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AF 447 Thread no. 4

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AF 447 Thread no. 4

Old 30th Jun 2011, 14:23
  #581 (permalink)  
 
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From my armchair I have had fitted an old battery powered A/H on each instrument panel on my own ABs (they are cheap enough for me to have two). Whilst not as accurate as the full glass panel, working as it ought to. One or the other should be enough to to give me time to check the aircraft's pitch and bank
are not excessive, so I have time to check both my speed and altitude sufficiently adequately, using my GPS. And the check lists...

(We had to use the Astrocompass to check the compass's Deviation before we could land using the SBA. I cannot do that in my A or B, now.)

Some Tiger Moths had a spring loaded vane as an ASI. It was unheated.
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Old 30th Jun 2011, 15:40
  #582 (permalink)  
 
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......

Last edited by grity; 30th Jun 2011 at 22:40. Reason: corrected version on the next side..... grity
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Old 30th Jun 2011, 16:08
  #583 (permalink)  
 
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@grity

Congratulations at reverse engineering that FDR data, I guess there's no chance of a FOI request for the actual data after all this time - along the lines the 9/11 data some of which is know in public domain.

To cross-check your FPA calc I reckoned the peak climb rate of 6,000ft/min was achieved at CAS of 250kts = 45,000ft/min TAS @ 37,000ft. FPA = asin (6/45) = 7.6 degrees.

Is the difference just my eyes?
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Old 30th Jun 2011, 16:24
  #584 (permalink)  
 
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sensor_validation your 7.6 is a good middle value between my 0 and 15 in the climb

?!?
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Old 30th Jun 2011, 17:26
  #585 (permalink)  
 
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Pitch

thanks Grity,

I will modify my two extra A/Hs to flash a warning light if my pitch exceeds say 5 degrees but this should be modified to allow for lower altitudes - and I am trying to manage without Pitot or Static inputs to my armchair !
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Old 30th Jun 2011, 18:08
  #586 (permalink)  
 
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Originally Posted by PJ2
I will not say that the checklist is without its problems. It has been modified a number of times since its appearance in ~2002. I have said before and will say it again here: The UAS drill and memory items are confusing and that is a "support" factor, ('support' meaning well-written drills, checklists and procedures), which may even be relevant to this accident.
This paragraph is a key point in your last few posts.
And sadly, the way the UAS procedure is written is a true reflect on how neglected that procedure has been dealt by Airbus for a situation at cruising altitude.

As a matter of fact, pre AF447, how many times have we trained for UAS at cruising altitude ?
In my own experience ... never !

Following the Air Caraibes incidents, there was an apparent willingness to address the issue – That was in October 2008 – 7 months before AF447.



2 years after AF447A suivre … did not yet materialize.

Your concept Do nothing is mainly correct but is certainly not suggested by the UAS procedure the way it is still written up to now.
The way you detail it, is, IMO, mainly your own interpretation, and not supported by the text. It is not clear what is part of the memory items, what is not, what leads to what ... ?

As a starting point, what does mean If the safe conduct of the flight is impacted ?
In my book, the safe conduct of a flight is always impacted, from start to end.

And if the procedure has to be divided in two different course of action, as a start, it should be clearly mentioned to relieve any ambiguity :
  • If the safe conduct of the flight is impacted …
  • If the safe conduct of the flight is not impacted …
Where is such unambiguous bifurcation point ?
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Old 30th Jun 2011, 18:37
  #587 (permalink)  
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BOAC;
PJ - can you explain the logic of the angle of attack protection
Thank you for the question. I want to say something.

I am a mere bread-and-butter retired Airbus pilot who loves technical and human factors knowledge and who labours under a peculiar fascination concerning this aircraft which I flew and this design and its history. Years ago I heard ET's presentation on "Why We Designed Them the Way We Did" (and have the paper on same), and have alternately embraced and puzzled over the airplane since first flying the A320 in 1992 and the A330/A340 in 1999. I have been educated by those with far more experience than I on the Airbus and by some engineers who are possessed by an unusual patience and ability to explain things to a pilot.

Though I would like it to have been otherwise, I know nothing of aerodynamics or computer control systems. I know something about flying the Airbus and its "habits", and how to stay alive flying airplanes, a bit about flight safety and organizational factors in accidents and a bit more about flight data analysis.

The singular thing this thread has taught me is how little I really know, and what a pleasure it is to learn from others, a relationship which I hope is reciprocal. The older and greyer I get the more willing I am to let stuff lie in the weeds because this stuff always surfaces. I am less willing to "pronounce" on the why, the how and the what in sophisticated systems into which I have the merest cracks to peer through. On staying out of trouble in the Airbus, I think I can say something of value and have. But, despite the usual conspiratorial crack-pot views, for easily understood reasons I lean to trusting the BEA on this one and am willing to wait to see what they have to say on various points so intelligently raised but frustratingly pondered here.

My views on the AoA item?...I think its "ordinary" vice "extraordinary". I would guess that in this AoA Protection Law we are simply looking at a response to the standard right-hand side of standard buffet curves, I can only posit that the airplane would pitch up "on the Alpha Prot AoA" in accordance with the design, perhaps with input from the High Speed Protection Law, who knows? We know from the AAIB report (if not from access to AMMs, AWMs & TSMs, etc), that when the Alpha Protection Law is invoked due to high Mach No., a pull on the stick would take the aircraft (in Normal Law) to Alpha-Max and no further. The risk of an accelerated stall is assumed to be low to nil in Normal Law. We also know that the pilot can intervene fully, with a stick-forward (ND) response to essentially cancel the AoA Law once below the Alpha Protect Law triggering point. Rather than second-guessing the designers and the engineers on each point and at every turn, perhaps thinking about why the design is the way it is in toto to see what problems are being solved? I think it is fair to say that some credit after all, must be given these people who, with the exception of one or two who have contributed to the thread, know far more about the design. Would we have the aircraft pitch down as per the low-speed Alpha response?...I don't think so. I think we have to think about it a bit, in the context of the Airbus design and not in the context of non-fbw designs and expectations.

To me, the AoA response makes complete sense as a pilot of the Airbus. What has not been either appreciated or grasped by many, is, from the beginning, this design has required a different way of thinking, a different approach to training, to flying, to anticipating behaviour and to interacting with the machine, and it absolutely requires a positive attitude and approach towards it. If one is forever either fearful or hostile or otherwise actively diffident towards the design and the airplane, like prejudice itself, no amount of discussion, facts, knowledge or perhaps even actual engagement and understanding, is going to change one's mind. And that too, is a human factor.
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Old 30th Jun 2011, 19:04
  #588 (permalink)  
 
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To me, the AoA response makes complete sense as a pilot of the Airbus. What has not been either appreciated or grasped by many, is, from the beginning, this design has required a different way of thinking, a different approach to training, to flying, to anticipating behaviour and to interacting with the machine, and it absolutely requires a positive attitude and approach towards it.
Would it be fair to state that the AB pilot, except for direct law, is really flying the autopilot and not the airplane? Assuming, of course, that the AB FBW system, with its various protections, is really an autopilot with several different interfaces.

It seems to me that, once they stalled, the proximate cause of their not realizing they were in a stall was the fact that the stall warning behaved badly. Put simply, if the aircraft knows that AoA is above the stall number, the stall warning should go on and stay on until the aircraft is not stalled any more.
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Old 30th Jun 2011, 19:46
  #589 (permalink)  
 
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What I know about FBW I have learned from PPRuNe. Whenever there is a discussion about a problem with flight control systems, it always seems to be about A and not B.
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Old 30th Jun 2011, 19:49
  #590 (permalink)  
 
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Understanding Angle of Attack.

PJ

I too am an old retired Boeing and Airbus pilot. My take is that AoA is important when dealing with very slow flight, i.e. when a Navy pilot has to bring it in on a very short deck with rolling seas. Or an F-16 pilot is carrying assymetrical external stores which alters stall speeds and AoA and has to restrict “G” loads after bombing runs.
Air carriers uusally have more than sufficent runway lengths thus never have to be very slow. Thus “Stall speeds and approach speeds” are pertinent. Therefore merely keeping a sufficient extra speed eliminates any need to even consider AoA.
And we have never had to even consider or train for it. In the plane or simulator.

We are not taught how to use it and do not have an AoA indicator that I’ve ever seen.

In auto any mode it may be there but to me invisible.

Here in 447 a plane runs into wild gyrations. Everything kicks off. The only task is to maintain control of the aircraft. Nothing seemed to work, not any of the automated protection systems. And zero guidance for the crew.

It is not possible to have any human train for such an eventuality. Nor for any human to cogently understand and deal with this myriad of failures all at the same time.

Other than to avoid getting close to this perilous situation.

All of the wise council regarding, “Well look at how many times pilots did not encounter this situation”, is not good enough for me.

Going into or near violent thunderstorms and their unknown qualities carries a risk that a paying passenger does not want, nor need to put up with.
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Old 30th Jun 2011, 19:53
  #591 (permalink)  
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PJ - you will find on another thread that I endorse your views that a " different way of thinking, a different approach to training" is needed and that I do not think it is in place.

I firmly believe that in this transitional period where humanity is coming to terms with a technology that is advancing at an incredible pace, aviation design should in simple terms try to conform to 'the norm' ie what would the average competent pilot do here? I have an overspeed situation - would I pull up 4000ft? No, I would control my speed another way. I am stalled - do I expect my warning system to quit? NO. I would like it to carry on telling me I am stalled - it is no secret - it knows! The system has trimmed my tail to the point where I may not be able to fly out of it. Just as with the AMS 737, I would expect some 'big numbers' sign to warn me and preferably to be asked if I really wanted that. Not '"Don't ever touch that wheel - you don't need to". That is what I mean by the 'logic' of the system.

Many years ago I began watching Airbus develop the fbw technology in a state of geeky technophile awe. The shine has long since departed. Friends who have 'crossed over' tell me it is a great system. A great system when all is going well is the kindest thing I can say.
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Old 30th Jun 2011, 19:56
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Cool

Hi,

To me, the AoA response makes complete sense as a pilot of the Airbus. What has not been either appreciated or grasped by many, is, from the beginning, this design has required a different way of thinking, a different approach to training, to flying, to anticipating behaviour and to interacting with the machine, and it absolutely requires a positive attitude and approach towards it. If one is forever either fearful or hostile or otherwise actively diffident towards the design and the airplane, like prejudice itself, no amount of discussion, facts, knowledge or perhaps even actual engagement and understanding, is going to change one's mind. And that too, is a human factor.

PJ2
So .. we return to starting blocks ... again
If you know that (a different approach to training) ... why (it's seem's by all I read here from professionals) .. that the training is qualified as "low" at AF and certain other companies ?
If you know that a different approach is needed .. certainly Airbus and consequently .. companies know that.
Why .. after sooo many years .. some voices for more training and revised procedures .. ?
Who was blind or negligent ?
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Old 30th Jun 2011, 20:18
  #593 (permalink)  
 
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What would the average competent pilot do here?

...ie what would the average competent pilot do here?
A competent pilot driving in darkness toward known convective activity would have his eyes glued to the attitude indicator and occasionally cross check other indicators. As soon as the autopilot clicks off a competent pilot would take a deep breath and look about for possible reasons, but not do anything unless the flight path of the aircraft is changing. If the aircraft had been in trim before autopilot disconnect, there would not be any major departures from the previous attitude, unless there is a flight control system hiccup.

I have read, and reread, the BEA note over and over and I do not see any direct statement that the pitch up of AF447 was uncommanded. If someone else sees otherwise, let me know.

Someone earlier stated that, ordinarily, an autopilot disconnect should not be considered an emergency yet it appears that many AB pilots think it is. Clearly the AF447 pilot thought that way and he acted inappropriately.
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Old 30th Jun 2011, 20:46
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BOAC, "The system has trimmed my tail to the point where I may not be able to fly out of it."

The system includes the pilot. And it was direct pilot input that caused that trim setting to exist. I also note it MAY be time for a remedial read on the BEA release again. The trim stayed sane until after the PF input full NU (and full left.)

Originally Posted by BEA
At 2 h 10 min 51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight.
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Old 30th Jun 2011, 21:04
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Whenever there is a discussion about a problem with flight control systems, it always seems to be about A and not B.
Do a search on B737 RSEP.
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Old 30th Jun 2011, 21:45
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Smilin Ed
" If the aircraft had been in trim before autopilot disconnect, there would not be any major departures from the previous attitude, unless there is a flight control system hiccup.

I have read, and reread, the BEA note over and over and I do not see any direct statement that the pitch up of AF447 was uncommanded. If someone else sees otherwise, let me know."

Then what caused the 7000 fpm rate of climb? If not strong updrafts. Which can cause attitude changes, and thence auto trim inputs.

The nose may be in a nose down attitude at the same time it is carried aloft.
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Old 30th Jun 2011, 21:48
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Cool

Hi,

DCA09IA064
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Old 30th Jun 2011, 22:34
  #598 (permalink)  
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BOAC;
Many years ago I began watching Airbus develop the fbw technology in a state of geeky technophile awe. The shine has long since departed. Friends who have 'crossed over' tell me it is a great system. A great system when all is going well is the kindest thing I can say.
Well, I guess there is no point in continuing then. You have your mind made up re Boeings, in the face of a very successful airliner series which works very differently than the old B737.

The world is apace with technological change - has been for fourty years. Although you say philosophically that you 'firmly believe in this transitional period...', you shrink the argument to Airbus system design, resisting every point of explanation regarding the "new" technology offered by those who actually know and fly the machine.

The AF 447 accident is not going to be solved in this fashion, and the A vs B is never going to be resolved, but merely surpassed.

Thanks for the opportunity in our dialogues to do a lot of learning about both my airplanes. I loved the Boeings, Douglases and Lockheed in which I spent thousands of hours and when it came to move to the left seat on the A320 I can tell you it was very hard work and not many people knew very much about the airplane, (we didn't even have VNAV). I wouldn't take the Airbus "over" any other aircraft, (my favourite by far was the L1011-500) but it and the other two were a joy to fly and puzzle over, for fifteen years. For me the shine never left but I can understand why it might.

However, I think our concern should be for a new generation coming into the industry who "never flew an airplane" and were, as one A330 captain recently wrote about how to think of the A330, 'gamers' (not pilots), and I suspect there, we would find a few evenings over ales!
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Old 30th Jun 2011, 22:37
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the newer version with better CAS/TAS correction, thank you sensor_validation
of the FPA and AoA for the A340....during the zoom climb

with the given values of Altitude and CAS/TAS for every 5 sec. I calculated FPA (arcsin FPA = delta altitude / distance in 5s) yellow line;
and then with the given Pitch value the AoA (AoA=Pitch-FPA) blue line

the red and black line for Altitude and CAS has no scale....

if the AoA-protection-law was in regiment in the time between the MMO-exeed and 2 s after the first push with the sidestick, then the graphic show that in this time the AoA was not higher than 5 deg

"the AoA protection law seeks to hold the angle of attack constant at alpha prot" wrote the AAIB Bulletin.....

AoA is not the angel for the wing-flow, it is the angel between the direction of the fuselage and the flightpath (FPA) and the calculation did not include the turbulences.....

(I take away the first version)
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Old 30th Jun 2011, 22:38
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Originally Posted by bratschewurst
Put simply, if the aircraft knows that AoA is above the stall number, the stall warning should go on and stay on until the aircraft is not stalled any more.
This is precisely what the manual advertises ... but live experiment prove it wrong.

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