Something I’ve never really wrapped my head around is what the purpose would be between knowing that IAS and TAS are different.
I THINK I know what they are: TAS is simply your speed, in the basic way anyone would think about it; and IAS is how the speed your machine is “feeling” like with different factors taken in to account like air pressure/altitude, ambient temperature/humidity (which is just an extension of air pressure anyway). Is this right?
IAS is the main speed measure used by pilots - at least in civilian a/c - it is a better indication of stall speed for example - and therefore how far off it you are.
Think of IAS as airspeed on the plane, and TAS being speed relative to the ground. IAS is more important because it’s a better indication of the maneuverability of the plane at altitude. If you’re flying at 6km, you’ll have a high TAS but a moderate IAS, and this IAS is what your maneuverability is based on.
TLDR: IAS lets you know the speed of wind on the airframe, and hence the maneuverability the plane is capable of.
IAS: Turning ability, climb ability, risk of stalling, control surface authority, lift.
It describes how much and how fast air flows over your wings and control surfaces.
TAS: Closure (how fast you get close/escape) and kinetic energy for zoom-climbing and making turns that exceed your sustained turn rate (instantaneous turn rate)
It describes how fast you’re actually moving.
Corner speed: The speed at which your control surfaces, bank angle, lift produce the best SUSTAINED turn rate.
These videos helps with how IAS/TAS affects turn rate:
The second video is more about jets, but he goes into more detail about the relationship of turn rate, Gs sustained and speed.
