Ever wonder how air temperature affects airplanes? From takeoff times to climbing performance and even fuel performance, air temperature can affect many aspects of flight. It’s not something that most passengers think of, but experienced pilots know how to account for these changes.
Air Temperature and Density
There’s a direct correlation between air temperature and density. When heated, air molecules spread out, resulting in lower density. Conversely, air molecules group together more closely as the air temperature drops, resulting in greater density. This change in air density can affect airplanes in many ways.
Takeoff Times
It typically takes airplanes longer to take off in hot weather than in cold weather. Hot weather means the air molecules are spread out. Airplanes generate lift by moving air over and under their wings. High-pressure air moves under the wings, while low-pressure air moves over the wings. With hot air, though, there are fewer air molecules moving over and under the wings, so airplanes generate less lift. They can still take off, but it will take airplanes longer to generate sufficient lift.
Climb Rate
Air temperature can affect an airplane’s climb rate. Climb rate is the speed at which an airplane ascends or “climbs” into the atmosphere. It’s typically measured in feet per minute (fpm) or meters per second (m/s). The faster an airplane ascends and gains altitude, the higher its climb rate will be.
Hot air can cause a slower climb rate. Like with takeoffs, this is because airplanes generate less lift with hot air. Research, in fact, shows that a 20-degree Fahrenheit temperature increase can slow an airplane’s climb rate by as much as 50%.
Fuel Efficiency
Another way that air temperature affects airplanes is fuel efficiency. Most airplanes, including jet and propeller-driven, have airbreathing engines. They draw air into a combustion chamber where it’s mixed with fuel. A spark then ignites the air-fuel mixture, creating a controlled explosion, which propels the airplane forward.
Airplane engines are typically less fuel efficient in hot weather than in cold weather. In hot weather, they draw fewer air molecules into their combustion chambers. Therefore, airplanes must burn more fuel to compensate for the lower air content.
Ice Buildup
Of course, excessively cold air can bring a myriad of problems on its own. Ice, for instance, can build up on the wings, propellers, windshields and other parts. It can also cause hydraulic systems to stiffen. Batteries may also lose their charge quickly.
