Density Altitude
Density altitude is pressure altitude corrected for temperature. Increasing temperature makes the air less dense. Remember how a plane flies. You create a downward force that is equal to the weight of the plane. When that downward force is greater than the weight of the plane you are flying. Your takeoff run will increase, when the temperature is higher, later in the afternoon than a takeoff in the coolness of the morning when the air is more dense. You increase the speed of the airplane to reach a downward force of air that is equal to the weight of the plane. If everything is equal at takeoff you need more runway to achieve that downward force.
If you think of a container at one temperature contains 20 molecules of air. If you could weigh the container it would weigh more than a container that contains just 15 molecules of air. You weighed the first at 60 degrees and the second at 75 degrees. The density altitude is less at higher temperatures.
High altitude has fewer molecules in the container just like the container at 75 degrees.
Flatlander pilots sometimes forget the altitude effect when taking off from mountain airports that are significantly higher than sea level flying. Expect longer takeoff runs in the mountains.
Winds Aloft
Winds Aloft are important to fuel management on long cross country flights. Pick an altitude with the least resistance as possible that provides comfort and structure avoidance altitude.
You can use winds aloft to pick a tail-wind for a quicker flight to a destination or return to your home base.
Winds are critical in both low and high altitude locations where turbulence could occur.
Altitude Brightness in mountains! Proper googles may be a choice. You know what you need.
Altitude Brightness in mountains! Proper googles may be a choice. You know what you need.
At high altitudes forecasts pay close attention to ridge and mountainous wind aloft reports. Density altitude and turbulence can affect your planes performance in critical situations. In mountains the 9,000 to 12,000 foot forecasts are important both from plane performance and oxygen availability and use.
In eastern regions the wind velocities are lower. Turbulence can occur and thunderstorms are more frequent and just as dangerous as mountain flying.
Flight Planning is very important to a safe flight and winds aloft can make a difference.
