Butch Gordo from Winnemucca, Nev., sent in this: “I used to preheat my 172 with exhaust from my pickup piped into the engine compartment with clothes dryer duct. Half hour later it was pipin’ hot, for free. Some guys said they heard you shouldn’t do it that way, but no one seemed to know why.”
So what do our readers think?
The Handiest preheater is putting a Trouble Light ( Old style filament light bulb ) under the engine in the cowling . I turn it on the day before I plan on flying , put a sleeping bag over the cowling to hold the heat in .
The heat soaks thru the whole engine and is easy to start . Old School and simple .
In reference to a “free way to preheat”: Moisture is an issue. The engine compartment becomes drenched and after the engine starts it and it takes some time before the majority of the moisture in the engine compartment is gone. Cables such as carb heat and mixture freeze, even linkage will freeze. A starter relay mounted in the engine compartment may stick. This may not happen if your heating in only marginal temperatures but in cold temperatures, after having tried it once in an urgent situation, I won’t try it again. I would recommend against using this technique in any but the most urgent situation ant then take off only after a long ground run. In my case the throttle linkage froze for a period of time.
After removing the heat, the engine compartment isn’t instantly warm, it cools off after the heat is removed. After the engine is started it will take some time before there is enough heat generated by the engine to dry the whole engine compartment out.
Electric Blankets are cheap and on low they keep things warm 24/7. No preheat needed.
Bruce, that is a great option provided that you are in a personal hanger and have the required electrical connection (not all do). If you are parked on the ramp as most aircraft are then that is out of the question and the exhaust method that was put forward is still the better of the possible solutions. That is unless of course someone can come up with an intelligent reason to the contrary that is based on provable facts and not pure speculation.
Butch, nothing in life is “Free”. While you have a more economical solution to preheat, idling your vehicle for 1/2 hour means that you are using your vehicle’s fuel, oil, and time on the engine which costs money—not highly significant but not free. I’m not an engineer, but I would question the effects of carbon monoxide to the integrity of the aircraft engine’s metallurgy and its accessories.
The environment also suffers by your unnecessary production of carbon monoxide to the atmosphere.
I would recommend (if you have a hangar or tiedown with convenient electrical access) to run a couple of incandescent high wattage light bulbs via extension cords in the cowling and then put a heavy moving blanket or 2 on the outside of the cowling. Removal of the blankets and light bulbs before flight would be quick and convenient.
With regards to the comment that if you can’t afford a preheater than you should not own an airplane you should be more open minded. What are the benifits to this approach, well lets see; First you do not have to purchase, maintain and store a separate piece of bulky equipment that is only used during a limited time of the year and is only available at your home base. Second the preheater will need a power source to blow the hot air that it produces so what if there is not a convenient source nearby (i.e. out on the ramp vs in a hanger. Third just think of how much easier it is to simply stop near the front of the aircraft and then connect a simple piece of inexpensive flexiable duct to the vehicle and aircraft vs bringing out that bulky preheater and get it all connected and started (and then stored). As for the “Chicken Little” comment on CO in the cockpit there should be no engine compartment air getting into the cockpit regardless so running exhaust through there for preheat is a non-issue. Keep in mind that some preheaters use combustion for their heat source so they would be just as likely to cause that problem.
Assuming there are no significant demonstratable down side to this process than I can see no reason to want to use the commercial preheater regardless of financial situation. As pilots we are considered to be intelligent and rational pearsons so lets stop and use those talents before condeming such a practice.
Not a very smart thing to do Butch
The exhaust from your truck (and in fact from any gas or diesel engine) is filthy. One of the major constituents of engine exhaust is water, and that combined with blow-by gasses and other combustion byproducts will give you a fine mist of soot, carbon, dilute sulfuric acid (which is why older steel exhaust systems rot out so fast, and why all modern cars use stainless steel exhaust systems) and and this crap is now being pumped directly onto your expensive aircraft engine. Aside from making everything under the cowling dirty, it will deteriorate rubber parts and everything steel or aluminum that isn’t corrosion-proofed.
Try this as an experiment. Take a clean but worn out facecloth (because your wife will kill you if you use the good ones) and hold it directly in back of the tailpipe. Run the truck for ten minutes, then look at the facecloth. That will only be the part you can SEE, what you can’t see will be even worse.
Further, you are enveloping the entire front of the airplane in an invisible cloud of tasteless, odorless, colorless carbon monoxide. Some of it IS going to leak into the cabin, and since the airplane isn’t moving, it will stay there to greet you when you get in to fly. (I suppose this is a way to test your Dead Stop ™, but it seems awfully involved . . . )
There is no such thing as a free lunch, and this is no exception. Sorry, time to go to plan B.
The exhaust contains a lot of moisture as well as contaminants from combustion which can cause some serious corrosion. Especially on the airframe..
Your right, nothings free, but it may be cheaper than what an FBO will charge you.
Risk vs Reward – the aviation way!
I think if you cannot afford to buy a real preheater, you probably shouldn’t own a plane.
How about a big let’s see. Carbon Monoxide getting into the cabin causing death. As well as previously stated WTH is free using your car engine?
What’s FREE about running a truck engine?