows or stops, I have and you will burn the paint off the cowl Preheat takes about 15 minutes. My current heater is a commercial type that you can buy. I found mine abandon in a hanger. I just had to clean it up (read no investment.) Before that I built my own using a surplus 12 volt fan and stove pipe duct (read very little investment.)

Bruce, you and I are thinking alike. I have never owned such a heater, but need a nice one for the shop. Don't know how much flame they shoot out...hope it is not much because I don't want to catch my pants on fire in the shop I intend for the stove pipe adapter to cool off the hot air a bit before it enters the engine bay so there will be no open flame or excessively hot air to melt things. The light bulbs and ceramic heaters are fine if you have a few hours to wait, but I need to preheat in 30 minutes. I do have an old oil dipstick heater laying around that I used to use in my MG...has anyone used one of these to heat the oil in the pan

I'd suggest to everyone to be careful trying to warm up these engines too quickly. A bonfire applied directly to the engine will certainly make it feel warm to the touch rather quickly, but at what cost? Scorched hoses, wires, and fire hazards? Does it do any good to have a warm crankcase with a large quantity of cold oil in it? The best pre-heat has to be the one that does it thoroughly without damage or hazard over a reasonable period of time to allow all the parts to be warmed. That crankshaft and cam are pretty well buried within the engine. You're not going to warm them up in 20 minutes without injury to the surrounding parts.

I've been using this type of heater ("torpedo") for 30 years with aircraft and to heat my hangars. It works well if used correctly. I have both the 100,000 btu and the 150,000 btu.
[b]Warning: [/b] There are very high temperatures and a potential fire hazard if the heater is not in good condition or used correctly. Carbon and dust build-up in the heater can cause it to emit sparks. Do not use a confined duct to route air to the cowl.

Advantages if used correctly:
- relatively fast, safe pre-heat
- preheats everything FWF - not just block
-safer than unattended heat source
- can preheat cockpit and instruments also

My 30 year proven method:

1. Open oil access panel or a top cowl section to allow flow-thru.
2. Attach a tarp to propeller and wrap around the right-hand side of cowl back to right wing strut. Secure so that it fits snug against r.h. of cowl. This should be like a "tent" with the cowl at the top and the left hand side of the cowl open. If it's really cold I even add tarp under the belly right at the gear legs- then there 3 sides closed and only the left side open.
3. Warm up the heater a few minutes pointed away from the aircraft in case there are sparks from dust in the heater.
4. Point the heater at the opening into the tent but not too close. I test this by holding my hand at the tent opening in front of the heater. If it feels real hot to you hand the heater is too close. My 100,000 BTU heater is typically positioned 4-6 feet away from "tent."
5. This will provide a good total preheat of everything in the cowl. You can tell when it's enough by checking for a warm touch to top components under the cowl. Typically takes 30 mins on a cold winter day.
6. Optional: Position tarp to route air into cabin during or after engine preheat. This will warm up the interior in 10 minutes or so.

I have successfully used this method with no incidents in 30 years. I do not leave the area during pre-heat.

I carry a Colman single burner camp stove in my plane during the winter. I place the camp stove on the ground under cowling and run a 4" flexible metal hose into the bottom of the cowling. These stoves run for about 1 hour on a small tank of Colman fuel and is plenty of time to heat engine, even at -30 degrees. With a good insulated engine cove the whole engine will be warm within a hour. During this opperation I never leave the plane and always have a fire extinguiser on hand. About every 15 min I have to pump more pressure into fuel tank. Standing there watching this heater for a hour is like watching paint dry, however it has never caused any problems and always managed to get me going.
Trapper

John:

Preheat is a great idea but... you live in Virginia. For the three days when its below freezing, go ice fishing.

It will take longer to preheat than it will for spring to arrive. Trust me. I live in Anchorage and my in-laws live in Charlottesvile.

I had a Cessna 120 before and I always used a car interior heater that you plug in, you can buy them at Wallmart or Canadian Tire. I usually placed it on top of the cylinders with the outlet pointing across to the opposite cylinders across the dividing wall. This may not work on some other planes because of baffles etc. It is probably not legal but it works good. The heaters have plastic outer casings like a blow dryer so I never thought it would catch fire as there was nothing combustible around the outlet. I always plugged it in overnight with an engine cover on the engine so everything was heated up. and while doing my preflight checks I plugged in another heater of the same type in the cabin to warm that up and melt the frost off of the windshield. I am waiting on the outcome of my offer on a 51 170 so hope fully I will hear back soon. I will be preheating this one the same way unless baffles etc get in the way.

Ken

The #1/2002 170 news had an article by an Illinois member about using a 1500 watt ceramic heater (like what I use for the cabin) for engine preheat. He used some foil/fiberglas ductboard to fabricate a double-elbow duct so as to direct the warm air into the bottom of the cowl from the heater which sits on the floor. Looks pretty effective,only problem is that the thermostat in the heater would be sensing the hangar temperature,not the temp inside the cowl,so it'd probably run all the time. That's not necesarily a bad thing,though.
Like I said before,I think there's enough room to get the heater itself up into the lower cowl,if you're comfortable with that.

Eric

Hey Trapper,
That's exactly how I preheat my engine.
I used a whisper lite with the coleman fuel, for years.
It worked well but, I had to pump it up like you said every so often, and it might flame up at first. Couldn't leave the plane.
So I went to Walmart and bought the Coleman one burner PROPANE stove. Uses the Green Coleman Bottles. Awesome!
Turn the Valve / lite it off / turn to max. No Flame / no hassle.
It burns maximum output for 1 hr and I don't worry one bit.
When I get back from breakfast she's ready to go. Oil Temp reading 140 degs.
Dave

A great preheater, if you can find them, is the old small Coleman catalytic heater.

They are small enough so that you can usually tuck them right in the engine compartment and leave them overnight under the engine cover. They work really well, have no flame, and limited fire risk.

The problem is that they are hard to find these days. Garage sales and Ebay are about the only place to look.