If IAS is is the instrument reading for speed, what is the difference between TAS and CAS?

Question

Im still a little hazy as to what the difference is between IAS ,TAS, and CAS. The cockpit reading is always in IAS but has to be converted. Therefore what is the difference and how is it applied. ? Cheers.

Answer 1

Indicated airspead. What the meter indicates



Calibrated airspeed. Indicated airspeed corrected for position and installation errors.



True airspeed. Calibrated airspeed corrected for pressure and temperature at altitude.



Ground speed. True airspeed corrected for the effects of wind velocity and direction.

Answer 2

Indicated air speed is what you get out of the pitot tube and gets indicated on your gage inside the aircraft. It is in essence what the aircraft "feels"



Calibrated airspeed is IAS corrected for installation and positioning errors. For example, the pitot tube's airflow is being disrupted by part of the fuselage.



True airspeed is because at higher altitudes the air is less dense. This means less molecules in the pitot tube and means a lower speed is indicated. TAS uses temperature and air density to come up with the airspeed that the aircraft is actually traveling at. Most of the time a computer does the calculation. for example at 3,000ft your airspeed indicator reads 100knots. This is indicated airspeed. Now at 30,000ft your IAS will also be 100knots but you will be travailing much faster because of air density. Your True airspeed without any wind will be closer to 300 knots.( this means that if you travel at 300 knots at sea level you will be flying at the same speed at 100 knots at 30,000ft.

Answer 3

Indicated is what you read directly from your instrument.

Calibrated is adjusted for error(as stated above) from which a chart can be found in your POH.

True Air speed is relative to the air mass you are travelling in.

If you were travelling at a hundred knots and had a tail wind if 30 knots you would be travelling faster than indicated.

Ground speed is actually the most accurate one as it is relative to distance covered over the ground in a specific amount of time.

Answer 4

Indicated Airspeed (IAS) is what you read off the Air Speed Indicator (ASI) in the cockpit.



Caliberated Airspeed (CAS)is the airspeed corrected for positioning and instrument errors.

Invariably, CAS will be read off the ASI if the calibration has been done.



True Airspeed (TAS) is the actual distance covered (on the ground) per hour by an aircraft during flight.

Answer 5

Indicated airspeed (IAS) is the airspeed read directly from the airspeed indicator on an aircraft, driven by the pitot-static system. IAS is directly related to calibrated airspeed (CAS), but includes instrument errors and position error.



An aircraft's indicated airspeed in knots is typically abbreviated KIAS for "Knots-Indicated Air Speed" (vs. KCAS for calibrated airspeed and KTAS for true airspeed