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AF447 Thread No. 3

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AF447 Thread No. 3

Old 27th May 2011, 17:49
  #121 (permalink)  
 
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Roll oscillation sounds like dutch roll!


BOAC VC 10 got a high fly wrong and rolled through the vertical - day time with instructor and a horizon.


checkbord - posted blocked static - increase alt = ias decreases.
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Old 27th May 2011, 17:52
  #122 (permalink)  
 
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Maybe this question has been asked before in the previous topics but I dismissed those as way too much speculation:

Is it common to have airframe icing at FL350 outside a CB in those areas?
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Old 27th May 2011, 17:59
  #123 (permalink)  
 
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Official AF reaction to today's news -- the aircraft's instruments failed and the pilots reacted completely professionally.
Air France - Corporate : AF 447 - Air France
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Old 27th May 2011, 18:04
  #124 (permalink)  
 
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Stick input

Well BEA made the case too easy for an Airbus and too complicated for general public by just saying there was constant pitch up input from PF without actually saying the reason for it.

Maybe this will be revealed in the course of investigation maybe not. However all later findings would be biased by this "pilot error" suspicion.

Hope that French court would be as demanding as PPRuNe society.

Coming from very centralised country (France is very alike) I think that Airbus will be set free and pilots will be to blame.

Sad.
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Old 27th May 2011, 18:04
  #125 (permalink)  
 
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Quick question: on what basis does the BEA reports that the speed measurement became valid again at 2:12:21 ?
2:12:21? No, not then.

The report states that about 15 seconds after 2:10:51, the ISIS speed measurement abruptly jumps to 185KT, at which point it is consistent with the other recorded speed (ie the LH speed, as the RH speed is not recorded). It notes no further disagreements between the two recorded speeds for the remainder of the flight; rather, it notes that at various points that "all recorded speeds became invalid" (presumably when they fell below 30KT) or became valid (climbing above 60KT), indicating that they remained consistent with each other.

If I'm not mistaken, with at least two consistent speeds, they would be considered reliable even if the third (which was not recorded, and so we don't know if it differed) was different.

[edited to correct error on min speed at which speed is considered invalid; 60KT, not 30KT (see BEA report, note at bottom of p.2 of French version)]

Last edited by spagiola; 27th May 2011 at 20:59.
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Old 27th May 2011, 18:12
  #126 (permalink)  
 
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checkbord - posted blocked static - increase alt = ias decreases
Actually checkbord - posted blocked static - increase alt = ias increases.

Pitot tube has Dynamic Pressure (airspeed information) AND static pressure in it. The Air Data Unit (ADU) subtracts the sensed static pressure (from the static port) from the pitot total pressure to determine the dynamic pressure alone, and thus calculate the airspeed.

If the pitot becomes blocked, the dynamic pressure & static pressure at the time of the blockage remains the same. As the aircraft climbs, the sensed static pressure reduces (with the reducing altitude) so the ADU subtracts a smaller static pressure from the pitot total pressure, and thus comes up with an increasing airspeed. The airspeed guage is now working something like an altimeter.

... Now that's the theory - it actually depends on the nature of the blockage and the leakage within the "blocked" pitot system.

Last edited by Checkboard; 27th May 2011 at 18:36.
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Old 27th May 2011, 18:17
  #127 (permalink)  
 
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Originally Posted by studi View Post

Am I the only one here thinking that the climb was not induced by the pilots but by some sort of ill functioning protection?
Sorry if I have to be rude to you:
Did you care to read the report of BEA ???

What do you think 'Nose-up Input maintained by the PF' means ??

What is ambiguous about this statement ?

I'm completely at a loss how the first reaction of our conspiracy brigade (not only you) can be total denial of the most basic and easily determinable findings of the FDR i.e. sidestick position???

Yes it is difficult to understand why a pilot would pitch up signifcantly after loss of airspeed indications but the sensation of turbulence can play nasty tricks on you. Maybe they hit some bumps or holes in the air during AP disconnect and lost some altitude exactly at that moment. Such things can be badly misleading....
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Old 27th May 2011, 18:23
  #128 (permalink)  
 
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Condition of verticle stabilizer?

Does the new report shed any light on the structural condition of the air frame? Early on, many believed the VS separated before the impact with the water.
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Old 27th May 2011, 18:24
  #129 (permalink)  
 
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The non-recorded speed is an anoying thing.

Who was PF. the left hand or the right hand?

If the PF was the one flying on the non recorded speed, is it possible that he was pitching up because he saw speed too high and increasing?
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Old 27th May 2011, 18:24
  #130 (permalink)  
 
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Weather Conditions

I am not a pilot, but many knowledgeable posters feel that a factor has been overlooked which would help in understanding why the pilots reacted as they did.

Could that factor have been the local weather? Could there have been a large downdraft or updraft that caused the pilots to misunderstand what was happening to their aircraft? At night, without external references, it may have been very confusing.
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Old 27th May 2011, 18:26
  #131 (permalink)  
 
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I'm completely at a loss how the first reaction of our conspiracy brigade (not only you) can be total denial of the most basic and easily determinable findings of the FDR i.e. sidestick position???
Well, The FDR really tells us nothing about sidestick position - you need a camera for that - it only tells us about the sidestick command. A sidestick failure, giving pitch up commands regardless of stick position is a (slim) possibility. The actual FDR graph of stick command would show if it is a possible culprit though - and as it has not been mentioned (and it would by now) you can discount it.
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Old 27th May 2011, 18:30
  #132 (permalink)  
 
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Am I the only one here thinking that the climb was not induced by the pilots but by some sort of ill functioning protection?
pull zoomclimb stall chrash....

A340 TC-JDN:
the first elevator moving to +4 deg, 4 sec after the autopilot self-disengaged as the aircraft exceeded the speed limit, +4 deg only for 2 sec was enough to start the zoom climb for the A340 TC-JDN (en-route from Istanbul to New York) and was defenitiv not triggerd by the sidestick of the pilot (the first sidestick pitch was 20 sec later).....


AF447:
2 h 10 min 05 autopilot self-disengaged
2 h 10 min 15 "alternate law"

what is with the g-protection in the time between ???
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Old 27th May 2011, 18:31
  #133 (permalink)  
 
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Official AF reaction to today's news -- the aircraft's instruments failed and the pilots reacted completely professionally.
Well, the exact words are:

It appears that the flight deck crew was monitoring the changing weather conditions and thus altered the flight path, that the initial problem was the failure of the speed probes which led to the disconnection of the autopilot and the loss of the associated piloting protection systems, and that the aircraft stalled at high altitude.
This seems to be an interpretive version of the events - what protections were 'lost'? Protections still exist in Alt - however they are not the same as in Normal.
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Old 27th May 2011, 18:41
  #134 (permalink)  
 
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Instruments at all?

The PF reaction is typical of a pilot flying IMC with no instruments at all, or no reliable basic instruments at all.

How come a huge airline transport aircraft can come down just because the computers gave up after a false airspeed indication?

I have the impression the pilots lost all the information they needed to maintain attitude. Worse, they had their displays going crazy on them...

BEA is clearly "inducing" public opinion to believe the pilot did wrong.
We only see on the report parts that makes us believe the aircraft responded accordingly. They insisted on the "PF kept commanding pitch up" thing.

They (BEA) are trying to make us beleive that the only thing that failled were the pitot probes. The pilots "messed up" after the perfect AP disengaged...

Not what I see. I see pilots struggling to fly an uncontrolable airplane, with no attitude indication, at night with no horizon.

I don't believe the pilot would command aft stick knowing his nose was already up. Not even a student pilot would do this.

The aircraft went crazy on them.
Why?
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Old 27th May 2011, 18:43
  #135 (permalink)  
 
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Could the thrust and pitch have resulted from following a procedure?

Passenger here with a question for the professionals.

The BEA report notes that TOGA thrust and pitch up were selected at least some of the time.

Is it at all possible that this could have resulted from following an Unreliable Airspeed or Stall Warning Procedure that turned out not to be optimal for the circumstances?

I ask because there appear to be several different power and pitch recommendations depending on the phase of flight in which the problem occurs. For example, the unreliable airspeed procedure recommends TOGA and 15 degrees if the problem occurs before reducing thrust, but lower thrust and pitch at higher altitudes.

I am in no way trying to place blame here. I am certain many factors will prove to be involved. I ask because some have suggested that the procedures were confusing and wondered whether they could have led the crew astray. For example, was it clear whether a stall warning should be respected (and that procedure followed) or not?
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Old 27th May 2011, 18:49
  #136 (permalink)  
 
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BEA is clearly "inducing" public opinion to believe the pilot did wrong.
And you know that how? What a nice world it would be if a thread could stick to facts for at least 10 pages.
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Old 27th May 2011, 18:54
  #137 (permalink)  
 
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checkboard, this is intriguing

If the pitot becomes blocked, the dynamic pressure & static pressure at the time of the blockage remains the same. As the aircraft climbs, the sensed static pressure reduces (with the reducing altitude) so the ADU subtracts a smaller static pressure from the pitot total pressure, and thus comes up with an increasing airspeed. The airspeed altimeter is now working something like an altimeter.
From that, here is how it could play out. (Possible, not probable)

pitot blocked -> assume AP off and pilot flying -> (add trigger like possible turb/updraft that creates alt incr?) -> AS apparent incr -> back stick command -> alt incr -> AS apparent increase -> backstick command -> alt incr -> AS apparent incr -> backstick command -> rinse and repeat for x interations -> pilot's cross check on alt and / or att indicators alerts him "whoa, I'm climbing" -> PF reaction seen in change 7000 fpm climb to 700 fpm climb (or was that due to power redux???) -> pilot probably slightly behind aircraft at this point -> stall warning or stall indication-> then loss of stall warning -> AS unreliable for X amount of time -> AS comes back -> stall warning returns -> pilot now likely on back up inst scan or partial panel scan on his own display ...

How often did anyone practice this one in the sim?

Not sure how well that picture conforms to reality, perhaps not at all. When a pilot gets behind acft, tends not to say much until back with or ahead of aircraft ... though I've heard a few talk themselves back into a scan on hot mic ...
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Old 27th May 2011, 18:55
  #138 (permalink)  
 
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They (BEA) are trying to make us beleive that the only thing that failled were the pitot probes. The pilots "messed up" after the perfect AP disengaged...

Not what I see. I see pilots struggling to fly an uncontrolable airplane, with no attitude indication, at night with no horizon.

I don't believe the pilot would command aft stick knowing his nose was already up. Not even a student pilot would do this.

The aircraft went crazy on them.
Why?
Where did you dig that from?

The FDR and CVR data will eventually come out into the open, so it would be ridiculous to suggest the BEA are reporting anything other than what happened.

At a minimum stick to interpreting what is known, not what you want to believe - those are very different.
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Old 27th May 2011, 18:56
  #139 (permalink)  
 
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Peripheral Vision

In all the shaking, rolling, whistles and gongs, could the Pilot Monitoring possibly not realize the PF was holding aft stick? Could the PM, if in the right seat, override or at least neutralize the PF holding aft stick if he did know what the PF was doing?
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Old 27th May 2011, 19:00
  #140 (permalink)  
 
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To clarify ... if I am in RH seat, I move side stick, LH seat side stick does not move. Do I have that right, or wrong? Block diagram (old) suggests to me that would be the case. If the sticks inputs are summed and PNF's stick moves when PF stick deflects, you'd get twice the input you were looking for, right?

Last edited by Lonewolf_50; 27th May 2011 at 19:12.
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