"I think you may be missing the point in the posts above.
The plane doesn't measure the air movement or wind."
Er... yes, no... maybe
I've been told that TAS and the wind vector cannot be computed without air data coming from the ADC's (or at least the ADC side of the ADIRU's), according to my other Boeing training manuals. Some (kind of) measurement of air movement must be "in the mix" somewhere... No?
The inertial side of the ADIRU is measuring the forward motion of the aircraft (track and groundspeed). TAS, I presume, is being measured above 100Kts by the ADC side of the ADIRU's(?). TAS, on Boeings at least, is simply(!) pitot static data put through the blender (compensated, mixed with TAT, etc)
"If you're doing 100kts CAS with a course of 90deg. and the inertial figures you're doing 50kts along a 90deg track then you have a wind of 90deg at 50kts. (and that's a bit simplified but we don't need to be getting into TAS, GS, IAS, and CAS now do we?)"
That's exactly what I'm trying to say (in a roundabout way). Why not paint a 50Kt vector at 90degrees (dead ahead) on the ground on the ND above 100kts? (Or if the angle of the wind is, say, 30 degrees (relative) to the aircraft track, paint a wind vector at 90 degrees, but 43kts (50kts x cos30deg?) in strength.
I very much understand that pitot sensing errors are going to arise in the TAS calculation if the wind is blowing at an extreme angle... just as it would with the IAS/CAS. I also realise that the aircraft cannot predict (on the ground) the effect a crosswind would have on the aircraft in the air. I simply want to understand what is stopping the aircraft computing the strength of the wind (dead ahead) and displaying that data on the ground. Although, now that I think about it, if this was displayed on a HUD in front of the pilot, I have to ask would this data be any use in visually displaying a rapid change from a headwind to a tailwind, as might be experienced in a microburst? Anyway, I'll leave that for another day
Thanks for all your efforts.
Cheers.
Q.