If you’re not properly preheating your aircraft in cold temperatures, you’re likely causing substantial––not to mention expensive––damage to internal engine components. In fact, running a cold engine for just 60 seconds can cause as much wear on your engine as 500 hours of normal cruise operation. And, if the temperature drops low enough, one cold start can cause major destruction of your engine right after takeoff. That’s why it’s so critical that you take the aircraft preheating process seriously.
Because engine components are made up of different metals, from aluminum to steel to cast iron and more, cold temperatures cause them to expand and contract at different rates. Pistons, cylinders, crankshafts, connecting rods and rings are especially susceptible to damage when temperatures are below freezing, as space between these moving parts tightens up. Cold starting a plane when these parts become too tight against one another will force these parts to rub and grind, irreparably damaging them. Proper pre-heating drastically reduces these mechanical problems, along with other wear and tear, and substantially extends the life of your engine.
In addition to potential engine damage, a plane that isn’t properly preheated will suffer during takeoff. Takeoff demands anywhere from 90 to 100 percent of an engine’s horsepower, meaning the entire engine needs to be performing optimally. And you certainly don’t want to experience engine failure on the runway.
How Cold is Too Cold?
It’s generally recommended to preheat your aircraft anytime temperatures drop to freezing or below. Of course, that’s just a guideline – there are certain circumstances where you may want to preheat your plane even if it is warmer; certain components like batteries, hoses and cylinders benefit from a warmer operating temperature. Just remember, if you need a winter coat to preflight your plane, preheating is a smart idea before you take off from the ground.
Below are a few examples of cold temperatures and their likely effect on an aircraft’s engine:
- 20°F is the minimum engine temperature that will prevent damage at startup.
- 40°F is easier on the battery during startups and reduces startup wear.
- 60°F is when you’ll see additional benefits in reduced engine stress and cylinder wear and more efficient run-up times.
The Best Way to Preheat an Engine
The best and easiest way to preheat your aircraft engine is to rent a parking spot in a heated hangar. Unfortunately, not everyone has the money or access to such a luxury. However, there are other options.
The next best way to heat up your engine is by using an electrical or whole engine heater. These evenly heat all engine components to the same temperature, rather than heating one component at a time (again, we don’t want parts expanding/contracting differently). So, even though you have cast-iron cylinders and aluminum pistons, these types of heaters will bring everything up in temperature uniformly, unlike forced-air heaters which heat the engine unevenly. On our fleet of aircraft we use Tanis Aircraft Preheat systems coupled with engine blankets when they sit outside between flights.
If you preheat your aircraft at your fixed base operator (FBO) and you don’t have a Tanis heater, you’ll likely be given a forced-air cart. These carts, powered by diesel, gas or propane, will unevenly heat your engine, leading to more wear and tear upon startup. While better than nothing, it’s generally best to stick with an electrical or whole engine heater.
Also, don’t believe that good oil pressure means that everything is running smoothly, either. Today’s multi-viscosity oils will easily flow in cold weather and give the false impression that engine parts are being properly lubricated during a cold start. So, never use oil pressure as a gauge for how warm your engine is. We recommend that multi-viscosity oils such as 15w-50 or 20w-50 be used during cold weather flight, while straight weight oils should be avoided.
Mastering the Preheating Process
Now that you know why preheating your aircraft is a big deal, you’re well on your way to mastering the process so you can enjoy flying in any temperature. Remember that without proper preheating, you can seriously damage your aircraft engine and put your safety at risk. Always ask for guidance at the service airport if you have any questions about properly preheating your aircraft.
Check out this video from Tanis on Cold Weather Operations.
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