Originally Posted by HN39
There is no evidence at all that these updraft velocities existed in the CBs that AF447 was trying to avoid, nor that they were actually encountered.
If I may be pedantic for a moment, the absence of evidence is not evidence of absence.
The range of potential updraft and downdraft magnitudes you present, (28 kt to 60kt, depending) bounds the issue wally is pointing to well enough.
There is no reason to believe there wasn't some vertical movement in the vicinity. The questions are:
a. Did they hit a patch of it at some point during the event?
b. What was the magnitude?
Vertical air column velocity, were it encountered, would vary from about 2800 fpm to 6000 fpm based on the numbers you offer in your response to wally. That cannot account for the 7000 fpm climb by itself. It seems pretty obvious that the "big climb" was an energy tradeoff, if not in whole than at least to a substantial degree. There may still have been some vertical airmass aiding and abetting this excursion.
Take the smaller magnitude, for example. Assume for a moment that the plane encounters a 2800 fpm up draft as the pilot has begun to operate in alternate law. To get the 7000 fpm vertical rate, the pilot contributes about 4200 fpm to that via trading energy for altitude ... that's a hell of a change from level flight.
If the magnitude of air column movement is at the higher end, 6000 fpm, then the pilot (or the pilot and the plane, if that's how one sees this event) contribute about 1000 fpm to that dramatic initial climb toward 37,000 plus.
That climb input fits wally's 1000 fpm standard, doesn't it? Sure, but one still needs to consider the pitch attitude. As I was trained, when penetrating turbulent air in instrumnt conditions, you set a pitch attitude (wings level) and do your very best to maintain that pitch attitude as you get bounced around, until you get to the other side of the turbulent patch of air. The FDR data points to attitude increasing, not remaining at a particular value.
Given that data, it is unreasonable to assert (wally) that an updraft is the sole, or even primary, cause of that initial rapid climb.
That doesn't mean that vertical air movement necessarily had no input. It's an unknown, but there may be some indirect evidence that BEA can analyze to get a better grasp on that.
A gust load of that magnitude from outside would, I think, leave a trace in the g sensed by the flight control system. Whether or not this is a parameter captured by FDR is another matter. I don't understand the FDR well enough to say. I also don't grasp how the flight control system filters such external loads in the various laws.
OK's point on rate and dampening suggests to me that the system does filter of such external inputs, perhaps as part of the stability features.