Originally Posted by
RetiredF4
could you point me to the indication, that the THS is moving? THS is the blue straight line on the bottom?
You need to be zoomed right in, but you can see movement in the THS line after an elevator movement of any size. Unfortunately, due to the low resolution of the image in the PDF it only shows as a series of 1-pixel notches in the line, but there is definitely a correlation between elevator activity and those notches at that point. Earlier in the sequence , those notches appear just prior to movement of the THS in reaction to elevator movement. Even a small amont of elevator movement seems to trigger them, but the elevator commands need to be held for a significant amount of time before the THS will respond in anything other than increments which are barely perceptible at the resolution in which the graphs are presented.
But by chance, how should THS move when after 15 sec. of SS ND the elevator peaks max at -15°NU (the magenta line)? Would the THS start moving prior elevators move to the ND range? How long is SS ND and in what magnitude required to get the elevator in a ND position?
In all honesty I don't know, but if you look on page 111 of the French report, you can see the sidestick traces, directly below which is the elevator response, and directly below that is the THS, which gives a nice representation of how the autotrim works. Notably, the big THS movement happens during a time in which some quick "blips" of nose-down are made, but the overriding trend from the sidestick and elevators is for nose-up, and so the THS follows that.
Originally Posted by
ChristiaanJ
What personally bothers me, is that the report does not stress sufficiently that the quoted "airspeeds" are those measured by the ADS and displayed in the cockpit and recorded on the FDR, and NOT the real airspeeds.
Originally Posted by
mm43
CJ;Exactly, ... and if they had done so they would have provided the reason why they are different.
Well, this is an *interim* report after all, and in the FDR traces, below the indicated airspeed (both "conventionelle" and "I.S.I.S"), they have included the ground speed trace, which gives a better picture of what the actual speed would have been.
@JD-EE - I'm pretty sure that "Assiette" can refer to pitch or trim, but in this case I think it means pitch. If it is a valid trace then yes, the nose fell down, but I suspect not in a controlled manner. In any case, the THS position, along with that of the elevators meant that as soon as the nose was down it would immediately come back up due to aerodynamic forces.