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AF447

Old 30th Jun 2009, 08:44
  #2541 (permalink)  
 
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Originally Posted by [URL="http://www.pprune.org/members/302559-clippedcub"
ClippedCub[/URL]]Three pitots is double redundant, at best.

1. lose one, down to two - 1st level of redundancy, and singly redundant if you exclude human interaction.
2. IF one of the remainder disagree, the pilot chooses which one he likes - 2nd redundancy level, but only due to human interaction.
3. Lose the last one, no backup. System is doubly redundant.
That is not strictly true. The level of redundancy is a count of the available resources, not the number you can afford to lose. Where you have three sensors, i.e. three pitot sensors, all of them are redundant, i.e. none of them are essential on their own for the system to work, therefore you have triple redundancy. It would take three failures for a triple redundant system to become inoperative.
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Old 30th Jun 2009, 09:51
  #2542 (permalink)  
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I'm sure I asked this before, but cannot now recall if was answered/deleted whatever.

I hear 'undercurrents' that are talking about loss of attitude data. There is nothing specific on anything posted here from the ACARS list to suggest that. The question (again?) is would the loss of the AD part of an ADIRU render the IRU part unusable/unavailable either de facto or due to software intervention?
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Old 30th Jun 2009, 09:56
  #2543 (permalink)  
 
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Mojomoh
It is a fact that the BEA might very well work on this possibility. I might be wrong but in this case the latest ACARS fault :
0214 21-31-00-2 WRN ADVSRY
CABIN VERTICAL SPEED
LOSS OF ADR DATA
that has just be re-ordered by Desert Dawg, would have been the first warning, not the latest to have been be sent....
Normally the BEA should publish a preliminary report today and not the 2nd of July. At this date is the press point.
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Old 30th Jun 2009, 10:23
  #2544 (permalink)  
 
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Squawk_ident:
Mojomoh
It is a fact that the BEA might very well work on this possibility. I might be wrong but in this case the latest ACARS fault :
0214 21-31-00-2 WRN ADVSRY
CABIN VERTICAL SPEED
LOSS OF ADR DATA
that has just be re-ordered by Desert Dawg, would have been the first warning, not the latest to have been be sent....
Normally the BEA should publish a preliminary report today and not the 2nd of July. At this date is the press point.
1. of course, the BEA is investigating the Water/Waste fault reported May 31 at 2245Z as well as all the faults reported during F-GZCP's carreer. But this article (from a regional newspaper) is only a re-shoot from another one published several days ago from another unreliable source (general public information using unverifiable sources and adding counterfactual data to write another "storyline").

2. CABIN VERTICAL SPEED is an ADVISORY (a green button will flash by intermitence on the cabin pressure panel). A cabine decompression issue would be a major issue and full alarms would be displayed by sound and message all over the cockpit. At this point, this fault is about one cabin pressure controller (a second one is in stand-by). This cabin controller needs a differential pressure to work (Cabin pressure & outside air pressure). When two or more ADIRUs are faulted, the outside air pressure is lacking and the cabin pressure can not be monitored automatically anymore. That's why Mandala noted: LOSS OF ADR DATA.

=> This is not a decompression issue.

3. No preliminary BEA report is expected today as it should be released thursday at the press conference.

S~
Olivier

Last edited by takata; 30th Jun 2009 at 10:58.
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Old 30th Jun 2009, 11:42
  #2545 (permalink)  
 
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Originally Posted by Squawk Ident
It is a fact that the BEA might very well work on this possibility. I might be wrong but in this case the latest ACARS fault :
0214 21-31-00-2 WRN ADVSRY
CABIN VERTICAL SPEED
LOSS OF ADR DATA
that has just be re-ordered by Desert Dawg.....
This re-ordered list of ACARS messages was not done by me. It was done by Mandala499 on a.net. All credit to him
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Old 30th Jun 2009, 12:35
  #2546 (permalink)  
 
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BOAC:
I'm sure I asked this before, but cannot now recall if was answered/deleted whatever.

I hear 'undercurrents' that are talking about loss of attitude data. There is nothing specific on anything posted here from the ACARS list to suggest that. The question (again?) is would the loss of the AD part of an ADIRU render the IRU part unusable/unavailable either de facto or due to software intervention?
BOAC:
Maybe the answer to your question is here.
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Old 30th Jun 2009, 12:48
  #2547 (permalink)  
 
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ACARS Detail

This is the first I have seen of the detail of the failures reported by the ACARS, the number after chapter, such as the -15-0 after 34-11. Indeed, what is the source of this detail? Was it obtained from the original transmissions, or?

GB
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Old 30th Jun 2009, 12:57
  #2548 (permalink)  
 
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Altimeter Fail, Too?

The other iced pitot incidents did not mention loss of altitude indication, yet this ACARS report shows loss of air data to the transponder. The transponder has no reason to use airspeed. This is one failure that does not relate to the others.

GB
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Old 30th Jun 2009, 13:11
  #2549 (permalink)  
 
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The level of redundancy is a count of the available resources, not the number you can afford to lose.
Depends on your reference frame and interpretation. If you're a passenger, you like to think of three pitots as triply redundant.

If you're a computer, three pitots are singly redundant, since the computer can't decide who's bad when down to two. And if you have five computers, the computers themselves are triply redundant for the same reason.

Last edited by ClippedCub; 30th Jun 2009 at 13:44.
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Old 30th Jun 2009, 13:14
  #2550 (permalink)  
 
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egg and chicken again - who/what/which came first ?

0209 START
0210 34-11-15-0 FLR EFCS2
EFCS1, AFS - PROBE PITOT 1+2/2+3/1+3 (9DA)
9DA=HEATING ELEMENT PITOT 1 (6DA1/PHC1)
Heating Element Pitot 1 suspected failed.


0210 27-93-34-0 FLR EFCS1
EFCS2-FCPC2(2CE2) WRG:ADIRU1 BUS ADR1-2 TO FCPC2
No Data from ADIRU 1, ADR 1 & 2 no sending signal to FCPC2
No ADR Data from ADIRU 1 to PRIM2.
Someone came with the answer to my question at last.
Thank you !!!

From flight qantas 72 interim report:

Probe heat computer
Some of the PFR messages indicated a potential fault with the number-1 probe heat
computer (PHC). Those messages could be generated by either a PHC fault or by an
ADIRU fault. The PHC (serial number 2083) was tested by an authorised agency
and no fault was found. Based on a review of available information, the messages
related to the PHC were considered to be spurious.
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Old 30th Jun 2009, 13:26
  #2551 (permalink)  
 
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Do we assume now that the pingers are dead at this stage?
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Old 30th Jun 2009, 13:37
  #2552 (permalink)  
 
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phc

from post 1190:

Quote:
At FL 370 with a SAT to -51 C and a wind from 080 to about 18 Kts on AWY UB612 with OFF SET 1R, between the OBD and MLK in radio contact with Khartoum, as we were at the edge of layer cloudy with some light turbulence, I tied PAX.

We were at dusk with low brightness.
Then we entered the layer, and soon after we started having a slight BURNING SMELL that lasted about twenty seconds and that did not appear to be of volcanic origin (no smell of rotten eggs), but rather electrical smell to me and smell the air conditioning for the OPL. Then the smell has disappeared. The odor was confirmed by the PAX booth and PNC between rows 3 and 14 thereafter.

from a poster at the (already famous) Tim Vasquez website:

Quote:
I am an Airbus A330/A340 Senior Training Captain (IRE/TRE) with Cathay Pacific in Hong Kong. As I'm sure you can imagine we experience our fair share of CB activity; and between June and October - Typhoons. We regularly get small ice deposits on the windscreen wipers and ice detector as cold as -54C. Very small amounts, but ice none the less. It only occurs in the upper levels of the anvil of active Cbs and enough to justify the use on engine anti-ice.

On 28th Sept 2004 ( I was a a brand new Captain) there was well defined typhoon ( I can't remember the name) centred on airway A1 between Taiwan and Kagoshima in southern Japan. The SAT at FL390 was around -56C. Heading South, it looked like we could make it over the top of the storm. As we reached the southern rim of the eye the temperature rose instantly to -39C and we entered a violent Cb. The ice build up was dramatic to say the least. Most of the lower half of the windscreen became encrusted and we encountered an electrical BURNING SMELL (which is not uncommon in the A330 in upper cloud).

Once we exited the cloud, the ice disappeared pretty quickly. There was no noticeable effect on the instruments
I posted this some days ago...
Do the PHCs share any buses with other computers/controllers ?
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Old 30th Jun 2009, 13:40
  #2553 (permalink)  
 
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Pingers

No! The expiration time is the guaranteed minim performance, and have been known to last for up to another four weeks after this period
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Old 30th Jun 2009, 14:01
  #2554 (permalink)  
 
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3 pitots...

0
210 34-11-15-0 FLR EFCS2
EFCS1, AFS - PROBE PITOT 1+2/2+3/1+3 (9DA)
9DA=HEATING ELEMENT PITOT 1 (6DA1/PHC1)
Heating Element Pitot 1 suspected failed.
Bye Bye dual/triple pitot failure hypothesis...
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Old 30th Jun 2009, 14:14
  #2555 (permalink)  
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Any more messages preceding 0210Z sculling around anywhere
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Old 30th Jun 2009, 14:31
  #2556 (permalink)  
 
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Bleve post # 2562: that's a good article from AERO.

On the 330/340 you can put ''aoa'' into the ACMS on MCDU 3 and this gives a direct readout of aoa typically 2.2 - 2.4 degrees nose up at fl 370 M.81. Now if only AB would copy that info to the PFD, and better still to a separate instrument on the instr panel....
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Old 30th Jun 2009, 14:43
  #2557 (permalink)  
 
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Quote:
210 34-11-15-0 FLR EFCS2
EFCS1, AFS - PROBE PITOT 1+2/2+3/1+3 (9DA)
9DA=HEATING ELEMENT PITOT 1 (6DA1/PHC1)
Heating Element Pitot 1 suspected failed.

Bye Bye dual/triple pitot failure hypothesis...
Why? A single pitot failure unlikely downs an A330.

That this failure indication shows a failed PTC heating resistor/or wire connection or that it was impossible to keep the PTC at a high enough temperature remains unknown at this stage.
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Old 30th Jun 2009, 15:05
  #2558 (permalink)  
 
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Short of asking the computer to record a "burning smell", then tag it and transmit to mx, the question remains in general what brought this a/c down in a "seemingly" familiar way to other incidents? I am curious about the logic re: pitot sampling. With three pitot heads there are three possible pairs of "source", but when one head "fails" there is only one "source" left since the computer will fail both remaining if there is a "disagree?" Besides, why are pitots still "pointy"? Ice starts at the sharp bits.

Interface. The weakness as I see it. At the very least, I see the foundation as basically backwards. At a critical time in terrible weather at night, I don't want the box to fall all over itself telling me what's wrong, and what to do to fix the computer. I want the box to give me a few crucial cues so the a/c can continue to fly. In other words, give me the good news about what is working, not why the computer has to flop the a/c into my lap. The important cargo is not the computer.
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Old 30th Jun 2009, 15:06
  #2559 (permalink)  
 
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augustusjeremy:
210 34-11-15-0 FLR EFCS2
EFCS1, AFS - PROBE PITOT 1+2/2+3/1+3 (9DA)
9DA=HEATING ELEMENT PITOT 1 (6DA1/PHC1)
Heating Element Pitot 1 suspected failed.
Bye Bye dual/triple pitot failure hypothesis...
This is way too much reading into this ACARS sequence. ACARS are only triggered for post-flight maintenance once landed. They are not a kind of FDR giving the full data flow involved behind each events, neither they are a sequential explanation of the in flight cockpit events.

The ground maintenance will download the complete data report from each real time fault or event displayed by ACARS; once it is done, it will appear that nothing is wrong with the probes: from the other reports, by Airbus and Air France, which are describing this sequence of pitot-static line icing, the point is that nothing is discovered "failed" once landed, neither the probe heat units, neither the probe heat computer, neither the probes themselves: ice obstruction is gone.

This ACARS is just pointing at "what may have failed" (9DA: Heating element pitot 1) in order to get this part ready, but also, it is on the first pitot-probe because it is a shortened message send by an expensive system (SATCOM); this doesn't mean that the sequence of faults is anyway complete and that the following won't include one or two remaining probes. Moreover, the Rudder Control Limiter system wouldn't be stopped without an unreliable speed condition concerning two or more units. A single unit fault is considered a minor issue almost transparent for the flight management.

S~
Olivier
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Old 30th Jun 2009, 15:30
  #2560 (permalink)  
 
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inertial reference (again)

Takata,

I am really getting very confused with all this conflicting information.

In the following message:


0211 34-12-34-0 FLR IR2
EFCS1X,IR1,IR3, ADIRU2 (1FP2)
ADIRU2(1FP2) - ADR2 self monitoring & PHC rejects own data
Loss of discrete data from ADR2 = PITOT 2, STATIC 2L, STATIC 2R, TAT 2, AOA 2.
NAV DISAGREE CONCLUSION DELAYED - ADDITIONAL FAILURES - RECOMMENCE FAULT ISOL
I know you didn't post it... but what do you think is a guess and what is indeed documented ?

How can you get a fault of a inertial reference unit out of conflicting raw air data ? Isn't inertial reference data independent from air data ?

And isn't this fault detected by simple comparison involving INERTIAL DATA only ?

This is a mess...
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