Well, the bit of the envelope you're talking about is the low end of the
speed envelope fro every airplane. The coffin corner really only applies to
high alt/high speed transonic airplanes. When you climb up above transition
and reach th ealtitude where the airplane is mach limited the rules
changed.
I've attached a diagram of a typical flight envelope showing the constant
indicated max/min speeds up to transition where they taper in. The point in
dashded lines at the top is the point Bob was talking about where both
happen at the same time. To maintain a margin a max altitude dictated by a
G is determined. Going to fast or sow or pulling too much G at or near max
will result in a buffet and loss of lift, just for starters.





I've just reposted this because I've gotten some e-mail complaining that
the attachment didn't come through. I'll repost that in
alt.binaries.pictures.aviation


Bertie