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AF 447 Thread no. 4

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AF 447 Thread no. 4

Old 20th Jun 2011, 20:12
  #221 (permalink)  
 
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Lonewolf_50 writes :

the system not working as advertised
Yes, my set of hypotheses sees it having worked as programmed, not as expected, even by its designers, making the expression by design completely meaningless.

Lonewolf_50 again :

electrical ghost faults
Going further into detail, I am of a mind that the WRG message is not a physical wiring fault, but a communication problem, software-related, between PRIM2 and ADR1. This would therefore not be a ghost fault. It would be reproductible.

One would need to mount the whole identical system (all computers, soft versions, P/N, etc...) on a simulator and introduce the specific 10 seconds monitoring process, and see what happens. This 10 seconds process being likely the only case for which communication breakdown would occur between these two computers.

GarageYears remarked :

I seriously doubt the control law in effect was Normal during the "zoom-climb" event
You are certainly welcome to show this healthy skepticism regarding the whole PRIMs sour business I have posited.

May I summon A33Zab great technical information for help ?

There’s only 1 PRIM in control and that will be the one which can deliver the highest possible law and in the sequence PRIM 1, 2 & 3
(emphasis mine)

This means Normal law is preferred over any inferior laws. This is the very core of this flight controls design.

If PRIM 2, in your view, is in control and able to deliver NORMAL LAW this means that PRIM 1 was not able to compute NORMAL LAW protections
Quite right, except PRIM1 is not faulted before 02:13. Which PRIM becomes master if PRIM1 is ALT2 and PRIM2 is Nz ?
In my view, at that time PRIM 1 was in control, PRIM 2 and 3 couldn’t compute NORMAL LAW either.
Due to the PITOT problem they had all the same ADR information.
With all due respect to your extreme technical knowledge, may I introduce this disagreeing parameter ?
WRG:ADIRU1 BUS ADR1-2 TO FCPC2

This means PRIM2 does not have the same ADR set available to it than the other two PRIMs have.
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Old 20th Jun 2011, 20:21
  #222 (permalink)  
 
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Originally Posted by Svarin
At the end of these 10 seconds, each PRIM will either confirm and latch Alternate 2 or revert to Normal law, based on differences between ADR values. This is the purpose of this 10 seconds checking. This happens at 02:10:15.
Hmm, but if Normal law was available again, wouldn't there also have been the stall-protection active again ???
From what is happening in the next two minutes I do not see much what resembles the expected reaction of Normal Law, given the AoA and speed.
Could you point me to any single behaviour that you would logically expect in Normal Law ?

Somehow, this theory strikes me as a bit strange.
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Old 20th Jun 2011, 22:08
  #223 (permalink)  
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We have a whole bunch of disagreement on this from those who claim to know the system, and I wonder what chance two lads had in the middle of the night in the ITCZ?

Cold anyone venture a definitive answer to what they had left in baro terms with those ACARS warnings?
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Old 20th Jun 2011, 22:27
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the probable cause of this accident was preoccupation with an inflight malfunction and failure to monitor properly the airplane's flight instruments which resulted in losing control of the airplane.
The flightcrew's statements about the ADIs failing were not substantiated by the facts. It is most likely that the flightcrew became spatially disoriented during the upset.

They were unable to believe the information displayed on the ADIs, did not recognize the unusual attitude of the airplane, and were unable to take the correct action to recover the airplane until it began to emerge from the clouds.
The increased automation has not necessarily reduced pilot workload, however, but has shifted it to monitoring tasks which the pilot formerly had to perform, and there is evidence, from both research and accident statistics, that people make poor monitors.
Research also indicates that the excursion from a stabilized condition might be exaggerated even after a system anomaly is detected, because of the period required for a pilot to transition from system monitor mode to system controller. Time is needed to "ascertain the current status of the airplane and assess the situation," 13/ before the pilot can reenter the control loop and take corrective action.
The above is not a new AF447 leak or even Airbus related. It is from the 1985 NTSB report on the China Ailines 747 loss of control initiated by a single engine failure at altitude. (my bold)
China Airlines B747SP Loss of Power and Inflight Upset

Fortunatly they did break out of clouds in time to recover, although with some injuries and extensive damage.
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Old 20th Jun 2011, 22:37
  #225 (permalink)  
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Originally Posted by Svarin
My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law.
So PRIM2, which is missing on set of ADR data completely (according to this interpretation of ACARS messages), doesn't care about the missing data and computes with only 2 sets as if there had been always only 2 available and never 3? I'd rather expect that, given the importance of the these data, PRIM2 would be less likely to return to NORMAL.
 
Old 20th Jun 2011, 23:04
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MurphyWasRight;

Well said.

It is time to stop trying to apportion blame to aircraft systems, and time to take a long hard look at the automation ~ human interface. It has often been said in these threads that the automation is 99.9^n% right, and now is the time to look at the human interface and the the well known fact that the same degree of reliability is and can not be expected of mere mortals.

We have spent endless pages arguing over which pilot was seated where, and which of the two F/O's was PF. There is no need to go there in the meantime, but the outcome may help in determining who was where.

I know this Aviation Weekly & Space Technology link has been posted by PJ2 previously, but it drew no response. I suggest that it is read and digested, compared with the China Airlines incident that MurphyWasRight has mentioned, and let the discussion start on training and how to keep the pilot in the automation loop.

I suspect that the crux of this accident is not hardware or software, but a human condition, i.e. industry, management, training and CRM, that needs to be addressed.
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Old 20th Jun 2011, 23:26
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Originally Posted by svarin
At the end of these 10 seconds, each PRIM will either confirm and latch Alternate 2 or revert to Normal law, based on differences between ADR values. This is the purpose of this 10 seconds checking. This happens at 02:10:15.

My take is PRIM2 reverted alone to Normal, while PRIM1 & PRIM3 latched Alternate 2. This is because PRIM2's set of ADR data, being different (only ADR2 & ADR3), would have allowed differences into the 50 kts range that triggers reversion to Normal law.
From BEA's explanation of PROBE PITOT fault message (Interim #1 p.51):
This message, transmitted by the FCDC2 (EFCS2), means that the FCPCs (or PRIMs) triggered one of the speed monitoring processes: they have detected a decrease of more than 30 kt in one second of the “polled” speed value. The three ADRs were considered valid by the EFCS2 at the time the monitoring was triggered, because the prior rejection of an ADR would have generated a class 2 fault message and there would therefore have been an asterisk in front of the source. In this case, the “polled” value is the median value.

At the time this monitoring is triggered, the FCPCs open a window during which they operate with alternate 2 law (see following graphic). The rudder deflection limitation function is also frozen, but the associated alarm is inhibited. At the end of the window, if the difference between the values polled at each end of that window is less than 50 kt, the FCPCs return to normal law. Otherwise, they continue in alternate 2 law, the rudder deflection limitation function remains unavailable and the corresponding alarm is generated.
Note: the alternate 2 control law is a load factor law for pitch and a direct law for roll. Only the load factor protection remains available. In certain cases, the high and low speed stabilities may also be lost.
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Old 21st Jun 2011, 00:02
  #228 (permalink)  
 
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Basics

BEA put out their initial findings to quieten the press clamour, as predicted in thread 3, all is quiet as they complete their investigation, at which point speculation can stop, and discussion begin .. I say that with no disrespect to some very informed input from some people here .. others less so.

If we, as aviators, look back to brass tacks, not one of us would want to be in the situation whereby we are trying to figure out how an aircraft is trying to stop us from having an accident, whether that is through protections, stick shakers, buffet .. whatever, brass tacks is about making the decisions to avoid being in a position where those protections kick in, here I err towards the rational of those pointing out the deviations of previous aircraft, and the personally observed fallability of AWW. From first reading, there are issues that will become clear when the final report is issued, they will probably focus on training and awareness rather than discuss big red buttons to give the airplane back to the pilots.

The wider point is surely, that loss of situational awareness took THIS aircraft into a regime that it could not make sense of, and took the crew and passengers with it, where as other aircraft did not encounter the same conditions, primarily by not being there in the first place.

Whilst all the technical discussions as to what the aircraft, crew, and training culture subsequently did to neautralise a dynamic situation are appropriate to patching the responses in future, (even if the effect turns out to be that under stress all those protections cancelled one another out) it is surely the avoidance of the situation in the first place which closes the first hole in the Swiss cheese model.

Lets wait for the report.

Last edited by Teddy Robinson; 21st Jun 2011 at 00:03. Reason: Sticking F ...
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Old 21st Jun 2011, 01:47
  #229 (permalink)  
 
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Whilst all the technical discussions as to what the aircraft, crew, and training culture subsequently did to neautralise a dynamic situation are appropriate to patching the responses in future, (even if the effect turns out to be that under stress all those protections cancelled one another out) it is surely the avoidance of the situation in the first place which closes the first hole in the Swiss cheese model.
Of course well spoken (all the stuff I left out of the quote), but it is well to remember that it is harder to prevent the initiating causes then it is to provide mitigation or accomodation to these surprises.

I think about all the stuff that can go wrong every time I fly, but in the end I convince myself that even average pilots can save the day.
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Old 21st Jun 2011, 04:36
  #230 (permalink)  
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but in the end I convince myself that even average pilots can save the day.

Indeed, most of us would be far more concerned about getting killed driving to and from the airport - although I sometimes shudder at some of the third world operators into whose tender care I have entrusted my life over the years.

Risk principally is tied up with probability/seriousness of outcome/exposure period/frequency. It is human nature to accept mitigated risk. Caveat - young men, being programmed genetically to be less worried about risk than the rest of us, might tend to be less concerned about the mitigation bits and more about the adrenaline buzz.

We just have to accept that, every now and again, the ducks all line up nicely to give Lady Luck a clean shot at the heart. It is this phenomenon which drives much in the way of regulated technological development.

There are no guarantees, only probabilities.
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Old 21st Jun 2011, 07:01
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Originally Posted by john_tullamarine
There are no guarantees, only probabilities.
Absolutely 100% spot on.

If when something unusual happens (figures plucked out of the air for effect)

the plane is 99.99999% reliable
SOPS are 99.9% reliable
A captain 98 % reliable
A first officer 90% reliable

You are going to get occasions when you lose the aircraft. Fortunately on the rare occasions that the plane gets it wrong one of the pilots has a clue, it should come as no surprise that sometimes both of them don't.
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Old 21st Jun 2011, 08:01
  #232 (permalink)  
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john;

There are no guarantees, only probabilities.
Yes, and possibilities. The notions can be complementary or independently considered. It may be possible but not probable, it may be possible and probable and the other way around. The thinking opens previously blind paths to understanding an event. The discussion surrounding the Fukushima accident is one such event where the probability was considered "rare" that the generators would be flooded by a tsunami, but, despite a number of engineers calling for consideration of the "possibility" of flooding (and following through with an examination of the outcomes of that possibility), it was never done and within an hour or so, the pathway to the worst nuclear disaster in history was set at Fukushima.

Lee Clark, Possibilistic Thinking
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Old 21st Jun 2011, 08:06
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Originally Posted by BOAC
We have a whole bunch of disagreement on this from those who claim to know the system, and I wonder what chance two lads had in the middle of the night in the ITCZ?
It's not disagreement over the systems behaviour, it's a group of people who know the systems and are willing to stick to the facts as presented versus a group of people who may know the systems, but are bending every bit of minutae of that knowledge to advance their agenda that the aircraft (and consequently the manufacturer) must somehow be completely to blame.

Quite how this seemingly endless reservoir of venom towards Airbus and the BEA came about I'm not entirely sure...
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Old 21st Jun 2011, 08:45
  #234 (permalink)  
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DW - that's accepted, but you need to open your horizons and consider the possible effect the whole 'automation' mentality is having on the industry - read mm43's post above and my somewhat extinct thread on 'Safety and CRM and Q&A'.

In addition, perhaps you could give us a definitive analysis of exactly who is providing the accurate information here and who is 'bending every bit of minutae of that knowledge to advance their agenda' and we can then disregard these other posts, since for those of us who are not 'experts' it is exceedingly difficult to know who is spouting rubbish.when statement after statement is challenged by someone else 'claiming' to be expert.

With your expertise, could you also tell us (as I have asked) exactly what baro information would be available to which pilot with the given failures? I also have not had an answer (to Svarin) in post 207 "Lastly, can you comment on what effect (if any) a low (reported) airspeed in the system might have on autotrim?" - perhaps you could oblige? Is the autotrim function SOLELY based on elevator demand or is there a speed input?
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Old 21st Jun 2011, 13:18
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In addition, perhaps you could give us a definitive analysis of exactly who is providing the accurate information here and who is 'bending every bit of minutae
I hope that no names are given as it defeats an open forum discussion.

Point and counterpoint will suffice for most of us.

Often I have no expertise in the discussion but do admire a posters ability to rationalize arguments with facts rather than just analysis of minutae to furthur a suspicion.
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Old 21st Jun 2011, 13:25
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I know this Aviation Weekly & Space Technology link has been posted by PJ2 previously, but it drew no response. I suggest that it is read and digested, compared with the China Airlines incident that MurphyWasRight has mentioned, and let the discussion start on training and how to keep the pilot in the automation loop.
With respect, I disagree with that last, and suggest to you that the point is to keep the pilot in the control loop. Automation is already there, and either substitutes for, or aids, the pilot in a variety of cockpit task areas.

The pilot is required to be in command. What may need some tweaking is making a better fit for him in the control loop to better enable his exercise of command. It come's with the pilot's badge.
I suspect that the crux of this accident is not hardware or software, but a human condition, i.e. industry, management, training and CRM, that needs to be addressed.
Which ones will be addressed, and how thoroughly? We shall see.
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Old 21st Jun 2011, 13:36
  #237 (permalink)  
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loma - don't forget that 'names' here are not 'names' and an accusation that posters are 'misleading' folk is potentially equally wrong, may yet turn out to be part of a different 'agenda' and needs to be clarified.

"Point and counterpoint will suffice for most of us" - therein lies the rub - whose 'counterpoint' do we listen to? So far, AB software 'expert' opinion has been challenged repeatedly so that none of us know who is right, and as I said earlier, what hope for a crew in an upset?
.
Now then - anyone willing to answer my queries - definitively, correctly and without fear of contradiction?

Lonewolf - spot on.
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Old 21st Jun 2011, 15:05
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In addition, perhaps you could give us a definitive analysis of exactly who is providing the accurate information here and who is 'bending every bit of minutae of that knowledge to advance their agenda' and we can then disregard these other posts, since for those of us who are not 'experts' it is exceedingly difficult to know who is spouting rubbish.when statement after statement is challenged by someone else 'claiming' to be expert.
It ain't that easy to tell. I'm by no means an armchair aviator: aeronautical engineer, F-4 and helicopter flight test engineer, pilot (ATP but not used as such), 3,000 total hours, part-time flight/instrument/aerobatic instructor, rated in airplanes/gliders/helicopters, flown in national glider contests, etc. I was absolutely certain that they had lost control into a spiral dive, figured it out, and were just too late on the recovery and pullout. Posted that three times, different ways. No way they were in a flat spin because they almost certainly could not have recovered and therefore would not have crashed into the water with no significant yaw rate ("en ligne de vol"). Didn't even consider that they could not only have stalled it but managed to keep it stalled for 35,000 feet without falling off on a wing into a spiral dive or a spin. Impossible. Gob smacked I was.

I once convened my production test pilots, all very experienced, to discuss a simple power margin procedure that customer pilots were using and getting different results from ours. They all wondered why I asked since it was so straightforward and well known. Then each of the six told me how they did it, none exactly the same, maybe eight ways in total since a couple of the guys had alternatives. And the dispersion of the results when I had them fly the same aircraft was unacceptably large. It took a while but we finally agreed on and documented a specific procedure that gave reasonably consistent results. So it's no surprise to me that pilots disagree amongst themselves. Also see the debate about what controls airspeed and flight path (n.b. I use stick and throttle together or one or the other as required.)

In that regard, one of the things that is apparent from the discussion is that the Airbus protections and fall backs are very, very complicated. Even the knowledgeable and/or formally trained appear to disagree (or at the least quibble) about how the software and computers work. That doesn't seem like a good thing...
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Old 21st Jun 2011, 15:27
  #239 (permalink)  
 
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Tailspin Turtle:
I use stick and throttle together or one or the other as required.
Likewise.
next bit Deleted as irrelevant to A330.
Part of the idea behind teaching that way was to keep the student from trying to fly by just moving the stick. (I wonder if autothrottle lends itself to that functional habit? )
Next bit deleted as irrelevant to A330.

EDITED per BOAC's valid complaint.

Last edited by Lonewolf_50; 21st Jun 2011 at 19:07.
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Old 21st Jun 2011, 15:53
  #240 (permalink)  
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This is so irrelevant as to be unbelievable! Please continue on the Flying Instructors' thread? What ON EARTH has this to do with AF447?
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