Quoting DL-EDI:-
"Is the "first duty" nowadays to listen to the systems or is the "first duty" still to fly the aircraft and use the systems as tools to achieve that end? Hasn't the latter been the general philosophy since the first instrument was added to an aircraft?"
The professionals on here can advise you better, DL-EDI - but my understanding is that in this sort of situation (autopilot/autothrust 'sign off,' 'unreliable speed indications,' etc.) the PF should 'fly pitch and power' (basically keep the pitch attitude at an appropriate level to maintain altitude and (given that one of the few things we can be certain of is that the speed indications had gone haywire) manually apply the correct throttle setting to maintain flying speed). The duty of the PNF, as shown above, is to work through the warnings/messages so as to inform the PF as thoroughly as possible on what has gone wrong. So it's a mixture, with the emphasis on keeping the aircraft at a correct attitude and at a safe speed until (hopefully) the instruments come right (in this case, first and foremost, that the ice in the pitots and ports hopefully melted).
That's the way the AF447 pilots reacted; and it looks as if the PF did in fact manage to keep the aeroplane level and maintain airspeed for some 18 seconds; in other words, 'fly pitch and power' in accordance with the recommended procedure. I've no doubt that, if and when we ever get details of the CVR recording, the two pilots will have been going through the procedure illustrated above - checking each message/warning in turn, trying to find out what had happened/was happening.
What we DON'T know, of course, is what other instruments may have been misbehaving, in addition to the Air Speed Indicators.
Then came the (so far unexplained) zoom-climb, with no evidence of any sidestick input from the PF. Again, the PF appears to have 'done the right thing,' countered the zoom-climb with forward stick and pretty well levelled the aeroplane out again. Further, at some point during this period (the BEA 'neglects' to inform us when this process started and finished) the "Trimmable Horizontal Stabiliser' (what used to be called the 'tailplane' in my day) unaccountably went to 'full up.'
Finally, the stall warning sounded - and once again the PF appears to have 'gone by the book' as it applied at the time, carrying out the recommended procedure at the time - full Take- Off/Go Around power and try to maintain level flight.
At some point during this phase the "Trimmable Horizontal Stabiliser' (what used to be called the 'tailplane' in my day) went to 'full-up'; which would have made it just about impossible to maintain level flight. There have been several accidents due to that happening; Perpignan was one (though pilot error was definitely involved in that accident as well). Another was an MD80, Alaska Airlines Flight 261 - this accident was put down to lack of maintenance, the un-lubricated jackscrew operating the THS first of all jammed with the THS at a 'nosedown' setting, and then broke off altogether. For the record, the Alaska pilots had both to haul their columns back with all their strength just to maintain some sort of level flight, just from the 'down' THS attitude, even before the THS actually broke).
Alaska Airlines Flight 261 - Wikipedia, the free encyclopedia
TV dramatisation here too if you fancy watching it - though I warn you, it's long.........
Trouble is, due to what I will politely describe as the BEA's 'reticence' on the contents of the FDR and the CVR, we can form no opinions on what caused the zoom-climb. That brings us to the main difference between modern airliners (particularly Airbus, though Boeing are moving in the same direction); that older aircraft types always left the pilot with the final word; whereas modern 'systems' are designed to overrule them if the systems 'conclude' that the pilots' actions are in some way endangering the airframe or doing other things that (in the opinion of the designers) are dangerous.
Both Boeing and Airbus modified their 'stall avoidance' procedures soon after AF447 went in; the drill now is 'adjust power but don't necessarily use full power, concentrate first on getting the nose down.'
Hope some of that helps.......