rframe
pǝʇɹǝʌuı
Actually, In a discussion about being slow (i.e airspeed in relation to stall speed), CAS is irrelevant.
Not true, it's very relevant, and the only way to accurately calculate performance numbers.
Lets look at your 172 example:
Calibrated VS0 (full flaps) with maximum forward CG in a Cessna 172 is 47KCAS.
47 * 1.3 = 61 KCAS = 60 KIAS
POH listed short field approach speed in the same 172 = 60 KIAS
Magical.
For the students on here, CAS (Calibrated Airspeed) is a correction to KIAS published by the manufacturer to allow for a more accurate calculation of True Airspeed (TAS). When operating the aircraft, the only speed you should be using is Indicated. Indicated airspeed is important, as it tells you how fast the wing is moving through the airmass regardless of altitude or temperature. This is why the manufacturer publishes all limitation and operating airspeeds in KIAS.
No they dont, not necessarily. Here's a stall speed chart for a Cessna 150, where do you see anything listed in indicated airspeed?
You have to go look at the IAS/CAS conversion chart for yourself. Why? Because IAS is what you see in the cockpit but is not an accurate measurement of your actual speed through the air.
I know you know (but for students), this is due to the fact that the pitot tube is cutting through the air somewhat sideways at a high angle and not picking up as much impact air pressure as it does with a lower angle of attack. This is why performance is calculated by CAS, or the actual speed of air flowing over your wing and control surfaces.
Yes, you obviously make the conversion to IAS so you know what to look at as you fly, but that's the last step, not the first.