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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 26th May 2011, 20:02
  #2481 (permalink)  
 
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Originally Posted by Lonewolf 50
Note: what has been discussed in this thread is that in some previous Unreliable Airspeed incidences, there were pitch up, but not in all.
I don't remember that, and did not find it in the BEA report. Where did you see that?
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Old 26th May 2011, 20:07
  #2482 (permalink)  
 
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HN39:

I am not referring to the BEA report, but on the continuing series of threads on this crash.

Some pages back, there was the A340/A330 incident where was discussed "a near miss" where one plane did a bit of a zoom climb. Also, when I went back to some of PJ2's older posts, I found something he'd dug out of another report. That is what I put in qoutes in the post where I address Takata and PJ2.

EDIT: here is what caught my eye.
The post was PJ2 responding to you:

HN39;
I was unable to locate "Appendix B". If the report has something to contribute to an understanding of the AFS especially the reconfiguration of flight laws from Nz to AlphaProt Law, I'm sure what there is in this report will be available and its relevance hopefully established. There are some primary differences in that event: For an AlphaProt Law response, the aircraft must be in Nz Law as the response (HIGH AoA and PITCH ATT) wouldn't be available in either Pitch Alternate law.

As we are aware, the AD that was released on December 22, 2010 states, "However, in some cases, the autopilot orders may be inappropriate, such as possible abrupt pitch command. In order to prevent such event which may, under specific circumstances, constitute an unsafe condition, this AD requires an amendment of the Flight Manual to ensure that flight crews apply the appropriate operational procedure."

The AD does not mention those "specific circumstances", nor do we know to what event(s) the characterization of "abrupt" refers, if any. Perhaps the dots are still too far apart to see viable connections but this event and the one to which I refer above concerning the UAS QRH Drill, are possible areas to focus upon along with weather.
http://www.pprune.org/tech-log/44963...ml#post6435101

To be clear, PJ2 took the position during that element of the discussion that the aircraft was stable, (see the part of the post where he addressed takata before he addressed you).

If you think I have misinterpreted this, or I am making too far of an intuitive leap, please advise.

What I gathered from the 340/330 near miss was that an uncommanded pitch input was made, and the pilots got it sorted out in a few thousand feet, and returned to flying on altitude and airpseed, and arrived at destination. What made that interesting was that another aircraft saw it. As I understand it, the report was initially more concerned with the "near miss" than perhaps anomalies in flight control inputs.

The other incidents discussed, which included uncommanded flight control inputs, altitude excursions, and various upsets that the pilots recovered from have been part and parcel to this discussion at various times. Air Carriebe and Qantas were two of them.

If my synthesis is turning out a stew, instead of a cake, please advise.

Last edited by Lonewolf_50; 26th May 2011 at 20:20.
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Old 26th May 2011, 20:30
  #2483 (permalink)  
 
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Lonewolf_50;

The discussion I had with PJ2 was about an A340 AIRPROX incident due to turbulence, which activated High-AoA protection. It was not an UAS incident, and it has afaik no connection to AF447. The BEA analysis of 13 UAS incidents does not contain any reference to an uncommanded pitch-up, nor does the table in app.7 . The report states:
With regard to crew reactions, the following points are notable:
The variations in altitude stayed within a range of more or less one thousand
feet. Five cases of a voluntary descent were observed, of which one was of
3,500 feet. These descents followed a stall warning;
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Old 26th May 2011, 20:40
  #2484 (permalink)  
 
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Thank you, sorry for having crossed my own wires on that.

Appreciate your clearing that up.
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Old 26th May 2011, 20:45
  #2485 (permalink)  
 
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Lonewolf_50

The airprox report is summarized in this post

http://www.pprune.org/tech-log/44963...ml#post6434021

and the UK AAIB report can now be found complete with appendices at

Air Accidents Investigation: Airbus A330 C-GGWD and Airbus A340 TC-JDN
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Old 26th May 2011, 20:52
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Originally posted by takata ...

Alerts are supposed to catch their attention only if their situation awareness is low because they are distracted by something else.
That will undoubtedly be the crux of the matter - the aviate, navigate and communicate chain became broken.
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Old 26th May 2011, 21:10
  #2487 (permalink)  
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mm43

Hi mm. I am not sure what you are saying here......

"...That will undoubtedly be the crux of the matter - the aviate, navigate and communicate chain became broken."

"ne comprends pas" means one thing, "ne...riens" another. This snippet, if accurate, says so much. It is a closure, a juncture of CRM. The flight is being re-set in the view of at least one pilot. I think the comment is within the boundaries of "Aviate," alone, not comms or Nav. No one would get to this point re: the mundane. Not even atrocious and frightening weather weather. The airplane is an unknown to him here, and shows a frustrated pilot partially into a situation with which he is greatly uncomfortable, and has no experience of. This moment is the initial onset of upset, or the immediate prelude. Again, if accurate, a year's worth of speculation coalesces into epiphane for all of us connected in any way with this tragedy. They are speaking to us.
 
Old 26th May 2011, 21:19
  #2488 (permalink)  
 
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bearfoil

My oblique reference was related to matters discussed many thousands of posts ago, and I don't intend to elaborate further.
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Old 26th May 2011, 21:24
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respectfully, mm, no sir. takata's statement that you qouted is not correct, insofar as what the intention of an alert is, nor the context he claims.

The conclusion you drew from it at odds with what appears to have happened: things had boiled down to aviate alone, which became (for whatever reason) an overhelming task. Task saturation isn't a pretty sight.

EDIT: never mind, I see what you were getting at.
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Old 26th May 2011, 21:24
  #2490 (permalink)  
 
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Well, I've been reading this for a while. It's been quite interesting, including the C vs. Ada fights and the veiled reference to flying the Skyraider.
That expert report table with the 36/43 incidents is pretty impressive, as is the note that nearly two-thirds of the events were reported after AF447 (although most of them occurred beforehand).
Isn't the industry standard one catastrophic failure ever 30 or so incidents?
One of the "take-aways" from this discussion could be that, regardless of whether FBW plays a role in this accident, what it does do is increase the criticality of a certain piece of equipment, and it did so based on underreported reliability data (even if the Thales AA was a particularly bad design, from this data every pitot tube should suffer from underreported failures).
Or, in other terms: in-service reliability figures are scientifically worthless.
The "responsibility/authority" distinction is at least superficially appealing. Another way to put it is that if a system design routinely drops a load in the operator's lap, the designers cannot expect more than 29 out of 30 operators to make the right decision. On the other side, at least 20 out of 30 operators are going to do everything they can not to be #30.
And the Swiss cheese analogy has its charms too, if only because the next slice is more likely to have the same holes as the previous one than not.

please carry on.
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Old 26th May 2011, 21:34
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As a result of the blocked static ports the basic flight instruments relayed false airspeed, altitude and vertical speed data. Because the failure was not in any of the instruments but rather in a common supporting system, thereby defeating redundancy, the altimeter also relayed the false altitude information to the Air Traffic Controller.

Although the pilots were quite cognizant of the possibility that all of the flight instruments were providing inaccurate data, the correlation between the altitude data given by ATC and that on the altimeter likely further compounded the confusion.

Also contributing to their difficulty were the numerous cockpit alarms that the computer system generated, which conflicted both with each other and with the instruments. This lack of situational awareness can be seen in the CVR transcript. The fact that the flight took place at night and over water thus not giving the pilots any visual references was also a major factor.
sound familiar? It ain't the bus at fault it is sadly human limitation as to how much can be processed at any given moment when everything is going wrong.

Aeroperu 603
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Old 26th May 2011, 21:50
  #2492 (permalink)  
 
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HN39, I knew I remember something about a pitchup ...
http://www.pprune.org/rumours-news/3...ml#post4966826
It was a guess by one of the posters here based on something in an A330 (not the A340 in the AIRPROX event)
Another IRU fault resulting in sudden departure from controlled flight?

Several months ago an A330 transiting across Australia suffered a transient electrical fault in IRU1. It caused AP1 to think the aircraft had pitched down ~40 degrees. Needless to say it pitched up in response. Fortunately they recovered and the aircraft landed safely after diverting.

I wonder if this did similar, only in the opposite sense?

ECAM Actions.
Of other interest ...

http://www.pprune.org/rumours-news/3...ml#post4967466
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Old 26th May 2011, 21:52
  #2493 (permalink)  
 
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One thing I have noticed, or missed, is that with all these 'leaks' and speculations, there is no mention of why AF447 flew into the CBs, and appeared to make a last minute adjustment to their course. I wonder if that will be revealed tomorrow?
Also with all the past accidents involving pitot tube, gung-ho pilots, flying into storms, computer failures, isn't it time for manufacturers to produce aircraft and softwares that can prevent the constant repetition of these accidents?
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Old 26th May 2011, 21:59
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Originally Posted by Porker1 View Post
- yes the pitots iced up, the flight computers gave up and passed the control to the pilots;
- yes the a/c stalled but (as you'd expect!) the crew then correctly applied the textbook approach to deal with the stall but this did not work;
- yes the captain had briefly left the cockpit but was back in the cockpit for the critical part of the incident.
Wasn't going to look at any more "leaks" but that sounded just too interesting - thanks for the link.

To me the most interesting thing is not what it says, but that it appears to completely contradict the earlier leaks. If the crew did everything by the book and still ended up in irrecoverable stall, then (IMHO) it can't possibly be true that the aircraft is exonerated and the crew at fault.

At least one set of leaks is therefore wrong - and always possibly both. Roll on tomorrow.
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Old 26th May 2011, 22:01
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Lonewolf_50;

If the reference is to QF72; it pitched down uncommanded approx 10 degrees (from +2.5 to - 8), then during recovery in response to pilot sidestick command 7 deg up to approx -1 degree.

Regards,
HN39
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Old 26th May 2011, 22:08
  #2496 (permalink)  
 
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CogSim, the last line of your recognizing icing posting prompted an "Oh goodie!" from me - in a very sarcastic tone.

"Under some icing conditions, even a 3-minute exposure can substantially affect the handling of the aircraft."

Riiiiight - and who knows what the handling feels like when the computer has been flying? And then the computer, where all this handling data lived as bits and bytes, flips the pilot the bird and says he has the stick. No WONDER pilots get confused when things pickle. They don't have critical data and there may be no good way to transfer that critical data to the pilot in time.

If pilots are going to be expected to take over when things get tough they should be far more involved in the routine flight of the plane so they have this feel. That phrase proves this to me.

{o.o}
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Old 26th May 2011, 22:18
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sensor_validation, I get the impression that one of the best improvements for a pitot would be some form of airflow measurement out of the drain hole. If either the probe or the hole ices the airflow through will diminish. With a moniker like yours that's a design challenge for you. Measure the existence of airflow without increasing the chances of the probe icing.

{^_^}
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Old 26th May 2011, 22:31
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From about two years ago, from poster snaproll3480
According to the QRH and based on a weight around 210t:
(speeds are approximate)

Green Dot (minimum clean speed): 245 kts

Turbulence penetration speed: 260 kts

Vls w/ 0.3g buffett margin: 235 kts

Speeds are all indicated so no ISA deviation necessary.
HN39

Thanks for the detail, HazelNuts, yet again I doff my cap.

In re the pitch down versus pitch up.

With the above airspeed limits in mind, how benign do you think an unexpected ten degree nose down pitch is while on IMC, and possibly in turbulent air, with those limits considered?

NOTE: this is not a declaration nor an assertion that such is what happened with AF 447, but an inquiry regarding, as a pilot, your tolerance for a sudden ten degree nose down event. The closest thing like it from my own experience was a runaway nose trim event (which was a bugger, but manageable) but that was not on a FBW aircraft, so my personal points of reference are vague at best.
I will refer to AMF's comments on upset response from about the time AF 447 went down, which sentiment seems to not be confined to him.
Originally Posted by AMF
The fact is, most pilots train for unusual attitude recovery where the recovery is accomplished in benign conditions with all flight controls working normally, a full panel, not to mention the engines running and outside visual reference. Many places don't even give "jet upset" training...i.e. loss of aerodynamic control at high altitude.

And a real-world jet upset, let alone sever or extreme turbulence involving all the forces, cannot be rendered or trained well in a simulator because the test pilots during certification don't even put the aircraft through those paces.
Also something that caught my eye ... http://www.pprune.org/rumours-news/3...ml#post4972892

Regards

LW50

Last edited by Lonewolf_50; 26th May 2011 at 22:45.
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Old 26th May 2011, 22:33
  #2499 (permalink)  
 
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JD-EE
I get the impression that one of the best improvements for a pitot would be some form of airflow measurement out of the drain hole.
That is actually a very astute idea to validate a pitot tube's proper functioning.
Properly designed, that measurement could be done with a hot wire anemometer.
Basically, if there is flow, it is likely to be a valid measurement.
No flow, and the measurement is invalid.
We still have the problem of what to do when the reading is invalid on multiple sensors.
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Old 26th May 2011, 22:41
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If pilots are going to be expected to take over when things get tough they should be far more involved in the routine flight of the plane so they have this feel.
I had thougth about that as well. If the automation in cruise effectively makes flying the a/c like watching paint dry, it would be human nature to become a little complacent and perhaps even produce a tendency to fall asleep. No blame in that either, as the sort of people who are of the required personality to do the job are easily bored with routine.

Anyway, enough. With the air crackling and pregnant in anticipation of the next report, let's not forget what the whole exercise is about: Finding the truth, whatever colour it may turn out to be...

Regards,

Chris
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