The airspeed indicator is your plane’s speedometer. It indicates what your speed is through the air in knots (nautical miles per hour). How does it do this?
The airspeed indicator compares the speed of air at the edge of the wing—actually at the pitot (pronounced PEE-toh) tube—against the static airspeed in a more protected location such as on the side of the aircraft. From these it calibrates the plane’s speed through the air. Because air is thinner the higher you fly there are some adjustments to be made to get a true airspeed. In training, you’ll learn how to figure ground speed by adding or subtracting the wind speed depending on which direction it’s coming from.
Airspeeds are sometimes referred to with the letter V for velocity, so they are called V-speeds. The most common are
- VSO (stall speed with flaps down),
- Vs1 (stall speed with flaps up),
- VX (best angle of climb),
- VY (best rate of climb),
- VNO (maximum cruise speed), and
- VNE (never exceed).