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AF447 Thread No. 3

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AF447 Thread No. 3

Old 28th May 2011, 09:16
  #301 (permalink)  
 
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blind pew

No evidence so far released to consider hypoxia as a factor.
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Old 28th May 2011, 09:17
  #302 (permalink)  
 
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I wonder what the investigation will find, why the PF refrained from simply attitude flying. All attidude indicators should have been functional all the time and are the only hope to survive hand flying at night over ocean with partial panel. With the turbulence, roll and falling sensations vertigo had definitely set in. You can't fly by the pants over the ocean at night in a thunderstorm. The pilots had a mostly blue attidude indicatior in front of them, with ROD unwinding like hell. With all electrics operational inertial systems are very reliable. Can one of the Bus drivers comment if the flight display shows the attitude indicator in the situation they where in and not some garbage error messages?
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Old 28th May 2011, 09:23
  #303 (permalink)  
 
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Was the first stall warning valid?

How did they gain 3000 feet at a rate of 7000 feet/minute if they started off in a stall? Is it possible they were trying to climb over the weather? Or that they were in a strong updraft?
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Old 28th May 2011, 09:25
  #304 (permalink)  
 
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jcjeant
Read the BEA document again: it doesn't say that invalid speed condition lasted less than one minute, it says that inconsistency between LH speed display and ISIS speed display lasted less than one minute.
Note: The inconsistency between the speeds displayed on the left side and on the ISIS lasted a little less than one minute.
(my bold)

We can probably infer that further invalid speed conditions were equally reported on LH panel and on ISIS.
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Old 28th May 2011, 09:29
  #305 (permalink)  
 
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Aussie
guess you have never had a whiff of oxygen in cruise at night and seen what effect it has on the eyes.

others
BA 747 - why did they declare a mayday into egcc if they new what they were doing.

Didn't say they put full back pressure on the stick for 30 secs but I have witnessed pilots unintentional inputs when stressed.

Often in sailplanes had guys push right rudder or both when they thought they were not going to stop.

Never witnessed a anyone take the autopilot out in cruise at night to hand fly it - but then again I only worked for three flag carriers.

But then again we had SOPs which said we weren't allowed to fly manual if CWS was available - same with A/T on several types.
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Old 28th May 2011, 09:33
  #306 (permalink)  
 
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Originally Posted by JPI33600 View Post
jcjeant
Read the BEA document again: it doesn't say that invalid speed condition lasted less than one minute, it says that inconsistency between LH speed display and ISIS speed display lasted less than one minute.
(my bold)

We can probably infer that further invalid speed conditions were equally reported on LH panel and on ISIS.
We can also probably infer that the crew, having had fluctuating and differing airspeed indications, did not trust anything they saw on any ASI by the end, even if they had settled down.

G
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Old 28th May 2011, 09:34
  #307 (permalink)  
 
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Could anybody tell me why on a airliner that should have at least 3 sources of speed indicator (pitot tubes, GPS and inertial system), why the crew did not rely on the 2 sources that have been concomitant : GPS or inertial ?

Last edited by peplum; 28th May 2011 at 09:49.
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Old 28th May 2011, 09:45
  #308 (permalink)  
 
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We can also probably infer that the crew, having had fluctuating and differing airspeed indications, did not trust anything they saw on any ASI by the end, even if they had settled down.
As a pilot you know you are going to die at night over the ocean in a thunderstrom if you trust no instrument at all. I expect more will to survive from any pilot.
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Old 28th May 2011, 09:48
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blind pew

No,I only see it during the day in my operating theaters. So what kind of oxygen saturation then are you pilots registering then, in cruise. Why do your companies think this appropriate to normal flying. Why would pilots not insist on some oxygen supplementation normally, or don masks during such an abnormal circumstance.
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Old 28th May 2011, 09:50
  #310 (permalink)  
 
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Genghis
We can also probably infer that the crew, having had fluctuating and differing airspeed indications, did not trust anything they saw on any ASI by the end, even if they had settled down.
Sure. So we are back to my very first question: before discussing how they could have detected/fixed the stall condition, I'd like to understand why they didn't apply the unreliable airspeed procedure (fly pitch/thrust) in the very first place, which would probably have prevented the stall condition from developing.

As I read it from the few comments of 'bus drivers here, this seems to be the initial human cause of the issue (just after the technical cause associated with pitots malfunction).

Last edited by JPI33600; 28th May 2011 at 09:55. Reason: grammar
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Old 28th May 2011, 09:53
  #311 (permalink)  
 
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Cool

Hi,

Well .. it's come already over 300 posts !
And it's all speculations ... like any speculations .. or debuncking made after leaks in the press
I think I can name the BEA communication as "an official leak"
Just like in the newspapers (fragmented information who can only lead to more speculations) but this time the newspaper name is "BEA Time"
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Old 28th May 2011, 10:00
  #312 (permalink)  
 
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Originally Posted by JPI33600 View Post
Genghis
Sure. So we are back to my very first question: before discussing how they could have detected/fixed the stall condition, I'd like to understand why they didn't apply the unreliable airspeed procedure (fly pitch/thrust) in the very first place, which would probably have prevented the stall condition from developing.

As I read it from the few comments of 'bus drivers here, this seems to be the initial human cause of the issue (just after the technical cause associated with pitots malfunction).
That does seem to me to be the single biggest question - these chaps were experienced and current pilots unlikely to make such an elementary error. It seems likely that there is some other factor that we just can't see in the evidence at the moment.

G
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Old 28th May 2011, 10:24
  #313 (permalink)  
 
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Pitots

Three identical pitot tubes icing up uniformly and finally and collectively failing to provide AS information was the route cause of this accident.

Had they been manufactured by different companies they might have had a differential failure rate.

Just a thought.
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Old 28th May 2011, 10:24
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What could have bee arrived if the crew would have forgottent to rely on the pitot and would have tried to sustain 400kts ground speed below FL300 using GPS or inertial ?

Please answer.
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Old 28th May 2011, 10:27
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@ Blind Pew - Re the BA747 - just because they declared a mayday doesn't mean there was an actual threat to the aircraft present. The circumstances of the incident are now public knowledge. The aircraft was safely flyable with sufficient fuel at all times. There was no danger present, although the incorrect suspicion that there might be led to an abundance of over-caution.

On the subject of the back-stick input, it's well known that people can thrash the controls under extreme stress without realising it. However to maintain that input for a prolonged period is concerning.

Few people will disconnect an autopilot at cruise levels for a jolly, but most of us will have been required to do so at one time or another. The A320 is a far easier aircraft to fly at altitude than a 747 as it exhibits the same behaviour throughout the envelope. I presume the A330 is the same.
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Old 28th May 2011, 10:32
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Make the math ... and the result is not "little less than one minute"
The speeds were invalid because of disagreements between the sources ("incohérence") from 2:10:05 to 2:10:51, which is indeed a little less than one minute.

They then became invalid again at 2:11:40 until 2:12:02+15 -- but, as the report pointedly states, because of IAS falling below 60KT, NOT because of disagreement between the sources.
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Old 28th May 2011, 10:35
  #317 (permalink)  
 
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Aussie
we fly at cabin altitude of 8000ft.
the partial pressure of O2 is further decreased by recirculating the air through the cabin.
On long high flights it can result in severe headaches amongst other symptoms.
Anything over eight hours I developed bad ones.
Age paid it's price as well.
Many of our guys used our masks for 10 mins before we started descent on long haul night flights as well as when we were tired on short haul or hung over.
I've also used O2 around the ITCZ.
Once erroneously deviated 100+miles off track (with permission) due to miss reading the wx radar. Putting on the mask helped me to literally see the picture.

The air /O2 quality issue has somewhat been addressed by the dreamliner and O2 scrubbers.

But it goes back to cost and recirculation fans burn less kerosene than bleed air consumption.
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Old 28th May 2011, 10:50
  #318 (permalink)  
 
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hand solo
I know there wasn't any threat to the 747 but the crew didn't.
They declared what they thought was a genuine mayday and that there was a serious fault with the fuel system.
The cross feed procedure had been changed by BA to use the jettison pumps.
Although the manuals were correct none of the crew understood the basics of jettison pump feed.
The incident resulted in a change of checklist procedures as well as training.
It's all in the report.

This was a simple system not rocket science.

And the three of them had hours to refresh their knowledge as well as totally valid information.

Don't forget that our american cousins were seriously p*****d off with this fiasco.

My point is the air france boys had the cards stacked against themselves and I sincerely believe with the little that we know so far that it was an accident waiting to happen and but for allah I would end up in the same boat.
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Old 28th May 2011, 11:05
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Originally Posted by CONF iture View Post

henra, I don't think there is anything as Alpha Floor protection in case of A/THR failure.
I was also puzzled about this fact. On the one hand the text says A/THR failure.
I am not sure if this is the same as A/THR disconnect or if it strictly means failure.
On the other hand there seems to be no indication of Alpha_floor activation. But this could also be due to ADR disagree.
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Old 28th May 2011, 11:10
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Somehow, I feel that there is much discussion about the safety of the FBW-systems but not from control theory point of view. From control theory point of view the functionality is more important that the means the functionality is implemented. The same functionality can often be implemented with computers or analog devices. As far as I have understand, computers are often more reliable.

With computers you can implement features that can not be implemented with analog devices. However, the basic questions remains the same. You have to solve at least stability, reliability, controlability and observability problems.


I have a feeling that that the pilot aids are not the core problem but the practices. I don't know if the sales men, who promote the new protections, or technical persons who don't reorganize the potential problems, should be blamed.


When you have deep enough understanding on the control theory, you should understand that every time a inequality constraint is changing the status, the risk level is increased. When there are too many inequality constraints in the system, it becomes practically impossible to analyze it completely.


The common sense says that when system is driven against too many constraints, the control system capabilities are misused. It corresponds the reasons of the financial crisis: “insure” instruments were used as money making instruments.


I feel that every time a control law is driven against “hard” protection constraints, someone has made, at leas a small, mistake in the chain form design to practice. If it is a common practice to solve problems by driven the system against protections, there is something fundamental wrong in the culture.


I feel that every time protection is activated the situation should be studied afterward and practice to avoid the activation of protection should be learned. If it is acceptable to use protections in a normal operation, the safety gains of the protections are destroyed. Most likely the safety is decreased because the skills of the pilot are not gained.


As far as I have understood right, the cause of this accident is pilot error. It is hard to deny it. The real question is: what lead to the errors. We might found out that they acted relatively reasonable...


As a control engineer I feel that would be relatively easy to substitute the pilot in the “normal” conditions. I feel that the pilots are in on board to solve unexpected situations. Humans are better than computers in those conditions. However, human has to learn how to act. If in the training everything goes too smoothly, I have to ask what in hell the pilots do in the cockpit? The problem solvers have to trained to solve problems.
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