I have a 1983 manual for a Cessna Skyhawk, which recommends pre-heating anytime the temperature is below 20degF. I disagree with that; I have started an engine from a Cessna 150 at that temperature and the engine acted as though it was going to climb down from the cowling to look for oil. (A conspiracy buff might note that Cessna is part of Textron Lycoming, so they may have a bit of an interest in selling you an overhaul or a zero-timed engine to replace the one you wore out by not pre-heating.) If it is cold enough to freeze, I pre-heat the engine.
There are basically two types of pre-heaters; electrical and combustion. Electrical heaters are made by Tanis and Reiff. The advantages of electrical systems is that they are safe enough to be turned on and left alone and that you can also use the electrical line to set a small space-heater in the cabin to warm up the cabin and the instuments. The disadvantages of them are that they need 110v electrical power to work and they only heat the rest of the engine compartment by heat radiating from the engine, so if you have a remotely-mounted oil filter, that is not heated.
Combustion oil heaters use propane or a similar fuel to heat the engine. A common unit seen at airports is a Red Dragon heater.
A much smaller (and slower) system is the Sure Start.
The propane source is a small bottle that hooks up to a line that is stored behind the temperature control panel:
You should use the electrical port from a vehicle, as it takes awhile to pre-heat the engine if it's cold and if you are using your airplane's electrical system, you may run the battery down before you try to start the engine.
This is how one looks all set up:
I do have a quibble with this photo though, for if this pre-heater was really being used on a cold day, the pilot should have a blanket or an insulated cover over the cowling to keep as much of the heat in as possible. I also think it is better to heat from the other end, as the heat flow with then rise up over the engine and it will also go through the oil cooler, which it probably will not here.
The worst part of the combustion pre-heaters is that they have to be monitored while running.
But whatever type you use: preheat when it is cold!
(p.s.: the rules are different for turbine engines.)
7 comments:
Hmm, learned something new today, always a good thing.
You seem to have quite a good grasp on mechanical theory and application.
I have never dealt with airplanes but have always been fascinated.The inside stuff you post here I soak right up.I'll keep looking for more.
It actually has nothing to do with what the block is made of. Most small cars today have aluminum blocks and start up just fine in below-freezing weather. As long as your anti-freeze is at the correct strength. Which is a Clue(tm).
One thing you might mention to your readers who are not familiar with single-engine piston aircraft of today is that these engines are air-cooled, like old VW's (indeed, the original VW engine was derived from a design for a small aircraft engine). That is the biggest reason why they must be preheated on cold days -- the cooling fins on the cylinders and heads will not allow them to heat up rapidly enough otherwise if you start them cold.
Your average small aluminum-block car doesn't have this issue because it doesn't have cooling fins on its cylinders, it has a radiator, and a thermostat to block the flow of water from the radiator when the engine is cold. So why, you ask, do light planes not have water-cooled engines to handle this issue? Well, obviously there have been water-cooled piston engines used in aircraft before (cue: Rolls-Royce Merlin), but those were military aircraft where the chances of crashing due to people shooting at you was higher than the chances of crashing due to a water pump failure, a radiator leak, or whatever. The FAA and light-aircraft engine manufacturers have traditionally been very conservative (I mean, we're talking about folks who prefer mechanical dual-magneto ignition systems literally decades after everybody else has moved to electronic ignition). They would not approve a water-cooled GA aircraft unless it had a backup cooling system in case of loss of coolant in one system. Design of such a dual-jacket cooling system is an exercise left to the reader :-}.
Not that it matters. Most current GA aircraft were designed literally decades ago, and have no space for a radiator anywhere and their manufacturers are not going to redesign them anytime soon. GIven that, there's not sufficient market for a water-cooled engine even if one passed FAA muster. The Subaru engines used by the experimental aircraft guys have proven at least as reliable as the certified engines, but would never pass FAA muster for general aviation as-is, and designing a new engine that would is horrendously expensive, far too expensive to do just for the few hundred examples that a new aircraft might sell per year.
Except for the fact that Mooney tried to fly a water-cooled engine in the PFM series and there was some Cessna 414s that were re-engined with water-cooled engines, yeah. Makes little sense to haul water aloft when you have all the air for free for cooling *and* air cooling means less shit to break in-flight.
Well, for high-horsepower motors like the Merlin you pretty much have to make them water cooled. However, nobody builds those kinds of piston engines anymore, if you need that much horsepower you go to a turbine, which is far lighter and more compact for a given power output.
That said, the lack of water cooling for the heads in particular greatly limits the fuel economy and power of current aviation piston engines. It is difficult to produce an air-cooled head that does not have "hot spots". The end result is that you must run a richer mixture and retard the timing to avoid detonation, and/or run super-high-octane gasoline that soon will not be available. It is also difficult to produce an air-cooled head which has sufficient cooling to the valve seats. The end result is a short valve seat life. The TBO of a typical aviation piston engine compared to a typical automotive engine is abysmal, although granted that's padded for aviation engines because, well, it's what keeps you in the air. But a typical automotive engine can have as much as a 5x greater TBO than a typical aviation piston engine... aviation engines are more akin to a 1980's motorcycle engine insofar as TBO is concerned, i.e., they'd need an overhaul by around 70-80,000 miles had passed if they were used in a car.
These pre-heaters can be switched on remotely using your mobile phone. So on your way to the hanger you can switch on the pre-heater and when you arrive the engine is already heated.
Wont put a link but if you google www.gsm-auto.com you will find details.
Found a compact little cell-phone pre-heating device for my system called the gsm switch which is a plug and play and only cost me 160 bucks and works a treat.
I have used a T Mobile pre-pay sim Card and it cost me nothing to switch the heater on which i do an hour before i want to fly.
site is www.gsm-switch.com if any body is interested.
Oh this system has the 110 power supply already installed on the control board.
hope this will be useful
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