High Density Altitude

Lake-effect Snow and Whiteout Conditions in the Great Lakes Region; Below-average Temperatures in the East

Heavy lake-effect and lake-enhanced snow will persist downwind of the Great Lakes and produce some whiteout conditions that could cause difficult travel conditions. A coastal low will produce moderate to heavy snow over parts of southern and eastern New England into the afternoon. Below average temperatures are expected across the eastern U.S., particularly with chilly morning temperatures. Read More >

High density altitude accounts for 7.3% of all U.S. aviation weather-related accidents.

Density Altitude: The altitude in the standard atmosphere at which the air has the same density as the air at the point in question. An aircraft will have the same performance characteristics as it would have in standard atmosphere at this altitude.

High Density Altitude: A condition of the atmosphere that reduces an aircraft’s performance capability to below a level of standard performance at a specified altitude.

Cold, Dry Day

Low Density Altitude

Hot, Humid Day

High Density Altitude

Air density is determined by Pressure, Temperature, and Humidity.

On a hot, muggy day, the air becomes "thinner" or less dense, and its density at a pilot's location is equivalent to a higher altitude in the standard atmosphere. Thus the term "high density altitude."

Pilots must determine if high density altitude will impact their flight by calculating density altitude and checking their aircraft performance charts.

High Density Altitude Hazards

Reduced Power (engine ingests less air to support combustion)

Reduced Thrust (propeller has less "grip" and jet exhausts less mass)

Reduced Lift (air exerts less upward force on the airfoils)

Longer takeoff roll is required

Smaller rate of climb

Lowers aircraft's service ceiling

Longer landing roll required

High Density Altitude and Heat

High

The higher the altitude, the thinner the air.

Mitigation: reduce aircraft gross weight for safer operations

Hot

The warmer the air, the less dense it is.

Mitigation: flight operations early morning or late afternoon are safer

Humid

Not considered a major factor because the effect of humidity is related to engine power rather than aerodynamic efficiency

Mitigation: add 10% to computer takeoff distance and anticipate reduced climb rate