Let's imagine the plane is flying with GS=620 knots, however with a tailwind of 150 knots. So, even with......

Question

..... this high GS, they are around mach .86 (because mach= TAS/speed of sound). What would happen if in a few secondes, the wind would just change in the other direction (so 150 knots headwind). The mach would be now extremely high (because TAS is going way up), about mach 1 or so maybe. This could be extremely dangerous, because mach .9 is the maximum? So, could such a situation happen (well, would be extremely rare, with wind changes that fast...)...

Answer 1

If it switch from a tailwind to a headwind the speed of the aircraft would decrease. A tailwind increases and a headwind decreases the speed. Same thing in a car. If you turn a corner and hit a strong headwind you'll have to give it more gas to maintain the same speed as before.

Answer 2

620 kt groundspeed - 150 knot tailwind = 470 kt TAS.

A shear from a 50 knot tailwind to 150 knot headwind would be a 300 knot shear, and would temporarily increase TAS.

.9 mach is not a maximum.

You are asking if a plane could exceed its Mmo just due to wind shear.  Yes.  In fact, if flying at Vmo or Mmo a sudden temperature change can put you over.

Answer 3

it would be in a very high turbulence area, and hopefully you'd get some warning - cause from an external reference frame, you'd have a 300knt change at the nose of the plane -

your gs would decrease to 320!

the high mach numbers cause dutch roll - or control reversal.  http://en.wikipedia.org/wiki/Control_rev...

there are kinks in the tropopause which cause some weird behavior, but not like that.

Answer 4

It isn't possible for the wind to change that abruptly; you would have two colliding airstreams, and where would the air then go?  But the question is nonetheless valid; turbulence can play games with the indicated air speed, so an aircraft can be slowed down a bit if turbulence is encountered or expected to keep the Mach number under control -- and reduce the buffeting to the passengers.

Answer 5

well, would be extremely rare, with wind changes that fast...) WELL ITS NOT THAT RARE I READ THIS THING THAT THAT WAS I WIND ABOUT 150-160 KNOTS AND IT CHANGED DIRECTIONAND THE WAS A PLANE LANDING!!!

Answer 6

I did 640 knots groundspeed a year ago and our mach was about .80

That much tailwind (we had about 190k tailwind) is the result of a well-formulated flow. Quite possibly a jet core. It is not one which would reverse itself in a few seconds, although there could well be CAT near the boundary of the flow.  Of course, low level wind shear, microbursts, etc., are a different situation. Our ride was smooth---and fast.

Answer 7

Your TAS is completely independent of wind velocity.  A shift to a headwind would not change mach number or TAS at all.

You would still indicate .86 mach in your example.