The Earth
The Solar System & Time
Using Aeronautical Charts
Basics of Navigation
Distance, Speed & Time
Vertical Navigation
Fuel Planning
Practical Navigation Techniques
Radio Navigation
Practice Exam

CRP-1: True Airspeed

Calculating True Airspeed (TAS)

The CRP-1 airspeed window is used to calculate TAS when given a calibrated airspeed (CAS), outside air temperature, and pressure altitude.


You are flying at a calibrated airspeed (CAS) of 110kts at a pressure altitude of 7,000 feet. The outside air temperature is 16°C. What is your true airspeed (TAS)?

1 In the airspeed window, align the outside air temperature (16°C) with the pressure altitude (7,000ft)

2 Locate 110 knots on the inner scale and read off the true airspeed (TAS) of 126 knots on the outer scale

The inner scale is calibrated airspeed (CAS).
The outer scale is true airspeed (TAS)