You're right, Jim, but the SOPs would be to fly only as high as you can,
safely. The Tornado GR1/4 flies just between Mach buffet and pre-stall buffet
in some regimes -- heavy, high and with wings forward. So you adjusted your
flying: not too high when heavy, and with wings slightly aft of fully forward.
In fact you adjusted your wing sweep to give you the best cruise AoA for the
IAS that you wanted. On the way home from a 2hr sortie you would cruise around
7,000 ft higher than on the way out, using less fuel but doing a better Mach No
and groundspeed.
I don't believe that an airliner would be dangerously close to the stall in the
cruise, but I'll ask some airline pilots I know.
Chris
On 26 Aug 2011, at 06:23, Jim Nichols wrote:
> I trying to recall something I read a number of years ago. In an upper
> corner of the flight envelope, the cruise AoA can approach the stall AoA.
> Think of it this way: The aircraft weight does not change, except for the
> fuel that is burned off. As you climb to jet cruising altitudes, the air
> density falls rapidly, so the dynamic pressure, or "q", falls off as well.
> This means that, in order to support the weight, the wing requires higher
> and higher angles of attack. When the flight AoA approaches the stall AoA
> for the flight Mach number, it takes very little stick force to get into
> trouble. For crews flying fly by wire systems with computers in the loop,
> they very seldom experience the subtleties of hand flying in this regime.
> Loss of pitot pressure on a dark night under such conditions is a worst-case
> scenario.
--
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