Originally Posted by
thebat
As an uninformed observer of this discussion I pose this question to the FT's:
Airspeed = Groundspeed + Windspeed.
Or is this too much of a simplification?
And, if the above is true, obviously GPS can't record airspeed?
As I have stated above, airspeed is same as ground speed for our purposes. Of course some aircraft such as high performance fighters can go vertical. In that case ground speed is almost zero. For our practical purposes during cruising, the airplane is traveling mostly horizontal, thus airspeed is same as ground speed.
The aircraft is designed to fly at certain speed, let's say, 567MPH for a
747-400. If it encounter 200MPH
tailwind over Japan, then its speed would be 767MPH.
There is a definition for True Airspeed (
TAS, Vt=Vg-Vw). This is speed of the aircraft in relation to the air surrounding it. In the above example of the 747-400, maximum would be 567MPH. This is selected by the pilot in consideration to fuel economy, time schedule etc. GPS receiver cannot measure it, there are no in-device calibration for it, and it is irrelevant to what most people are interested. This is what the other poster is referring.