Originally Posted by
threemiles
I read it that this must be shown only for speeds between minimum for steady, unstalled flight and VLO/VFE. MCAS operates when flaps are retracted. The rubber word "appropriate" may be the secret.
But... 25.173 is for static longitudinal stability, the item of note is mis trim case which comes under 25.255 and that has a further set of criteria which if anything are inadequate for this case, or the underlying potential to get out of trim that exists on the B737 in general. The MCAS is covered in 25.672 and either will be determined to meet the requirement or be inadequate to show compliance with that. The out of trim case that resulted from the characteristics of MCAS is the major concern IMHO, which raises the matters of unloading the stab etc, which has it's own set of questions. That nexus is going to take lawyers to sort out, and that is not good for the operational outcome. That an aircraft can get out of trim excessively is not purely a Boeing matter, the Max just happens to be the current headline. A few years back it was A320's like the Perpignan event, a departure or two out of Reagan, and before that, it was A310s galore in-dispersed with A300-600's. Some of those ended up in smoking holes, some missed the ground on a number of occasions in the same event. If the conditions can occur that the pilot is at odds with the plane, it deserves more than a passing comment in the FCTM or a note in the FCOM.