AF 447 Search to resume
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Stalled?
Originally Posted by alph2z
Since people are talking quite a bit about a high altitude stall here is a video from the ASB (Australian Safety Board) of a 777 stalling at high altitude ...
The report doesn't say that the airplane actually stalled, but maybe we can take the AoA as an indication that it did, or came very close?
PS:: The airplane was pitching down at the time (17:03:52 - 17:03:59) the AoA was recorded. Therefore the vane AoA may have been greater than the airplane AoA.
Last edited by HazelNuts39; 19th Apr 2011 at 21:31. Reason: PS added by me (HN), not 'Jetdriver'!!!
Salute!
BJ and mm43 have cracked the code.
The info I can find on the DFDR's reveals very slow sampling rates, and I am not sure if the data is time-stamped at the sensor or by the "black box" when it receives the data.
My background was in military testing, and we sampled the digital data at 50 hz or better. Our analog data from accelerometers and pots were recorded on old-fashioned tape! However, the digital stuff was parallel on the tape (7 channels), so we had a mechanical means of synchronizing the data.
As the referenced report by BJ states, the sampling rate was too slow to get an accurate replay of the rudder reversals by the 587 jet.
For my business we needed to see very good parallel data streams of control position, force inputs, and aircraft/missile attitude, gee, etc.
The serial data recorder using a single memory device has to use various update rates depending upon the parameters of interest. And I agree with the observation that filtering the data as it is being recorded is not a good thing. Our data reduction facility could filter as necessary, but we captured the "spikes" and such as raw data.
BJ and mm43 have cracked the code.
The info I can find on the DFDR's reveals very slow sampling rates, and I am not sure if the data is time-stamped at the sensor or by the "black box" when it receives the data.
My background was in military testing, and we sampled the digital data at 50 hz or better. Our analog data from accelerometers and pots were recorded on old-fashioned tape! However, the digital stuff was parallel on the tape (7 channels), so we had a mechanical means of synchronizing the data.
As the referenced report by BJ states, the sampling rate was too slow to get an accurate replay of the rudder reversals by the 587 jet.
For my business we needed to see very good parallel data streams of control position, force inputs, and aircraft/missile attitude, gee, etc.
The serial data recorder using a single memory device has to use various update rates depending upon the parameters of interest. And I agree with the observation that filtering the data as it is being recorded is not a good thing. Our data reduction facility could filter as necessary, but we captured the "spikes" and such as raw data.
Quote from JD-EE (posted Apr18/2341z):
"...If the accident happens in a third world area, the report quality is poor because of the untrained and inexperienced investigators. If the accident is not politically charged and is in a "first world" nation the reports tend to be pretty good..."
Apologies for slight thread-drift. As a BBC Radio4 addict, I recommend this fairly balanced programme on the problems of accident investigation in third-world countries – strictly only for those who can manage without pictures...
"...If the accident happens in a third world area, the report quality is poor because of the untrained and inexperienced investigators. If the accident is not politically charged and is in a "first world" nation the reports tend to be pretty good..."
Apologies for slight thread-drift. As a BBC Radio4 addict, I recommend this fairly balanced programme on the problems of accident investigation in third-world countries – strictly only for those who can manage without pictures...
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Lazerdog
Ile de Sein is due to leave las Palmas april 21st to start the search. Apparently, the ship has been doing sea trials yesterday off the coast. (Testing new equipment?)
Ile de Sein is due to leave las Palmas april 21st to start the search. Apparently, the ship has been doing sea trials yesterday off the coast. (Testing new equipment?)
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mm43
With most respect, I tend to disagree re: your studious conclusion about the found spoiler, and by inference other composite panels. The spoiler was found on the surface beaten up badly, and fractured, but retaining its full size and shape. Given the scope of the destruction to metallic forgings and extrusions evident in the seabed photos, I have to say the spoiler without doubt was removed by air loads, extreme airloads. The actuator attach was badly fractured, but the damage was tight to its location, and gave way to a retention of integrity just inches into the panel's skin surrounding the fasteners. In my experience, FRP has a signature failure in high energy impacts that is unmistakable. It explodes. I believe that if the spoiler panel (#4??) had been on the wing at water impact, there would be virtually nothing left to find. This has also to do with my admittedly stubborn conviction that the Vertical Stabilizer and Rudder were not on the fuselage at impact. The Radome is even money, I think it is likely to have left the airframe prior as well, perhaps in overspeed, or due to hail damage.
I am thrilled at the location of the aircraft's site, and my optimism is high. I think that here on PPRuNe, this thread is as incisive and academically brilliant as any accident report I've seen. You and the others are absolutely brilliant in your knowledge, logic, and utmost respect for one another.
kudos, and back to read....
With most respect, I tend to disagree re: your studious conclusion about the found spoiler, and by inference other composite panels. The spoiler was found on the surface beaten up badly, and fractured, but retaining its full size and shape. Given the scope of the destruction to metallic forgings and extrusions evident in the seabed photos, I have to say the spoiler without doubt was removed by air loads, extreme airloads. The actuator attach was badly fractured, but the damage was tight to its location, and gave way to a retention of integrity just inches into the panel's skin surrounding the fasteners. In my experience, FRP has a signature failure in high energy impacts that is unmistakable. It explodes. I believe that if the spoiler panel (#4??) had been on the wing at water impact, there would be virtually nothing left to find. This has also to do with my admittedly stubborn conviction that the Vertical Stabilizer and Rudder were not on the fuselage at impact. The Radome is even money, I think it is likely to have left the airframe prior as well, perhaps in overspeed, or due to hail damage.
I am thrilled at the location of the aircraft's site, and my optimism is high. I think that here on PPRuNe, this thread is as incisive and academically brilliant as any accident report I've seen. You and the others are absolutely brilliant in your knowledge, logic, and utmost respect for one another.
kudos, and back to read....
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lonewolf :
I strongly suspect (but don't have doc's to qoute) that the data arrives at the black box at a much higher rate than it is recorded and that the recorded sampling rate is set by the black box.
What could be done to help with correlation is to snap-shot all the data at relevant frame boundries, to use PJ2's analogy synchronize the strobes. The data could then be saved over the frame time.
This would avoid artifacts such as phantom splits in control surfaces due to "sampling lag"
On the other hand there may actually be more value in sampling the data as it is recorded, helping to fill in gaps using semi-related parameters.
To put it in engineering terms "no matter how hard you try Nyquist wins". (And wagon wheels will continue to go backwards in movies)
Also a big thank you to PJ2 for the analogy in re data sampling, although I did cringe at the memory of strobe lights and the disco era. (At least you didn't meantion leisure suits and polyester shirts! 
)
Good point.
)
For syseng68:
Quote:
Although messages may not be written in real time, or perhaps even in strict sequence of arrival is irrelevant, since each message will have it's own timestamp.
Quote:
Although messages may not be written in real time, or perhaps even in strict sequence of arrival is irrelevant, since each message will have it's own timestamp.
What could be done to help with correlation is to snap-shot all the data at relevant frame boundries, to use PJ2's analogy synchronize the strobes. The data could then be saved over the frame time.
This would avoid artifacts such as phantom splits in control surfaces due to "sampling lag"
On the other hand there may actually be more value in sampling the data as it is recorded, helping to fill in gaps using semi-related parameters.
To put it in engineering terms "no matter how hard you try Nyquist wins". (And wagon wheels will continue to go backwards in movies)
Originally Posted by syseng68k @3650
Sorry to disagree, but the recorders would not affect the time relationship between messages. A much more likely scenario would be for each message to be timestamped as it arrives at the recorder, then queued for writing. The queue would be of a length to ensure that no messages are lost.
Although messages may not be written in real time, or perhaps even in strict sequence of arrival is irrelevant, since each message will have it's own timestamp...
Although messages may not be written in real time, or perhaps even in strict sequence of arrival is irrelevant, since each message will have it's own timestamp...
grity;
Fuel transfer and the CG is managed by the FCMC [Fuel Control and Monitoring Computers]. There are no procedures established to move the CG forward to "guard against stall" - in fact, no airplane which would require such an intervention should be flying as a commercial transport. The aircraft is certified to be loaded and fueled in certain ways and CG limits are established as part of the design and certification process.
Procedures are in place to handle the abnormalities.
If for any reason the CG ends up too far aft, an ECAM message comes on requiring the forward transfer of the fuel. This is different than "deciding that the CG is 'too far aft' " all on the crew's own. You can get into an equal pile of trouble with too forward a CG, so even though the method is available, (by transferring the trim tank fuel forward, (requires a 3-deg ND pitch to do so)), you wouldn't do it without the ECAM message, just because you thought it would be a good idea.
Thanks gums, understand now. For clarification, flight data is not "timestamped". It is recorded, using synchro words for each parameter when recorded in the data frame. This enables each parameter to be synchronized in time.
The process you're describing would be great for event and accident investigation, but many here, perhaps even yourself, have seen how slow the FAA (and TC in Canada) are in keeping up with available recording technology. "Mandating" the recording of 88 parameters is actually embarrassing.
Back to the subject at hand.
The BEA Report indicates that AF447 had an SSFDR that records about 1300 parameters. AF also runs a FOQA Program and as I have mentioned before, at least a search for the QAR, (in the EE Bay underneath the cockpit) should rule-in/rule-out it's availability and use, although the way the forward section is understood to have impacted, the survival of the electronic gear (and their memory cards) may be questionable.
MurphyWasRight;
Re "arriving at the 'black box' at a higher rate than is recorded" there is no mystery or magic to this stuff - it is in its essence, bread-and-butter digital data transmission and recording, (which, aside from what I've commented on, I know unbelievably little about), so no, there is neither "higher rate" or "more" data, not, at least without the original equipment such as the sensors, the DFDAU [Digital Flight Data Aquisition Unit] software and data buses [ARINC 537, 429 standards etc) to support the designed and intended installation.
I really don't want to divert the thread into the minutae of recording. My comments were intended as a caution about too loose an interpretation on what is seen in the traces regardless of airplane, recorder sophistication and so on.
For those who would really like to understand this further, (and frankly, without some understanding of how data is generated, interpreted and recorded one cannot make comments that are relevant to the very simplified way I've outlined a couple of characteristics), I recommend the two sites below - they're great for a good understanding of the process; the third site is on FOQA in general, by the FAA.
Please see Appendix B of http://www.caa.co.uk/docs/33/CAP731.PDF , and pages 9-13 of the BEA document at http://www.bea.aero/etudes/use.of.fdr/use.of.fdr.pdf , and perhaps the following FAA document which is excellent on FOQA Programs in general,
http://www.ihst.org/portals/54/Attac...D_AC120-82.pdf
ChristiaanJ;
You're right in the sense that it would be the FDIMUs or DFDAUs, (which receive the incoming data from sensors all over the airplane, and change either the analog or digital/binary information into engineering units such as rates, discretes, positions, degrees, etc etc. It would be here that the DFDAU software could "filter" any and all data depending upon programming. It's these boxes that do the heavy lifting...the SSFDR and QAR where installed, are just the recording mediums.
The notion of "filtering" is perhaps another way of saying "manipulated". I would characterize it this way, because where there is no information, ie, no digital signal because the process is "in-between" signals, one has no information to say anything with, and so if one says something, (ie, the DFDAU "fills in the places in-between), one has manipulated the data; that is an entirely legitimate process providing one knows the basis upon which the data is thus manipulated, and providing the holes in the data aren't too large and that rates of change are not incommensurate with the rate of data capture. In standard flight data animation products, such smoothing is necessary, otherwise a series of images based solely upon the data rates with no smoothing, would be very jerky and difficult to interpret. This comes down to "why videos?" in the first place. They are a contextual tool, not a diagnostic tool and as such have great use, but, (for those who have read these cautions before), those who create such videos very often do not have an understanding of how the animation is possible and can draw some seriously incorrect conclusions from just watching the video. That is why this stuff does not belong in non-trained hands...it can badly mislead and the consequences can be serious. But in trained and experienced hands and eyes, it can tell a very accurate story, because the warts are seen and understood.
One can, as has been suggested, make some reasonable inferences from other systems, (mm43's hydraulic example is a good one). But I don't think this is merely a philosophical point: Where there is no data, "smoothing the data points to manufacture datapoints in the in-between, regardless of the mathematical methods used, is not "data" - it is inference, however conceived.
Such inference can be quite reasonable to the point of appearing to be accurate in, for example, a video or film, where our mind "knows" what the changing motions on the screen are "about" and we intuitively make those connections without difficulty, and with a high degree of accuracy.
However, in reading data points which are far enough apart for other things to occur that are beyond the capacity to measure, (like using a yard-stick to measure a foot...it can't be done "accurately" even though it could be inferred, if for example the object being measured is four feet long, which is "a yard and a bit"!),, those events will not have occurred so far as interpreting the data is concerned. They may be so-recorded in other parameters, which is mm43's excellent point, but in the end, one cannot make up data where it doesn't exist even though smoothing in some cases is a legitimate process.
Last edited by Jetdriver; 20th Apr 2011 at 10:38.
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I'll take the risk of confusing the story....
Isn't most of the 'filtering', etc. done in the FDIU or FDAU (Flight Data interface or Acquistion Unit)?
Been there, done that, but too long ago to really be able to contribute anything useful. And no doc to hand....
Not even sure how and when the tme-stamping was done.
Isn't most of the 'filtering', etc. done in the FDIU or FDAU (Flight Data interface or Acquistion Unit)?
Been there, done that, but too long ago to really be able to contribute anything useful. And no doc to hand....
Not even sure how and when the tme-stamping was done.
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bearfoil:
The spoiler's condition is consistent with it being pushed up and off the wing from below by the much larger flaps.
In my experience (aerospace and motorsports) one signature does not fit all! Depends largely on which Fiber(s), the amount and direction of Reinforcing, and the type of Plastic.
Please make an argument as to how the VS and four of its entire forged lugs were together ripped up and forward from the tail section by loads achievable while in the air.
...if the spoiler panel (#4??) had been on the wing at water impact, there would be virtually nothing left to find.
FRP has a signature failure in high energy impacts that is unmistakable
stubborn conviction that the Vertical Stabilizer and Rudder were not on the fuselage at impact
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Brazilian Air Force
According to reporter Nadia Guerlanda Cabral (Folha.com), the Commander of CENIPA (Center for Investigation and Prevention of Aviation Accidents) assured today (19th) that Colonel Luiz Claudio Lupoli will be on board the ship Ile de Sein representing the FAB (Brazilian Air Force) on the rescue mission.
Colonel Lupoli said that it is difficult to estimate how long the rescue will last, since this depends on how many trips the "equipment" will have to make.
This equipment needs three hours to reach the bottom (@3.900 meters).
It seems to me BEA kwows exactly where to go with this "special mechanism" and bring up only the "essential"...
Colonel Lupoli said that it is difficult to estimate how long the rescue will last, since this depends on how many trips the "equipment" will have to make.
This equipment needs three hours to reach the bottom (@3.900 meters).
It seems to me BEA kwows exactly where to go with this "special mechanism" and bring up only the "essential"...
Originally Posted by sensor_validation @ #3667
I believe vertical wind more likely to have been an issue. And then we are back to the effect of speed calculated from frozen pitot tubes and real altitude rise with working static ports...
That said, loss of airspeed information does not automatically result in loss of control as, (say) loss of attitude information would. So something else happened, and these points have been made throughout the thread. But my point remains, it has no relationship with the A319 event which was "local" and mostly roll not pitch related as someone has already keenly observed. BTW, they changed the VS on the aircraft.
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There are no procedures established to move the CG forward to "guard against stall" - in fact, no airplane which would require such an intervention should be flying as a commercial transport.
shurely no commercial airplane should fly into a CB....
I did not mean a "guard against stall" just the few percent less risk, if one lift the aerodynamic stability on a truly higher level in case of expected turbulences, using existing technics......
I wonder, but it shows again the trust into the control system
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sensor validation, I'd say "most likely within 40nm" is something a little less conservative than saying "most likely the Sun will not have gone out when it should rise in the morning." I'd use most likely for that annulus I described rather than for the entire region. The rest of the 40nm region is less likely but not utterly unlikely - erm, with the exception of the area +/- 30 degrees of the reverse course. To the rear the region would be punched in. That's why I always sorta head scratched over their nice perfect circles.
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* Note linked to your other discussions on sampling/filtering - it is possible to detect this by 'listening to the noise' and there are patented and commercial pressure instruments in the process industries that do "impulse line blockage detection".
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Exploding FRP
Hi Bearfoil...
Just humour me here, please.
What's your experience?... and can you point me to a Youtube video of this stuff exploding please. I'd love to see it.
I drove a Reliant Robin into a wall once, but that just cracked.
In my experience, FRP has a signature failure in high energy impacts that is unmistakable. It explodes.
What's your experience?... and can you point me to a Youtube video of this stuff exploding please. I'd love to see it.
I drove a Reliant Robin into a wall once, but that just cracked.
ACA190 versus AF447
Quote from PJ2 (Apr19/0714z, currently post #3646):"I don't think there is anything in the A319 event that relates to the AF447 event. The AC event was wake turbulence...quite different than TCu's."
PJ2 is absolutely right to remind us that wake turbulence is a very different phenomenon from turbulence in towering cumulus (or Cb storm-cells). I reckon he has experienced both, as I have.
For whatever reason, posts have been coming thick and fast over the last two or three days, and it's possible that even PJ2 may have missed something here. There are arguably at least four points of similarity between ACA190 (the Air Canada A319 wake-turbulence encounter that sensor validation kindly reminded us about) and AF447:
1) both involved Airbus FBW aircraft, whose artificial handling qualities are deliberately similar;
2) both occurred at medium subsonic-cruise altitudes;
3) both involved the PF suddenly and unexpectedly having to "hand-fly" the aeroplane, using the sidestick (the use of rudder pedals in ACA190 is another matter);
4) in both cases, for one reason or another, control laws were degraded.
Few line pilots dispense with the autopilot for regular handling practice at cruise altitudes, even in smooth conditions. Passenger comfort is our main priority. As for deliberate degradation of control laws (by selecting one or two of the 5 flight-control computers off, as someone once wanted to do on a flight with me in the early months of A320 operations), that is definitely taboo on the line.
PJ2 is absolutely right to remind us that wake turbulence is a very different phenomenon from turbulence in towering cumulus (or Cb storm-cells). I reckon he has experienced both, as I have.
For whatever reason, posts have been coming thick and fast over the last two or three days, and it's possible that even PJ2 may have missed something here. There are arguably at least four points of similarity between ACA190 (the Air Canada A319 wake-turbulence encounter that sensor validation kindly reminded us about) and AF447:
1) both involved Airbus FBW aircraft, whose artificial handling qualities are deliberately similar;
2) both occurred at medium subsonic-cruise altitudes;
3) both involved the PF suddenly and unexpectedly having to "hand-fly" the aeroplane, using the sidestick (the use of rudder pedals in ACA190 is another matter);
4) in both cases, for one reason or another, control laws were degraded.
Few line pilots dispense with the autopilot for regular handling practice at cruise altitudes, even in smooth conditions. Passenger comfort is our main priority. As for deliberate degradation of control laws (by selecting one or two of the 5 flight-control computers off, as someone once wanted to do on a flight with me in the early months of A320 operations), that is definitely taboo on the line.