"Morgans" wrote
No, I think the post above yours got it pretty much right..Vne is
significant, in that it demonstrates itself by nasty things like
flutter, or control reversal.

Nope! Mike got it right.


"Jim" wrote
Another "coffin corner" I have heard discussed is the convergence of
Vne and Vs as altitude increases.

Nope! Mike got it right.

Coffin corner
From Wikipedia
Coffin corner is a dangerous portion of the flight envelope that must be
carefully approached by high altitude high subsonic speed aircraft, such
as the Lockheed U-2 aircraft.
Mach Limit
A subsonic aircraft must not exceed its Mach limit, some fraction of the
speed of sound near, but not at 1.0. At the low air densities encountered
at high altitude the speed of sound is lower. Exceeding the Mach limit
can cause loss of control and/or structural failure.
Stall Limit
At high altitudes the low density air is less capable of supporting the
aircraft and so the stall speed increases (as expressed in true air
speed).
The Corner
At some limiting altitude these speeds converge, and the aircraft cannot
be flown, as a slight pitch down will cause the Mach limit to be exceeded
while a slight pitch up will cause an aircraft stall with a subsequent
pitch down.


I've been to "coffin corner" in a Navy T2-V and very near to it in a
Boeing 707 and neither time was I close to Vne..Critical Mach
Number..yes, but not Vne.


Bob Moore
ATP B-707 B-727