IAS or actual air speed

BashDaBish Guest

Hi all and thanks in antcipation for your answers 😀

IAS is the speed setting I am using at the moment but noticed actual air speed was also an option. I know the difference between the two but wondered what the pro's and con's where of both settings?

Answers 5 Answers

Jump to latest
Pro Member Chief Captain
Alex (Fire_Emblem_Master) Chief Captain

TAS (True Airspeed) Pros- You know for sure how fast you're going

Cons: All the aircraft checklists are in KIAS (Knots Indicated Airspeed), which make it confusing to read.
You can get a close approximation from the GPS, bottom left corner, G/S is the abbreviation, then below that, is the speed. While it's ground speed, you won't really need it all that much anyway.

Guest Ed Guest

The reason indicated airspeed is most important and useful is that it's a direct measurement of the aerodynamic stress on the plane. For instance, you can't lower the landing gear above a certain indicated airspeed, because the force of the air at that speed would rip it off, or at least damaged it. It doesn't matter what our true speed is in this case, what matters is how much aerodynamic stress is on the plane.

So you should keep your airspeed indicator displaying indicated airspeed, and if you want to know your true speed over the ground, refer to the GPS.


BashDaBish Guest

Thanks chaps....I knew it was important to use KIAS, I tried TAS once and err....well I shan't be doing it again. My 747 is buried somewhere near Manchester.

Pro Member First Officer
horrgakx First Officer

The indicated air speed is the important one because it is irrelevant to your ground speed. It took me a while to get my head round that (there are documents on the Internet explaining it all) but imagine a 30kt wind speed - flying into it your ground speed will be less, fly with the wind and your ground speed will be higher. However your indicated airspeed won't alter.

Last edited by horrgakx on Wed Mar 23, 2005 5:38 pm, edited 1 time in total
Pro Member First Officer
leadfoot First Officer

IAS is also critical to keep you from stalling the plane or rotating to early on takeoff. Remmember, the airspeed indicator reads aerodynamic pressure. By doing so, its information remains the same regardless of atmospheric conditions. ALWAYS use the IAS setting on the airspeed indicator.

Still does not answer your question? Ask a new question!

If the question and answers provided above do not answer your specific question - why not ask a new question of your own? Our community and flight simulator experts will provided a dedicated and unique answer to your flight sim question. And, you don't even need to register to post your question!

Ask New Question...


Search our questions and answers...

Be sure to search for your question from existing posted questions before asking a new question as your question may already exist from another user. If you're sure your question is unique and hasn't been asked before, consider asking a new question.

Related Questions

Flight Sim Questions that are closely related to this...