I have a stupid question

[lunatic1]

why does IAS show slower speed  than actual air speed and ground speed in E6B while flyin

[BowHTR]

Google is your friend.

https://en.wikipedia.org/wiki/Airspeed

[hitech]

Actual air speed is an undefined term and for discussion purposes is meaningless.
Terms
IAS  Indicated air speed.
This is the air speed that the air speed indicator in a real plane shows. It is measured by a pitot tube facing into the wind, and is basically measuring a pressure change between static (I.E. normal atmospheric pressure changing with alt) and the pressure caused by the air being force into the tube.

As you go higher the change in air pressure changes the reading on the air speed indicator. Also as you change angle of attack, the tube is no longer facing directly into the wind, so this also creates a small error.

Then the speed is corrected for the AOA error, we have something called
CAS: Calibrated air speed.
This is what an air speed indicator would read if it was always facing directly into a clean slip stream.

Next we go to
TAS: True air speed, this is the speed you would be traveling across the ground if there is no wind.

And Finally
GS: Ground speed. The speed at which you are moving across the ground, this IS TAS corrected for  Wind Speed.

IAS is what is most use full for general flight because the plane will always stall at the same IAS no mater what altitude and temperature your at.

Converting between CAS and TAS is a function of pressure (I.E. Altitude adjusted for current barometer setting) and temperature.

To compute GS from TAS you simply subtract the wind vector.

HiTech

[Drane]

no such thing as a stupid question 

https://www.decodedscience.org/airspeed-of-an-aircraft-indicated-airspeed-ias-and-true-airspeed-tas/5035

http://www.airliners.net/forum/viewtopic.php?t=737503

[Dawger]

The simplest answer is as follows:

Indicated Airspeed is what your airplane feels and cares about. Think of it as your indication of aerodynamic performance.

True Airspeed is what your navigation solution requires. It is better thought of as your velocity. It is your true velocity from a physics standpoint.

At sea level the two are the same.

As altitude increase, the air thins and your airplane "feels" less air, but it is traveling through the air mass at a speed much greater than what the airplane and its instrument "feel" or detect. Hence the difference in the names. Indicated Airspeed (IAS) is what the instrument sees. True Airspeed (TAS) is your actual velocity through the air mass.

If you get high enough, your indicated airspeed is will read zero but your velocity will be very high, high enough to exit the atmosphere. That is reserved for ballistic objects however.

[lunatic1]

Actual air speed is an undefined term and for discussion purposes is meaningless.
Terms
IAS  Indicated air speed.
This is the air speed that the air speed indicator in a real plane shows. It is measured by a pitot tube facing into the wind, and is basically measuring a pressure change between static (I.E. normal atmospheric pressure changing with alt) and the pressure caused by the air being force into the tube.

As you go higher the change in air pressure changes the reading on the air speed indicator. Also as you change angle of attack, the tube is no longer facing directly into the wind, so this also creates a small error.

Then the speed is corrected for the AOA error, we have something called
CAS: Calibrated air speed.
This is what an air speed indicator would read if it was always facing directly into a clean slip stream.

Next we go to
TAS: True air speed, this is the speed you would be traveling across the ground if there is no wind.

And Finally
GS: Ground speed. The speed at which you are moving across the ground, this IS TAS corrected for  Wind Speed.

IAS is what is most use full for general flight because the plane will always stall at the same IAS no mater what altitude and temperature your at.

Converting between CAS and TAS is a function of pressure (I.E. Altitude adjusted for current barometer setting) and temperature.

To compute GS from TAS you simply subtract the wind vector.

HiTech

Thank You sir

[toddbobe]

Hitech:
Thats a lot of math to do while flying, texting, looking out for red planes and drinking a beer... I prefer to just be going that way at whatever the needle says. :-)