AF 447 Thread No. 9
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Lyman,
What I said about the C chord generator burning out was tongue-in-cheek. I know nothing about how it functions. As I said, does it really matter?
JCJ,
Regarding the meaning of the captain's "prends ça", Otelli wrote that it is difficult to know what he was referring to but the BEA investigators favoured the idea that it was the FPV.
Why do you call Otelli's book "useless"? Not only does it contain the entire CVR transcript but the transcript is an improvement on the bare-bones version released by the BEA in that the reader gains an impression of the tone of voice used (exclamation, question, etc.). Also, Otelli has filled in some of the blanks in the BEA release (whether that's accurate or not is another matter, of course). Finally, Otelli has keyed the CVR to the FDR and thus provides background to at least some of the crew's statements and actions.
Clearly the key to the tragedy of AF447 is the CVR transcipt. For those of us who possessed a copy of Otelli's book (published in late 2011), the release of the BEA final report was very much an anti-climax.
What I said about the C chord generator burning out was tongue-in-cheek. I know nothing about how it functions. As I said, does it really matter?
JCJ,
Regarding the meaning of the captain's "prends ça", Otelli wrote that it is difficult to know what he was referring to but the BEA investigators favoured the idea that it was the FPV.
Why do you call Otelli's book "useless"? Not only does it contain the entire CVR transcript but the transcript is an improvement on the bare-bones version released by the BEA in that the reader gains an impression of the tone of voice used (exclamation, question, etc.). Also, Otelli has filled in some of the blanks in the BEA release (whether that's accurate or not is another matter, of course). Finally, Otelli has keyed the CVR to the FDR and thus provides background to at least some of the crew's statements and actions.
Clearly the key to the tragedy of AF447 is the CVR transcipt. For those of us who possessed a copy of Otelli's book (published in late 2011), the release of the BEA final report was very much an anti-climax.
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jcjeant and philip2412:
Gruess di'.
In the final BEA report it is written that the investigation was not able to ascertain what the 3 pilots were doing for the 72 hours they were in Rio. PF did have his wife on board AF447 and she spent his layover time with him in Rio.
What else the three crew members did was not able to be determined.
Gruess di'.
In the final BEA report it is written that the investigation was not able to ascertain what the 3 pilots were doing for the 72 hours they were in Rio. PF did have his wife on board AF447 and she spent his layover time with him in Rio.
What else the three crew members did was not able to be determined.
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Hi Rockhound...
Tongue likewise in cheek in my question...
Is it important? Yes, and no. To a technical person, whose specialty is ergonomics, perception, sensories, etc. But to you? Perhaps not. The take away from the report is that it is minimalistic. In its brevity, BEA allows popular comment and perception to remain in the discussion, rather than exhausting all reasonable questions. An exquisitely important CVR artifact, the comments re: ambient temp in cockpit could have several causes, where is this addressed in the report. Where is the elimination of possibilities, and in the elimination, the establishment of a probable cause? The cause is allowed to be dictated by PPRuNe, evidently, incompetent pilotage....
Tongue likewise in cheek in my question...
Is it important? Yes, and no. To a technical person, whose specialty is ergonomics, perception, sensories, etc. But to you? Perhaps not. The take away from the report is that it is minimalistic. In its brevity, BEA allows popular comment and perception to remain in the discussion, rather than exhausting all reasonable questions. An exquisitely important CVR artifact, the comments re: ambient temp in cockpit could have several causes, where is this addressed in the report. Where is the elimination of possibilities, and in the elimination, the establishment of a probable cause? The cause is allowed to be dictated by PPRuNe, evidently, incompetent pilotage....
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Clearly the key to the tragedy of AF447 is the CVR transcipt.
In addition to his writings about the transcript is not accurate .. thus we have seen in the transcripts appearing in the final report
We have many "Otelli" in this forum (or at least able to write a book like Otelli) .. they can write it .. this will not change a ounce about what happened and what is engraved in stone in the BEA final report ...
The only place where the final report can be .. (maybe) challenged .. is the judicial court ...
And be sure that Otelli will not spoke a word there
Last edited by jcjeant; 19th Jul 2012 at 16:22.
about time...
Don't know if someone else posted this link, but seems relevant.
Airbus reviews instrument logic in aftermath of AF447
What I don't understand is why the flight directors don't just display last attitude or maybe a benign pitch attitude when the air data goes to la-la land.
Then there's all the audio warnings and AoA issue.
Decent article, IMHO.
Airbus reviews instrument logic in aftermath of AF447
What I don't understand is why the flight directors don't just display last attitude or maybe a benign pitch attitude when the air data goes to la-la land.
Then there's all the audio warnings and AoA issue.
Decent article, IMHO.
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@Gums,
Thank you for the three ref.
About FD, I can find no correlation between the pilot action and the parts of FD displayed. Does anybody ?
The problem was C* as you pointed it with retiredF4, and now the BEA final report. Thanks !
@ChisN,
Thank you for the strange attractor (of course !) it is such one effectively, but not for the famous Lorenz system but A330 ! (to compute!) It is an important concept for stability of non linear dynamic systems.
Thank you for the three ref.
About FD, I can find no correlation between the pilot action and the parts of FD displayed. Does anybody ?
The problem was C* as you pointed it with retiredF4, and now the BEA final report. Thanks !
@ChisN,
Thank you for the strange attractor (of course !) it is such one effectively, but not for the famous Lorenz system but A330 ! (to compute!) It is an important concept for stability of non linear dynamic systems.
Last edited by roulishollandais; 21st Jul 2012 at 17:24. Reason: spelling
from post #392, clandestino, (a few days ago)
(my bold)
It appears the 'magic' agree number is ANY two ADR's <20 knots difference, no matter how 'off the wall' the actual values are as long as they meet other engagement criteria. [Of interest, this can be the two PFD displayed values OR one of the displayed and the other not selected ADR value (i.e. the other displayed PFD >20 knots difference with both 'agreeable' ones).]
This appears to also be the point at which the FD's return.
Pardon if this figure has been provided before in other threads, I may be late for dinner here, but does anyone have a reference for confirmation of this value, if in fact it is correct? A33Zab?
@A33Zab: With ALT2(B?) 'latched', the SPD LIM flags displayed and no characteristic speeds displayed (including no VLS), and no FMGEC VLS (dashes), the A/P pb latching appears to depend only on 2 ADR's within 20 knots, not FMGEC VLS. The A/P pb apparently latches with the 2 values in 'agreement' below actual VLS. Is there a reference somewhere? Once again, apologies if it has already been provided previously.
@RF4: The report states that ALT2B was 'latched' so I would assume there were never any intermittently available speed stability functions, but I erroneously thought the same of the A/P pushbutton. 
Seems that FCS gives up restoring itself back to normal law after it detects long lasting ADR disagreement, however AFCS keeps checking indefinitely and will restore itself as soon as two ADCs agree, not necessarily at correct value. Page 86 of the report refers.
It appears the 'magic' agree number is ANY two ADR's <20 knots difference, no matter how 'off the wall' the actual values are as long as they meet other engagement criteria. [Of interest, this can be the two PFD displayed values OR one of the displayed and the other not selected ADR value (i.e. the other displayed PFD >20 knots difference with both 'agreeable' ones).]
This appears to also be the point at which the FD's return.
Pardon if this figure has been provided before in other threads, I may be late for dinner here, but does anyone have a reference for confirmation of this value, if in fact it is correct? A33Zab?
@A33Zab: With ALT2(B?) 'latched', the SPD LIM flags displayed and no characteristic speeds displayed (including no VLS), and no FMGEC VLS (dashes), the A/P pb latching appears to depend only on 2 ADR's within 20 knots, not FMGEC VLS. The A/P pb apparently latches with the 2 values in 'agreement' below actual VLS. Is there a reference somewhere? Once again, apologies if it has already been provided previously.
It would be interesing to know, if the law Alt2b changed intermittently when the speeds came back on line or the above limited protections reactivated itermittently.
Last edited by OK465; 19th Jul 2012 at 18:31. Reason: OCD about sentence structure
If the FD was intermittently on and off, working and not working, I may have a better guess at the answer to my old question regarding the PF: what was he seeing?
If what I guess is close to right, then I begin to understand another factor in his confusion and frustration, particularly if his habitual instrument scan relied heavily on the "bird."
Mind you, this is guessing. Maybe a puzzle piece that fits better than others, maybe not.
If what I guess is close to right, then I begin to understand another factor in his confusion and frustration, particularly if his habitual instrument scan relied heavily on the "bird."
Mind you, this is guessing. Maybe a puzzle piece that fits better than others, maybe not.
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Perhaps, Lonewolf, the PF did not comprehend what he was seeing. He probably never saw things on that flight deck that night, before in his entire career.
This possibility, together with sensory overload, preoccupation with weather, ignoring of various "bells and whistles", the so called startle effect, his losing focus on the task at hand (fly the damn plane), little communication with the PNF, piss-poor CRM (including the Captain), total lack of situational awareness and a host of other issues and is it any wonder he was pulling back the entire time? To this non aviator it would seem the guy was scared ****less and had no idea what the hell was going on around him.
When the **** hits the fan, as I learned several moons ago, it's fight or flight. He went the latter path. He didn't choose it though. It overwhelmed him.
This possibility, together with sensory overload, preoccupation with weather, ignoring of various "bells and whistles", the so called startle effect, his losing focus on the task at hand (fly the damn plane), little communication with the PNF, piss-poor CRM (including the Captain), total lack of situational awareness and a host of other issues and is it any wonder he was pulling back the entire time? To this non aviator it would seem the guy was scared ****less and had no idea what the hell was going on around him.
When the **** hits the fan, as I learned several moons ago, it's fight or flight. He went the latter path. He didn't choose it though. It overwhelmed him.
Last edited by rgbrock1; 19th Jul 2012 at 19:23.
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rgbrock1. You have spent a paragraph focused on PF and what he felt, how he may have felt it, and what he may have seen and done. That is perfectly ok. There is a lot of it, and a lot of repetitive opinions on feelings, startle, fatigue, experience, what they did prior to launch, ad nauseous, again ok.
"What is that smell?". "it's hot.." "Yes it is gotten hot in here..."
"Ozone"....". (end of). Re: the increase in cabin temp? Nothin'......
STALLSTALLcricket... What is that? ( no answer, no answer, no answer)
BEA "probably his reaction to STALL WARN" fine, case closed, end of...
No answer to cabin calls, none... No problem? end of......
Constant and vigorous speculation on the pilots, mostly about things that will never be known,,,,, Mechanical issues? Not so much...
"What is that smell?". "it's hot.." "Yes it is gotten hot in here..."
"Ozone"....". (end of). Re: the increase in cabin temp? Nothin'......
STALLSTALLcricket... What is that? ( no answer, no answer, no answer)
BEA "probably his reaction to STALL WARN" fine, case closed, end of...
No answer to cabin calls, none... No problem? end of......
Constant and vigorous speculation on the pilots, mostly about things that will never be known,,,,, Mechanical issues? Not so much...
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Because the physical evidence recovered does not correlate with mechanical or electrical problems (aside from the pitot tubes), and no amount of wishing will make it so.
Remember, just because it's not in the final report doesn't mean it wasn't investigated.
I ask again - what makes it so tough for you to believe?
Remember, just because it's not in the final report doesn't mean it wasn't investigated.
I ask again - what makes it so tough for you to believe?
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Ref this post.
The aircraft is only statically neutral with the aid of the FBW computers. In Direct Law (stick deflection proportional to control surface deflection) they are (beautifully) dynamically stable.
This is the bit with which I'm having difficulty although my reading of the various links (and thanks to those who PMd/emailed other suggestions) may answer my questions ..
Neutral static stability infers a more aft CG than "normal". The box then can give the pilot an impression of stability (and, at the end of the day, it is this impression that is required). If, now, the box departs controlled operation .. the aircraft CG is still where it was (until it can be moved) and the pilot potentially now is stuck with neutral static stability .. OK if you recognise it and know what to do .. but, otherwise, a recipe for rapid disaster ...
The aircraft is only statically neutral with the aid of the FBW computers. In Direct Law (stick deflection proportional to control surface deflection) they are (beautifully) dynamically stable.
This is the bit with which I'm having difficulty although my reading of the various links (and thanks to those who PMd/emailed other suggestions) may answer my questions ..
Neutral static stability infers a more aft CG than "normal". The box then can give the pilot an impression of stability (and, at the end of the day, it is this impression that is required). If, now, the box departs controlled operation .. the aircraft CG is still where it was (until it can be moved) and the pilot potentially now is stuck with neutral static stability .. OK if you recognise it and know what to do .. but, otherwise, a recipe for rapid disaster ...
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@OK465;
If you can follow the logic schematic posted by A33Zab, you will note there are a number of variables that must meet specified values before the p/b can be effectual.
The latching of ALT 2B was a result of diverging ADR speeds. ADR2 was nominated the "median" value and when speeds hadn't returned to within 50KTS of the median in 10 secs, law reversion to ALT 2B occurred and remained for the rest of the flight.
A33Zab has previously pointed out that the FD may be engaged on the ground in V/S mode, and on AF447 the A/P was inhibited due to CAS < VLS from 02:10:08.
AP Engage is inhibited:
if abs(φ) > 40°,
or θ < -10°, or θ > +22°,
or CAS < VLS,
or CAS >(VMO/MMO or VLE/VFE)
In respect of the FD Bars, they do appear to have been available when 2 ADRs (also 2 IRs) agreed within 20 KTS. The same agreement is also a provision of A/P engagement, plus FMGEC, FCPC (also no breakout by SS or pedals), plus the φ, θ and CAS conditions being met per the schematic.
The A/P pb apparently latches with the 2 values in 'agreement' below actual VLS.
The latching of ALT 2B was a result of diverging ADR speeds. ADR2 was nominated the "median" value and when speeds hadn't returned to within 50KTS of the median in 10 secs, law reversion to ALT 2B occurred and remained for the rest of the flight.
A33Zab has previously pointed out that the FD may be engaged on the ground in V/S mode, and on AF447 the A/P was inhibited due to CAS < VLS from 02:10:08.
AP Engage is inhibited:
if abs(φ) > 40°,
or θ < -10°, or θ > +22°,
or CAS < VLS,
or CAS >(VMO/MMO or VLE/VFE)
In respect of the FD Bars, they do appear to have been available when 2 ADRs (also 2 IRs) agreed within 20 KTS. The same agreement is also a provision of A/P engagement, plus FMGEC, FCPC (also no breakout by SS or pedals), plus the φ, θ and CAS conditions being met per the schematic.
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John, I agree, neutral stability means the CG is at it's aft limit area to save fuel but it needs a computer to keep it stable. A pilot would have a hard time to keep it at a constant altitude. I guess a good pilot could still fly it by hand but it would be difficult. They would probably with no autopilot transfer fuel forward to make it easier to fly.
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neutral stability means the CG is at it's aft limit area to save fuel but it needs a computer to keep it stable
Not quite right. For a conventional aircraft (and I presume this is what the Airbus becomes in the event that ALL computers roll over and die), the aft CG limit may (amongst other requirements) be limited to give an acceptable positive static stability .. neutral stability would be a fail and require either a further constraint of the aft limit or another flight test engineering fix.
It follows that, if the CG is sufficiently far aft to result in neutral stability, then it wouldn't be certificatable or, perhaps, the probability of box failure demonstrated at certification is sufficiently low to be acceptable.
However, this latter consideration may be tied in with the present mishap - inextricably. Are we not all concerned with the possibility that this crash may have been involved with events so out of left field (but only because of presumptions regarding training and competence standards) that the original certification program may not have considered them at all ?
I don't know what the certification story was for the Airbus FBW machines but would sure be interested to find out ..
A pilot would have a hard time to keep it at a constant altitude
True, but that's only a part of the problem. The typical pilot, faced with a sudden deterioration in the stability he/she feels/sees is more likely to rip the wings/tail off while trying to figure out what might be going on ..
a good pilot could still fly it by hand but it would be difficult
More a case of needing to recognise the problem and then be aware of/trained in the changed techniques required to fly the aeroplane. TPs cover this during their training course and there are documented cases of the occasional TP having to drag a statically unstable aircraft around the patch to get it back onto the ground .. but for Captain Average Joe Pilot .. the story, in all probability, is going to have an unhappy ending.
Not quite right. For a conventional aircraft (and I presume this is what the Airbus becomes in the event that ALL computers roll over and die), the aft CG limit may (amongst other requirements) be limited to give an acceptable positive static stability .. neutral stability would be a fail and require either a further constraint of the aft limit or another flight test engineering fix.
It follows that, if the CG is sufficiently far aft to result in neutral stability, then it wouldn't be certificatable or, perhaps, the probability of box failure demonstrated at certification is sufficiently low to be acceptable.
However, this latter consideration may be tied in with the present mishap - inextricably. Are we not all concerned with the possibility that this crash may have been involved with events so out of left field (but only because of presumptions regarding training and competence standards) that the original certification program may not have considered them at all ?
I don't know what the certification story was for the Airbus FBW machines but would sure be interested to find out ..
A pilot would have a hard time to keep it at a constant altitude
True, but that's only a part of the problem. The typical pilot, faced with a sudden deterioration in the stability he/she feels/sees is more likely to rip the wings/tail off while trying to figure out what might be going on ..
a good pilot could still fly it by hand but it would be difficult
More a case of needing to recognise the problem and then be aware of/trained in the changed techniques required to fly the aeroplane. TPs cover this during their training course and there are documented cases of the occasional TP having to drag a statically unstable aircraft around the patch to get it back onto the ground .. but for Captain Average Joe Pilot .. the story, in all probability, is going to have an unhappy ending.
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We did the fuel transfer thing to the aft tank in the 70's in a Lear jet. You get level at FL410, set power for .82 mach, transfer fuel aft and bring back the power to maintain speed as speed increases, FREE SPEED.
Aft CG as everybody knows means the horizontal stabilizer doesn't have to push down as much because of the forward fuel.
Aft CG as everybody knows means the horizontal stabilizer doesn't have to push down as much because of the forward fuel.
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.. but, I suggest, with the aft tank loaded .. the aeroplane was still statically stable (ie still had an acceptable stick force gradient) for certification ?
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Confused a tad by your comment. Presumably, with aft tank loaded you still were within the aft CG AFM limit ? At the published aft limit, one would still expect to see acceptable LSS.