Page 514 - PPL-engelsk 2025

Principles of flight

In practice, we do not use any of these speeds, but economic cruising speed,

where we get the farthest on a tank of gasoline.

This speed is called the speed for best range.

The best range is found at high altitude.

If we have to wait to enter a control zone for landing, we can use the air speed

that gives us the most flight time in the air.

This is the speed at which we use the least fuel to keep the plane flying.

The greatest flight time in the air is called “best endurance”.

The greatest flight time is found at low altitudes with low engine power.

- The principle is illustrated here.

- The yellow curve shows induced

drag.

- The orange profile drag.

- The red shows total drag.

- Where the tangent (the green

line) intersects total drag is the

best range.

If you look in the “aircraft performance” section, you can see charts that show

speeds for best range and greatest achievable flight time.

You can also see which altitudes it may be advantageous to fly at.

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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 514