Hi all,
Took a day's "sabbatical", getting too involved...
Originally Posted by
Graybeard
DWBirgenair was different, because the lower ranked FO knew what was happening
As did the PNF in this case, judging by the CVR.
The FO could have overpowered Capt. by pushing harder on the yoke. Could he have done that with a joystick?
If he'd called "I have control" and pressed the priority button, of course he could have. The issue for the Birgenair F/O, as it was for the AF447 PNF was that he wasn't assured enough of his assessment of the situation to take positive control and hold it.
As for your argument that the 777 backdrive can fail: it's built to the same safety standards as the Cat IIIc autoland, i.e., 10 -(7?) probability of undetected failure.
As are the Airbus systems, so why trust one system and not the other?
Originally Posted by
xcitation
are you saying that the nose ups did not cause the stall warning.
I'm saying the stall warnings were triggered by the flightpath, not the input - so to say the situation regarding stall warning needs addressing is true, but to argue that the stall warning significantly and repeatedly stopped the PF from doing the right thing (nose down) because the warnings were triggered *as a result* of his nose-down input is untrue.
Fair enough in its way, Dozy, mate.
But looking at it another way, for a bit longer than aeroplanes have been around, bicycles have. It would be perfectly possible, with today's 'electronic aids,' to design a bicycle that didn't need handlebars; so that the rider could turn just by 'body lean,' with his/her hands in their pockets....
But no-one has yet designed a bicycle that works that way. I'd venture to say, because yer av'rage rider would get a bit confused......
But in fact there have been plenty of alternative bicycle designs that riders have adjusted to (I see them every time I'm in town), so I don't see the correlation.
So precisely WHY, in your opinion, did Airbus opt for 'no feel/no feedback' etc.? A revolutionary change, after the best part of a century of producing aeroplanes that all 'worked' the same way?
My own view is that it was a matter of 'less weight/lower cost.' I can't think of any other reason?
Maybe you can?
Well yes - for a start there's systems complexity, which is the engineering axiom that for every feature you introduce, what comes with that feature are additional potential points of failure. This was the first FBW airliner - it follows that you'd want to keep the systems as simple as possible. These requirements had been drawn up since 1982 *with input from pilots*, who didn't think that going from yoke to sidestick would be a big deal. Indeed, if it was as big a deal as some make it out to be, why have there been no hull-losses caused by the lack of interconnected sidesticks, and why is there clear evidence that at least one airliner with "classic" controls suffered the same fate?
What bugs me about the whole Airbus FBW deal and how a specific subset of the piloting community perceives it is that it started with the press. It was the press that started asking questions like "How long until we have a pilotless airliner"? It was the press that was used to spread misinformation such as "The A320 thought it was landing and overrode the pilot". Over the years I've looked into it I've seen statements from otherwise sane men and skilled pilots that include rubbishing the A320 versus the B737 by comparing the Citroen 2CV with the Ford F-100. I've read assertions that Airbus make "plastic planes" that will disintegrate at the first sign of trouble despite the fact that the first A320 to crash mushed into a forest and remained intact, an A320 landed on the Hudson and everybody got out, and that the only airliner to survive a missile strike and land safely via engine power despite the loss of all hydraulics was an A300. I've seen accusations that Airbus are the only manufacturer to try to influence the outcome of accident investigations despite the infamous DC-10 "Gentlemen's agreement" and Boeing's efforts to pin UA535 and USAir427 on pilot error in the '90s. All of this has been borne from a prejudice that seems to stem from the idea that Airbus have been trying to sideline pilots - including by introducing the 2-person cockpit (not true - the first 2-crew aircraft were the BAC 1-11, DC-9 and Jurassic 737), by introducing complex computer systems that pilots were unable to understand (again, not true - the first accident caused by overreliance on a sophisticated autopilot was EAL401 - an L-1011, and another famous one was AA965 at Cali - a B757) and by designing and building an aircraft that was a "beancounter" and engineering dream, but froze out pilots in the design process (see before - pilots were involved in the A320's requirements-gathering phase). I've also seen plenty of references to Bernard Ziegler, and some of the less-than-clever (with hindsight) things he said, but very few references to Gordon Corps, who was a pilot's pilot and very much enthusiastic about the A320's potential.
All of these misconceptions could have been avoided by doing a little reading and finding out what the actual state of affairs was, but instead the easy option of bashing Airbus for apparently being anti-pilot, anti-safety and (God forbid) French seems to still have a surprising hold amongst some pilots, and all of it came from the same lazy reporting that is so frequently decried on these forums when the press gets something wrong.
I know some on here probably see me as an apologist for Airbus and for technology, but I can assure you I am completely neutral - I just can't abide prejudice that stems from being misinformed.
That’s the contradictory bit. As far as I can see, from the chart on page 111, the THS movements simply weren’t ‘consistent’ with the pilots' inputs at all. Indeed it appears only to have made the one movement – to ‘full up’- during the whole episode.
If you follow the general trend of the inputs over time, you'll see that the THS was just doing as it was designed to do - compensate for the pilot's inputs and hold trim accordingly. The problem is that if you compare the amount of flight surface movement commanded by the FMC to maintain altitude and heading in turbulence with the amount that was commanded from the PF's sidestick following FMC disconnect, you see a glaring difference. The THS did what it did because the PF was inexperienced at high-altitude manual flying and was overcontrolling.