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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.

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