Engine Preheater

As pilots we’re trained to understand how temperature can affect every aspect of flight. From aircraft performance to the weather and even our mood, too much heat or too little can make a big difference. But what about on the ground? Like many pilots, piston aircraft sometimes need a little extra help to get started on a cold day. But unlike warming ourselves up with a hot cup of coffee, with a piston aircraft, preheating is not just about getting the oil temperature up, it’s also about taking care of the overall health of our engines and the components that help them run properly.

Aircraft engine components are made up of different kinds of metals that contract and expand at different rates based on the temperature. To save weight, the crankcase, pistons, and cylinders are all made of aluminum. Parts that need to be stronger, like cylinder casings, connecting rods, and the crankshaft are typically made of steel, but can also be chrome or other metals.

Why should I preheat? 

When cold weather strikes, the metal components will contract, causing the space between internal components like the crankshaft, piston, rods, and cylinders to shrink. When you attempt a cold start, these components could rub and grind together causing damage to the engine. Another reason to preheat your powerplant is to promote proper lubrication. The colder the oil, the thicker and less viscous it is, meaning it may not lubricate the engine effectively during start-up. Other components, like batteries, can also benefit from preheating. Most experts recommend preheating when the temperature drops near or below freezing, but some manufacturers recommend starting at 40 degrees Fahrenheit.

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Some aircraft owners and operators create their own solutions to preheating like cowl covers, blankets, electric room heaters, heat guns and flexible ducting, and even camping stoves. As with most hot tools, it’s recommended to always monitor your homemade heating apparatus.

Forced air portable preheaters are popular among flight schools and FBOs. They use propane, diesel, gas, electricity, or a combination of the two to blow hot air at the engine through the front of the cowl or through the exhaust opening. Note there are some cons to using forced air preheaters. First, they may not evenly heat your engine; typically you end up with the front of the engine being warmer than the back. This means you may have components expanding or contracting at different rates.

Electric heating systems are installed in your aircraft. Their electrical heating elements can be attached to your crankcase, cylinders, and oil pan, meaning you’ll have a warmed-up engine in about one to two hours. Tanis, an electric preheater manufacturer, recommends preheating for at least six hours to reach an “average state of thermal equilibrium.”