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AF447

Old 22nd Jun 2009, 18:54
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Pitot Envy

Thanks for the correction, ALCS; I thought Rosemount had been bought by Thales, and not Goodrich. I just visited the Goodrich site, and see you are correct. I'm sure I had read somewhere in this thread that Thales had acquired Rosemount. Not so.

Whose probe business did Thales acquire?

I'll delete my post of Today: 08:40

GB
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Old 22nd Jun 2009, 19:03
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Language Issues

Gosh a few dumb language comments:

"instruction judge" = "investigating magistrate": in France, the police collect evidence and a judge supervises the investigation, with a final say on how everything gets pieced together. This also makes life easier on the prosecutor.

The "judicial enquiry" is therefore the police investigation.

I haven't time now to pick through the rest of this translation.

However, I will note that French techies across a range of fields will coopt English acronyms and terms because that way everybody is sure of what you're talking about.

French equivalents tend to be unwieldy and confuse newbies. Translations of operating & maintenance manuals tend to be unsatisfactory (not the case at Airbus, I understand!) so that when something breaks down, the techies go to the English original to figure out how to cope. Moreover, by the time somebody fixes up the translation, the manufacturer has come out with revisions, upgrades and updates and the whole process starts all over again.

My bottomline is that the use of English acronyms, in itself, does not indicate the document was drafted with the intention of being leaked out.

Nitey nite from Zhengzhou (CGO)
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Old 22nd Jun 2009, 19:08
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poit . . .
re your comment (regarding comparisons between AF447 and Air India 182).

You wrote:
"Note the condition of the bodies found in that case: no clothes on the majority of bodies found; fractures to hips, shoulders and other joints (known as 'flail' injuries, resulting from violent tumbling through the air); and no sign of drowning (ie they were not breathing when they hit the water)."

Your source is incorrect. You mention using youtube to get information from documentaries, so the first thing I must say is this: The internet is a vast source of information but if you want factual information (about an aircraft accident for instance) search the sites of the official national investigative bodies, and reputable aviation-based sites, not Youtube or TV documentaries.

In the case of Air India 182, of the 131 bodies recovered; only 8 exhibited classic flail pattern injuries, 26 showed signs of hypoxia, 23 had signs of injuries from a vertical force, and 21 were found with little or no clothing.

Although all victims exhibited multiple injuries, the PM examinations indicated many different “primary causes”, including 2 from asphyxia and 3 from drowning. (Note, drowning does not infer consciousness at the time of death.)

grizz

Last edited by grizzled; 22nd Jun 2009 at 19:39.
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Old 22nd Jun 2009, 19:14
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Two small criticisms of Takata's fine work

The first criticism may place the crash point for AF447 a little closer to the first location for recovered debris. Let's look at Takata's picture of the current profile in the area. Deep red is highest and deep blue is slowest
Please take note of the blue band at about 50 meters depth. From about 10 meters depth to 40 meters depth the speed of the current falls by about half.

Initially bodies sink, a bit. This depends on the water temperature per other observations here. Or they may have been released from a sinking broken fuselage and floated in that band. They may not have been at the surface all that time. They certainly were not seen even though the initial air searches did cover the areas they'd be expected. Thus would fit with the bodies being submerged below 20 meters for their seven days under water.

I'd also question any assumption that the second band of fast current, the one at 100 meters, is going in the same direction as the surface current. The region of slower current may be due to a sheer region between currents running different directions. Getting a direction profile for the surface, 50 meters depth, and 100 meters depth would certainly help prove the contentions made about final crash site.

The second criticism comes from presuming that the plane was still on course to 0214. The last reported position was 0210. Shortly thereafter the pilots could have instituted their turn, willing or not. The last position the plane was known to be controlled well enough to keep the SatCom antenna pointed was 0214. I would hazard the presumption that the plane became uncontrollable to the extent that the SatCom antenna software was no longer able to point the antenna.

So Takata might look into scenarios which might have a turn starting any time between 0210 and 0214 as well as have less time moving under control after 0214.

I do not expect a dramatic change from Takata's conclusions. But I do expect some change based upon examining both the above factors.

JD-EE
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Old 22nd Jun 2009, 19:38
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Takata's analysis suggesting a turn back toward Fernando de Noronha is interesting and well thought out, but I think there is one factor that has not been considered. By 0210Z the aircraft was evidently just NW of a very large CB cell and the hypothesized turn would have taken the aircraft right through this cell complex, with tops exceeding 50,000 feet. See the BEA flight path points plotted on the probable radar image reconstructed by Tim Vasquez at:

Jet Crash forum • View topic - Crash location

I suggest a different final location here. The now-discredited 0214Z "ACARS" location of N3.5777, W30.3744 that was attributed to FAB has always been intriguing because it is quite close to the location where bodies were recovered by FAB on 6 June (see the FAB cumulative PowerPoint presentation of 6-6-09). Now that it is clear that the aircraft transmitted position reports at ten minute intervals throughout the flight, we must ask ourselves what else was contained in those position reports.

Although I have no idea how the A330 system is configured, the aircraft GPS tracking devices with which I am familiar provide (in addition to latitude and longitude) ground speed, heading, and altitude. See for example the devices offered by:

EMS Sky Connect

Thus, in addition to latitude and longitude, the heading of the aircraft at 0210Z was probably known to BEA by the morning of 1 June. These headings are calculated by the GPS receiver based on the azimuth between present and previous positions, and these positions are typically calculated at about 1 second intervals. My hypothesis: BEA actually calculated the N3.5777, W30.3744 position from the heading at 0210Z, and projected that heading forward to 0214Z when the last ACARS maintenance message was sent. But that position requires impossibly fast speeds to cover the 38.2 nm distance between 0210Z and the N3.5777, W30.3744 position (573 kt, ~Mach 0.98). Could it be that BEA simply used an erroneous assumed speed for the calculation?

If you use the last calculated ground speed of AF447 between 0200Z and 0210Z, 463 kt, and project it forward along the path between the 0210Z and the "0214Z" FAB location, the aircraft would have covered about 30.9 nm and the 0214Z location would be 3° 27.8'N, 30° 25.0'W, about 7.3 nm south of the FAB 0214Z position. Assuming the aircraft made only one turn to the left, projecting the path from 0210Z back to intersect the planned flight path would place the hypothesized turn at about 2° 34.5'N, 30° 44.8'W. This would place the crash location south of the recovery location of the first bodies on 6 June, as appears to be required by the drift direction of the debris field.

Alternatively, perhaps the 0214Z ACARS maintenance time stamp is truncated, and the actual time might have been as late as 02:14:59Z. If BEA made this assumption to make a best estimate of where the wreckage might have been to aid the SAR teams on the morning of 1 June, from the 0210Z position at 463 kt the aircraft would cover 38.6 nm in five minutes, placing it only 800 m north of the "0214Z ACARS-FAB N3.5777, W30.3744" position.

I am unable to post images in this forum for some reason, but you can see a map of this scenaio on page 2 of:

Jet Crash forum • View topic - Crash location


-rer47

Last edited by rer47; 23rd Jun 2009 at 15:59.
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Old 22nd Jun 2009, 19:54
  #2146 (permalink)  
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Hyperveloce - there is a lot of information here that will help you with your questions, and many of the questions you have, are ones most who are on the thread have as well - there's been a lot of hypothesizing by very good contributors but few answers because there is so little data. Questions which will arise out of the reading you do - when they do, they are welcome because they are informed.

Cheers,
PJ2
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Old 22nd Jun 2009, 20:23
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I would hazard the presumption that the plane became uncontrollable to the extent that the SatCom antenna software was no longer able to point the antenna


Inmarsat Aero-L used by ACARS makes use of a solid state antenna.
The "radiation" diagram of the antenna is omnidirectional (azimuth) and hemispheric (elevation).
Two satellites cover the area, one to the E (AOR-E sat), the other to the W.
As long as the antenna sees the sky the link is possible.
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Old 22nd Jun 2009, 21:13
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To muddy the picture of the surface current, so to speak.

This is the surface current plot for June 5, the box is centered on 3N 30W.

Red / orange marks the strongest surface current.

The page with the chart in the pdf file is titled:
Previsions 3D de courant quotidiennes a J+1 et J+6

The chart is titled:
courants marins (0m) du 05/06/2009 echeance 24h



The only charts included are those for June 5, though the page title indicates there are other dates not provided.

The current direction is SW to NE which would suggest that if AF447 crashed east of 30W, the debris and bodies would be carried to the east. Instead the bodies and wreckage have been found west of 30W.

It is possible the the charts for the surface currents on June1-4 -- if the current changed -- would allow for bodies and wreckage to be carried from east to west.

The other current chart included in the pdf is for 1000 meters; that current is very light and moving from east to west.

Source:
pdf p 5 of this document:
http://www.bea.aero/fr/enquetes/vol....hom.050609.pdf
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Old 22nd Jun 2009, 22:10
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Takata:

Then, the advisory (no warning, no check list) at 2014Z might be also linked to the unreliable Air data provided by the pitots as Thales and Goodrich probes are interchangeable.

From pdf:

Air data probes also
provide information for secondary purposes such as
engine control and
cabin pressure differential.
I think Takata makes an interesting point and don't think I have seen it mentioned previously. That is that an ice clogged pitot might also be related to the cabin pressure ACARS msg as I assume the pressure differential is between cabin pressure and outside pressure. Previously I think the options discussed were either a climb or dive greater than 1800fps, or possibly some sort of cabin depressurization.

Can anyone with more probe knowledge comment on what readings in terms of AS, AOA, and ALT we would expect to see with an ice clogged pitot?

I guess then it gets more complex in terms of determining how the computers would have reacted to this sudden change.
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Old 22nd Jun 2009, 22:23
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I think Takata makes an interesting point and don't think I have seen it mentioned previously. That is that an ice clogged pitot might also be related to the cabin pressure ACARS msg as I assume the pressure differential is between cabin pressure and outside pressure. Previously I think the options discussed were either a climb or dive greater than 1800fps, or possibly some sort of cabin depressurization.
Cabin pressure is related to outside pressure, but this is measured by the static ports, not pitot. Pitot and static lines are typically on the same probe assembly for smaller a/c, but not on A330.

The effect of a blocked pitot has been discussed elsewhere in this thread...

Chris
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Old 22nd Jun 2009, 23:17
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ACLS65;
Previously I think the options discussed were either a climb or dive greater than 1800fps, or possibly some sort of cabin depressurization.
Let's be clear about this piece of information as well. It is the cabin-rate-of-climb (or descent) that is being referenced here and not the aircraft rate of climb or descent.

The concept is perhaps not as easy to understand as one might expect - while the aircraft is climbing to cruise altitude, say, FL350, at a rate which is typically between 1500fpm and 2500fpm depending upon a lot of factors, the cabin is being pressurized such that it's pressure is equivalent to that found at between 6000 and 8000ft, approximately.

Briefly, air taken in by the engines is partially diverted (at the second and third stages of compression in the engine), through an air-conditioning "pack" into the cabin. The outflow valves in the aft fuselage close so that the air escaping the cabin through these valves is slightly less than the air being routed into the cabin through the air conditioning packs, thus pressurizing the cabin. The cabin "climbs" from it's starting pressure which is that of the departure airport, to a pressure that is equivalent to an altitude described above. Cabin "altitude" is stated in hundreds of feet, such as, "the cabin altitude is 7600ft". That means the passengers are breathing air (not oxygen, as many think) as if they were at 7600ft, or just a bit higher than Denver, Colorado or walking up the road to Machu Pichu, etc.

The "cabin-rate-of-climb" is thus the rate of pressurization from it's starting altitude to it's cruising altitude. Typically, if one departs near sea level, the cabin rate of climb is around 300 to 500fpm, controlled by the Cabin Pressure Controller(s). Part of the input to these computers would be the static pressured outside the aircraft so the CPC "knows" how high the aircraft is.

Now it makes sense to talk about a "cabin rate of climb/descent" and one can readily see now why a cabin rate of climb of "1800fpm" up or down, is not only excessive, it is an indication that the CPC is not able to control cabin pressure, for whatever reason.

Hyperveloce and others will now understand why a cabin rate of climb has nothing whatsoever to do with, nor is it an indicator of, an aircraft "stall" condition. It is an indication that not all is well with the CPC, the outflow valves, the cabin itself or...?

One can also now understand what a pilot means when a pilot says "we caught the cabin" - it means that the aircraft altitude is the same as the cabin, usually in descent, and to keep up, the cabin begins to follow the aircraft rate of descent.

Obviously if one thinks about it, there is a cabin climb schedule which matches the aircraft rate of climb so that "catching the cabin" does not occur. In climb this rarely if ever, happens but if one is descending very quickly, one can get to the altitude that the cabin is at and then the cabin will descend with the aircraft - very hard on the ears.

The ACARS advisory message, (see the earlier description of same) advises the crew of this rate of climb/descent. The cabin pressure warning (red master warning, steady chime, red ECAM message "CAB PRESS") do not occur until a cabin altitude of just under 14,000ft.

We cannot know the full meaning, (ie, was this a depressurization, a CPC fault or...?) of the advisory but we do know that at some point the fuselage/cabin structure was compromised/breaking up, at some point between 350 and sea level.
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Old 23rd Jun 2009, 00:13
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Originally Posted by PJ2
Obviously if one thinks about it, there is a cabin climb schedule which matches the aircraft rate of climb so that "catching the cabin" does not occur. In climb this rarely if ever, happens but if one is descending very quickly, one can get to the altitude that the cabin is at and then the cabin will descend with the aircraft - very hard on the ears.
To add to that well drawn picture, there's a focus on cabin rate of descent because the human ear is more sensitive to increasing than decreasing pressure. Speeds down mines for instance being limited to about 20 ft/s (1200 ft/min) certainly for members of the public.
IIRC - a working maximum (increasing pressure) was about - 800 fpm

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Old 23rd Jun 2009, 01:15
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PJ2

.......but we do know that at some point the fuselage/cabin structure was compromised/breaking up, at some point between 350 and sea level.
Excuse me, but how do we know this?
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Old 23rd Jun 2009, 01:30
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PJ2 and HarryMann, thanks for both the quality explanation and patience.

If I follow this right then the CPC's receive inputs from the FMGS and ADIRS. I assume the altitude information from the ADIRS is determined in part from the static tubes.

Is the system normally flown in Auto mode?

Do you know if the ACARS msg corresponds to the Max Differential Pressure Limiter Function limit being hit or Cabin V/S 1800+-fpm?

I was mainly wondering of the cabin press ACARS msg was a sign of an actual problem (breakup, rapid altitude change, etc), or if bad altitude information either from ice buildup on the tubes or anomalous ADIRS info could have convinced the CPC that the A/C altitude had changed significantly beyond an amount it could compensate for, triggering the warnings and ACARS msg.

Also are the two pneumatic safety valves completely mechanical in nature? Everytime I turn around I run into another computer, so I thought it best to ask.
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Old 23rd Jun 2009, 01:32
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Originally Posted by PJ2
but we do know that at some point the fuselage/cabin structure was compromised/breaking up, at some point between 350 and sea level.
Originally Posted by wes_wall
Excuse me, but how do we know this?
Because of all the debris floating around?
 
Old 23rd Jun 2009, 02:04
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ACLS65;
Do you know if the ACARS msg corresponds to the Max Differential Pressure Limiter Function limit being hit or Cabin V/S 1800+-fpm?
Unless I have missed the interpretation of the ATA code somewhere, no, I don't think it corresponds to anything except the advisory message. Someone?
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Old 23rd Jun 2009, 02:39
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wozzo

I'd be pedantic and also note that the plane COULD have ascended a little in an updraft. Then I'd say the plane broke up somewhere between and including 37000' and sea level to satisfy the fussy folks.

It rather obviously broke up SOMEWHERE.

I'd also note the plethora of messages virtually minute by minute from 0210 to 0214 and nothing subsequently. Thus one can say the plane was (relatively) in control with things rapidly turning to slime through 0214 and probably broke up within two or at most three minutes.

That's not guaranteed - the chain of failures MIGHT have ended at 0214. But that pushes my "but coincidences like that don't happen" buttons.

JD-EE
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Old 23rd Jun 2009, 02:39
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I feel compelled to take a step back for reflection at this stage, being minded that if Takata's track and crash site deductions proves remotely correct, then it's likely a quite titanic struggle to stay airborne took place that night...
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Old 23rd Jun 2009, 02:46
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Breaking up

As a reply to the above questions about wheather the aircraft did break up before it hit the surface of the water is at this stage impossible to say as said before . We simply do not know if it hit the surface in low or high speed such would explain why some pieces of seemed less damaged pieces were found .Even if it maybe would seem more logical that fuselage hit surface with high speed it must be proven first . Aircraft could have made a ditch or broken up in it's decend to the surface at some point.To my knowledge impossible to prove any of this scenarios just now. Both of them would almost give the same results in form of found debris at this point, or am I wrong ?
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Old 23rd Jun 2009, 03:03
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To be absolutely 100% safe, you'd have to say the aircraft broke up somewhere between 37,000 feet and the bottom of the ocean. I don't believe for a minute it landed intact and broke up as it sank, but I'm not sure we can conclusively rule it out (anyway, ships often break up on the way to the bottom).

I suspect the recovered debris contain the information needed to determine where the break up occurred. But the pictures of the debris may not.
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