HN39;
Originally Posted by HazelNuts39
2 h 10 min 42 -- La vitesse verticale est de 1 900 ft/min et la vitesse verticale sélectée est de 1 300 ft/min.
La vitesse verticale refers to the Vertical Speed indicator on the PFD. The IVSI, (Inertial Vertical Speed Indicator) on the right indicates climbing at a rate of 800fpm.
The
la vitesse verticale sélectée refers to the Vertical Speed Selector knob located on the FCU, (Flight Control Unit), shown below. The VS shows a selected rate of "2500"fpm.
This knob also sets the FPA, (Flight Path Angle), when the HDG-VS/TRK-FPA button is toggled to "TRK/FPA".
For these FCU controls to have any effect on the aircraft, the autopilot must be engaged.
Just to acknowledge,
DJ77 describes the function in his post above, and mentioned correctly that the VS resets instantaneously if the FDs become available.
The difference referred to here (1900fpm, vice 1300fpm) merely refers to the difference between the indication on the PFD, and the VS setting in the FCU window. I'm unsure why it is mentioned in the report except perhaps to indicate that the FDs were at that moment, functioning.
ADD EDIT after examing page 114:
There is an "ADR" and "IR" vertical speed selection I see. The Vertical Speed has two components which work together to provide the most accurate VSI - a barometric component and an inertial component. The parameter is showing the switching between the two.
I made a cursory examination of what was occurring in the data at the time the Vertical Speed indication switched from IR to ADR and it appears to be the point at which the stall had fully developed, at 02:11:47 or so; a number of other parameters change significantly at this point as well. The THS had reached its maximum setting, the thrust levers were momentarily closed to idle and the engine N1s reduced, (but not to Idle), and the stall warning was inhibited for reasons with which we are now familiar.
