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AF 447 Thread No. 9

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AF 447 Thread No. 9

Old 6th Jul 2012, 13:10
  #81 (permalink)  
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Done to death, rg, on previous threads. Me no, not with the expected 'thickness' of the zone. A few years back I asked some of the 'crusty' senior BA 'chaps' and they said rest was rostered on a flight at a specific time and these follk would normally take it at the assigned time. Many others have said not. You need to see AF flight crew orders to answer the question there.

NB The ITCZ is NOT an emergency; it is not an ABNORMAL occurrence; it is crossed many times by many aircraft all over the world every day. 2 COMPETENT F/Os are more than capable of traversing it. In essence it is just a large weather front, but it appears to have gathered some special 'mystique' for some here.
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Old 6th Jul 2012, 14:59
  #82 (permalink)  
 
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Hi DozyWannabe,
FDs need to be changed in terms of their appearance in marginal systems behaviour
I agree.

On page 3 of Appendix 2 FDR Chronology, at time 2.10.47 "The FD 1 and 2 become available again (modes HDG/VS). The selected heading is 34. The vertical speed is 1,500 ft/min."

The FDs will presumably command a pitch attitude to satisfy +1500ft per min, whilst displayed.

At time 2.11.22 - 2.11.35 "The vertical speed changes from -3, 900 ft/min to -6,800 ft/min." At time 2.11.40 "The FD 1 and 2 become unavailable. The angles of attack 1 and 2 become invalid (NCD status) while the angle of attack 3 is 33."

I suggest the flight directors will have commanded high nose up pitch attitudes, in order to satisfy +1500 ft per min even as the aircraft entered the stall and started to descend rapidly.

I understand the wisdom of turning off the flight directors during "Unreliable Airspeed", but when the FDs disappear out of view automatically, it's difficult to remember to still have to switch them off.
There was no help from the automatic reappearance of the FDs.

Last edited by rudderrudderrat; 6th Jul 2012 at 15:06.
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Old 6th Jul 2012, 15:19
  #83 (permalink)  
 
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Hi rudderrudderrat - welcome back to the conversation.

According to the presentation, when the FDs intermittently reappeared they were no longer in V/S acquisition mode, and in fact changed mode multiple times during the sequence - but they didn't elaborate on which mode they were in. Hopefully this weekend I'll have a chance to give the report more than a skim.
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Old 6th Jul 2012, 15:40
  #84 (permalink)  
 
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Graceful degradation?

I did not see any recommendations on changes by Airbus so that the pilots get a heads up before they are handed the plane.
1- Guys, getting inconsistent Airspeed indications here.
2- AP will drop out, you are heading for Law 2B
3- Set pitch and thrust
4- See you on the other side.

Not too much to ask surely?
Training for 'startle' sure, but why not remove as much as you can?

Last edited by paull; 6th Jul 2012 at 15:42.
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Old 6th Jul 2012, 16:24
  #85 (permalink)  
 
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Paull...."I did not see any recommendations on changes by Airbus so that the pilots get a heads up before they are handed the plane."

In a way your comment holds the philosophy up for rigid examination. Pilots of this aircraft are not privy to volumes of periodically life threatening data. Three pitots? To serve the computing master alone? YES. The pilot is only allowed to see a synthesis of indicated airspeed. This amalgam is an average, and controlled within certain parameters, and when out of limit, the startle begins. The pilot is outside the decision to quit, and all data leading up to it. There seems to be no provision for pilot monitoring of the data that will challenge his manual skills at altitude. And yet the data is available. Is the pilot considered superfluous to bad data in? Here, yes.

Ever been at a restaurant and have the waiter spill your meal in your lap? Changes everything. These two had hot enchiladas thrown in the face; screws with one's 'presence of mind', eh?
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Old 6th Jul 2012, 16:31
  #86 (permalink)  
 
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Concerning FDs, basically they shouldn't do anything different from AP. If Georgie quits, one should be very carefull to trust the yellow bars....
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Old 6th Jul 2012, 16:34
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Why was the trim at 13 deg. nose up ?
Did the system autotrim responding to sustained back stick ?

.
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Old 6th Jul 2012, 17:32
  #88 (permalink)  
 
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Why was the trim at 13 deg. nose up ?
Did the system autotrim responding to sustained back stick ?
Now here's a question that even I can answer.

Yup.
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Old 6th Jul 2012, 17:45
  #89 (permalink)  
 
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Thanks !

.
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Old 6th Jul 2012, 18:17
  #90 (permalink)  
 
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The other report, the judicial one, is out next week ... Is it out for all to be seen, or restricted to a limited audience ?

Will it be also as an empty shell that the BEA report is ... ?
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Old 6th Jul 2012, 18:36
  #91 (permalink)  
 
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Why was the trim at 13 deg. nose up ?
Did the system autotrim responding to sustained back stick ?
That is a very good question!

Another one is:

Would the pilot have trimmed a conventional aeroplane to such an extend?
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Old 6th Jul 2012, 18:51
  #92 (permalink)  
 
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Originally Posted by CONF iture View Post
Will it be also as an empty shell that the BEA report is ... ?
I'd say the BEA report is pretty comprehensive - more so than I expected it to be. What do you find lacking about it objectively (i.e. other than it does not fit your agenda of blaming Airbus for everything and demanding they go back to a conventional control layout)?

Last edited by DozyWannabe; 6th Jul 2012 at 18:51.
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Old 6th Jul 2012, 19:11
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Somewhere in there is the "Tiptoe" dance BEA does around obscuration of the sticks one from the other, no? Stress 'tiptoe'.

jcjeant: Imagine what the "AP OFF" call portends? Here is Captain, seconds away from impact with the Ocean, entertaining that the problem could be originating with the autopilot? Can one be that removed from an awareness of his aircraft?

"So, wait...." Clutching at straws? It does demonstrate the Captain's awareness of the then current drill for UAS..... DO NOT re-select Autopilot.

Also, switch off flight directors, AutoThrust, etc. For me, it is emblematic of the tragic disconnect demonstrated by 'qualified' pilots of this a/c. The report has couched all the evidence toward incompetence, with minor bones thrown to involve the airframer and airline. This accident is unbelievable, as presented by the report. Suspension of disbelief is required to read it without bias. One is tempted to assign some skulduggery to its plot. The pilots obviously eliminated Stall as a possibility, for to believe otherwise is to entertain a laughable consideration of the facts as presented. If so, they must have been baffled by the lack of "response" to commands to "climb". Out of ideas from the git, not to mention the experience of actually Stalling an a/c at altitude.
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Old 6th Jul 2012, 19:51
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Hardly a "tiptoe dance". It gets mentioned, but given that the design is now a successful one that has proven itself in safety terms, it's rightly mentioned at the appropriate point and left there.

I'd say the report (admittedly on a quick rather than thorough reading) is fairly even handed - the implicit primary thrust of it is towards the industry who left these pilots so ill-prepared rather than hanging the pilots themselves out to dry. The sequence of mis-steps is long, detailed and painful to read, but at no point is it suggested that this was the fault of the crew in isolation. The manufacturer comes in for censure for the way it handled certification of the Thales pitot tubes and disseminated information when the first problems occurred. Bear in mind the fact that as a civil service report it had to use very dry language and I'd say it stands up very well.

Regarding "AP OFF" at that time - well, the tendency in a situation like that is to try everything. The procedures do call for various automatic systems to be explicitly disabled and as we know, none of those procedures were followed. I wouldn't be surprised if the Captain wasn't simply taking a belt-and-braces approach to the problem. None of the DFDR traces from the point of automatic disconnect are consistent with autoflight re-engagement so ultimately it was a futile gesture, but it probably made sense to him at the time. If you're attempting an implication that autoflight was engaged at any point after the initial upset, then "clutching at straws" is putting it mildly!

Last edited by DozyWannabe; 6th Jul 2012 at 19:55.
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Old 6th Jul 2012, 20:14
  #95 (permalink)  
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Would you have, as Captain, taken a rest break right before traversing the ITCZ?
Yes, discussed to death; to repeat an earlier response, "no", I never took my rest period during an ITCZ crossing, (A343, Pacific routes, NA - Australia). It was a matter of policy, (mine, not my airline's), not of crewing, trust, or anything else; the cockpit is where "the captain" belongs, in my opinion, as the crossing is an area that presents specific operational challenges and decision-making opportunities, if I can put it that way. The only think I was never entirely happy with was the notion of "RPs", (great guys & gals, but the position is not cleared to fly below cruise levels and therefore the RPs are entirely unpractised in what little manual flight there currently is available - I always thought that was false, short-term economy).

The ITCZ conditions described in the Report are precisely as they are during most crossings. Sometimes deviations were necessary, sometimes not. HF was mostly good but the advent of ADS and especially CPDLC were a god-send for such requests.

The radar would be on, tilt and gain used according to standard operating principles, (scanning up and down, calculating tops of the moisture, gain on automatic as well as manual settings). Sometimes one would have a full moon to help pick one's way between cells and avoid the over-hangs, (where necessary, almost always diverting upwind). While not frequent, St. Elmo's was often seen as was lightning, (which would also help light the way ahead if the build-ups were isolated enough). Light to occasional moderate turbulence was the rule as was the occurence of ice crystals; I know that sound that they make on the windshield.

Some common images, (obviously before nightfall), some of which I have posted before for those who may not see this from the pointy end and are trying to imagine the process of navigating ITCZ weather - it is in my opinion an art as much as it is a technical process:




CPDLC clearance to deviate:




Standard track off-set technique:




The weather deviated around:




Typical ITCZ weather:












At the time, we were informed that aircraft icing never occurred at cruise altitudes, below -40C, and while the problems with pitots and UAS events were occurring then, we never heard a thing about them and never once were shown or practiced the event in the sim, nor was the info ever presented in annual recurrent training or safety reviews.

I hope this is helpful for those who may not have seen this kind of weather or flown it.

Last edited by Jetdriver; 7th Jul 2012 at 04:42.
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Old 6th Jul 2012, 20:32
  #96 (permalink)  
 
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Originally Posted by DozyWannabe
Hopefully this weekend I'll have a chance to give the report more than a skim.
Why don't you wait before making the following comment then ...
I'd say the BEA report is pretty comprehensive - more so than I expected it to be.
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Old 6th Jul 2012, 20:38
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Because I have done proofreading before, and I'm good at isolating details. Of course, if you'd like to tell me where it's lacking, I'll cheerfully keep an eye open for it when I do a proper in-depth read this weekend.

Last edited by DozyWannabe; 6th Jul 2012 at 20:38.
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Old 6th Jul 2012, 20:54
  #98 (permalink)  
 
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Added to BEA website

Link to:

Presentation webcast

FF to Q&A.......Valid questions....confusing answers. (if translated correct?)

Last edited by A33Zab; 6th Jul 2012 at 22:12.
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Old 6th Jul 2012, 21:14
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Well, looks like the BEA left it up to the PPruners to figure it out. How many threads will it take to do so?

For me, this was either a situation where the holes lined up (and you can't eliminate that probability no matter what): or a situation where a system presented it's human operators too little usable information. If the first, we can just go on, praying it doesn't happen to us, or if the second we will need to understand what inputs humans need and can decipher when their world is turning to worms.

Now for my editorial comment. Airbus AND Boeing, need to present information regarding primary aircraft control in such a way that allows the aviator to scan and know vs a display that forces the pilot to scan and interpret. IOW, airspeed tapes, altitude tapes, IVSI's buried between other info, and ECAM systems that demand attention are great for video games. They suck for actually flying an airplane when one needs a clear picture of the essentials for life.
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Old 6th Jul 2012, 22:40
  #100 (permalink)  
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Tex, absolutely agree.

Who was it said "what's gonna kill me?"

I know, that was on take off, but its still pdg advice.
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