Aircraft Engines: Liquid-Cooled vs. Air-Cooled

Aircraft Engine Cooling systems are designed to control and reduce the temperature of an engine, particularly, cylinder barrel heads. Without a cooling system, temperatures would rise to such high extremes that it would be unsafe to operate; engine failure would be unavoidable. There are two types of cooling systems that aircraft use today: air-cooling and liquid-cooling.

The concept of an air-cooled engine is simple— let the air flow over the engine to keep it cool. It has no need for coolant, radiator, hoses, or any other part that a liquid-cooled engine requires. They also utilize an engine cylinder design that incorporates cooling mechanisms around the engine; typically fins and vents. Some aircraft engines have complex systems that channel high-pressure air into the cooling fins. As the aircraft is flying, air is directed towards the engine to dissipate the heat. The fins draw heat away from the cylinders and radiate away the hot air through vents. Engines that are cooled by air have a harder time maintaining a constant operating temperature; this can affect its functionality during extremely cold climates, or intense heat conditions. These engines tend to warm up fast and don’t run the risk of having the coolant freeze, which is beneficial if you’re flying in frigid temperatures.  

Liquid vortex cooled engines utilize fluid to regulate engine temperature. This liquid is a combination of water, antifreeze, and rust inhibitors that are cooled using air, or a liquid coolant, which runs through a heat exchanger (radiator). This type of cooling comes with a weight penalty but is offset by the advantage of having total temperature control. A thermostat sits in between the engine and the radiator which maintains the temperature of the coolant. The thermostat also controls the flow of coolant into the radiator. After the coolant absorbs the heat from the engine, it gets transferred to the radiator, where it exchanges heat to be dissipated. The open and close mechanism of the thermostat allows the internal engine temperature to be regulated efficiently.

Some engines function with a hybrid design that use a liquid-cooling system mixed with air-cooling components. These systems tend to use smaller radiators combined with air cooled areas to dispel heat and maintain a lightweight configuration. There are advantages and disadvantages to using either system, or a combination of both, depending on the application.


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