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AF 447 Thread No. 5

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AF 447 Thread No. 5

Old 6th Aug 2011, 00:28
  #1661 (permalink)  
 
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Vertical speed.

Hi Takata,

Well in fact this question was raised by me.......and I did read the full reports but maybe I did missed this one.

Ok, try to formulate it another way.......for what reason could Inertial Data be not available?
IR part of ADIRU can operate normal even if ADR is providing unreliable information.

Quote:
FCOM
1.31.40

INDICATIONS ON PFD

VERTICAL SPEED:

The displayed vertical speed information is normally based on both inertial and barometric data.
If inertial data is NOT available, it is automatically replaced by barometric information.
In this case, the window around the numerical value becomes amber.



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Old 6th Aug 2011, 00:34
  #1662 (permalink)  
 
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Takana, thank you for your views in regards to you native understanding of the CVR Transcript. You have (as the English quotation puts it) hit the nail on the head. Regardless of faults in the design philosophy of the aircraft (and the BEA have hinted them in their recomendations as well as AD's that EASA have introduced since), a servicable aircraft seems to have been lost with all souls due to a massive failure of CRM IMHO. While I will not take the view that the flight crew were not totally professional (because I did not know them and cannot comment as such), I would wager most Captains in such a situation would be have been more self preserving that what the CVR transcript leads to have been the actions of Captain Dubois in not taking control, especially when the PF was unsure of his actions. He did have the time (and height) to do so. Air France may continue to defend their crews most vigiously and that is only to be expected and conmmended as an employer. However the accountants heading the company must realise that AF's standing in the world is only upheld if they are fully free to ensuring every facet that caused AF447 to smash into the ocean is investigated, independantly reviewed and actions taken to prevent such events ever occuring in this manner again, to anybody.
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Old 6th Aug 2011, 00:47
  #1663 (permalink)  
 
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Takata

Hi Takata

"(...)" itself may never be known (as opposed to deliberately omitted, and even then it could easily be ambiguous).

There is a widespread misconception that CVRs are easy to decipher. They most definitely are not. The hardest day's work that I ever did (and certainly the most emotionally draining), was not landing my Buccaneer on a flight deck or landing a 747 on various runways where ideally wide bodied jets should not go anywhere near (thankfully fewer in number these days), but a day at the AAIB helping investigators to make sense of what a F/O that I knew had said shortly before his death on duty.

It's hard work for the BEA, even with input from close colleagues of the deceased flight crew.

The cockpit issues you refer to are troubling, border line the other extreme to the CRM Van Zanten/Meurs issues.
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Old 6th Aug 2011, 01:42
  #1664 (permalink)  
 
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Originally Posted by A33Zab
Ok, try to formulate it another way.......for what reason could Inertial Data be not available? IR part of ADIRU can operate normal even if ADR is providing unreliable information.
What reason, what reason... would you like a +/- 10,000 ft treshold exceeded for inertial vertical speed? It is always the same reason, a designed parameter exceedance.

A baro inertial loop is integrated in the inertial V/S computation to bring the stability in time of the air data (no drift like inertial data). Degraded data: When the inertial vertical speed is not available, the baro vertical speed is automatically displayed. Failure : In case of vertical speed failure, the scale is replaced by a vertical speed flag.

In case of excessive vertical speed, the digital and analog indications
become amber. Excessive V/S when :
- V/S > 6000 ft/mn or V/S < - 6000 ft/mn,
- V/S < -2000 ft/mn below 2500 ft Radio Altimeter,
- V/S < -1200 ft/mn below 1000 ft Radio Altimeter.


But It looks to be set at +/- 10,000 ft in order to show a degraded status.
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Old 6th Aug 2011, 01:56
  #1665 (permalink)  
 
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Originally Posted by Welsh Wingman
"(...)" itself may never be known (as opposed to deliberately omitted, and even then it could easily be ambiguous).
Sure, but this one was understood and deliberately omitted... and I may understand why.
See legend:
(…) Words or groups of words not relevant to the conduct of the flight
(*) Words or groups of words not understood

IMO, it was relevant for understanding what the captain expressed.

Last edited by takata; 6th Aug 2011 at 02:21.
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Old 6th Aug 2011, 02:23
  #1666 (permalink)  
 
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Cool

CDB: (…) C’est pas possible
I do think I am right in saying that the captain words should be an exclamation indicating disbelief or surprise to see something beyond his understanding or completely abnormal or completely wrong

So in the (...) can be the words
Mais ....
Putain ....
Merde ...
Bon dieu

So .. full speculation .. so many open possibilities ..
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Old 6th Aug 2011, 03:51
  #1667 (permalink)  
 
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Hi jcjeant,
Originally Posted by jcjeant
I do think I am right in saying that the captain words should be an exclamation indicating disbelief or surprise to see something beyond his understanding or completely abnormal or completely wrong
Spagiola's explanation of expressing a sentiment of extreme frustration close to anger, was much better than yours. That's the reason why it is usually introduced by a volley of profanities; some of those words you quoted are sometime all used at once for good effect : n... de d... ! de p... de b... de m... ! c'est pas possible !

Originally Posted by Spagiola
please note that "c'est pas possible" could also quite easily be a generalized expression of frustration. For example, if you arrive at the movie theater only to be told that the movie is sold out, you may well exclaim "c'est pas possible!" It doesn't mean you think that it's actually impossible that the movie is sold out, or that you don't understand how it came to be sold out.
Disbelief is not the primary sentiment, as in fact, one will clearly acknowledge that the situation is real but very frustrating.
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Old 6th Aug 2011, 04:28
  #1668 (permalink)  
 
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Cool

Hi,

Spagiola's explanation of expressing a sentiment of extreme frustration close to anger, was much better than yours.
When you don't understand something ... you can be frustrated a max .. certainly if you (or think) know many things ...
So .. c'est pas possible can be an exclamation caused by something beyond his understanding
Anyways all is open .. and again .. this must be not important in the cause of the accident
The most important words are "j'ai les commandes" and the actions immediately following.
If those actions can be explained by other thing than a "pilot error" ... maybe this accident will bring some (new) progress for the aviation safety

Last edited by jcjeant; 6th Aug 2011 at 04:41.
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Old 6th Aug 2011, 04:31
  #1669 (permalink)  
 
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ADR Switching

ADR Switching:

From my experience, I've noticed the information isn't presented instantaneously but rather 'scrolls' to the particular value.

At least this is what I've noticed with normal working ADRs, when using the ADR switch on the 320 family.

Now for their situation, having the AIR DATA switch placed to 'CAPT on 3' after the captain entered the cockpit, would revert the PF's altimetry information back to ADR2 - which, if in the (highly unlikely but possible?) event that one or both the F/O Static Ports were blocked - I imagine would start 'scrolling' UP indicating a climb (to the original altitude at the time of blockage). This of course would be highly confusing, especially coupled with the lack of V/S information on the PF side, and would certainly hinder their progress in recovering the situation.

(Once again - we do not have the ADIRU 2 information as it is not recorded by the FDR. Unfortunately I think that information would be the key to understanding the PF's actions).

Anyone have more experience with this ADR switching 'scrolling' aspect?
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Old 6th Aug 2011, 06:55
  #1670 (permalink)  
 
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confusion, leadership

Some people here critizise, that no leadership was taken by either PNF or CDB.
I would say CRM still worked because as we say: If you dont have any better idea, just keep quiet. PNF had some good ideas but he wasnt so sure because otherwise he would have insisted more or taken control of the aircraft (which he did from time to time, but without pressing the takeover P/B) So again, nobody really was in control because inputs add up or are neutralized.
Confusion was high but I am very sure CDB noticed the aircraft pitch attitude as he was walking into the cockpit because at that time (02:11:43) it varied between 10degrees up and even more and this is definitely different from what he experienced the other 100plus times when he entered the cockpit in normal flights. What he then saw when he entered the flight deck brought up the "c'est pas possible" because he (and nobody else of us) has never seen a combination of those readings before.
Old sentence but true:
In an emergency you will not rise to the occasion but fall back to your level of training. Were they trained for this situation?

@Neptunus Rex: ...inner ear pressure.
I would say if you are stressed like they were you dont feel anything

@takata: I have been trying to get info about VS indication on PFD(not data) and could not find any tests (AMM) were this system is checked. Maybe you have another source?
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Old 6th Aug 2011, 07:08
  #1671 (permalink)  
 
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Originally Posted by airten
There should be an increased effort to help pilots understand the very basic laws of physics involved, in very simple, and practical terms.
Are you kidding ?
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Old 6th Aug 2011, 07:30
  #1672 (permalink)  
 
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Hi peefactor,

Anyone have more experience with this ADR switching 'scrolling' aspect?
good point, but on the A330, the "new information" (in this case ADR3) is presented much more instantaneously than on the "rolling" A320
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Old 6th Aug 2011, 09:33
  #1673 (permalink)  
 
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@Takata:

What reason, what reason... would you like a +/- 10,000 ft treshold exceeded for inertial vertical speed? It is always the same reason, a designed parameter exceedance.
Thx, clear now.

The 'stable' inertial V/S was replaced by unreliable and fluctuating ADR V/S.

'Another slice and hole for the swiss cheese model'
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Old 6th Aug 2011, 09:49
  #1674 (permalink)  
 
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Originally Posted by xcitation View Post
The inexperienced PF did try stick forward however a/c still stays nose up no response, as elevator is at -30 deg due to full THS! So behaviour is bizarre and only explained if you have a full understanding of the situation in 60 seconds.
Hmmm, where did you find this situation in the plots ????

Where was any indication the PF was trying to get the Nose down ??
In contrary the Nose descended a couple of times despite continued NU commands from the PF, albeit slightly reduced from full NU to half NU a couple of times.
In the last minute the PF even fought the ND commands of the PNF by himself applying Full NU.

Having a look at the traces I do not see anything there which would confirm your assertion that the PF was seriously trying to get the nose down.

Last edited by henra; 6th Aug 2011 at 10:06.
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Old 6th Aug 2011, 10:52
  #1675 (permalink)  
 
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takata posted the speed graph. It does not show something I expected. In climbing from 35000 to 37500 it should have lost just a whole lot more speed than the graph shows, which suggests the plane was in a rather significant updraft with most of its upward motion being provided by wind energy.

That ought to be food for thought here, too. It would likely be more conflicting or exaggerated data for the PF to digest.
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Old 6th Aug 2011, 11:07
  #1676 (permalink)  
 
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I though the 0.5*(v1^2-v2^2)=gh equation had been looked at earlier and found to be broadly consistent ?

In the more general discussion, has consideration been given to maximum altitude limitations if turbulent conditions are expected and unreliable airspeed remains a credible fault event which has to be accounted for?

The BEA report indicates that the AoA margin between stable cruise and warner was only 1.5 degrees. Given the coarse nature of the manual inputs it would seem that loss of autopilot precision is at best a serious matter at those altitudes and related/concurrent loss of air speed data and protections cuts one safety rope, then throw in turbulence.....In those conditions it seems that excursions towards a stall are likley even if one could hope that transition to full stall was avoided.
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Old 6th Aug 2011, 11:08
  #1677 (permalink)  
 
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3holelover types, " I'm presuming those of you asking it are not pilots, because I can't imagine a pilot who could ever not know if he's stalled, PDQ, after the fact."

Then the PF on AF447 was not a pilot?
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Old 6th Aug 2011, 11:17
  #1678 (permalink)  
 
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Neptunus Rex says, "The reaction on their inner ears should have told them that they were in a rapid descent."

No. Their inner ears can only tell them they accelerated downwards at some point. Once they are in a constant speed drop their inner ears would not sense the drop. They ears might detect something when pressure changed. Ears are tilt and acceleration sensors. They also have pressure on their backs to tell them the nose is pitched up - about the same as the instrument in front of their face tells them the same thing.

Neptunus Rex also says, "Plus, the Captain should have noticed the aircraft deck angle as he walked, or rather climbed, to the cockpit."

That one's a gimme.

Now, just how much of the acceleration into the fall they'd sense is up for grabs if the plane is in violent turbulence.

(Has learned far more about inner ears than she ever intended to learn due to a malfunction in my left ear similar to what the astronaut Alan Shepard had.)
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Old 6th Aug 2011, 11:22
  #1679 (permalink)  
 
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You seem to be up at an early hour JD-EE. At that rate of descent I would have thought the pressure change rate would have ears popping. then there would be the increase in temperature, however if all else failed there was always the altimeter.
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Old 6th Aug 2011, 11:30
  #1680 (permalink)  
 
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Black Sheds, one might ask about what part of the plane being at fault for providing bad data in the period immediately after the aircraft went to ALT 2 mode. Airspeed was out. "Protections" were out. PF pulled stick up enough to cause a serious zoom climb that left the plane with an "apparent" airspeed of about 215kts. (Assumption here based on airspeed coming back briefly and the number reported being within reasonable bounds for the kinetic energy transferred into potential energy.)

What led the pilot to disregard stall warnings all the way down?

But most of all why did the pilot pull nose up on the plane right after (within a second or two) the AP and ATHR disengaged? He had accurate data up to that moment. And an average kid can extrapolate into the future.... The drill is "leave it alone, fly pitch and power until you have air speed back. Do not make any large sudden changes in either pitch (no nose up) or power (no TOGA)."
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