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

AF 447 Thread No. 5

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

AF 447 Thread No. 5

Old 12th Aug 2011, 03:13
  #1921 (permalink)  
 
Join Date: Oct 2007
Location: France
Posts: 136
Likes: 0
Received 0 Likes on 0 Posts
About the videos (jcjeant post)

2nd video (may 27 2011, before BEA 3rd report, but after BEA "Note":
... [0:53] Personne n'a le droit, pour l'instant, d'émettre une quelconque hypothèse sur ce qu'il s'est passé [0:58] ...
... [0:53] Nobody has the right, for now, to make any assumption about what happened [0:58] ...


1st video, may 29 2011 (just after 3rd BEA report press conference):
... [0:51] bien évidemment le pilotage, en manuel, en haute altitude, dans une (régio...) zone turbulente, en mode alternate, c'est probablement très particulier [0:59] ...
... [0:51] Of course flying in manual, high altitude, in a turbulent (regio...) zone, in alternate mode, it is probably very special [0:59] ...

Knowing the CV of this man ( Air France - Corporate : Eric Schramm, Executive Vice President Flight Operations ), it seems (IMHO) this wording is quite as astonishing than the one of the AF447 crew. Have we to think this "Qualified as Boeing 777 flight captain" doesn't know how flying is like in altitude when external and internal conditions are not smooth???

Is it the same in other compagnies?
Shadoko is offline  
Old 12th Aug 2011, 03:23
  #1922 (permalink)  
 
Join Date: Aug 2009
Location: Germany
Age: 67
Posts: 1,777
Likes: 0
Received 0 Likes on 0 Posts
Cool

Hi,

Have we to think this "Qualified as Boeing 777 flight captain" doesn't know how flying is like in altitude when external and internal conditions are not smooth???
Maybe it's the reason why they keep this man in the offices instead let him flying ........
jcjeant is offline  
Old 12th Aug 2011, 06:54
  #1923 (permalink)  
 
Join Date: Aug 2009
Location: Brussels
Age: 72
Posts: 10
Likes: 0
Received 0 Likes on 0 Posts
@Sensor_Validation (post #1765)

Quote:

Has it been confirmed what AoA sensors were fitted?
Pretty likely the Thales C16291AA given the choice of Pitot tube, if so one could have been suffering an extreme variation of the known fault at low temperature:-

According to La Tribune newspaper, the EASA is about to require the change of about 1,600 Thalès AoA sensors known to have a flaw. It seems the fabrication process might be responsible for some oil to be left unnoticed in the mechanism. With decreasing temp, the oil can slow or even block the sensor movement. This problem happens at random during manufactoring according to the article. Also, it restricts the affected Thalès AoA sensors to A320. But we would need to cross-check that, wouldn'd we ?

Source:
Airbus : des sondes thales de mauvaise qualité
vbp.net is offline  
Old 12th Aug 2011, 07:23
  #1924 (permalink)  
 
Join Date: Feb 2001
Location: right here inside my head
Age: 65
Posts: 178
Likes: 0
Received 0 Likes on 0 Posts
Hey, I've got an idea!.... It just came to me in a flash.... Maybe all airlines should remove anything that Thales built and replace it with something from a reputable manufacturer?
3holelover is offline  
Old 12th Aug 2011, 08:04
  #1925 (permalink)  
 
Join Date: Aug 2011
Location: Near LHR
Age: 58
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
@vbp.net:
Originally Posted by vbp.net
According to La Tribune newspaper, the EASA is about to require the change of about 1,600 Thalès AoA sensors known to have a flaw. It seems the fabrication process might be responsible for some oil to be left unnoticed in the mechanism. With decreasing temp, the oil can slow or even block the sensor movement. This problem happens at random during manufactoring according to the article. Also, it restricts the affected Thalès AoA sensors to A320.
The EASA AD kindly found & linked by sensor_validation in his post #1765 specifically mentions A330 & A340 and not A320?! IMHO the answer we don't yet know, is whether that model of AoA sensor was installed on AF447...

Reading the comments from other contributors here, it seems unlikely that whatever was wrong with AoA sensor #1 had a material impact on the events on this flight, although yet another fault added being into the mix is obviously a worry. Or do you believe the issue with this AoA sensor #1 was significant in the events that occurred?

@3holelover: I was going to apply for a job at Thales. I'm now re-thinking that plan
Diagnostic is offline  
Old 12th Aug 2011, 08:16
  #1926 (permalink)  
 
Join Date: Jul 2009
Location: UK
Posts: 134
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by 3holelover
Hey, I've got an idea!.... It just came to me in a flash.... Maybe all airlines should remove anything that Thales built and replace it with something from a reputable manufacturer?
It's not as simple as that - what AoA inst were involved in the Perpignan crash?

Ans:

D-AXLA was equipped with three Goodrich angle of attack sensors with type number 0861ED
Thales make a lot of great kit and and its used extensively throughout many aircraft flight control systems - NB all with appropriate Airbus/EASA approval.
sensor_validation is offline  
Old 12th Aug 2011, 08:24
  #1927 (permalink)  
 
Join Date: Aug 2011
Location: Paris
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
I think that David Learmount is right when he talk about the flying skills of old pilots. New pilots apply procedures instead of "flying", that's the way Airbus told us to use his aircrafts to lower the number of accidents.
This new technology has saved many lifes, but new accidents appears and I think that, by applying procedures only, we just transfer human errors from the pilots to human errors from enginers that create those fully automated aircrafts.
If we want to progress in flight safety, we must mix old flying skills with new flying procedures. CPT Shullenberger proved us it works.
CaptainGef is offline  
Old 12th Aug 2011, 08:24
  #1928 (permalink)  
 
Join Date: Jan 2005
Location: W of 30W
Posts: 1,916
Likes: 0
Received 0 Likes on 0 Posts
AoA 1

Reading the comments from other contributors here, it seems unlikely that whatever was wrong with AoA sensor #1 had a material impact on the events on this flight, although yet another fault added being into the mix is obviously a worry. Or do you believe the issue with this AoA sensor #1 was significant in the events that occurred?
Diagnostic,

The first worry above all is how the BEA didn't talk a single word about it ...

Second worry is that such oversight is not isolated.
CONF iture is offline  
Old 12th Aug 2011, 08:36
  #1929 (permalink)  
 
Join Date: Aug 2011
Location: Near LHR
Age: 58
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
@sensor_validation:
Originally Posted by sensor_validation
what AoA inst were involved in the Perpignan crash?
I thought those (Goodrich) AoA probes had been effectively mistreated (due to the incorrect pressure wash forcing water past the seals), so they were not to blame. At least that's how I remember it, from when I read the report years ago... My memory is not perfect, of course.

Originally Posted by CONF iture
Diagnostic,

The first worry above all is how the BEA didn't talk a single word about it ...

Second worry is that such oversight is not isolated.
I take your points, thank you. I try to see the best in people, and so the apparent oversight at this stage, might just be caused by them not having yet added this detail into the latest interim report, and perhaps it may be mentioned (as inconsequential?) in the final report. But, it may not be mentioned even then - and them totally missing something like that even in the final report, would indeed be a worry!
Diagnostic is offline  
Old 12th Aug 2011, 08:39
  #1930 (permalink)  
 
Join Date: Jun 2009
Location: somewhere
Posts: 451
Likes: 0
Received 0 Likes on 0 Posts
@CONF:

The first worry above all is how the BEA didn't talk a single word about it ...

Second worry is that such oversight is not isolated.
-The AOA replacement program was already in progress before publication of the 3rd BEA report.

-They did found the cause: 'machine oil residu left after the fabrication process' and so they know the solution too.

-There was no relationship whatsoever with this case.
A33Zab is offline  
Old 12th Aug 2011, 08:51
  #1931 (permalink)  
 
Join Date: Aug 2011
Location: Near LHR
Age: 58
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
@A33Zab:
Originally Posted by A33Zab
-The AOA replacement program was already in progress before publication of the 3rd BEA report.
Understood - but in that case there seems no reason for them not to say "FYI, we saw AoA #1 misreading - but this issue is already known, see EASA AD ...". If they wrote something like that, it would show that they recognised, evaluated, and dismissed that this needed further investigation. By not mentioning it at all, that leaves open (at least in my mind) the possibility that they didn't recognise it, although as I just mentioned a few mins ago, it might become a footnote in the final report - we'll have to wait until then to see if it is mentioned.
Diagnostic is offline  
Old 12th Aug 2011, 09:14
  #1932 (permalink)  
 
Join Date: May 2011
Location: UK
Age: 62
Posts: 48
Likes: 0
Received 0 Likes on 0 Posts
Since the BEA went to the trouble of including that parameter in the (very small) subset of FDR parameters that they included in the interim report, it seems very unlikely that they didn't notice such an obvious apparent discrepancy. Why they didn't mention or explain it, however, I don't know.
HeavyMetallist is offline  
Old 12th Aug 2011, 09:48
  #1933 (permalink)  
 
Join Date: Aug 2009
Location: Brussels
Age: 72
Posts: 10
Likes: 0
Received 0 Likes on 0 Posts
AoA et al.

@ Diagnostic & Sensor_Validation

Quote : Reading the comments from other contributors here, it seems unlikely that whatever was wrong with AoA sensor #1 had a material impact on the events on this flight, although yet another fault added being into the mix is obviously a worry. Or do you believe the issue with this AoA sensor #1 was significant in the events that occurred?

Very hard to tell, but I would say probably not since we know the STALL warning went OFF as soon as the speed was deemed to be less than the prescribed 60 kts. What we are really seeing when looking at the AoA traces of the data is another story, IMHO. Keep in mind, though, that the "speed" (of the falling aircraft-object?) was certainly well above that : only the derived horizontal vector of it was calculated to be less than the trigger. Calculated from the pitot, at an angle out of the normal range... What I mean to say is the following: the AoA sensor was probably giving meaningful output since the flow of air around its actuator was certainly capable of moving it adequately. So, it remains very strange that the STALL warning would be muted in these circumstances when the "system" knows pretty well: 1. the aircraft's altitude and 2. there is no weight on wheels. I have little doubt that, recommendations from BEA or not, Airbus will implement some changes there in the future.

I wouldn't like to seem cynical, but can you imagine the benefits to be derived from the data retrieved from the bottom of the sea? A fully stalled 200+ tons aircraft data during the whole descent. No wonder Airbus did finance some of the recovery costs. To them, this is a goldmine. And they pretty well know how to interpret the data! Future aircraft generations (and even the current ones) will benefit from this disaster, whatever the BEA conclusions and recommendations will be. I'm confident.

This leaves the industry with the problem so adequately pointed to by the excellent video brought to our attention by CaptainGef (post #1867). Captain Sullivan also tried to wake up an almost empty audience in the Congress about the same problem. Trouble is: nobody seems much interested...

Last edited by vbp.net; 12th Aug 2011 at 10:22. Reason: Typo
vbp.net is offline  
Old 12th Aug 2011, 09:48
  #1934 (permalink)  
 
Join Date: Aug 2011
Location: Near LHR
Age: 58
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
@HeavyMetallist:
Originally Posted by HeavyMetallist
[...]it seems very unlikely that they didn't notice such an obvious apparent discrepancy. Why they didn't mention or explain it, however, I don't know.
Agreed. I know from my writing of RCA reports when things go wrong (but thankfully not accident reports), that it is important to mention what data has been considered & dismissed (and why), exactly in order to avoid people spotting things that I did see in the data but were not causal and hence not addressed by a "fix", but they would otherwise think I didn't see them...

I'm sure the BEA have people with much more skill & practice in this area than me, which is why their omission is odd, and leaves open multiple interpretations - from "there wasn't enough time in this interim report to mention it, but of course we saw it, and it wasn't important here", through to "oops, we didn't notice that", and everything in between.
Diagnostic is offline  
Old 12th Aug 2011, 09:56
  #1935 (permalink)  
 
Join Date: Aug 2011
Location: Near LHR
Age: 58
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
@vbp.net:

Many thanks for your comments. That helps to crystalise some of my own thoughts about what is important. Although discussions about the stall warning logic were removed from this 3rd interim report, like you said, I'll bet that there will be changes implemented in that area!
Diagnostic is offline  
Old 12th Aug 2011, 10:06
  #1936 (permalink)  
 
Join Date: Jan 2005
Location: W of 30W
Posts: 1,916
Likes: 0
Received 0 Likes on 0 Posts
FDR data

Originally Posted by A33Zab
-The AOA replacement program was already in progress before publication of the 3rd BEA report.
-They did found the cause: 'machine oil residu left after the fabrication process' and so they know the solution too.
-There was no relationship whatsoever with this case.
That an AoA replacement program was already in progress is one thing, that AoA 1 on AF447 was stuck at 2.1 deg is another.

It may be your call to state that there was 'no relationship whatsoever', I may think differently, but it is BEA duty to touch the subject in a third Interim Report.


1- HN39 had already pondered one of your previous post :
Originally Posted by A33Zab
so AOA#1 could be effected, however didn't had any influence.
FCPC using median AOA (or outvoted AOA#1), AoAsw using highest AOA value.
2- There is no such thing as a "FCPC outvote an AoA"
If one AoA sensor is stuck, there is a possibility that its own ADR anemometric value will be rejected.
Now, remember that in the meantime, was taking place an ADR anemometric values rejection process based on pitot unreliable informations.

So, we end up with a very complex situation, maybe unknown territories ...


I can see too much insistance from BEA, media, people here around to put everything on the pilots back, when in the meantime, FDR data analysis is kept to a strict minimum.

Those FDR data are too serious to be left in the BEA and Airbus hands only.
Victim's families must obtain them too. Alternatives ressources for Analysis are available on this planet Earth.
CONF iture is offline  
Old 12th Aug 2011, 10:33
  #1937 (permalink)  
 
Join Date: Aug 2009
Location: Germany
Age: 67
Posts: 1,777
Likes: 0
Received 0 Likes on 0 Posts
Cool

Hi,

Those FDR data are too serious to be left in the BEA and Airbus hands only.
Victim's families must obtain them too. Alternatives ressources for Analysis are available on this planet Earth.
This is a judiciary investigation under progress ..
They will have the FDR data .. so it's not left in BEA and Airbus hands only.
jcjeant is offline  
Old 12th Aug 2011, 10:59
  #1938 (permalink)  
 
Join Date: Jun 2009
Location: Oxford, England
Posts: 297
Received 0 Likes on 0 Posts
takata, #1826

This is what the transducers are supposed to do. Feedback from every
control surface is recorded, digitalized and corresponding pressure is
applied back to each sidesticks axis.
I don't know where this myth came from, but if you look at the side
stick drawing, you can see that the only feedback is from self centering
springs. There is no force feedback from the control surfaces as there
are no motors etc in the side stick to provide this. Genuine "artificial
feel" provides stick feedback from control surface load, whereas the ab
stick is more akin to a video game controller, though I understand that
even some of these have real force feedback now.

A serous dropoff imho and may be compared to the difference between a
good sports car, where you can feel the road through the steering and
something like the old Jags, where over servoed power steering removed
all sense of tyre and chassis loading.

The sidestick transducers are there to sense position, they are not motors...
syseng68k is offline  
Old 12th Aug 2011, 11:51
  #1939 (permalink)  
 
Join Date: Mar 2010
Location: Sweden
Age: 87
Posts: 67
Likes: 0
Received 0 Likes on 0 Posts
AoA and ADR-data

CONF iture
The following excerpt from the Australian interrim report has already been posted in this thread. However, I will bring your attention to the statement which I have printed in bold.
"From AO2008070_interim, page 40-41
Angle of attack data processing algorithms
There was a potential for the AOA sensors on the right side of the aircraft (AOA 2 and AOA 3) to provide different values to the AOA sensor on the left side of the aircraft (AOA 1) in some situations due to aircraft sideslip. In order to minimise the potential effect of this difference, the PRIMs used different processes for AOA compared with other parameters when determining the value to use for calculating flight control commands. More specifically, the processing of AOA data involved the following:
• As with the other parameters, the PRIMs would continuously monitor the AOA values from the three ADIRUs. AOA data was sampled about 20 times per second.
• To confirm the validity of the AOA data, the PRIMs would compare the median value from all three ADIRUs with the value from each ADIRU. If the difference was greater than a set value for more than 1 second continuously, then the PRIM would flag the ADR part of the associated ADIRU as faulty and ignore its data for the remainder of the flight.
• To calculate a value of AOA to use for calculating flight control commands, the PRIMs would use the average value of AOA 1 and AOA 2. In other words, (AOA 1 + AOA 2)/2. This value was passed through a rate limiter to prevent rapid changes in the value of the data due to short-duration anomalies (for example, as a result of turbulence).
• If the difference between AOA 1 (or AOA 2) and the median value from all three ADIRUs was higher than a set value, the PRIMs memorised the last valid average value and used that value for a period of 1.2 seconds. After 1.2 seconds, the current average value would be used.
In summary, in contrast to other parameters, only two values of AOA were used by the PRIMs when determining flight control commands. However, several risk controls were in place to minimise the potential for data inaccuracies to affect the flight control system."

I have two points that may need clarification.
1. How big should the difference from the median AoA be in order to reject ADR1?
2. Could this be the cause of a) autopilot disconnect, (b) false interpretation as due to pitot problem if ADR1 was permanently rejected due to AoA error.

regards
Diversification is offline  
Old 12th Aug 2011, 12:11
  #1940 (permalink)  
 
Join Date: Oct 2007
Location: France
Posts: 136
Likes: 0
Received 0 Likes on 0 Posts
AoA sensor stuck?

If there was some kind of AoA discrepancy due to one sensor stuck, and calculators "saw" that, didn't have to be some ACARS about that? Otherway, except the study of this flight FDR, nobody would know this problem (if any) happened during this flight?
Shadoko 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.