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AF 447 Thread No. 9

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AF 447 Thread No. 9

Old 11th Jul 2012, 20:01
  #261 (permalink)  
 
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but we don't really know if the airplane was unable to recover from a stall.
Nor do we know that it could have been recovered from the stall induced by the PF. What we do know is that there was no procedure (certainly no tested procedure) known to the pilots for safely recovering from a fully developed stall. Obviously getting the nose down and unloading the wing - but for how long? And, if there had been a procedure, wouldn't it have used airspeed as a guide to when to start pulling up? I am skeptical that even a pilot more experienced in hand-flying large transport aircraft than were the PF and PNF (the captain of AF 447, for example) would have been able to fly AF 447 out the stall induced by the PF without breaking something, especially in the absence of reliable and trusted airspeed information.
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Old 11th Jul 2012, 20:46
  #262 (permalink)  
 
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Reliable spped

would have been able to fly AF 447 out the stall induced by the PF without breaking something, especially in the absence of reliable and trusted airspeed information.
The BEA estimate reliable speed after 29 seconds
Page 24 Final report
At about 2 h 10 min 36, the speed displayed on the left side became valid again and
was then 223 kt; the ISIS speed was still erroneous. The aeroplane had lost about
50 kt since the autopilot disconnection and the beginning of the climb. The speed
displayed on the left side was incorrect for 29 seconds.
Page 25
remained in the latter position until the end of the flight. Around fifteen seconds
later, the ADR3 being selected on the right side PFD, the speed on the PF side became
valid again at the same time as that displayed on the ISIS. It was then at 185kt and the
three displayed airspeeds were consistent. The PF continued to make nose-up inputs.
The aeroplane’s altitude reached its maximum of about 38,000 ft; its pitch attitude
and angle of attack were 16 degrees.
So if it was to be stall recovery .. they had good speed indications ..

Last edited by jcjeant; 11th Jul 2012 at 20:50.
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Old 11th Jul 2012, 20:55
  #263 (permalink)  
 
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BTW

it's BRATWURST

not

Bratschewurst
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Old 11th Jul 2012, 21:16
  #264 (permalink)  
 
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jcjeant

The BEA estimate reliable speed after 29 seconds
Page 24 Final report
Which is all very fine, but you know that now, they did not know what was good.

I'm not a pilot but I find it very interesting how many pilots called these guys idiots. For me, they were qualified, they were trained, it was certified, it happened. It could happen again, WE SHOULD BE WORRIED.

I would really like to see a survey of current pilots of similar equipment as to whether they think these guys were idiots. Give me a list of those who say yes and I will pull the emergency exit door if I hear them on the PA prior to take-off. (Just joking, probably get arrested for this if it were a tweat etc,...)
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Old 11th Jul 2012, 21:49
  #265 (permalink)  
 
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Originally Posted by RetiredF4 View Post
If PF would have only released the SS on his way up to the apogee (with decreasing speed) the FCS in ALT2B without protections would have deflected the elevators and in the following the THS Trim to full nose up to maintain the 1g (which is the demand with SS neutral) until the same result would have taken place,
Sorry for the nitpicking that will follow:
In a C* FCS law the g load command will progessively blend over to a pitch rate demand below a certain speed threshold.
But the result would be as you described (A pure g load law would even try to increase pitch in order to maintain g when aaproaching the stall).
The C* law would (try to) hold attitude (read pitch) constant at the value initially commanded by the PF.
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Old 11th Jul 2012, 21:54
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Originally Posted by roulishollandais View Post
The voting system between ADR and IR is not enough analysed for example.
Is there a voting system between ADR and IR ?

I understood there is a voting system between the ADR's and a voting system between the IR's. And that logic was described.
But between the two? How would you vote between Air Data and Inertial Data? Normally they are complementary (not competing) data.

Could you reference to a document or a link where this is described?

Last edited by henra; 11th Jul 2012 at 21:55.
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Old 11th Jul 2012, 22:21
  #267 (permalink)  
 
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Originally posted by henra ...
The C* law would (try to) hold attitude (read pitch) constant at the value initially commanded by the PF.
Which is the reason the THS started to move NU on the final climb into the stall, even though the elevator was around 7° NU.

Last edited by mm43; 12th Jul 2012 at 02:47. Reason: spelling!
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Old 11th Jul 2012, 22:37
  #268 (permalink)  
 
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Would the THS have stopped had a shaker/pusher been installed? What manner of seductive force was applied to the regulator such that a shaker/pusher was not required on this aircraft? Would it have mooted all discussion by virtue of preventing the pilots from maintaining the STALL?
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Old 11th Jul 2012, 22:45
  #269 (permalink)  
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I'm not a pilot but I find it very interesting how many pilots called these guys idiots

I suggest that comment is quite unreasonable.

The problem of concern (relating to the chaps in the front at the time) involves consideration of their training (which then involves consideration of their employer's training programs and philosophies) and subsequent piloting skill set, as well as experience overall.

It is reasonable to presume that they were typical fellows with typical mental capabilities and survival instincts .. but certainly not idiots.

We are all at potential risk of failing if the conditions are too far out of our personal comfort zones .. indeed, as is observed periodically, the simulator can be used as an instrument of torture to overload any pilot to the point where he/she cannot cope and, hence, fails. Pointless exercise but it happens.
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Old 11th Jul 2012, 23:15
  #270 (permalink)  
 
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Originally Posted by mm43 View Post
Which is the reason the THS started to move NU on the final climb into the stall, even though the elevator was around 7° NU.
The concurrent action of the PF slamming the sidestick against the back stop and holding it there probably contributed to the extreme THS angle.

Originally Posted by Lyman View Post
Would the THS have stopped had a shaker/pusher been installed? What manner of seductive force was applied to the regulator such that a shaker/pusher was not required on this aircraft? Would it have mooted all discussion by virtue of preventing the pilots from maintaining the STALL?
Because stall prevention works differently in a FBW airliner. Stick "pushers" were a relatively crude safety device that grew out of '50s technology, and the proliferation of T-tail designs from the late '50s to mid '60s. The only regulator that required them (regardless of empennage configuration) was the UK's CAA.

To my mind the only line accident where the stick pusher was a factor was the BEA548 Trident crash in Staines, and in that case the crew disabled the stick pusher in the middle of a stall, sealing the fate of the aircraft.

There are numerous cases of accidents where a stick shaker was ignored or dismissed as erroneous by the crew - including Birgenair.

One of the BEA's recommendations is for Airbus to bolster the auditory stall warning with extra visual clues.

However, based on prior experience it seems that if a stall warning or automatic recovery does not fit the crew's mental model, then even if you wire the stall warning to a cattle prod there's a chance that it will not be heeded.
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Old 11th Jul 2012, 23:37
  #271 (permalink)  
 
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sriajuda @ 16:54

I think the goal is definitely not to produce identical pilots, but to train all pilots to minimum standards. The standard is set, though arbitrarily, by other than the crew, and experience and skill are varied, it is human nature.

For example, if there were two identical PF's and one had acquiesced to the other, the result on 447 would have been the same? No, because the position is different, the perspective is different, etc. No matter, it is clear that at least at the start, PNF had the picture correct....

How many have said the PF should have handed over to PNF? Merely looking at route experience, that would be logical.

My point above is meant to demonstrate the benefits of incorporating separate designs into two devices that accomplish the same task on an airliner. What defeated the Thales (microgranular water ICE), historically had less effect on Goodrich, type for type. So in grading the two, Thales is found wanting in ICE resistance; perhaps Goodrich has a different weak spot. Redundancy in the face of common fault is worse than no redundancy at all. Back up with a separate design approach is far better.
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Old 11th Jul 2012, 23:45
  #272 (permalink)  
 
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Originally posted by DozyWannabe ...
The concurrent action of the PF slamming the sidestick against the back stop and holding it there probably contributed to the extreme THS angle.
I can accept that, but my comment was in relation to when the THS started moving in an attempt to hold pitch attitude constant at the value initially commanded by the PF, as airspeed went south.
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Old 11th Jul 2012, 23:55
  #273 (permalink)  
 
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Absolutely - but THS behaviour is entirely predicated on command trend over time. If the sidestick command was an initial nose-up followed by neutral then the THS woudn't have moved. What caused the movement was the best part of a minute where the sidestick commands were half nose-up for extended periods of time.
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Old 12th Jul 2012, 00:01
  #274 (permalink)  
 
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Thank you for the various contributions to " Sensitive Altimeter" suggestion. It would only have been of benefit as a possible attention getter once stalled.

As an ignorant newbie I sat myself in PF's seat on 5th. Aug. last year Thread 5. #1577 to see how I would feel in his circumstances. ( I have learned a lot since, thanks to the very wide ranges covered by contributors to PPRuNe.)

For Lyman and others I used "...A/P Off.." as a shorthand for " not functioning at the moment whatever the position of a switch" !
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Old 12th Jul 2012, 00:21
  #275 (permalink)  
 
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@Linktrained

A decade or two ago, there was a lot of debate around digital altimetry display versus the old "steam gauge" design - predicated on the idea that the old analogue design could be "read" at a glance whereas the digital display had to be read completely. Of course, with the "tape" display behind the precise altitude, this difference is mitigated. In the sim I could certainly read the descending trend at a glance once the stall was established!

I think most of us understood what you meant by "AP OFF". For everyone's future reference the AP was not only "OFF", but latched off (i.e. impossible to re-engage) as soon as the law changed to Alt 2.

[ I suspect Lyman's fishing for "AP was mysteriously re-engaged"... ]
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Old 12th Jul 2012, 02:00
  #276 (permalink)  
 
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DozyWannabe;

I think we have had this THS discussion previously.

As BOAC would say, "that Oozlum bird is circling again!!"
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Old 12th Jul 2012, 02:23
  #277 (permalink)  
 
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Dozy regarding my fishing.... It is Airbus who warns not to reselect Autopilot: "The autopilot may command undesirable Pitch attitudes, resulting in damage to the aircraft" (or something like that.) It is not I who first asked re: the autopilot in AL. If as you say reselect is impossible, why do Airbus warn pilots not to "reselect"? For that matter, why do they direct the pilot to turn off a/p as part of the drill? Isn't it already off, and "latched out"? Hmmm?

I assume an apology is out of the question.

Re: BEA salaries and the Law. My statement addresses the "Appearance of impropriety". The appearance is there, not my opinion, it is there. I cannot prove skulduggery, nor can you prove its lack... I can prove that Airbus profits go into the Government fund that pays the salaries and benefits of all its agencies. To that extent, you are barking up a tree.

The agency that regulates our banks in this country, (and the ones in France) also derives its budget from the regulated, through fees and charges. Do you claim that the Banks are treated with objectivity equal to a harsh analysis thereof?

Last edited by Lyman; 12th Jul 2012 at 02:47.
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Old 12th Jul 2012, 03:17
  #278 (permalink)  
 
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Originally Posted by DozyWannabe View Post
Originally Posted by airtren
With the current design, the 3 pitot tubes are not only of the same type and same manufacturer, but they are also located pretty much in the same place - under the nose...
Not quite true.... The tubes themselves are located on opposite sides of the airframe (with the standby just forward and below the Captain's primary pitot tube).
If you think that the placement on "opposite sides" under the nose, protects the pitot tubes from sharing the same fate facing the weather, you need a reminder that at a body width of 5.64 meter, the maximum cross-span of the A330 could be just that.

As the location of the pitots is not diameter opposite, the cross span is less than the diameter. Based on memorized photos, I would say it's rather 3 meters between opposites, and abouot 1-2 meters between neighbor tubes. But even if it were 5.64meters, that is nothing when compared to the considerable larger width of weather fronts that the A/C is usually crossing. That qualifies for a "pretty much the same place - under the nose".....

Last edited by airtren; 12th Jul 2012 at 03:23.
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Old 12th Jul 2012, 03:24
  #279 (permalink)  
 
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Originally Posted by Dozy
In the sim I could certainly read the descending trend at a glance once the stall was established!
The trend, yes. But.....

Were you aware of the actual altitude? Would you be able to read the actual altitude with a heavy buffet?
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Old 12th Jul 2012, 03:32
  #280 (permalink)  
 
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Originally Posted by bratschewurst View Post
Nor do we know that it could have been recovered from the stall induced by the PF. What we do know is that there was no procedure (certainly no tested procedure) known to the pilots for safely recovering from a fully developed stall. Obviously getting the nose down and unloading the wing - but for how long? And, if there had been a procedure, wouldn't it have used airspeed as a guide to when to start pulling up? I am skeptical that even a pilot more experienced in hand-flying large transport aircraft than were the PF and PNF (the captain of AF 447, for example) would have been able to fly AF 447 out the stall induced by the PF without breaking something, especially in the absence of reliable and trusted airspeed information.
This reminds me of the case of the September 1994 Tarom A310 event at approaching Orly/France , which is an example of pilots knowing what needs be done, at a stall - from manual flying training - and who in fractions of seconds, recovered from the stall - A/C almost vertical nose up - at a much lower altitude, and avoided any material or physical damage to the A/C or to the passengers - no-one was injured.

See:

Last edited by airtren; 12th Jul 2012 at 03:35.
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