Ask Elton
Your Flight Training & Ground School Specialist

The ask-elton.nz website is also available as an APP.

If you already have installed the ask-elton APP,
then please close this window and open the ask-elton (AE) APP

For help with the app installation, click here


close this Block

CPL » Navigation » Circular Slide Rule

Derive or compute TAS, given IAS, pressure altitude and air temperature in degrees Celsius.

To Find the TAS you will need the following:

  • Pressure Altitude
  • OAT (Outside Air Temperature)
  • CAS or IAS 

(Use CAS if it is available, otherwise use IAS)

Example one.

Question: 

Given CAS 110 knots, P.alt 18'000 feet, OAT 15ºC what is the TAS

Method: 

Using airspeed window set temp against OAT

Find CAS on inner scale

Read off TAS opposite on outer scale

Answer: 

TAS 156 knots

Solve mathematical equations: (a) multiplication (± 2%); 

Solve mathematical equations:  (b) division (± 2%); 

Solve mathematical equations:   (c) proportion (± 2%).

Calculate time, speed, or distance, given two factors.

To see more, you must subscribe for licence "CPL" or sesssion "Navigation"