I took a break. Several things are obvious upon reading to catch up. So I've caught up and herewith deliver this word bomb.
Nothing's changed, at least through the morning of the 6th.
(wordy annecdote)
There seems to be a lot of oversimplification in fields I work or have worked. For example, in some systems you cannot use "voting" type redundancy. The GPS satellite FSDU, Frequency Synthesizer and Distribution Unit, that takes the Rb and Cs clock 10.23MHz signals and applies carefully modifications before distributing the system clock to the two independant clock busses on the bird. There was a passive frequency distribution network from the clocks to the frequency synthesizer inputs. It combined all clock outputs into the three synthesizers' inputs. Since a 10.23 MHz sinewave is not something you can vote about only one clock and one synthesizer is powered at a time. (Otherwise you would get unacceptable spurious signals even with very high quality electronic relays to select clock signals.) I had to design for about 120dB isolation hoping to get at least 100dB. That's a 1 trillion to one isolation ratio as the target and 10 billion to one as a target. Trust me, clocks and synthesizers not needed were turned off. The outputs were all in parallel with a circuit designed to not short out the output bus if a transistor failed short circuit or open circuit. So that was, in essence, a passive voting system. The powered synthesizer drove the bus. With two busses a failure on one bus let the other survive and take over the full job. (/wordy)
PJ2 likes the first step of the UAS scenario concept. It fits very well when you consider it's claiming coincidence for all three pitots to fail the same way at the same time. If the PF side, which we do not see, showed even a brief overspeed just as the aircraft disconnected that would be the last thing the PF saw and he might have over trusted it. The off-again-on-again-finnigan stall alerts certainly could foster the view that they were spurious when overspeed actions fix what stall actions seem to bring back.
bearfoil wants and "easy" switch. It appears AirBus has patented such an idea. Way back in the June 2009 "era" of this discussion the idea of using the INS and GPS as a backup to the pitot tubes was broached. It was denied. Everyone figured long term, for which it cannot work. For short term, say a couple minutes, it should work just fine as an extrapolation tool. ABI seems to be planning to use this or is using it, likely on the A380. That's as "easy" as it gets. Warn the pilots to be on their toes and more attentive than usual. But fly through the mess, AoA, Thust, and GPS/INS. If at least one of the pitot tube readings does not become "sane" within 2 or 3 minutes or of altitude hold is too difficult then let the pilot ease into control. He's had a couple minutes to become well aware of what has been going on.
(By the way, the "easy switch" is the path towards a fully robotic plane, you know.)
BOAC seems to still desipise the glass cockpit and FBW. Right or wrong it is not going to go away no matter how much he rails about it. On a per million miles basis the glass cockpit in the A330 line shows half the accident rate and hull loss rate of the Boeing competitor he loves so much. Those are VERY loud words in mute bare statistics. I'd have more sympathy for him if the statistics were reversed. I suspect he will see a two person "executive" cockpit before he sees a return to cables or direct control. (The executive makes executive decisions about where the plane goes, never "files it", and is there rather than on the end of a long string of satellite relays away from Nevada. The other person is the relief executive. Both are trained with three special skills, giving the executive direction to the aircraft if something odd happens, telling the world about these changes, and reading the radars. He might even be trained to push a button to switch from one set of computers to another if something extraordinary were to happen.) It seems to me that is the direction it is all moving. And when the electonics can handle a hole blown in a plane with the plane still marginally flyable it will happen. "Get over it."
Confiture is remarking about the pilots seeming unawareness of what each was doing. If the quiet cockpit the BEA release conjures as a vision is real, at least one new feature must be trained into pilots: thinking out loud. Announce what you see and what you are doing about it. And acknowledge what the other has said. If that oddball scenario I mentioned above with PF seeing something quite different from PNF and recorded left seat only data then such an announcement of observation and intended action could have saved the plane.
PJ2 reposted (this time), for the Nth time, the schematic of where the various sensor signals go. I guess after RR_NDB's comments about redundancy it's time to wonder what makes the pitots redundant with only one going to any given ADIRU? I hope somebody did the numbers and decided this was better than feeding all three to all three ADIRUs. Or else there are data feeds between ADIRUs that are not shown. Anyway, I'll run an idea up a flagpole. Display all three to give speed with an error band with special displays for lost channels. Then there would be no chance PF would see something different from PNF. (I'd add a fourth channel to the picture, the consolidated GPS/INS report corrected for the last known calculated air speed.)
And we have the bozos who setup the cirriculum for AB330 pilots teaching them to keep their grubby paws off the trim wheels at all times and the designers who told the software people to never resume autotrim once the pilots mess with the trim wheels. Oy vey!
Detail regarding Captain seeing over shoulders of the PF and PNF: Note that he was found floating. The others were found belted in. He was probably standing observing closely.
As a hint for people who have a new thought it would be smart to revisit the BEA release and work it into the last 6 minutes and 21 seconds of the plane's flight. Ask, "How does this fit?" It might prevent your looking like a bonehead. (bearfoil continues his attempts at this proof.)
bearfoil, "Certification is mainly a mystery to me; I trust the system to certify a/c to be safe and reliable."
Sir, there is no such thing if you mean "never fails". The only way to achive "never fails" is to "never try." Stay on the ground and never fly. Then something other than an airplane will kill you.
Originally Posted by Mr. Optimistic
Bear, all I can say is that they have my blessing: they were intelligent, trained and wanted to get home.
Originally Posted by bearfoil
It is so reassuring to hear you say that, it is in short supply here.
Certainly not intentionally from me, bf. That is why I concentrate so hard on why they performed the damnfool stunt looking in training for the answer.
It's clear "what" killed the plane and the people aboard it. What is not at all clear is "why?"
Mr. O and bf mentioned "protections". They are NOT protections. They are limits. Calling then protections gives a false sense of security. I sense this all through this discussion, by the way. There is too much, "It can't fail." Can't is a very very big short contracted pair of words.
Originally Posted by PJ2
While cockpit design, cockpit displays, ergonomics, and aircraft/system drill and checklist design will influence outcomes, a "Standard" way of accomplishing complex tasks under both time and operational pressures reduces the potential for error. I know very well that it doesn't always work that way despite best efforts.
I remember asking WAY WAY WAY back in the June 4 2009 thread about some of this. If there is a standard drill for handling a plane in an unusual condition why does the plane not do it itself rather than expect the under informed (for instance no AoA) humans to take the load? There should be a better way.
Originally Posted by PJ2
This is the standard Aviate, Navigate, Communicate rule that we have seen mentioned.
Please forgive me here if I "bitch" about this a littlte. You have a TEAM in the cockpit. They are not telepathic. As you aviate tell your partner what and why. Think out loud, as I said above.
Originally Posted by bearfoil
I am amazed that so distinguished a group as this one hasn't thought the PF was indeed acting on bad data (not his "fault"), and was doomed to a guessing game either way, No?
Do you read more than you post or do you post more than you read? (As it happens I rementioned this above.)
Quoth ChristianJ, "Personally just looking forward to the next BEA report... and the way that will put the fox among the chickens, once again."
Amen.