All combustion engines generate heat when running — and airplane engines are no exception. They work by igniting fuel and air in a combustion chamber. As these substances burn, heat is generated.
While airplane engines can withstand some heat, too much heat may result in damage. Excessive heat can warp engine surfaces, create cracks, vaporize oil and cause other forms of severe damage. To prevent this from happening, airplane engines must be cooled.
The Basics of Airplane Engine Cooling
Most airplanes feature air-cooled engines. In other words, they leverage the air traveling over the airplane’s frame to cool their engines. Air-cooled engines are designed with cooling fins. They are small and thin pieces of metal that protrude from the engine heads and barrels.
Cooling fins work by transferring heat from the engines to the exterior of the airplane. They’ll absorb heat from the engines with which they are used. Heat will transfer from the engines to the cooling fins. And because the cooling fins are located on the exterior of the airplane, heat will safely dissipate while subsequently protecting the engines from damage.
Automobiles, on the other hand, typically feature a liquid-cooled engine. Cars, trucks, SUVs and other automobiles with combustion engines use liquid to protect against excessive heat. Known as coolant, this liquid typically consists of a 50:50 mixture of antifreeze and distilled water.
In the past, liquid-cooled engines were somewhat common in airplanes. Both military and civilian airplanes often featured liquid-cooled engines. Today, however, most airplanes have air-cooled engines.
Why Most Airplanes Have Air-Cooled Engines
Why do most airplanes have air-cooled engines exactly? When compared to liquid-cooling, air-cooling offers several advantages for airplanes.
Air-cooling reduces the total weight of airplanes. Airplanes with air-cooled engines don’t require coolant or other liquids. As a result, they weigh less than airplanes with liquid-cooled engines.
Air-cooled engines are also less likely to fail than their liquid-cooled counterparts. They only require fins, which are simple pieces of metal that transfer heat. Liquid-cooled engines, on the other hand, require additional parts. They must have a radiator, thermostat and hoses.
There’s no risk of freezing with air-cooled engines. While coolant contains antifreeze, that doesn’t mean it’s immune to freezing. Coolant can still freeze when exposed to low enough temperatures. And because airplanes fly at high altitudes, their engines are exposed to low temperatures that may cause liquid, such as coolant, to freeze. Air-cooled engines don’t have coolant, so there’s no risk of freezing.
FAQs
The water is circulated around the engine and picks up heat from the cylinders. The water then returns to the radiator through the two return hoses located on the top of the engine. In flight, air flows through the vanes of the radiator and the heat is transferred to the air and carried away from the aircraft.
How do air-cooled engines not overheat? ›
Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures.
How do plane engines not overheat? ›
Modern jet engines run efficiently by controlling temperatures and using cooling mechanisms. Cooling mechanisms include oil systems, air routes, and multiple air stages during combustion.
How is a Cessna 172 engine cooled? ›
Light aircraft engines are almost all air-cooled. This cooling is achieved by a carefully designed system of directing outside air in through cowl openings, over the engine and back into the atmosphere during flight.
Why aren't air-cooled engines used anymore? ›
Bigger, more powerful engines typically generate more heat and have cooling needs that air can't meet. This partially explains why most carmakers began moving away from air-cooled engines in the 1970s as cars got bigger, heavier, and more powerful.
Do jet engines use antifreeze? ›
And because airplanes fly at high altitudes, their engines are exposed to low temperatures that may cause liquid, such as coolant, to freeze. Air-cooled engines don't have coolant, so there's no risk of freezing.
What is the major disadvantage of air-cooled engines? ›
Air-cooled engines are more prone to overheating, can be costlier to build, and may sacrifice power efficiency due to large cooling fans.
Do air-cooled engines require special oil? ›
Use high-quality oil suitable for air-cooled engines, and follow the manufacturer's recommendations for oil change intervals.
What is the maximum temperature for air-cooled engine? ›
At its highest, an air cooled engine is almost always running hotter than a water cooled engine. Air cooled aircraft engines (which always have CHT gauges) typically have maximum allowable Cylinder Head Temperatures of around 350–375f (about 175–185c) which is well above the boiling temperature of water.
Why can't planes fly when it's too hot? ›
Hot air is less dense than cold air, its molecules zipping around at higher speeds, meaning planes have less lift when the mercury rises. That makes it harder for them to take off and stay aloft.
A passenger jet could glide for up to about 60 miles if it suffers a total engine failure at its cruising altitude. Here's an example. A typical commercial aircraft has a lift to drag ratio of around 10:1. This means that for every 10 miles it travels forward it loses 1 mile in altitude.
Why don't turbine blades melt? ›
By coating the metal in a type of ceramic called a Thermal Barrier Coating (TBC) we prevent the blade from reaching the extreme temperature of the engine.
Where is plane engine loudest? ›
In general, the noise is loud at the front of the plane, quietest about 30% of the distance to the rear, and then rises to its maximum value at the rear.
Why is there unusable fuel in a Cessna 172? ›
The fuel in aircraft is listed as "total fuel" and "usable fuel". The "Unusable fuel" is the fuel that remains in the tanks and fuel lines after all usable fuel has been used. This is fuel that is UNAVAILABLE in flight. This means that your engine will cease working if your fuel level falls under that amount.
What temperature does aviation oil break down at? ›
If the engine indicates over 220 degrees F with a properly calibrated oil temperature gauge, that means peak oil temperatures are approaching 270 degrees F, which is high enough to initiate thermal breakdown in mineral-base aircraft oils.
Do airplane engines have radiators? ›
Instead of a radiator, they feature cooling fins. Cooling fins are thin protrusions that allow heat to dissipate. The heat produced by an airplane engine may travel to the cooling fins. As air flows over the cooling fins, the heat will be released.
Are air-cooled engines good or bad? ›
Air-Cooled Engines
| Pros | Cons |
|---|
| Easy Manufacturing | Not optimal for high-performance |
| Affordable | Inefficient |
| Easy Maintenance | Can cause engine seizure |
Nov 24, 2023
Marine Engines are cooled by freshwater-seawater circuit. Whereas freshwater is used to cool the engine itself, the hot freshwater is then cooled by seawater. Normally freshwater is used to cool cylinder head and jacket. Rest of the internals are cooled directly by lubricating oil which also acts as coolant.
All combustion engines generate heat when running — and airplane engines are no exception. They work by igniting fuel and air in a combustion chamber. As these substances burn, heat is generated.