Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

AF447 Thread No. 3

Tech Log The very best in practical technical discussion on the web

AF447 Thread No. 3

Old 30th May 2011, 00:58
  #661 (permalink)  
 
Join Date: Apr 2008
Location: US Virgin & British Virgin,Islands
Posts: 75
Likes: 0
Received 0 Likes on 0 Posts
What caused the roll just before the AP went off....?

Excellent question after following this terrible event for two years-----where exactly was the VS at this point in time?Does anyone know for sure as yet?
What would the flying characteristics be----if any?
Just a thought from a low-hours person...which I am sure all of you guys,and the BEA,have already considered?
Loerie is offline  
Old 30th May 2011, 01:06
  #662 (permalink)  
 
Join Date: Mar 2008
Location: At home, retired 2012
Age: 75
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
infrequentflyer789,

We had to wait for the THS to move forward and regain flying speed, longer than I had, wrongly, anticipated. Nose down pitch had to be maintained pushing the stick. Usually, once pitch is set, the stick may be released, but not that time, until THS was in position. Nothing wrong with flight controls, loss of altitude because we delayed recovery on purpose.
jcarlosgon is offline  
Old 30th May 2011, 01:13
  #663 (permalink)  
 
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 81
Posts: 1,461
Likes: 0
Received 0 Likes on 0 Posts
Takata
Well, I think that's a bit jumping too early at those trim wheels.
Could be, but, "Use it or lose it" still applies. It shouldn't be a stranger.
You need to train a few exercises where you have to find out where the darn thing is set, preferably in response to a scenario, and thereby get it into your scan and thought processes.

Don't you think if the AF447 crew had seen the trim position - the light bulb would have come on? And the Perpignan crew also?
Machinbird is offline  
Old 30th May 2011, 01:25
  #664 (permalink)  
 
Join Date: Jun 2009
Location: Paris
Posts: 691
Likes: 0
Received 0 Likes on 0 Posts
Hi Loerie,
Originally Posted by Loerie
where exactly was the VS at this point in time?Does anyone know for sure as yet?
Beside few die-hard tailsuckers, everybody seems fairly convinced that the VS was still planted exactly where they put it at the factory.
takata is offline  
Old 30th May 2011, 01:35
  #665 (permalink)  
 
Join Date: Sep 2005
Location: N/A
Posts: 131
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by milsabords
Cher cousin, it does not sound ambiguous to me: "en butée" (full stop) applies to "gauche" (left) and "à cabrer" (nose up).
Otherwise it would be: "à cabrer et en butée à gauche", or "à gauche et en butée à cabrer".
Let me clarify: the way the French version is written, the term "en butée" could either apply to both the left and up inputs, or to the left input only, the up input not being to the stops. The English translation implies full left AND full up input (both to the stops)
Minorite invisible is offline  
Old 30th May 2011, 01:37
  #666 (permalink)  
 
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 80
Posts: 1,330
Likes: 0
Received 0 Likes on 0 Posts
Originally posted by takata ...
Some questions I'm asking myself:
1. was the first stall warning "real" when AP went off?
2. what caused this roll just before AP went off?
The answer is undoubtedly related to these:-

2:11:49 FLR/FR0906010210 34111506EFCS2 1,EFCS1,AFS,,,,,PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA),HARD
2:11:55 FLR/FR0906010210 27933406EFCS1 X2,EFCS2X,,,,,,FCPC2 (2CE2) /WRG:ADIRU1 BUS ADR1-2 TO FCPC2,HARD

The first opportunity for these FLR messages to be transmitted.
mm43 is offline  
Old 30th May 2011, 01:56
  #667 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 76
Posts: 2,483
Received 0 Likes on 0 Posts
TLB;
Originally Posted by TLB @ 29th May 2011 15:44
Originally Posted by JD-EE
TLB - TO/GA was not asserted until the second stall warning. At about the time of the first stall warning, perhaps before it upon AP/AT disconnect, the PF simply raised the nose a little and left the CLB default throttle setting.
JD-EE,

Thanks. But this is exactly the point I am trying to raise. If the PF initially thought his main problem was an unreliable airspeed situation, then his initial response (raised the nose a little and left the CLB default throttle setting - your words) was exactly the right thing to do, according to the C/L.
With respect TLB, no, this is not "exactly the right thing to do" for an Unreliable Airspeed event in cruise.

Please reference post #2269, and the First BEA Interim Report, Page 69 and Appendix 7.

The UAS drill has two sections - the memorized items are to be executed when the safety of the flight is at immediate risk, which is primarily at and just after takeoff, (as the Birgenair and Aeroperu accidents demonstrate). When to apply the memorized items is stated in the expanded training documents for the A330 and so should be no mystery to those who know their stuff. It's how drills and checklists are run.

After the qualifying conditional, (is the flight at immediate risk, yes/no), and the AP/AT are disengaged etc, there are the three conditional statements which refer to the A330 acceleration altitudes, stating pitch and thrust settings which provide an immediate "safe zone" until the aircraft is at a suitable altitude.

The qualifying conditional statement at the bottom of the memorized drill, is actually the second statement in this drill IF the flight is not in immediate danger.

The statement requires that the aircraft be leveled off for troubleshooting. Troubleshooting means, while stabilizing the aircraft (essentially "doing nothing"), getting out the QRH for the pitch and power settings for the weight and altitude, (in this case, FL350), and then calling for the "ECAM Actions" when the aircraft flight path is stabilized.

This guidance is in a number of Flight Crew Training Manuals and has been the SOP for a UAS event since around 2005, perhaps earlier.

Whether the pitch-up is this particular response, or a response which is entirely unrelated to the UAS event remains to be determined and we cannot determine this with the information we have. But there are documents cited here which tell us that such a response was a concern. As I have said a number of times when discussing this scenario, one way or another, it needs to be confirmed or dismissed as part of the overall investigation as to why such a response was executed.

mm43;

I know that you will know this but, for the benefit of those who don't, the ACARS messages do not capture any information about a stall, nor the associated warnings or indications, just as the CMC does not record Overspeed warnings. It is, after all, a maintenance system, not a diagnostic flight data tool as some have tried to make it.
PJ2 is offline  
Old 30th May 2011, 01:59
  #668 (permalink)  
 
Join Date: May 2011
Location: Brazil
Age: 54
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Agreed

bubbers44 said!

Somehow the pitot tube icing up caused the pilot flying who hadn't probably handflown the airplane much before lost his airspeed thought Airbus says it won't stall so pulled back so when the static source at his higher altitude gave him with the trapped pitot pressure caused the overspeed warning he retarded the throttle, then came the stall warning which he ignored so put it in a deep stall 3,000 ft above his assigned altitude. You cannot zoom climb an airplane that large without running out of airspeed. Everybody knows that. Other than monitoring the autopilot I wonder how many hours he had flying manually in an airliner. I heard he had 800 hrs in type and less than 3,000 total hours. How many hours was not monitoring the autopilot?
Like I said in my first and previous post, I´m not a pilot, I´m a
doctor. But something tells me, bubbers44 has it figured out!

Inexperienced pilot for that kind of complex machine, flying in a corrupted
environment, faced with a dual challenge (what´s going on outside, and what´s going on inside), miss-reacted maybe naively (expecting) thinking all the protective envelopes would prevent the a/c from a high altitude stall - just as he might have been told in training for that type of a/c!

Who knows? In my line of work, we´re sold a lot o BS for truths! And many inexperienced doctor just buy the idea; never question, do as your told. I figure in the aviation world similar approaches are used to sell you erroneous info!


Don´t mean to offend anyone here, but the sum of circumstances is
building up to this unfortunate reality.

At least this is my two cents worth!
NandoCarioca is offline  
Old 30th May 2011, 02:04
  #669 (permalink)  
TLB
 
Join Date: Mar 2009
Location: Ottawa, Canada
Posts: 67
Likes: 0
Received 0 Likes on 0 Posts
PJ2,

Thank you for your informed and detailed response.
TLB is offline  
Old 30th May 2011, 02:05
  #670 (permalink)  
 
Join Date: Jun 2009
Location: Paris
Posts: 691
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Machinbird
Don't you think if the AF447 crew had seen the trim position - the light bulb would have come on? And the Perpignan crew also?
In hindsight, with all these informations available to us, they would certainly have acted differently. But it looks like a tunnel vision issue up to this point, like if something took all the PF attention: it is not even sure that a giant red warning "THS +13 degree" painted on his PFD would have made the outcome different if he was believing to do exactly the right thing.
This THS information would have been paramount only if he had tried to pitch full nose down but lacked from elevators authority. Now, was this even attempted before it was too late?
If not, the main issue about what crucial information didn't reach the PF in time lie certainly elsewhere.
takata is offline  
Old 30th May 2011, 02:15
  #671 (permalink)  
 
Join Date: Oct 2007
Location: France
Posts: 136
Likes: 0
Received 0 Likes on 0 Posts
Hi,

About the BEA paper: A little time after BEA read VCR, it appeared in the news (a leak?) that the Captain gone back and was heared "shouting orders to his pilots". This phrasing ("crier des ordres" in French) appeared curious to me and I remember thinking was it "shouting orders from the other side of the locked cockpit door"? Inaccurate thinking, but why BEA tells nothing about what the Captain said. It would be very interesting to know what was his perception of the situation, no? Especially after "the PNF tried several times to call the Captain back" was written by BEA (which could mean "between the lines" the PNF was dubious about PF actions).

In very different domain, about the Pitots icing problem: many, here, have given ideas. But there is very simple one, imho. Have one or two "inversed" Pitots, ie Pitots "looking" backward. The precision would be less accurate, as the extent of the measurement scale would be reduced between true pressure and zero, but this would be better than nothing. Why this would be not possible?
Shadoko is offline  
Old 30th May 2011, 02:16
  #672 (permalink)  
 
Join Date: Jun 2009
Location: NNW of Antipodes
Age: 80
Posts: 1,330
Likes: 0
Received 0 Likes on 0 Posts
PJ2
It is, after all, a maintenance system, not a diagnostic flight data tool as some have tried to make it.
Welcome back, and thanks for the timely reminder!

There is something about the AP/ATHR OFF that may be related to the questions takata is/was posing. Svarin has also shown keen interest in this area, and ultimately time will tell whether it was warranted or not.
mm43 is offline  
Old 30th May 2011, 02:18
  #673 (permalink)  
PJ2
 
Join Date: Mar 2003
Location: BC
Age: 76
Posts: 2,483
Received 0 Likes on 0 Posts
TLB;

You're welcome...not picking on you but impressions become realities for those who don't know any better and believe everything they read. The passengers and crew and their families and friends deserve as accurate a telling of these things as possible. If you dont' know, don't write it and don't make it up. Some here don't do the hard research, most don't fly these aircraft or know anything about the A330, some just plain don't know and write anyway and some actually go on the internet for "information"...Like George Carlin said, "it's all bull**** folks and it's bad fer ya".

Sorry. Grumpy.
PJ2 is offline  
Old 30th May 2011, 02:32
  #674 (permalink)  
 
Join Date: Apr 2008
Location: US Virgin & British Virgin,Islands
Posts: 75
Likes: 0
Received 0 Likes on 0 Posts
Thanks Tanaka....

Just asking---no need to get all bent out of shape about the question...something clearly went wrong and if it was not the chaps flying the Aircraft it must have been the Aircraft or their training in relation to that Aircraft,right?Or perhaps their training to deal with the situation....which was placed on their laps at some unexpected time.......don`t things always go sideways at 0200 or therabouts?
I am so sorry to have upset your sensibilities.From your address you are clearly a serious person close to the heart of everything,which is great.
I guess we will soon see who and what happened to cause such a catastrophe.
It would be nice to see some more information from the French Investigative people upon which to work by all you guys who fly the Aircraft,day to day.
Regards.
Loerie is offline  
Old 30th May 2011, 02:34
  #675 (permalink)  
 
Join Date: Jul 2009
Location: Not far from a big Lake
Age: 81
Posts: 1,461
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Machinbird
Don't you think if the AF447 crew had seen the trim position - the light bulb would have come on? And the Perpignan crew also?

Takata
In hindsight, with all these informations available to us, they would certainly have acted differently. But it looks like a tunnel vision issue up to this point, like if something took all the PF attention: it is not even sure that a giant red warning "THS +13 degree" painted on his PFD would have made the outcome different if he was believing to do exactly the right thing.
This THS information would have been paramount only if he had tried to pitch full nose down but lacked from elevators authority. Now, was this even attempted before it was too late?
If not, the main issue about what crucial information didn't reach the PF in time lie certainly elsewhere.
Well it certainly looks like they made nose down inputs, in a tentative fashion, and got stall warnings back for their efforts:

From the BEA statement

At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have
no valid indications".

At that moment, the thrust levers were in the IDLE detent and the

engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In

the following moments, the angle of attack decreased, the speeds became valid again and the

]stall warning sounded again.




Note: BOLD and underlined sections above were marked by Machinbird

Last edited by Machinbird; 30th May 2011 at 02:45. Reason: correcting quote marks, correcting a wrong word
Machinbird is offline  
Old 30th May 2011, 02:34
  #676 (permalink)  
 
Join Date: Jun 2009
Location: I am where I am and that's all where I am.
Posts: 660
Likes: 0
Received 0 Likes on 0 Posts
PJ2, nice you're back.

I've noted the PF's reaction to the AP/AT drop out. As written in the writeup:
From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).
The $64,000 question that moment in time poses is whether that all happened at once or smeared, in the order stated, over 11 seconds. If it was smeared over time in the order written, I'd presume that would be uncertain airspeed. If it isn't what would be the PF reaction taken as he says he has the controls?

If they all happened in a slightly different time sequence the PF might have a whole different chain of actions initiated.

Another question is how good the simulator training is for cascade failures, which certainly appears to be what happened here. PF starts uncertain airspeed knowing he's going 275kts CAS. And a stall warning hits, a sure disruption to his chain of thought. Is training good enough that there is a smooth transition to realizing it's false and the pitots are out or does it start a whole new chain of trained reactions or does it leave the pilot rattled?

(I'm rather fastened on that spurious stall warning that seems to have happened more than just this once and left pilots transfixed trying to solve the impossible. This seems like one obvious change required in the flight control systems. If kCAS indication drops dramatically and that is not matched by a similar reaction in the inertial reference unit, suppress the stall warnings even if they might be real as might be the case with 10 degree AOA and 268 kts. It a pilot knows he won't get spurious stall warnings (or its far less likely) then a real stall warning will be heeded properly. I'm simply relying on my computer training here. You can overwhelm systems with conflicting input. In fact it's a known hacking technique. I also think this problem may well have already been dealt with in the flight controls for the new fully autonomous drones.)
JD-EE is offline  
Old 30th May 2011, 02:37
  #677 (permalink)  
 
Join Date: Jun 2009
Location: Paris
Posts: 691
Likes: 0
Received 0 Likes on 0 Posts
Hi mm43,
Originally Posted by mm43
There is something about the AP/ATHR OFF that may be related to the questions takata is/was posing. Svarin has also shown keen interest in this area, and ultimately time will tell whether it was warranted or not.
In fact, I have no doubt about what caused AP/ATHR OFF (UAS/ALT). But there is no detail in BEA note about the weather as there is no reference to turbulence level, g variation, etc. Hence, I wonder about what could have caused this roll beside the weather or any uncontrolled pilot imput when AP went off.

On the other hand, I'm wondering also if there is not a mach correction of the AoA function -at high mach numbers- that could change the resolution of the displayed alpha and could cause a Stall warning following an unreliable airspeed. This happened many times during past UAS events and it is far from clear if those warnings were "real" or only caused by the change of AoA resolution. Another possibility would be that AoA probes could be affected by ice in some way (TAT probes seeems to be) at the same time as the pitots are clogged.
takata is offline  
Old 30th May 2011, 02:40
  #678 (permalink)  
TLB
 
Join Date: Mar 2009
Location: Ottawa, Canada
Posts: 67
Likes: 0
Received 0 Likes on 0 Posts
PJ2,

Totally agree. Hopefully, when all of the data points are eventually released (along with the full transcript of the CVR superimposed), we will have a much better understanding of what actually occurred during this tragic flight and - more importantly - what might be done to prevent it from happening again in the future.
TLB is offline  
Old 30th May 2011, 02:56
  #679 (permalink)  
Thread Starter
 
Join Date: Jan 2005
Location: W of 30W
Posts: 1,939
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Minorite invisible
The Stall recovery drill calls for nose down pitch control with thrust to be increased smoothly once out of the stall
Don't forget that this procedure is new from December 2010 and therefore was not in force at the time of AF447.

Because the auto thrust disconnected, if the pilots did not move the thrust levers, the thrusts would have gone to CLB on their own (A-330 thrust levers are set t CLB detent when in cruise on auto-thrust)
That is not exact. Thrust is frozen until thrust levers are moved, so it could be anywhere between idle and climb thrust depending how was the thrust level at the time of the malfunction.
CONF iture is offline  
Old 30th May 2011, 02:57
  #680 (permalink)  
 
Join Date: Jul 2009
Location: Planet Earth
Posts: 91
Likes: 0
Received 0 Likes on 0 Posts
If you dont' know, don't write
With all due respect, the richness of this forum (and others for that matter), stems from the tension that exists between the 'ignorant' and the 'knowledgeable'. I for one have learnt a great deal from this forum and would like to thank every single one who has taken the time to post here. If only the 'knowledgeable' posted here, we'd all be the poorer for it. That doesn't mean there is no bull**** posted here, there is; lots. But if there was no bull****, a lot less of the 'knowledgeable' folks would post to counter the bs. So please keep posting. If you don't know, do your research, use the search function to look at what has already been discussed. Ask in the Spectator's Balcony first, if you are not sure. Strive to make an informed contribution and help maintain the quality of this thread and of the forums in general.

Now back to topic.
CogSim is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.