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 10th Jul 2011, 01:20
  #21 (permalink)  
bearfoil
Guest
 
Posts: n/a
Mr Optimistic.

They commanded a climb because it was proper to do, at the time, airspeeds were fine. They noted "ALTERNATE LAW" eleven seconds AFTER the a/p quit. BEA haven't said where the THS was positioned at loss of a/p. They do say, however, that the a/c was slow to respond to PF's climb input. "At PITCH +10, the a/c began to climb." If the climb had established at AL snatch, what is the protocol for LAW change?

I do NOT believe the PF intended a climb rate at 7kfpm. Nor do I think he wanted necessarily to climb. He pulled back because what he saw and took in told him a roll left and NU was indicated......let's give them that.

At that point, the 340 zoom might or might not be instructive.

Bottom Line? My feeling is that if at a/p drop and then UAS the pilots were expecting, and given Direct Law, there would be no need to be cautious with the stick, to worry about Protections (or depend on them, falsely).

STALLSTALL at his initial pull? Probably a chirp due his unfamiliarity with the a/c response to his hand, and if he relaxed it, (I think he must have) this was the cause of the a/c lagging in climb response.
 
Old 10th Jul 2011, 15:16
  #22 (permalink)  
 
Join Date: Jun 2009
Location: Oxford, England
Posts: 297
Received 0 Likes on 0 Posts
Greybeard, #18
The A330 has an apparent up to 300 ft static port correction at low airspeeds. This is not unusual, but at a greater AOA than stall warning, the static pressure is sure to increase to the point the static ports nearly become pitot ports.
Interesting point, The higher static pressure would be translated to a decrease in altitude on the display.

However, if the a/c were stalled, the alt would have been unwinding
pretty fast anyway...
syseng68k is offline  
Old 10th Jul 2011, 15:23
  #23 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by bear
They commanded a climb because it was proper to do,
- can you support that statement of fact? I would suggest, that having discussed their 'inability' to climb due to the thermal structures of the atmosphere it would have been quite 'improper'?
BOAC is offline  
Old 10th Jul 2011, 15:59
  #24 (permalink)  
 
Join Date: Jun 2009
Location: VA, USA
Age: 58
Posts: 572
Received 0 Likes on 0 Posts
BOAC +1 ^

How was a "climb" the *proper* thing to do? At all?

Please educate me... given the situation (UAS) surely we ALL agree the proper thing to do is "more or less nothing" (stabilize the aircraft, fly pitch and power, figure out what is going on in a methodical structured manner).
GarageYears is offline  
Old 10th Jul 2011, 17:07
  #25 (permalink)  
bearfoil
Guest
 
Posts: n/a
Garage Years and BOAC'

My bad. "climb". "proper". I should have included the quotes, or parents.

The PF at a/p drop ("I have the controls"), Input back pressure.

BEA does not use "climb", nor should I. They state "INPUT".

We do not know the state (assiete) of the airframe at a/p quit, only that it was followed by PF's control ip.

"The a/c at PITCH UP of ten degrees, began to climb."

Did the pilots know at drop they were in UAS? NO. PNF states eleven seconds later, "So we have lost the Speeds, .....ALTERNATE LAW".

We can conclude PNF is reminding PF, or we can conclude he is stating something that has just been noticed.

We can also say that PF may have been trying to capture PITCH and POWER with his movements.

If the a/c had dropped ND a bit, and rolled right a bit in turb, he could have been establishing S/L then intending to P/P.

Remember, the a/c was in weather of some description, if PF had sussed immediately UAS, his first order was to regain S/L. P/P may have been needing an input of Left, NU. He may have been waiting to set N1, until after S/L was attained. Can't do everything at once.

I don't accept that PF ("I have the controls") started hand flying with an utter misunderstanding of the situation. I think his initial assessment was of loss of A/P and then A/T, things happen fast when the wheels are coming off.

My post was not meant to confuse; instead, I think I fell to what is present here, assumptions of events by mutation and groupthink reinforcement.



edit; Anticipating a release in some weeks, I am personally trying to prepare for more data. To start with, there is an embarrassing dearth of evidence to claim anything with confidence.

I still have on open mind, I think stasis in the findings will surprise, and favor a rather standard accident: Too many unusual and unanticipated events happen too quickly, and the a/c and pilot cease a mutually beneficial and safe rapprochement.

No virgins left at the end.

Last edited by bearfoil; 10th Jul 2011 at 17:18.
 
Old 10th Jul 2011, 18:15
  #26 (permalink)  
bearfoil
Guest
 
Posts: n/a
Deep bow, cap off.

Big fan of the F27.
 
Old 10th Jul 2011, 18:25
  #27 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,315
Likes: 0
Received 0 Likes on 0 Posts
I do have the impression that too many people here are 'parsing' all the 'subtleties' of the English-language translation of the BEA report, trying to 'tease out' information which isn't really there, and isn't there in the original French either.

Being an ancient, and lazy by nature, I haven't bothered yet to put the French and English versions next to each other, except to solve a couple of obvious misunderstandings...

I expect the same thing to happen when the next mid/end July BEA Interim Report is coming out.

As an engineer, I would like to see all the FDR traces - and it's unlikely they will all be put into the report, leave alone on the net....

The CVR might help with a few clues, but I'm not putting the same degree of reliance on it, that some people here seem to do.
"Oh, merde" may be perfectly obvious to the pilots in the cockpit, with one pointing to something visible to all, but no longer comprehensible to those trying to reconstitute the happenings up there, more than two years later.....

Give those people at BEA a chance, and try not to attempt to outguess them too much.

Last edited by Jetdriver; 11th Jul 2011 at 01:21.
ChristiaanJ is offline  
Old 10th Jul 2011, 18:46
  #28 (permalink)  
bearfoil
Guest
 
Posts: n/a
ChristiaanJ

I agree. The essential outcome of this two year ordeal could have been solved (and explained) with the discovery of the Boxes. Witholding data that is in and of itself innocent of bias is traditional, and creates a stage for politics and corporate competition. Except for ass covering and proprietary damage control, I fail to see the need for endless time given to "the Report".

Perpignan, and Habsheim have the stink of controversy yet, as does AA587. The offered report is puffed up and sold as the Truth. The saving grace here, with AF447, is a new vector, extensive and passionate commentary in a very wide audience.

In the last, and for not nefarious purpose, this "Investigative Process" has served to smooth the certain impacts on the commerce that would happen with instant access to the vulnerability of Air Travel to disaster.

Ignorance can be bliss, it can also augment the bottom line.
 
Old 10th Jul 2011, 19:25
  #29 (permalink)  
 
Join Date: Feb 2009
Location: Worldwide
Posts: 579
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by ChristiaanJ
...trying to 'tease out' information which isn't really there...
You mean like attributing made up quotes to the BEA such as
"The aircraft, at 10 degrees Pitch up, finally began to climb."
Or
"At PITCH +10, the a/c began to climb."
Or continually making wrong statements about the control laws such as
...the a/c was in Alternate Law... This provides no protection for Roll limiting, but includes AoA protection and direct control for both roll and pitch.
Or just making stuff up such as
So much authority that the a/c cannot recover......it says so in the FCOM!!
Or is it just the general smothering of posts with generalities and ambiguities at a level that normally isn't found outside of the horoscope section of a woman's magazine?
KBPsen is offline  
Old 10th Jul 2011, 19:43
  #30 (permalink)  
bearfoil
Guest
 
Posts: n/a
Please continue, but can you back up some of your nay saying?

Start with ALTERNATE LAW?
 
Old 10th Jul 2011, 20:04
  #31 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,688
Likes: 0
Received 0 Likes on 0 Posts
10 degrees pitch

Originally Posted by bearfoil
They do say, however, that the a/c was slow to respond to PF's climb input. "At PITCH +10, the a/c began to climb."
They didn't quite say that, but it may be a literal interpretation of what they wrote in the Update. I have a slightly different interpretation that I would like to throw up for debate. As I read it, one investigator has listened to the CVR and notes the words spoken at 2:10:16 and 2:10:50. Another investigator has studied the DFDR data and gives an account of various observations he has made between 2:10:05 and 2:10:51. He places those observations in a 'logical' order, more or less but not necessarily exactly in the correct time-sequence. For example:
The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left.
Was the nose-down input before or after V/S reached 7,000 ft/min? The reason I'm raising this is not that sentence, but the preceding one:
The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb.
I don't believe these two events occurred in that sequence. If they had, the airplane would be in level flight with pitch at 10 degrees and therefore AoA 10 degrees. At M=0.8 stall warning begins at 4.2 degrees, alpha-max is 5.25 degrees, and the airplane stalls at about 8 degrees. Furthermore, pitch angle does not jump instantaneously from the initial 2.5 degrees to 10 degrees. As soon as pitch angle starts to increase 'progressively', AoA and hence lift increases also, and the airplane starts to climb (give or take small g-variations due to 'chop'). Just can't wait for the real DFDR traces to look for myself ...
HazelNuts39 is offline  
Old 10th Jul 2011, 21:00
  #32 (permalink)  
bearfoil
Guest
 
Posts: n/a
Obviously, and especially after reading your last, I am struggling mightily to get a handle on the initial events. You say it so well, and I am ironically satisfied that anyone would single out my struggle for flame.

At some point after origination of PITCH UP, (not the command, the actual), the a/c "began to climb". Does this indicate a gaining of altitude, or arrival at, or transition through, sufficient AoA to enable altitude increase? It enters into question the lack of STALL wrn, but, due Cavalry Charge and MASTER CAUTION, (A/P loss), was a STALLSTALL missed? Logically no, for BEA say the WARNING was "two" in number. implying a cessation of the original WARN at PF's first inputs?

(HN39. Is it at all possible that PF's Right and Left roll commands were in pursuit of an angle steep enough to cause the Nose to fall? It seems too early for such a "desperate step"?)
 
Old 10th Jul 2011, 21:07
  #33 (permalink)  
 
Join Date: Oct 2009
Location: berlin
Posts: 152
Likes: 0
Received 0 Likes on 0 Posts
Thanks also to A337 for the refresher pix of the static ports.

The A330 has an apparent up to 300 ft static port correction at low airspeeds. This is not unusual, but at a greater AOA than stall warning, the static pressure is sure to increase to the point the static ports nearly become pitot ports.

Rather than, "What's it doing now?", the more I read the more I question, Why did they design it that way?"

the place of the pitots is even sensible, the "static" pressure is not constant over the different places of the fuselage.....the selected place for the pitot is the first place with a static pressure near zero for "normal flight" .....up front is the static pressure higher, behind he is lower, this place is a very good place because the different between the mesured static- and the pitot-pressure shows(indicates) good the airspeed,

with higher AoA the pressure in the static port will get up, (and the correction for the speed) with higher AoA s converted into very difficult.....or impossible

but this is also a chance for an alternativ speed indicating system.....the fuselage itself works like an half-pitot probe...the flow accelerates at the side of the fuselage, and with the different static presure between to different points over the front of the fuselage it must be possible to indicate the speed without a pitot probe!, and the static probe will be not so delicate against ice or ash or insects like a pitot-probe.....
grity is offline  
Old 10th Jul 2011, 21:10
  #34 (permalink)  
 
Join Date: Mar 2006
Location: Choroni, sometimes
Posts: 1,975
Likes: 0
Received 0 Likes on 0 Posts
Sorry to say,

PEANUTS.
hetfield is offline  
Old 10th Jul 2011, 21:30
  #35 (permalink)  
bearfoil
Guest
 
Posts: n/a
grity

In a similar discussion earlier, a combination Pitot/Static was suggested in the form of a "Tympanum", a membrane that resembles the skin of a drumhead, flexible, but impervious to water, Ice, or Hornet Nest. The Statics would be arranged about the perimeter, where least deflection of the membrane, and the "Pitot" portion would read at the center, where deflection is greatest. It would take a computer to weight the deltaP by geography, but it is feasible.
 
Old 10th Jul 2011, 21:35
  #36 (permalink)  
 
Join Date: Jul 2009
Location: France - mostly
Age: 84
Posts: 1,688
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by bearfoil
Is it at all possible that PF's Right and Left roll commands were in pursuit of an angle steep enough to cause the Nose to fall? It seems too early for such a "desperate step"?
I think you answered your question. At that point there wasn't any need for a "desperate step". If they'd wanted the "Nose to fall" they'd pushed the stick forward not pulled back, wouldn't they?
HazelNuts39 is offline  
Old 10th Jul 2011, 21:43
  #37 (permalink)  
bearfoil
Guest
 
Posts: n/a
HazelNuts39

I think you are correct, it seems too early. We do not know the situation the PF found himself in. I myself cannot eliminate some form of counter-intuitive aspect of the a/c that baffled the PF's experience and actions.

I cannot accept that the a/c was performing "as designed" whilst the Pilot initiates a radical climb into altitudes that were previously rejected by consensus, a climb that saw 7kfpm, and roll oscillations of plus/minus 12 degrees.

It is possible that all prompts, or most, were not to be trusted (whether they were or not is not relevant),

From a position of balance, given PF's level of skill (high), and the a/c's track record, (impeccable), the two were at odds almost from the outset.

I think the answer will be found in the twenty seconds that bracket the loss of the autopilot.

thanks for your comments, it is an honor to be in conversation with you.
 
Old 10th Jul 2011, 22:07
  #38 (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
I've been thinking about where BEA is likely to be going in their investigations of the human factors aspect of this accident.

I suspect the words 'cognitive fixation' will factor significantly into their report. (In French of course.)

In the course of reading up on the subject, I found that there are some simulation tools for predicting this type of problem and quantifying it.
Here is a 6 year old paper on aviation related work in this direction.
http://www.humanfactors.illinois.edu...ulebleiwic.pdf
Now if they were to take this set of models and apply it to the piloting tasks faced by the crew of AF447 that night there might be some clarity to the perplexing question of how they let the aircraft get away from them.

Of course with the CVR, DFDR and possibly ?? the high resolution recorder yielding information, that may be overkill. I think we have teased all the information from the initial BEA note that can be extracted at this point.
Machinbird is offline  
Old 10th Jul 2011, 22:27
  #39 (permalink)  
 
Join Date: Jan 2005
Location: France
Posts: 2,315
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by bearfoil
ChristiaanJ
I agree. The essential outcome of this two year ordeal could have been solved (and explained) with the discovery of the Boxes.
Judging by your comments, I take it you've never been involved in an accident investigation, nor have been involved in 'reading' and fully interpreting an FDR recordng.
Witholding data that is in and of itself innocent of bias is traditional, and creates a stage for politics and corporate competition. Except for ass covering and proprietary damage control, I fail to see the need for endless time given to "the Report".
The bias is all yours, I'm afraid....
Perpignan, and Habsheim have the stink of controversy yet...
Perpignan doesn't (company pilots playing "test-pilot" at low altitude without really seriously knowing what they let themselves in for).
Neither does Habsheim which had a pilot with no serious knowledge of the aircraft, getting himself somewhere in the envelope where he shouldn't have been, while switching off some of the systems, then blaming the aircraft and the systems, rather than his own incompetence.
Me262 and Meteor pilots were well aware, that a jet engine at idle needs time to 'spool up'. this jerk obviously didn't....
ChristiaanJ is offline  
Old 10th Jul 2011, 23:28
  #40 (permalink)  
 
Join Date: Jan 2008
Location: uk
Posts: 861
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by bearfoil
Right along with doubts about the climb whilst the PF is represented as commanding it, one must suitably indict the a/c for trimming for maximum Pitch UP. What was he THINKING.......

What was she DOING? Certification is mainly a mystery to me; I trust the system to certify a/c to be safe and reliable.

One understands the need for emphatic NU at TO and landing, but in the arena 447 found herself, why doesn't the THS have a LAW LOCK on it similar to the RTLU?
Curious, what would that achieve exactly ? Based on the info we have (and see the helpful timelines previously posted by others) elevator authority alone was sufficient to get 16deg pitch up and fully stalled. THS simply relieved the elevators.

Had THS not moved, and elevators held 16deg nose up instead, what benefit results ? Only (as far as I can see) perhaps quicker recovery - but THS trims for neutral elevator, so they should, and it appears did, still work if ND is attempted. Unless of course we are into deep stall situation (I would say we don't know if that was the case yet), but in that case THS position quite possibly doesn't matter.

It seems that what you really want is more an attitude-protection law - 10deg pitch up in cruise is silly so sorry dave I can't do that.

But we already have that, in a better way, with AOA & speed protections, but these are lost here - because the planes sensors (or at least some of them) are lying and it doesn't know what is happening with sufficient confidence to apply protections.

Should AOA protections degrade to attitude protections of some sort ? More laws / sub-laws ? More variables combinations to learn and find time to actually be trained on. Does that really help ?
infrequentflyer789 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.