Displaying alpha is only truly useful when the applicable limits are also displayed. Stall alpha at altitude is much less than at sea level, best seen by observing the slow march of the "feet" (low and high speed buffet boundaries) towards each other as you climb.
The MD 11 (and the B717) displayed a useful alpha indication by virtue of the permanent display of PLIs (pitch limit indicators) on the PFD. At all times during flight, the pilots had a clear indication of how much alpha was available - I say alpha rather than pitch, because the PLIs tended to 'float away' from the pitch attitude at low level more so than at high level. That came about for two reasons: first, the difference in the alpha envelope and, second, reflecting the difference in dynamic predictions and steady state alpha with altitude.
I can no longer remember whether there were circumstances such that the PLIs may have been inaccurate, although clearly it is possible. Certainly it would be affected by the altitude (static) input, but I don't think it was influenced by the speed (pitot) input.
But to use it, you had to
look at the PFD and
see the attitude - something that unfortunately seems to have disappeared from the skill set of our younger pilots, to be replaced by "magenta fixation" - whether it is the FD or the track display!
