Expert: D. Norkus - 10/27/2007

Question
What happens if TAS, IAS, AOA with an increase in altitude

Answer
Dave,

Do you mean what happens TO true airspeed, indicated airspeed and angle of attack as you climb?

Trying to keep it a simple as possible:

TAS/IAS
When climbing at a fixed IAS your TAS is going to increase. As a general rule, TAS increases over your IAS 2% (or about 3 knots) for every 1,000 feet of altitude above sea level.

Of course, if you are climbing at a constant indicated SPEED, then IAS will not change but your feet per minute rate will. Climbing at a constant airspeed over several thousand feet results in a gradually lower rate of climb as you progress into thinner air.

If you are climbing at a constant RATE (like 500 feet per minute), then you will experience a gradual decrease in IAS airspeed as you gain altitude.

AOA
As your altitude increases, your angle of attack will need to be gradually increased to compensate for the decreased lift in the thinner air. Your lift will be less if you do not increase your AOA during climb.

Here is an interesting .pdf, Airspeed vs Altitude, that has some good graphs illustrating speeds at various altitudes- http://www.tscm.com/mach-as.pdf (plus the mathematical formulas to calculate speed).

A page of interest of AOA- http://www.av8n.com/how/htm/aoa.html

Hope this helps.
Dottie