why is Vne a TAS?

"private" wrote
"Flutter limits high true airspeed operations, and it is possible to
get to the coffin corner where stall speed and Vne approach each
other."
Can I have the groups wisdom and further explanation of the reasons
for this and of how Vne changes with altitude.


It is probably not "flutter" that sets the high speed limit, but
rather "critical Mach bufett". Yes, even a glider has a Mmo but
no mach meter to indicate it, so an equivalent TAS becomes the limit.

Copied from a web site:

"The critical Mach number is the free stream Mach number at which sonic
flow first appears on the airfoil/wing.

Buffeting is the structural response to excitation produced by the shock-
induced flow separation, and is ultimtely related to the vortex formation
and breakdown. Buffeting may affect different parts of the airframe, but
the buffeting on the wing is the most important.

As the speed increases the wing is affected by shock stall, whose
appearance sets an upper limit to the speed. This limit is a function of
the flight altitude. Its envelope is called buffeting boundary."

Bob Moore