True Airspeed Calculation

0	Is there an easy to remember method to quickly get your true airspeed from knowing your indicated airspeed and altitude? airspeed groundschool asked May 22 '10 at 01:19 wbeard52 2066●6●25●45

2 Answers:

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The one I was taught but have never really used it in an operating aircraft is:

TAS = [IAS x 2%] x [ALT/1,000 ft] + IAS

But this is only really good depending on how good you are at mental math!

answered May 22 '10 at 23:30

Sean C.
766●3●9●26

You're right. The formula is a really good approximation to get your TAS. It might be off a couple of knots the faster you go but it is quick dirty math.

(May 23 '10 at 03:58) wbeard52

A handy way to get the TAS from your indicated airspeed and altitude without math is to use the amazing EB6 "whiz wheel."

On page 18 of the EB6 instruction manual on Sporty's tells you how: http://sportys.com/source/images/7205.pdf

To determine true airspeed you must first know the pressure altitude. Set your altimeter to 29.92 and read the altitude indicated; that is the pressure altitude. Note the outside air temperature and convert it to Celsius using the conversion scale at the bottom of the flight computer.

Set the pressure altitude in the window opposite the outside air temperature in Celsius.

Without moving the computer’s scales, read the true airspeed on the outer scale opposite CAS on the middle scale.

Read the density altitude over the arrow in the DENSITY ALTITUDE window. See Figure 13.

answered May 28 '10 at 19:18