Originally Posted by CONF iture
Speculation only from HN39
Originally Posted by CONF iture
Still waiting for the reference stating phugoid damping under high AoA protection but none under pitch command ...
Originally Posted by HN39 #707
Phugoid damping is a feature of the alpha-protection mode, because an airplane is prone to develop phugoid motions when constrained to a commanded angle of attack. Flying an airplane to a commanded pitch attitude does not result in phugoid motion, and therefore pitch-command mode does not require phugoid damping.
Firstly, both the Bilbao report and the Hudson river report mention phugoid dammping explicitly for the high angle of attack protection mode. If you have a reference stating that it is a feature of the pitch command mode then please provide that reference.
Secondly, I explained in post #707 why phugoid damping is necessary in alpha-prot and unnecessary in pitch command mode. I showed a phugoid motion that results from maintaining AoA after a disturbance of a steady flight condition. On the AF447 thread I showed similar simulations of airplane motion at constant pitch attitude after a pitch change, for example:
