4 TYPES OF AIRSPEED

Updated: Dec 31, 2020

What are the different types of airspeed?

How are they calculated?

When are they used?


Here's what you need to know.

INDICATED AIRSPEED (IAS)

What is it?

The airspeed read directly off the Airspeed Indicator during flight.

What's it used for?

Airspace speed limits.

Speed restrictions issued by ATC.

The aircraft's published V-speeds.

To calculate Calibrated Airspeed (CAS).


CALIBRATED AIRSPEED (CAS)

What is it?

It is Indicated Airspeed (IAS) corrected for pitot-tube installation. At varying angles of attack, the airspeed indicator may not be pointing directly into the relative airflow. For this reason, there may be small differences between Indicated Airspeed and the actual speed of the aircraft.


How is it calculated?

Using the Calibrated Airspeed performance chart found in chapter 5 of the aircraft's Pilot Operating Handbook (POH).


What's it used for?

To calculate True Airspeed (TAS).


TRUE AIRSPEED (TAS)

What is it?

The speed of the aircraft relative to the airmass in which it is flying.


How is it calculated?

Using the True Airspeed performance chart found in chapter 5 of the aircraft's Pilot Operating Handbook (POH). True Airspeed increases 2% per thousand feet of altitude gain. This is due to the fact that there is less aerodynamic drag on the aircraft at higher altitudes (less dense air).

What's it used for?

To calculate the aircraft's Ground Speed.


GROUND SPEED

What is it?

The aircraft's speed across the surface of the Earth.


How is it calculated?

By adjusting the aircraft's True Airspeed (TAS) for wind direction and velocity through use of the E6B. A tailwind will increase an aircraft's Ground Speed while a headwind will cause a decrease.

What's it used for?

Time and distance calculations.


Author - Nate Hodell

CFI/CFII/MEI/ATP - Creator of wifiCFI - Owner of Axiom Aviation Flight School.


This information is included in the Performance and Limitations Lessons on wifiCFI. Sign up today to watch videos, listen to podcasts, take lesson quizzes, join live webinars, print lesson quicktakes, and more by clicking this link >


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