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AF 447 Thread No. 5

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AF 447 Thread No. 5

Old 21st Jul 2011, 16:16
  #581 (permalink)  
 
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the only tidbits of conversation we know of express doubt:
"we have no indications", "je ne comprend rien".
That, and the call for the Captain to return to the cockpit. That's an SOS call, as I see it.

But when your confidence in those instruments has been shattered, I can see someone resorting to actions based on what their body tells them.
If I am IMC, and I don't believe any of my instruments, the thought that comes to mind is "I am well and truly ed." I then try to make small control movements to get something to move, or change, that makes more sense than what I am seeing, or not seeing, at the moment, and I try to figure out "how do I get to VFR conditions, and how soon can I do that?"
So, I wonder what most pilots would conclude from that feeling?
Try anything that might work, as what's going on now isn't working?
Task the PNF to:
Reset a few circuit breakers to get something to work again?
Cycle some switches on and off so that an instrument may work again.
What I need is:
Attitude reference
Altitude reference
Power reference
Airspeed (but I can work around that if I can get an attitude reference)
VSI
Turn and Slip

Give me what you can, PNF, that's why you are there.

But of course, maybe before we start turning things on and off ...

If your instruments are working, you take the controls, and I'll back you up.

That may be what finally happened somewhere near 10,000 feet on a dark and stormy night.
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Old 21st Jul 2011, 17:22
  #582 (permalink)  
 
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Originally Posted by airtren View Post
A kinetic versus potential energy conservation calculation shows that the BEA indicated height delta (2500 ft from FL350 tgo FL375) checks against the BEA indicated delta speed of 60 knots (from 275 to 215 knots). Same is true for FL380, and 185 knots.

dEk = Ek (275knots) - Ek(215knots) = dEp (2500ft)
Not wanting to nitpick, just for the sake of correctness, it has to be noted that the 275kts and 215kts were IAS.
For any kind of energy calculation you have to take TAS.
In this case that would be approx. 495kts and 390kts, repectively.

Edit:
This corresponds to ~4200ft but is still very well explicable by the increased drag of the maneuvers. So I don't contradict the statement that the kinetic energy figures are plausible.

Last edited by henra; 21st Jul 2011 at 17:40.
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Old 21st Jul 2011, 17:32
  #583 (permalink)  
PJ2
 
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Hello 3holelover;

Didn't mean to ignore your question! I sometimes struggle with hypotheticals because I wasn't there.

That acknowledged...

I think Lonewolf_50's last line says it all - fly pitch and power.

That is the drill for a UAS abnormal and that is what will keep the airplane stable while the problem gets sorted out. I think that every other response will likely destabilize the aircraft and make things much more difficult to recover from.

To your question regarding "what would one do?", faced with the losses you mention, I don't for one second pretend to know because I've never been faced with the problem. So hypothetically from my armchair, obviously given the views I have expressed in the past I would do nothing except maintain pitch and power and call for the UAS checklist. The memorized portion of the UAS drill requires that one "level off and troubleshoot" and "doing nothing" (except maintaining control) is being done.

If I began feeling "light in the seat" I would ask what other crew members were feeling while checking the aircraft attitude on the displays I had and try to maintain level flight. Reading the standby in turbulence is a real challenge by the way - the thickness of the little airplane symbol (on the steam instruments) is about 2deg of pitch...a lot when one needs to fine-tune pitch! The job of maintaining stable flight is challenging in turbulence anyway but it must be done.

For the following discussion, we need to understand the layout of the A330 cockpit to see where the following panels are. Here is a rough diagram:





In terms of available attitude information, if the artificial horizons (all 3) are failed it means that IRUs 1 and 2 have failed so, (if I had the presence of mind...again, from the comfort of my armchair), I would ask the PNF to switch the source of the attitude information to the #3 IRU, (ATT HDG, Capt or F/O ON 3), (see diagram below).

It would be unlikely that all 3 IRUs would fail, and there are no ACARS messages that indicate any IRU failures.








But let us continue the hypothetical case.

If a PFD display had failed, (mine), I would transfer control to the PNF if he had an attitude display that agreed with the Standby and call out pitch and bank information to help him maintain level flight while we got the QRH out for pitch-power settings.

I would leave the ECAM messages alone until control was assured and stable flight established - which means, when the QRH UAS drill and checklist are completed.

In the A330, one can switch data sources to another DMC (Display Monitor Computer - see schematic below).

So, if one, two or all of the IRUs were working but one's own DMC had failed, one can switch DMCs using the EFIS DMC Control Panel to select either the opposite side display or the #3 display.

One can even toggle one's own PFD information so that the PFD and ND exchange displays in case one's own actual CRT display has failed.

Again, it is unlikely that all 3 DMCs would fail. Here is the DMC switching panels which are located on the far left and right ends of the glareshield. the top knob has 3 selections: "NORM" for one's own DMC, #1 or #2 for the opposite side DMC, and #3 for the backup DMC.









In brief, for all attitude information to have been lost to the crew, all 3 IRUs would have to have failed, or all 3 DMCs would have to have failed or all 4 screens would have to have failed (PFD & ND information cannot be displayed on the ECAM and SD displays). To see how all this fits together, here is a schematic of the entire EFIS control and display system:







Once the attitude information had been regained, maintaining wings-level is paramount then maintaining about 2.5deg pitch attitude is next.

After all this trying, if one still doesn't have attitude information, it is a very bad day and very likely a loss of control, probably a spiral dive, would follow. I think it is reasonable to say that one cannot maintain level cruise flight in an airliner solely by the seat-of-the-pants.

I say a spiral dive and not a stall because maintaining wings completely level without any attitude information (external or internal) is far more challenging in the short term, than maintaining a level pitch attitude. A small amount of bank will start a turn, and also cause the nose to drop and the spiral begins, and quickly develops and tightens because the A330 is so clean and "slippery".

Even in general aviation it is well understood that if a pilot with little or no instrument training loses visual reference with the horizon a spiral dive is the most common outcome. The most well-known event of this kind was John Kennedy Jr's accident some years ago. That was the reason for the introduction decades ago of the requirement for some instrument instruction even at the private pilot level. So loss of attitude information without visual reference to a horizon almost guarantees loss-of-control of some kind, whether a high-speed spiral dive (very likely) or a stall, (less likely, for reasons given).

The BEA Update doesn't state that the #2 PFD attitude information is not recorded. However, the Update does clearly provide information on the bank and pitch attitudes throughout the report and this information had to come from somewhere. I think it is reasonable to assume that if the data was available on the SSFDR, for the reasons given above regarding failures of redundant systems, it was displayed on one/both PFD(s) and ISIS. There are no ACARS messages indicating failures which would prevent such display.

I think to claim that the pitch-up was the result of the PF reacting to a display that was different than the PNFs or the ISIS is not reasonable for two reasons: a) system redundancy and absence of failure messages, and b) the PNF would either have the same "wrong" display or would react and call out his own display showing something different. Also, at what time would such a failure have occurred? There is no connection between the pitot failures and a failures of attitude displays.

I fully realize that I am inferring a great deal here but I am also trying to think about your hypothetical scenario logically. If we are to think hypothetically, at least the hypothesis must be internally consistent - we can't just say this and that is "possible" without accounting for the design of the aircraft and its systems which preclude some scenarios.

I'm completely open to alternate explanations of the pitch-up but the explanations have to make sense and withstand reasonable objections.

At some point there has to be a rational explanation that makes "if-then" connections, ideally all the way back to the originating event at 02:10:05 even if some of those connections may be tenuous.

I know that isn't possible at the moment because we all have the same bit of information from the BEA Update. But some things may be inferred, (admittedly, some more "loosely" inferred than others).

I'm not stuck on the notion that the initial aft-movement of a sidestick was intentional. But at some point, first the initial pitch-up, then the continuing aft-backstick must both be explained.

I hope this is of some use 3holelover...as I say, it's all armchair work but those guys had to do it for real. As I have said many times, discussing crew actions is not "blaming the crew". In investigative work there are no "off-limits" areas however, and that can come across as "blaming". For reasons we're all familiar with, that unfortunately seems to be a way our culture thinks about these things.

Lonewolf_50;
Task the PNF to:
Reset a few circuit breakers to get something to work again?
Cycle some switches on and off so that an instrument may work again.
Yes, exactly. Although there are no circuit breakers that would accomplish this purpose in the cockpit, (the FMGEC cb's are on the overhead but they wouldn't help), the switching capabilities that I discuss above would be of immense help in any attitude failures, so long as there is attitude information available from an IRU.

Last edited by PJ2; 21st Jul 2011 at 18:03.
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Old 21st Jul 2011, 17:50
  #584 (permalink)  
 
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Originally Posted by Dont Hang Up View Post
gH = 1/2 x (V^2) where V is the speed change and H is the height change
So in metric units V=SQRT(2 x 9.8 x 914)
V=133 metres per second (approx 260 Knots decrease)
Hmm, I'm afraid you've got a little quirk in your calc.

Energy loss is 1/2 (V1^2 - v2^2) which is quite a different thing from 1/2 (v1 - v2)^2.

You might want to recalculate with the adapted formula and will then come to the conclusion which has been accepted here that the energy transformation matched quite OK.

Last edited by henra; 21st Jul 2011 at 18:24.
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Old 22nd Jul 2011, 09:48
  #585 (permalink)  
 
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Hi CONFiture,
Originally Posted by CONF iture
Where do you get that certainty of a triple ADR fault from ?
To the contrary, Low and High Speed Stabilities may well have been available.
Quite simply if, at any point, you've got 3 valid ADRs and a failure makes those 3 ADRs to be rejected by all PRIMs and Autoflight System (AFS)... it will certainly be called a triple ADR fault. That is what happened starting at 0210:05, in all certaincy (this is also stated as a fact from the 1st BEA report).

This relevant fault was: PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA).
Its meaning is quite clear: total pressure was out of boundaries and different at each probe-pitot source (9DA1, 9DA2, 9DA3) and the following consequences are well known on ADRs output channels as well as with other systems (A/FLT, F/CTL, NAV) using those values.

Hence, from this point, ALT2 without valid airspeed/Mach and SPEED LIMIT FLAG on PFD make it quite certain that Low and High Speed Stabilities were NOT available.

Originally Posted by OK465
However, you do need to experience complete AC electrical failure to get there.
Of course, you are right about that (batteries). The above quote sumarizes precisely what I meant by "complete [AC] electrical failure".

Last edited by takata; 22nd Jul 2011 at 10:09.
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Old 22nd Jul 2011, 18:39
  #586 (permalink)  
 
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henra:
This corresponds to ~4200ft but is still very well explicable by the increased drag of the maneuvers. So I don't contradict the statement that the kinetic energy figures are plausible.
If they are flying in a column of air that was moving somewhere betwen 1-2000 down (a down draft) you might get to about 3000 feet up with your figure there. Just a thought.
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Old 23rd Jul 2011, 00:55
  #587 (permalink)  
 
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@Takata:

Quite simply if, at any point, you've got 3 valid ADRs and a failure makes those 3 ADRs to be rejected by all PRIMs and Autoflight System (AFS)... it will certainly be called a triple ADR fault. That is what happened starting at 0210:05, in all certaincy (this is also stated as a fact from the 1st BEA report).


I will disagree with the statement "a failure makes those 3 ADRs to be rejected"
Out of 3 sources FCPC can reject only 1 outlier ADR, but the other 2 remain because FCPC is not able to determine which one or even both are delivering wrong information.
If both keep on delivering different information for more than 10s the NAV ADR DISAGREE message is triggerd. This message was not present @ 02:10:16 or subsequent seconds but ca. 2 minutes later.
The first UAS was only transient, ADR 1 lasted only few seconds, ISIS (ADR 3) was absent for nearly 1 minute.

The NAV IAS DISCREPANCY message, triggered when there is a difference in ADR1 (LH PFD) & ADR 2 (RH PFD) was not present.
ADR 2 therefore must have been (+ or - 30Kts) with ADR 1 at that time and was - like ADR 1 - only absent for few seconds (9s or less).

As said the NAV ADR DISAGREE message is presented because crew has to make a decision to elaborate the ADR in error by switching off this (or multiple ADRs) so it will not be available for the FCPC also.

This relevant fault was: PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA)
Its meaning is quite clear: total pressure was out of boundaries and different at each probe-pitot source (9DA1, 9DA2, 9DA3) and the following consequences are well known on ADRs output channels as well as with other systems (A/FLT, F/CTL, NAV) using those values.

Same for this failure message, in fact you should read: PROBE-PITOT 1+2 or 2+3 or 1+3 (9DA?).
Meaning there are 2 or more PITOT-PROBES affected but BITE/CMC can't determine which 2 (or more) are faulted.
This fault is indeed correlated with the first UAS event but same message would have been correlated to the second UAS event @ 02:12 however only the first occurance will be recorded en transmitted to CMC/CFR/PFR.
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Old 23rd Jul 2011, 11:25
  #588 (permalink)  
 
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Probe-pitot 1+2/2+3/1+3

Hi A33Zab,
Originally Posted by A33Zab
for this failure message, in fact you should read: PROBE-PITOT 1+2 or 2+3 or 1+3 (9DA?). Meaning there are 2 or more PITOT-PROBES affected but BITE/CMC can't determine which 2 (or more) are faulted.
Which is also exactly my reading of the fault:
total pressure was out of boundaries [meaning that ADRs polled airspeed value dropped by 30 kts in one second or less] but was different at each probe-pitot source (9DA1, 9DA2, 9DA3)

Then, your explanation is the same than mine : the system can't dertermine which source (pitot-probe) faulted, because all 3 values were at first valid and coherent (condition for triggering this fault and monitoring), then diverged without remaining consistant with each others, hence, there was NOT an ADR DISAGREE message that could be triggered at this point (0210:05). The system was not able to eliminate the outlier ADR during the speed monitoring sequence (DISAGREE condition false: elimination of 1 ADR and other two ADR imputs different). Consequently, all three ADR output would be rejected both at PRIMs (FCPC1 & 2) and AFS level (no matter if one ADR output could have been valid).

Also IAS DISCREPANCY would be triggered if PFD 1 & 2 readings were showing a difference of at least 16 kt during some time. This condition may not have lasted long enough for doing so, hence no ACARS if such fault would be sent (not sure) after consolidation (2-3 seconds). It doesn't mean that this ECAM wasn't displayed at all in the cockpit, but it could have been intermitent during a very short duration. Also, there is nothing in BEA narrative telling us that the crew noticed something before AP disconnected. In many other cases, crews were alerted by experiencing airspeed fluctuations; it seems not to be the case here: it was brutal.

Consequently from those conditions, I'm deducing that ADR2 was also faulty and could have been the very first to drop. This is fully coherent with an environmental fault affecting the same probes, the same way, in a very short time interval.

Originally Posted by A33Zab
The first UAS was only transient, ADR 1 lasted only few seconds, ISIS (ADR 3) was absent for nearly 1 minute.
Your conclusion doesn't match with the data:

In BEA last note :
1) 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).

2) The inconsistency between the speeds displayed on the left side [ADR1] and on the ISIS [ADR3] lasted a little less than one minute [inconsistency stopped before 0211:05]
From the BEA narrative:
- 0210:05 -> ADR1 followed by ADR3 sharp fall;
- 0211:06 -> ADR1 & ADR3 speeds coherent and "valid" again => 1 minute error;
- 0211:40+ few seconds -> all of the recorded speeds became invalid again (1). Note 1: When the measured speeds are below 60 kt, the measured angle of attack values are considered invalid and are not taken into account by the systems. When they are below 30 kt, the speed values themselves are considered invalid.

Consequently, the ADR DISAGREE message triggered (0212 => 0211:40+) is due to this second (or later) speed/alpha issues with ADRs, at which time conditions were different as 1 ADR would have been rejected at FCPCs level.

Your above conclusion doesn't match also with the first BEA report (see p.54-55) about this fault explanation:
"The presence of the F/CTL RUD TRV LIM FAULT message indicates that EFCS monitoring had been activated and that the alternate law had been maintained."
Hence, it was already obvious from all the systems declared INOP that the first probe fault was NOT transient and it was confirmed by the DFDR showing that the inconsistency lasted about 1 minute on both ADR1 & ADR3 (more than enough for a triple ADR fault condition).

You should also keep in mind that this sequence is not from a PFR (Post Flight Report) but a CFR/ACARS, hence, everything is not sent by this mean (e.g. no cockpit Stall, overspeed warnings). Failures are labelled following their logical compilation order and could have covered various system messages having the same ATA header => 341.

You may want to list every ATA 341 fault at FCPC and AFS level and see what they could have been during this 1 mn correlation window opened.

Also, AIRBUS acknowledged this PROBE-PITOT fault as being possibly part of an UAS signature, even if not the more frequent:
Originally Posted by AIRBUS
TELEX - OPERATORS INFORMATION TELEX
TO: A330/A340/A340-500/A340-600 Operators
SUBJECT: ATA 34 - REQUEST FOR INFORMATION CONCERNING IN-FLIGHT UNRELIABLE AIRSPEED
OUR REF: SE 999.0049/09/VHR dated 09 JUN 2009
[...]
2/ TYPICAL SIGNATURE OF UNRELIABLE AIRSPEED
To be sure that Unreliable airspeed events are correctly identified, please report events corresponding to the criteria as follows:
- Crew report indicates loss or discrepant IAS (Indicated Airspeed) on CAPT and/or F/O PFD and/or Standby Airspeed indicator (ISIS).
- Typical ECAM Warnings were seen:

NAV ADR DISAGREE
NAV IAS DISCREPANCY
F/CTL ALTN LAW
F/CTL RUD TRV LIM 1(2) FAULT
AUTO FLT AP OFF
AUTO FLT A/THR OFF
STALL WARNING (audio call-out)
AUTO FLT REAC W/S DET FAULT

- Fault Message "PROBE-PITOT 1+2/2+3/1+3" was possibly also seen.
- Maintenance report indicates that event was NOT due to a system failure.

The TBS (see below) mention about this fault "Disagree of the Pitot Probe Data in the FCPCs" that if the fault was transient, F/CTL ALTN LAW, would have been displayed only few seconds in the cockpit (then return to NORMAL, while an acknowledgement from the crew is also stamped 0210:16)- Beside, there would be no subsequent ECAM warnings and flags on PFDs.

Originally Posted by TBS
34-11-15 EFCS2 :
TASK 27-91-00-810-822
Disagree of the Pitot Probe Data in the FCPCs
1. Possible Causes
...pitot probe
2. Job Set-up Information
...A. Referenced Information
.........AMM 34-11-15-000-801 Removal of the Pitot Probe (9DA1, 9DA2, 9DA3)
.........AMM 34-11-15-200-801 Inspection/Check of the Pitot Probe (9DA1, 9DA2, 9DA3)
.........AMM 34-11-15-400-801 Installation of the Pitot Probe (9DA1, 9DA2, 9DA3)
3. Fault Confirmation
...A. Test
........(1)Not applicable, you cannot confirm this fault on the ground.
4. Fault Isolation
...A. If the crew made a report that the F/CTL ALTN LAW or F/CTL DIRECT LAW warning was shown on the EWD for some seconds only:
.........- no trouble shooting is necessary.
...B. If the F/CTL ALTN LAW or F/CTL DIRECT LAW warning is shown and stays on during the flight:
.........(1)Do the inspection of the pitot probe (9DA1, 9DA2, 9DA3)
.........AMM TASK 34-11-15-200-801
.........replace the defective pitot probe (9DA1 or 9DA2 or 9DA3)
.........AMM TASK 34-11-15-000-801 and AMM TASK 34-11-15-400-801

Last edited by takata; 23rd Jul 2011 at 11:46.
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Old 23rd Jul 2011, 15:23
  #589 (permalink)  
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A gracious good morning, takata.

Thank you for such specific and important data.

You mention that BEA do not state any "recognition" (by pilots) of noticeable a/s problems prior to a/p loss. You also mention that many prior cases of UAS did have such recognition by pilots. You call it 'brutal'. Can you explain?

It underscores the suddenness of the auto loss to the crew. I cannot recall a discussion of events probable at a/p drop before. Your fine tuning of the FCS' reactions and mitigations are enlightening.
 
Old 23rd Jul 2011, 15:27
  #590 (permalink)  
 
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@3holelover
but that isn't going to hold me back from saying I think some of you (Bearfoil) are appearing to be frighteningly closed to the notion that the airplane may well have been just fine, but the PF screwed the pooch.

Good grief man, from what we "know" so far, it's the most logical solution to all questions.
I do believe you have just proven one of Bear's previous points.


Perhaps what you meant to say that the PF/PNF were put into cognitive overload by the system failures, sequence of error messages, failed indications and aircraft behaviors and changes of laws.

You might do well to read the seminal paper by Reason on the swiss cheese model of error propagation. There plenty of slices of holey cheese to pass around in most aircraft accidents and incidents.


(Google "Reason Swiss Cheese Model" there are lots of hits to read)

Edit:
As an example read the prescient introductory paras in this wiki entry - Organizational models of accidents - Wikipedia, the free encyclopedia

Last edited by Ian W; 23rd Jul 2011 at 16:06.
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Old 23rd Jul 2011, 16:14
  #591 (permalink)  
 
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Originally Posted by takata
In many other cases, crews were alerted by experiencing airspeed fluctuations;
Is this your reference? -
BEA Interim #2, 1.16.3 Study of losses of or temporary anomalies in indicated speeds:
The recordings of total or static temperatures(9) show increases of ten to twenty degrees during the event, which sometimes began before noticing any speed anomalies, except in a case where the increase was lower;
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Old 23rd Jul 2011, 16:25
  #592 (permalink)  
 
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Hi Bearfoil,
Originally Posted by Bearfoil
You mention that BEA do not state any "recognition" (by pilots) of noticeable a/s problems prior to a/p loss. You also mention that many prior cases of UAS did have such recognition by pilots. You call it 'brutal'. Can you explain?
In many UAS events, (but not all), the attention of pilots was at first attracted by either airspeed fluctuations on PFDs, either autothrust changes before autopilot disconnected. In one case, it is mentioned that CAS made several yo-yos on both PFDs. In those recorded cases with fluctuations, this NAV IAS DISCREPANCY message would tilt on ECAM. It means that airspeeds displayed on each PFDs are outside a certain range, which is constantly monitored by the system, while certified instrument possible variations at cruise, depending on source, altitude and speed are below Mach 0.009 (=3-4 kt above FL350).

In fact, I noticed an incoherence about this NAV_ADR_DISAGREE message: In the documentation, like A33Zab mentioned it above, it is stated that in case of 2 or 3 ADR fault, this ECAM would be displayed, while I believe this is only true in the first case (2 ADRs) because it is contradictory with NAV_ADR_DISAGREE condition which needs first an ADR to be rejected by the PRIMs (this rejection of the "outlier" is discrete). Hence, in case of triple ADR fault happening in a very short time, without a single ADR drifting earlier from the other two, this condition won't be true.

Our case signature of this first ADR fault (0210) is a triple one. Beside, it is much more logical with the Probe-Pitot fault which is also a triple one, the system being unable to determine which one of the three has faulted. How could the system "eliminate" the first ADR by itself?

Hence, this is why I'm saying it was brutal as there was a fast ice build-up, a sharp speed drop, without erratic speed readings, affecting all the probes in few seconds that caught the crew by surprise. No warnings due to autothrottle behavior or IAS DISCREPANCY tilting on ECAM display.

But please, Bear, don't rebounce on my posting in order to advance your usual "structural" failures fantastic theories, as this was a genuine ADR fault due to severe probe icing in all certaincy.

Their huge problem was that when the first ADR fault self-cleared at 0211, a second followed at 0211:40 (invalid parameters), then possibly a third one at 0212 (ADR DISAGREE)...

Hi HN39,
Originally Posted by HazelNuts39
reference?
See the Expertise Judicial report link I posted few pages back. (here it is: rapport d'expertise Rio-Paris)

Last edited by takata; 23rd Jul 2011 at 16:44. Reason: addition
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Old 23rd Jul 2011, 18:48
  #593 (permalink)  
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Not really fantastic, at least in the case of 'superbe', no?

At last I believe I am tracking you, and surprised at how much we agree.
That three probes would block simultaneously, in rate as well as time frame, seems fantastic to me. How quickly does a/p respond to declining a/s's, and for how long is it "allowed" to? I am starting to suss the Law, so thanks to you, I have some actual data to consider, phrased in language I get.
 
Old 23rd Jul 2011, 19:08
  #594 (permalink)  
 
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Originally Posted by Bearfoil
How quickly does a/p respond to declining a/s's
What is monitored is CAS value, by two independant systems working in parallel: actually -> 0.45 second at autoflight level (1) and 1 second at FCPC level (2).
1) Fluctuation fo CAS resulting of 20 kt change in 0.45 seconds will cause A/P to disconnect, and further A/FLT systems if confirmed.
2) Fluctuation of CAS resulting of 30 kt change in 1 second will cause ALTERNATE LAW 2 to trigger, and further F/CTL if confirmed.

The next step is a 10 seconds monitoring test which retains the last valid CAS (median value of 3 ADRs) for comparison with CAS value at the end of this time window.
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Old 23rd Jul 2011, 19:15
  #595 (permalink)  
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Ahhh.... So the a/c flies for ten seconds on one read? Is that the ten second interval I suss @ 2:10:16 "so.....we've lost the speeds, Alternate Law?" (PNF?).

Am I close? If the a/c was ten seconds into flight calculated on one airspeed, what could the PF/PNF be seeing when the reads update?

Do they? Is PITCH and POWER any more difficult to acquire if the a/c has degraded in assiete, during "monitoring"?

thanks takata
 
Old 23rd Jul 2011, 20:12
  #596 (permalink)  
 
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Originally Posted by Bearfoil
Ahhh.... So the a/c flies for ten seconds on one read? Is that the ten second interval I suss @ 2:10:16 "so.....we've lost the speeds, Alternate Law?" (PNF?).

Am I close? If the a/c was ten seconds into flight calculated on one airspeed, what could the PF/PNF be seeing when the reads update?
NO again, you are far!
Autopilot disengages and ALT2 is triggered immediately without waiting for 10 seconds confirmation.
CAS_System is used by aircraft avionics systems (autoflight, flight controls); it is NOT displayed on PFDs.
* Captain's PFD: CAS1 = ADR1 = real value displayed if > 30 kt.
* F/O's PFD: CAS2 = ADR2 = real value displayed if > 30 kt.
* Standby: CAS3 = ADR3 (not displayed, in replacement for CAS1 or 2)
* ISIS: CAS3bis = same probes as ADR3, but analogical values (no ADMs computation) = real value displayed if > 30 kt.

Consequently, if Captain's Probe-Pitot becomes clogged and ADR1 airspeed drops immediately from 275 kt to 60 kt, Captain's PFD will actually display 60 kt even if the system CAS will retain the last valid value of 275 kt for monitoring all ADRs output during 10 seconds following the fall of ADR1. Same for F/O, ISIS with their respective ADRs.
That's how RTLU would retain the last valid airspeed if the 10 seconds airspeed test failed but, if the test is passed, it will function normally.
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Old 23rd Jul 2011, 20:27
  #597 (permalink)  
 
Join Date: Jun 2009
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bearfoil, the definitions of conspiracy follow:

conspiracy (plural conspiracies)
  1. The act of two or more persons, called conspirators, working secretly to obtain some goal, usually understood with negative connotations.
  2. (law) An agreement between two or more persons to break the law at some time in the future.
  3. A group of ravens.

Now, in the sense of the second definition do you believe there is a conspiracy involved in BEA?

I also personally wonder if you are still insisting things fell off the plane or quit working without any evidence in the ACARS messages, do you?
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Old 23rd Jul 2011, 20:44
  #598 (permalink)  
 
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Originally Posted by BEA
The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb.
Originally Posted by airtren
A factor of surprise for such a sudden response may have been the cause of the delay to the ND command, slowing the climbing vertical speed from 7000ft/min to 700ft/min.
More like, could a lack of response to an initial smaller NU response have led to continued NU application until the sudden response happened. They were in turblence, or chaotically moving air. Suppose that air movement was enough to momentarily negate the response of the aircraft to the pitch change. That might have altered the PF's response.

So he rather rapidly climbed and then reduced the climb rate. Pitots cleared. At least PNF got airspeed and both received a stall warning. And it all balled up at that moment with the PF response.

As an aside I'll be interested when the report comes out of PNF was kept abreast of what PF was doing as he did it, "I'm climbing for a little more altitude to (whatever)." If such statements as he was acting were not made that suggests to me a potential cultural problem for the team environment in the cockpit.
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Old 23rd Jul 2011, 21:05
  #599 (permalink)  
 
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Lonewolf_50, re A33zab's remarks note the bit about speed > 250 kts.
The load allevation is only available:
CAS > 250 Kts
FLAP LVR = 0 position
In NORMAL or ALTERNATE LAW.
With speed lost could MLA function at all?
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Old 23rd Jul 2011, 21:12
  #600 (permalink)  
 
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Originally Posted by grity
but with decreasing speed during climb no longer every energie of the turbines is required against air drag, so they provide more energie into the kinetic system....
That is why my initial calculation was based on zero speed with a delta. I used the fact that the plane was in a stable state with respect to power and drag. Then I calculated an energy tradeoff for the change in altitude. Admittedly this is at best a first approximation. Nonetheless, that was not accepted around here. Either calculation has a reasonable chance as a first approximation to what happened. The plane was in heavy turbulence moving through chaotic winds.

Above I mentioned it may have received stick up in response to a down draft, the plane then moving into a strong updraft and surprised PF. The chaotic winds they were going through may preclude a really accurate assessment of the energy tradeoff. It is suspicious that the number comes out so close to what was apparently observed.
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