Originally Posted by
ahmetdouas
no no, it doesn't work like that. Indicated speed and ground speed are completely different. 745 MPH Ground speed with a 100 MPH tailwind is still 645 MPH indicated speed, so the air indicator would still show like Mach 0.85 or so in the cockpit, nothing near 0.99 MACH indicated! Anything above 0.86 or so MACH in a 777 and you would be getting overspeed warnings which really isn't a good thing, the plane would have to be checked over and the pilots in big trouble.
So it is physically impossible for any commercial jet in the air right now to come anywhere near the speed of sound in level flight no matter how strong the tail wind is, they would have to do a crazy dive.
In one sense you are correct... ground speed does not indicate how fast the aircraft is travelling through the air.
On the other hand, you use the term "indicated airspeed" which is not correct either. As an aircraft climbs into thinner air the air has less effect on the airspeed indicator and so it under-reads... by quite a lot! So the indicated airspeed also won't show the real airspeed either and an adjustment has to be made to allow for the reduced density.
For example... an airliner doing a true airspeed of 500Kts at 38,000ft will likely have an indicated airspeed of around 280Kts!
The Mach meter on the other hand will show the percentage of the speed of sound in the conditions in which the aircraft is flying... the speed of sound depends on the density (and hence temperature) of the air so at sea-level it is about 660Kts and at 35,000 (-55C) it is about 575Kts
Sorry to get technical but it is an interesting topic of Indicated, vs True airspeed vs ground speed vs Mach number.