Why Planes (Usually) Perform Better in Cold Weather

Cold weather flying has its challenges and downsides. Namely, it’s cold. And you have to be more diligent about pre-flight inspection, prep, and de-icing. But many pilots love winter flying, not only for its unique beauty, but because their planes seem to perform better than in warmer temperatures. Here’s a (simplified) explanation.

First, to clarify: Aircraft may perform better in cold weather, but that doesn’t necessarily mean safer. The potential for icing and its affect on lift and handling is a dangerous threat in freezing temperatures. But icing aside, cold air can help a plane take off and fly more efficiently.

It’s about air density and engine power

So why do planes perform better in cold weather? Simply, colder air is denser than warmer air, which contributes to engine performance and air lift. But why?

A plane’s performance, including takeoff distance, rate of climb, and engine power, is greatly affected by the density of the air, also known as the density altitude.

Generally, both turbine and internal combustion/reciprocating piston engines run more efficiently in cold air because colder air allows the engine to use a greater mass of air/fuel mixture in the same intake volume. That translates into more power.

In propeller-driven planes, the prop is biting into denser air, and thrusting a greater mass of air backwards, which means more thrust and power.

More power allows a plane to accelerate more quickly on take off. That extra power increases the rate of climb, reduces take off roll, gives the wings more lift, and allows the plane to take off at a lower ground speed.

So. It’s not actually that airplanes fly better in cold air; it’s that their engines produce more power when they take off in cold air. Again, when the air is colder, and thus denser, a greater mass of air is able to get into the engine’s cylinders with each stroke, and that equals more power.

More power also means more fuel

Keep in mind that, while engines produce more power in cold air, fuel consumption increases along with power. Scientifically, air contracts when it is cold and denser. This means that the air your plane is taking in during combustion has more oxygen in it. When there’s more oxygen, the engine compensates by using more fuel.

The opposite is also true …

Generally, as temperature increases, a plane’s power and performance decreases. As air heats up, it expands and becomes less dense, or thinner, just like air at higher altitudes.

So on a hot summer day, a plane’s engine is taking in air that is less dense, with less oxygen. That produces less lift, and the plane has to travel faster and farther to take off and fly, like it is at a higher altitude. The up side is, because the air is “expanded,” you’ll use less fuel to get up.

Other advantages of winter flying

On cold, dry days, not only does colder, denser air help a plane’s engine perform better, but less convective heating means less turbulence.

Convective heating is the currents or thermals created when the heat from large bodies of land radiate heat into the cooler air, creating bumps, known as turbulence.

With less convective activity, there is much less chance of thunderstorms, so if winds are low, then flights are usually much smoother. Also, lower humidity improves visibility.

Another benefit of winter flying: less air traffic. That means less stress, and greater enjoyment of flying.

For more information on winter flying, read these Business Aircraft Center articles:

Preparing Your Plane for Cold Weather Flying

Winter Flying Tips: Think Strategically for Safety

Winter Prep and Safety Checklist

Safety Review: Winter Icing Pre-Flight Checklist

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