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AF447

Old 13th Jul 2009, 17:34
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Originally Posted by PJ2
I think we can assume that the radar could function up until the loss of the IRU data.
- I must have missed this in 3500 posts - has the loss of IR information been confirmed, then?
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Old 13th Jul 2009, 17:39
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Without appearance on ACARS of Wx Radar, I think it means that Radar is IRU dependent, not that IRU(s) failed.
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Old 13th Jul 2009, 17:53
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Originally Posted by PJ2
the radar would fail with the loss of all IRS data, (which had occurred by 02:13Z)
- Will - I should have included this quote.
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Old 13th Jul 2009, 19:23
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Thanks fantom, what you describe here is called weather deviation and has nothing to do with Strategic Lateral Offset Procedure SLOP to which Captain Bob was making reference but not knowing how strictly it applies.

Finally someone to consider that the AF447 crew was maybe not that blind or careless, but trying its best to avoid weather, like already did LH507 20 minutes before them, or IB6024 and AF459 12 and 37 minutes after them.

I really would have loved seeing the BEA stating that critical point instead of writing the erroneous following comment :
up to the last automatic position point, received at 2 h 10 min 35 s, the flight had followed the route indicated in the flight plan
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Old 13th Jul 2009, 20:16
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BOAC, Will;

I'm examining the fault message at 02:13:14:

"- .1/FLR/FR0906010211 34123406IR2 1,EFCS1X,IR1,IR3,,,,ADIRU2 (1FP2),HARD"

I know that the "IR1,IR3" messages are "identifiers" and that "IR2", a Class 1 fault, is the "source" of the original message. What I am searching for information on is the meaning of the IR1 & IR3 messages. I know there weren't "radar" messages as part of the 25 messages received but we know that there is a possibility of missing messages. For example, the CMC records only six "identifiers", (related systems); if there are more, they are lost. The BEA report also states that the messages are not necessarily received or displayed in the order of the equipment faults. I am pausing to consider the loss of 3 IRUs.

Will, yes, the radar is IRU-stabilized.
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Old 13th Jul 2009, 20:17
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I really would have loved seeing the BEA stating that critical point instead of writing the erroneous following comment :

up to the last automatic position point, received at 2 h 10 min 35 s, the flight had followed the route indicated in the flight plan
The statement is not erroneous. Up to (but not including) the the last point there is no sign of deviation. At the last point there is a sign of deviation.

There, how's that for showing that the BEA is inherently evil?
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Old 13th Jul 2009, 20:23
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"- .1/FLR/FR0906010211 34123406IR2 1,EFCS1X,IR1,IR3,,,,ADIRU2 (1FP2),HARD"

As I read the section on analyzing ACARS messages in the BEA preliminary report, I read it that "identifiers" indicate additional units that submitted messages during the 60 second fault window. These messages will have had the leading 3/4 (or was it 2/3?) digits of the message the same as the message reported. Therefore we know(?) that IR1 and IR3 also reported something that began with 34, or 341, or 3412, depending on how many leading digits were matched.

The above "analysis" is based on my memory of the pages in the BEA report which I read a couple weeks ago, so the details are fuzzy. It is also based on the assumption the BEA description is accurate; and that I interpreted it accurately. I'd encourage others to reread the BEA description, or even better, some original description in a maint. manual if you have one.
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Old 13th Jul 2009, 20:26
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IR2

I'm examining the fault message at 02:13:14:

"- .1/FLR/FR0906010211 34123406IR2 1,EFCS1X,IR1,IR3,,,,ADIRU2 (1FP2),HARD"
this fault is "timestamped" at 2:11 - was received (or transmited) at 2:13

Maybe it was triggered at 2:10 and received by the CMC at 2:11.

I suppose it means that only IR2 is "faulty"... But it wasn't followed by a message like 'NAV IR2 FAULT'.

What puzzles me is that almost at the same time - or a short time before - a fault relating to ADR1 not being recognized by PRIM2 - only - was also triggered

quite a concidence - or not.
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Old 13th Jul 2009, 20:34
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how about,...

we get "back to basics"...

"Air France is reviewing procedures and use of weather radar.."

based on preliminary findings..

I'd say, a good start..

Air France reviewing weather-radar use after AF447 crash: CEO
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Old 13th Jul 2009, 20:39
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Originally Posted by PJ2
I am pausing to consider the loss of 3 IRUs.
- which returns me to the (?unanswered?) question as to what effect all this MIGHT have had on ISIS attitude.
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Old 13th Jul 2009, 20:45
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root cause

To be honest, if no major upset is demonstrated getting the root cause of this accident will be mission impossible - Maybe even if the CVR/FDR are found.

You would probably need the readings for each ADR and IR channel to each of the PRIMs at least to identify an electronic fault if any - something that probably isn't availabe in the A330 FDR.

I suppose that it is time to give more attention to computer systems - and specialists - when dealing with aircraft accidents - be it Airbus, Boeing or whatever a/c involved.
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Old 13th Jul 2009, 20:45
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identifier

Right, PJ2; the WXR would annunciate failure of its attitude input with WXR ATT. SAT annunciates when the combination of pitch and roll exceed (saturate) the mechanical limits of the antenna to scan with respect to the horizon. That takes at least 45 degrees bank.

STAB, IIRC, is pilot selectable: de-selecting stabilization input.

Regardless, with no attitude input, the WXR will scan wings level, as if the plane were at 0 pitch and 0 bank.

While not annunciated, the unlikely case of the flat plate falling off the antenna pedestal will result in zero return, which would be obvious to the pilot.

As for ice on the radome, the only case I have heard was an MD-80 on approach to KLAS. The display went full red. Once at the gate, they took a half hour delay for chipping ice off the radome.

GB

Last edited by Graybeard; 14th Jul 2009 at 00:19. Reason: SAT for STAB
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Old 13th Jul 2009, 20:58
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One More Attitude Ref

Hmm, if your IRUs tumbled, and you weren't yet out of control, you could put 5 degrees downtilt, 80 mile range on the WXR, and fly by the ground return. Rough sea is a good reflector.

GB
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Old 13th Jul 2009, 21:39
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Graybeard

There are at least some suggestions that if they would have been as versatile as that in using the wx radar they would not have been in trouble in the first place.
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Old 13th Jul 2009, 22:23
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Being Disparaging of the BEA is Unwarranted

Everyone has an opinion on this and every subject under the sun. How about we take a step back from the known fact that 228 souls have been lost and a broken aircraft lies in a deep and rather inaccessible location of the North Atlantic.

Also remind ourselves that the BEA is the ultimate authority responsible for determining why this happened and how to avoid such a mishap in the future. In this regard, it is assisted by the AAIB and the NTSB, which means that there is little point in saying that the Preliminary Report or the Final Report will be other than objective. Also remember that the BEA has to deal with the jurisdictions of Brazil, Senegal and France while it attempts to objectively gather evidence. To ignore the political implications of not being diplomatic could well jeopardise its access to vital information - whether this is provided by international treaty or not.

The Preliminary Report has provided us with a number of confusing facts, but also remind ourselves that without the ACARS messages, 10 minute automatic positions and ADS-CPDLC Log On failures with DAKAR ATS - all via SATCOM, where would the speculation obvious in this thread have gone.

AVIATE - meaning to operate the aircraft with due diligence and within the parameters dictated by the current environment.
NAVIGATE - meaning to have positional awareness with respect to other aircraft, terrain, way points, navigational aids and weather, while at all times using the aids provided.
COMMUNICATE - meaning to use the radio communications facilities provided on the aircraft to receive and acknowledge ATC instructions. To pass essential navigation details to ATC as and when requested, get METAR / TAF updates, and monitor the 121.5 / 123.45 guard frequencies at all times when traversing Oceanic FIR's.

It is worth noting that the smaller word comes first and the largest last. So while AVIATE is at the apex of the triangle and COMMUNICATE at the base, I contend that without a solid base the apex of the triangle will become more acute and room for error decreases accordingly. In this regard, I believe that events missing from the base will have a very direct bearing on the least controllable events at the apex.

By all means speculate, but the result always has a beginning.

mm43
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Old 13th Jul 2009, 22:28
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GB;
Hmm, if your IRUs tumbled, and you weren't yet out of control, you could put 5 degrees downtilt, 80 mile range on the WXR, and fly by the ground return. Rough sea is a good reflector.
Yep - great idea, alongside using the GPS for speed and altitude info as some have mentioned. Buddy of mine purchased the Collins 700 radar manual last week. There's some bread-and-butter info in one of our FCOMs and it's better than it was (which was impossible not to accomplish given that there was nothing) but it's still real thin.

The "how" of this accident is the thing...Why? Loss of speed data doesnt' cause loss of control. I think there are some good notions here but I hope we'll have a more definitive answer some day - sooner, than later.
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Old 13th Jul 2009, 22:35
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System Info

On the idea of using 5 degrees radar downtilt if all IRU's are lost:

From where does the radar get information of the whereabouts of the horizon?
(info that is needed to determine where 5 degrees below the horizon is).

Uhm, from an IRU perhaps?
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Old 13th Jul 2009, 22:48
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mm43

By all means speculate, but the result always has a beginning.
Excellent post.
Getting to the beginning and where and why this happend is the key. The clues, I believe are in the ACARS messages. One thing that makes them so confusing is that they are not in sequential order.

This is an intense mystery that must be solved. And it seems it will have to be solved w/o the CVR/FDR.........
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Old 13th Jul 2009, 22:50
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As has been said before, GPS cannot give you airspeed - it gives you ground speed. It's airspeed that makes aeroplanes fly.
KISS - there can be nothing more basic and therefore reliable for measuring airspeed than an air pressure monitor sticking out into the air itself (pitot tube). The only thing that could affect this would be to obstruct the air to it. Apart from a physical object (bird?) which would possibly only effect one pitot then ice seems to be the only other thing that can cause obstruction.
As a pilot of smaller aircraft, I cannot believe that in this day and age it is beyond the wit of engineers to be able to eliminate any chance of ice build up on a pitot head of a large aircraft and for there to be a doubt about a pitot being able to resist ice (as seems to be the case) seems unbelievable considering the importance of the information from this item.
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Old 13th Jul 2009, 22:59
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Emit
On the idea of using 5 degrees radar downtilt if all IRU's are lost:

From where does the radar get information of the whereabouts of the horizon?
(info that is needed to determine where 5 degrees below the horizon is).
My prior post, apparently unclearly, stated if IRU input to the WXR is lost, the WXR will continue to paint, but with reference to the fuselage: 0 pitch and 0 bank. The 5 degree downtilt I suggested would be in reference to the longitudinal and horizontal axes of the plane, rather than the IRU reported horizon.

Bank right, and you get more ground return on the right, and less on the left. Same for nose up/down.

I realize now I made a mistake in terminology on that post, unrelated to this question, so I will edit.

GB
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