Re, "
and try to figure why one airline does this and one airline does that."
Now that's a question.
In a word, the manufacturer has no actual authority over what airlines do with their airplanes or how they fly them. The manufacturer writes what it considers the operating procedures for their product. Airlines are free, within a country's regulations, to change the procedures as they wish. They are of course accountable for such changes but the notion of "accountable" is often freely interpreted.
Most stick to "the book" and make small modifications. Some increase "guidance", and some simplifiy it. Line flying proves the procedures and it's why at an airline these things never stay the same...change is the only constant at most carriers, as learning from incidents and even accidents takes place.
Practically speaking however, an airline isn't free to radically alter the manufacturer's operating instructions, not, at least, without placing itself at risk should something occur. But some crazy things do emerge from airline folks who believe they know best...
Individual incidents and seeing how such incidents enable change is interesting enough and well understood within the industry but it's well worth finding some of the authors known for producing good work on flight safety to understand how the process works; for example, Charles Perrow, Sidney Dekker, Tony Kern, Robert Helmreich, Earl Weiner, the publications of the Flight Safety Foundation, the NTSB, (look up NTSB Docket). Such work has been used in the healthcare industry and also in medicine in recognizing that "human factors" aren't limited to only one industry which has risk associated with it.
At times, some modifications by one carrier might not make clear sense to another, or to many others. But the requirement to conform closely either to others or to the OEM SOPs doesn't exist even as the results may themselves be similar.
Such modifications are often positive, as many airlines have more experience operating a manufacturer's aircraft than the manufacturer does - the manufacturer must get the product certified according to standards already discussed here and elsewhere. The airlines must teach its pilots to operate the airplane safely and within the regulatory environment.
TurbineD;
Re, "
Information was available to airbus pilots explaining UAS as resulting from pitot tube icing starting with the A-300-600:"
Absolutely correct.
I see now that even the QRH UAS memory item in the above drill to increase pitch to 5° when above FL100 is being questioned and instead indicating that no change in pitch and power should occur during the drill.
However, the "do nothing, maintain pitch and power" response by the crew was already in place in some flight crew training manuals and presentations which provided instructions on how to handle the procedure when the "
safe conduct of the flight is not impacted", which it is
not in stable, level flight at cruise altitude.
As you know I've maintained from the time we knew what transpired that the UAS drill was confusing and misleading if followed "precisely" - but thirty other crews knew what would happen to the airplane and it made no sense whatsoever to pitch the airplane up at all...just keep doing what it was doing prior to the failure of the pitot, and, as you point out, the airspeed information returns to normal, (as AF447's did, within about 50"). I subsequently found the Airbus presentation cited below which makes this clear.
First, from a number of FCTMs:
->>>>>> enlarged printing ->>>
From an
Airbus presentation in 2006 on the UAS issue:
->>>>>>>>>from the same document->>>>>>>
