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AF 447 Thread No. 9

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AF 447 Thread No. 9

Old 16th Aug 2012, 23:01
  #1361 (permalink)  
 
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Originally Posted by korrol
He’s right - but if you feed pilots air at a cabin altitude of 8000 feet (much lower in oxygen content than air at a real altitude of 8000 feet) then when the chips are down crews will make mistakes - and they did.
Almost every crew nowadays is fed 8000ft air. That most flights end uneventfully and large majority of emergencies are dealt with properly completely rebukes your theory but thanks for the entertainment.

Originally Posted by Organfreak
If you said anything like that to a pilot's face in a bar, you'd get your lights punched out.
Nice argumentation there. Not.

Originally Posted by CONF iture
Interested in the FULL story, not a partial one, that's it.
How about impartial?

Originally Posted by mike-wsm
I am not a pilot and have no qualification beyond a vaguely relevant degree. I never fly.
Who cares who you are! Amateurs or non-aerospace professionals did contribute significantly to discussions here.

Originally Posted by mike-wsm
You seem to be falling into the simplistic trap of assuming the elevators and THS were behaving normally. They weren't.
However, this is plainly false.

Originally Posted by CONF iture
Autotrim all the way as long as the data are believed to be reliable.
Inertial data. Per design. Write to EASA if you want to have it changed.

Originally Posted by CONF iture
You did mention a few times AMS, but I am not sure you fully grab the complexity behind the erroneous data and what could be the possible consequences for the Airbus scenario ...
Need to fly pitch and power and disregard the host of false alarms, perchance? How complicated is that?

Originally Posted by TTex600
Yes, he will need a lot of force to lower the nose
Here: G-THOF serious incident at Bournemouth. A lot of force, thou sayst? No force could lower the nose and the crew didn't remember to use the manual trim.

The way many a PPRuNer glosses over the fact we need to have very powerful THS in modern turbofan transports and that when mistrimmed they can be lethal on any aeroplane, not just on Bus, would have me worried about the knowledge level in today's cockpits if it weren't for the red warning at the bottom of this page.
Originally Posted by CONF iture
To the contrary, if the normal operation of a system is a contributory factor in the crash, the report is the very place where that system has to be analyzed.
It was. Conclusion was it behaved as expected and no recommendations to change it were made. Something wrong with it?

Originally Posted by Retired F4
When the aircraft is descending, and you want it to return to the assigned FL, you have to climb. For that you have to raise the nose (SS NU) and maybe you have to add power (TOGA). If 5° pitch is not enough, lets use more........
...until you zoom through your initial altitude and then bust it by 2500 ft with rate reaching 7000 fpm? Wouldn't you agree that we may call such a feat "overreaction"?

Originally Posted by TTex600
It seems painfully obvious that the crew handled the UAS event incorrectly and unprofessionally, but we still need to understand why they didn't put "the stick forward until the nose arrives there where you want it".
They had no clue what to do.

Originally Posted by Ian W
There is no prestall buffet or normal handling effects if you pull into a hammer-head stall or tail slide this was not far short of that.
At it's best, AF447 was measly 72.1° short of vertical, which is quite a bit of stretch to call "not far short of". Aeroplane never stalls in properly executed hammerhead and is only briefly stalled at very low speed during during tall slide, thence no buffet. Thank you for putting forward this entertaining and quite false theory.
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Old 17th Aug 2012, 00:26
  #1362 (permalink)  
 
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Originally Posted by Clandestino
The way many a PPRuNer glosses over the fact we need to have very powerful THS in modern turbofan transports and that when mistrimmed they can be lethal on any aeroplane, not just on Bus, would have me worried about the knowledge level in today's cockpits if it weren't for the red warning at the bottom of this page.
Something just isn't clicking here Clandestino. I'm well aware of the need for a powerful THS, as I suspect most every other pilot is also aware and that is PRECISELY the reason I find it disturbing that the Airbus THS operates without pilot awareness so much of the time. As this trim discussion continues, I find myself questioning the system more and more.

Originally Posted by Clandestino
They had no clue what to do.
The PF took the controls and announced such. That was correct. The PM announced the state of protections. That was correct. Yet you state that they had no clue.

If "they had no clue" is the cause, why haven't we seen a program immediately placed in our training to ensure that we all have a clue?

Last edited by TTex600; 17th Aug 2012 at 00:27.
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Old 17th Aug 2012, 00:35
  #1363 (permalink)  
 
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Hello,

I am reading the CVR from AF 447 and I wanted to know if anyone knew what the two letters P L meant when the Captain says "t'es P L toi" at 1h56 into the flight.

Thanks



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Old 17th Aug 2012, 01:08
  #1364 (permalink)  
 
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You can download the english version of CVR transcript here:
http://www.bea.aero/docspa/2009/f-cp...nexe.01.en.pdf
Hope it's help !
Note:
"t'es P L toi"
Asking if he have the right license for make the job of PF (pilot flying) when the captain is not in the cockpit

Last edited by jcjeant; 17th Aug 2012 at 01:12.
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Old 17th Aug 2012, 02:31
  #1365 (permalink)  
 
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Originally Posted by HN39
Without autotrim the FCS will use more elevator to achieve the Nz demand.
I think I can see now where we don't seem to understand each other :
No autotrim means no alternate law no more Nz demand.
Direct, just direct law, where 20% displacement of the sidestick will produce 6 deg up of elevators.
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Old 17th Aug 2012, 02:52
  #1366 (permalink)  
 
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No pilot I know couldn't have flown this aircraft or any aircrat by just using pitch and power. How about using what it had when the auto systems cut out. Why do we hire these pilots with minimum time that can't do simple tasks without autopilot? This is the future unfortunately.
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Old 17th Aug 2012, 03:26
  #1367 (permalink)  
 
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Originally Posted by OK465
The Boeings have an electric stop a degree or so prior to full travel, from which the trim limits can only be reached by rotating the trim wheel manually.
The Perpignan report told us that the A320 THS has an electric pitch-up stop at 11 deg for a maximum THS deflection is 13.5 deg nose up.
For the A330, according to A33Zab, there is no such electric limitation.
After re-reading his post, I can see he had already produced a possible reason for which the THS did not reach the max deflection.

But once again, it was the BEA job to develop that stuff ...

Last edited by CONF iture; 17th Aug 2012 at 03:27.
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Old 17th Aug 2012, 06:07
  #1368 (permalink)  
 
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For the A330, according to A33Zab, there is no such electric limitation.
After re-reading his post, I can see he had already produced a possible reason for which the THS did not reach the max deflection.
But once again, it was the BEA job to develop that stuff ...
If I understand A33Zab post (read between the lines ... ) maybe he think at the law (another!) "Unusual attitudes" who inhibit the autotrim system
Nevertheless .. nowhere in the FDR extracts of the BEA is show a trace of this law been triggered ......
I can be wrong ...

Last edited by jcjeant; 17th Aug 2012 at 06:08.
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Old 17th Aug 2012, 06:29
  #1369 (permalink)  
 
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Originally Posted by CONF iture
No autotrim means no alternate law no more Nz demand.
Direct, just direct law, where 20% displacement of the sidestick will produce 6 deg up of elevators.
I don't disagree with that. But you miss the point, or you are evading the issue, so we still don't seem to understand each other. Maybe we should leave it at that.

EDIT:: One last try: If the system had been such that in Alt2B from the onset of stall warning the THS setting had been limited between setting at stall warning onset and 2° nose down (i.e. no further uptrim would be applied), but otherwise as is, i.e. Nz law without high-AoA protections, then the elevator trace on FDR would have been as shown by the purple line on the graph up to the point where the elevator reaches 30° at 02:11:41 (101 seconds after 2h10). Up to that point the airplane's trajectory and the stickforce felt by the PF would have been identical to those in the accident.

Last edited by HazelNuts39; 17th Aug 2012 at 09:25.
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Old 17th Aug 2012, 08:26
  #1370 (permalink)  
 
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It is just comforting to know they might be there if the shit hits the fan.
Might be there does also imply that they might not be there? Wouldn´t it be more usefull to know that they are there or to know that they are absent? Would it be comforting to have an antiskid system built into your car, but not knowing wether it is active or on leave? I can´t see any sense in your position.

what I meant is that in Alternate Law you are in any case better off than in a conventional plane, as even in the lowest protected level it still offers certain protection.
Last try, then i give up. What kind of certain protections besides the mentioned load factor limits does it offer you are talking about? Would you please name them and describe them, that i can understand what kind of protections you are talking about? You also can PM me.
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Old 17th Aug 2012, 12:25
  #1371 (permalink)  
 
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The longer the flight, the greater the accident rate

EXENG AF337 had been in the air for over four hours.

The longer the flight at altitudes like 35,000 feet, (at a cabin altitude of 8000 feet) the greater the likelihood that pilots will screw up - see J H Goode (Journal of Safety Research "Are pilots at risk of accidents due to fatigue?" Issue 34: Pages 309–313).
The pilots may feel fine - but they're not. It's not their fault. They haven't got enough oxygen in their bloodstreams. Their problem-solving capacity is degraded. Not a lot, but enough to make a difference in a complicated emergency.
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Old 17th Aug 2012, 14:03
  #1372 (permalink)  

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Korrol

Obviously you wrote your post at the incapacitating altitude. AF337???
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Old 17th Aug 2012, 14:17
  #1373 (permalink)  
 
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Well, the 337 is a twin. And also has to do with 02.

All things considered, O2 is of course a factor. Pilots get used to it, and it will not likely change. Saying it is no factor is simply simplistic.

Last edited by Lyman; 17th Aug 2012 at 14:21.
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Old 17th Aug 2012, 14:25
  #1374 (permalink)  
 
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Originally Posted by HN39
If the system had been such that in Alt2B from the onset of stall warning the THS setting had been limited between setting at stall warning onset and 2° nose down (i.e. no further uptrim would be applied), but otherwise as is, i.e. Nz law without high-AoA protections, then the elevator trace on FDR would have been as shown by the purple line on the graph up to the point where the elevator reaches 30° at 02:11:41 (101 seconds after 2h10). Up to that point the airplane's trajectory and the stickforce felt by the PF would have been identical to those in the accident.
You simply cannot obtain a similar trajectory with an identical stickforce with 2 scenarios as different as one with a THS set at 3 deg and another one with a THS moving from 3 to 13 deg.
A simulator experiment would clearly point the difference.

Trimming in a stall is an unknown procedure. It is dangerous stuff.
We need to ask Airbus why they think differently.
As the BEA avoids asking the tough questions, we need to do it.

Last edited by CONF iture; 17th Aug 2012 at 14:26.
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Old 17th Aug 2012, 14:33
  #1375 (permalink)  
 
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Originally Posted by korrol
flight at altitudes like 35,000 feet, (at a cabin altitude of 8000 feet)
That is just not correct. At FL350 the cabin altitude would have been around 6500 feet. I note that in the passenger forum you repeated the same incorrect information over and over, despite being corrected by several people who's correct information you chose to ignore. Now you do it here as if repeating it makes it correct.

If the premise your conclusion is based on is wrong, and you know that it is wrong, what does that say about your conclusion or you?
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Old 17th Aug 2012, 15:19
  #1376 (permalink)  
 
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Originally Posted by CONF iture
You simply cannot obtain a similar trajectory with an identical stickforce with 2 scenarios as different as one with a THS set at 3 deg and another one with a THS moving from 3 to 13 deg.
What a strange statement!

Last edited by HazelNuts39; 17th Aug 2012 at 15:33.
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Old 17th Aug 2012, 15:54
  #1377 (permalink)  
 
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Originally Posted by CONF iture View Post
Trimming in a stall is an unknown procedure. It is dangerous stuff.
We need to ask Airbus why they think differently.
Airbus don't think differently - they simply never countenanced the idea that a pilot would pull into a stall, keep pulling through the stall warning and pull *again* once the stall was established.

Limiting the trim movement under stall conditions would be simplicity itself in terms of implementation - but the secondary implications (of which there are several) need to be thought through.

It's not a "tough question" - not even every contributor on this thread believes it's a *relevant* question.
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Old 17th Aug 2012, 15:55
  #1378 (permalink)  
 
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Originally Posted by HN39
What a strange statement!
As I say, at this point if you don't get the difference on a theorical ground, you would certainly get it through the practical experiment - If you ever have the opportunity to put your hands on a simulator, just try it, the word 'strange' won't have the same meaning.
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Old 17th Aug 2012, 16:06
  #1379 (permalink)  
 
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HN39:

If I may make an input regarding CONF's statement...

The manual (hand flown) stall QTG's for the simulator are specified to be done in Direct Law with a specific stop manual trim speed. As you decelerate below this speed, without benefit of trim, SS movements tend to be exaggerated to some extent in both directions to maintain a stable flightpath, with varying levels of spring force to deal with.

If the entry is done in Alternate Law, as the rate of airspeed decay progressively increases with the drag buildup, the autotrim input essentially outpaces any necessary SS commands and allows a more 'relaxed' SS input, with less awareness of any spring force.

I think this what he is getting at, but I could be wrong, and don't want to speak for him.

(CONF: Thanks for the reference to the A33Zab post)
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Old 17th Aug 2012, 16:22
  #1380 (permalink)  
 
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Originally Posted by Dozy
they simply never countenanced the idea that a pilot would pull into a stall, keep pulling through the stall warning and pull *again* once the stall was established.
I need to borrow the formula of HN39 here :
What a strange statement coming from you !
Dozy, you keep coming back on how crews have been pulling back on controls all the way during stalls, but Airbus 'simply never countenanced the idea that a pilot would pull into a stall, keep pulling through the stall warning and pull *again* once the stall was established'.

So you know about it but Airbus don't ... Give them a call.

Last edited by CONF iture; 17th Aug 2012 at 16:23.
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