Only problem with that is that the mounts didn't fail (or rather the VS didn't fail around the mount points, as it did in with aa587) - they were still attached to the VS, but ripped out of the fuselage.

Something clearly happened to take the a/c back to where the search is now though. My feeling is that it was in the air, possibly with control partially recovered, for longer than thought - but I don't have any way to explain loss of satcom to back that up.

Hello HN39,
Edit: Ok about the mechanical device, but this alert is unrelated to it.

takata;

just a 'dodgy conclusion?'

HN39

No power.
No engine = no power = no Satcom.
That's my opinion also.
S~
Olivier

Well, not so dodgy as this alert is clearly associated to the CABIN PRESSURE CONTROLLER. Mechanical devices operates by themsleves without regards with CABIN VERTICAL SPEED control. You don't need to switch them to auto/manual.
S~
Olivier

Cabin v/s advisory
 

could it just be associated with cabin pressure?
HN39

Code ATA is about controller.

takata has published some spot depths, and the following graphic shows the general bathymetry in the area.

http://i43.tinypic.com/14ukqrr.jpg

mm43

takata;

There was a post a page or two back where it was implied that the BEA got it wrong about loss of SATCOM. However, take a look at this graphic where the LOS is right when the a/c probably passed through the center of the mesoscale event NNW of ORARO.

mm43

I was not talking about the possible partial loss of SATCOM during ACAR transmission (neither infrequentflyer789 if I understood what he meant) but about the fact that she was not sending anything more after 02.14 while she could have still been in the air.
I don't buy the upset-recovery-upset-crash theory.
Documented upsets at cruise altitude are ending in a fairly short time pretty close to their initial position. Most of the displacement is on the vertical plan or at very high speed down to the surface. None would imply a possibility of impact like in AF447 case.
Overspeed could be deduced from vertical stabilizer state, it would have certainly left some evidences on the leading edge.
No evidence of structural failures are given by ACARs transmission.
I don't know where AF447 was when ACARs stopped, but I'm suspecting why they stopped and it is then possible to understand why she could have ended 40+ NM (still not confirmed) farther and back on its track.

Beside, this is what Seabed Worker is searching at nearly 4,000 m deep, in mountainous terrain, and it should not be spread over 8 NM of seabed:

http://takata1940.free.fr/images1/debris3.jpg

I watched the BEA press conference but nothing very new:
- They do not want to speculate. It was answered to journalist question that the wreck probable location imply that AF447 turned back for unknown reason.
- 2/3rd of the search area was already covered, but exploitation is not made at the same time (drones are delivering data after 20 hrs of exploration).
- Two different signals were recorded by Emeraude sensors on 1st July. Signal analysis permited to acertain that they came from airborne distress balises: matching frenquencies, tempo, and modulations. So Navy/Thales people are pretty sure that they picked the right signals and it was confirmed again during another conference with experts.

S~
Olivier

mm43
Cabin pressure is normally controlled automatically but can be controlled by the aircrew in a manual mode if certain failures prevent the normal auto operation.

But, more importantly, if all else fails, the overpressure relief valves work on simple springs that operate autonomously should the pressure in the cabin go above normal differential limits. Also a negative pressure relief valve also works autonomously on simple springs to relieve pressure differential between inside the cabin and outside, if the internal cabin pressure becomes too negative.

I love your dedication, research and posts...many thanks and well done!

Possible implications of CABIN VERTICAL SPEED ADVISORY (cont’d)
 

Hi takata,

Quote from takata (Today, 0545z):
“This alert may be related to purely sensor/ADIRUs errors; it may be related to a real aircraft descent rate above 1,800 ft/mn from whatever altitude (in case external pressure is still feeded to the controler by another circuit - but whilch one?); it may be related to crew actions during troubleshooting...”

Can you explain what “external pressure” has to do with cabin pressure (cabin altitude) and cabin VS? What am I overlooking?

Alternatively, why would an ECAM warning of excessive cabin VS be spurious? The creation of the warning implies that cabin pressure data were still available. That being so, what would cause them to be corrupted?

Chris

Pinger Range
 

MM43 wrote:

I generally agree. I certainly should have mentioned the additional complications presented by the sound speed profile on the propagation of the pinger signals. The effect of variations in sound speed with depth is well known and long studied. The actual profile is highly dependent on local conditions and it changes over time. The primary influence in the warmer climates results in a higher velocity near the surface (10-300m) due to the warm surface water, giving way to lower velocity in the colder water at 1000-2000m, and gradually increasing again at greater depth due to the constant (2-4C) temperature and the ever increasing pressure. Salinity also plays an important role. These variations (and there can be several or many layers) bend the acoustic rays like lenses or mirrors. However, on any given day, only a sound speed vs. depth measurement will reveal what the present conditions are and what bending/reflection of rays will be in effect.

Generally, these sound speed variations are horizontally stratified over a wide area, and therefore have negligible effect on the propagation along a direct vertical path, perpendicular to the layers. Thus one would expect the path to be unobstructed when the receiver is directly over the source. However, the if the path is only 10 or a few 10's of degrees from vertical, there can be significant attenuation, or, oppositely, regions that concentrate and boost the sound. One common situation, once the receiver is well off the vertical path, is total internal reflection of the sound, creating large shadow zones. These effects will further limit the radius from the pinger where the sound will remain detectable.

The sea is also full of fronts and internal waves that refract and channel sound horizontally in ways that are current topics of research. These effects may play a role in this search also, but are probably less of a factor, because once the angle from the receiver to the source is far from vertical, the range will have reduced the signal strength below detectable levels, anyway.

Signal processing is not my specialty, so there is not much point in my speculating about that. I have some idea where I would start on that problem, but it would be a brute force approach and probably would not yield useful results. The problem is made more difficult by the fact that the frequency and timing tolerances of the pinger are quite loose; it obviously doesn't use a crystal, if I'm looking at the right data sheet.

mm43, good work continues from the original inspirational stab, it will be a year soon; many thanks to you, takata and others of course :ok:

Excuse my ignorance but I can't trace back to find a legend for the depth countours

Is red shallow and dark blue deep? or vice versa?

===
Any chance we can forego relentless discussion of CPC systems etc. I fear there may be little further to learn now. As we said in the old thread... we just need the boxes now, because whilst the ACARS msgs may indeed be factual they might nevertheless be misleading until we have some real boundary conditions for WIHWH and WHEN

No? Ok, then... :bored:

Pinger Range
 

auv-ee wrote:

Had I bothered to read the relevant sections of the two interim reports prior to posting, I could have avoided guessing the speed Emeraude transited while listening: 6-10 knots is listed in the second report.

Also, I see that the second report lists 2000-3200m as the assumed detection range for Emeraude, consistent with the above conclusion.

The report also cleared up something I was wondering about: why were the TPLs from the US Navy not towed deep enough to hear? In fact they were towed deep, but they covered only the northern "ALPHA zone". If the Emeraude analysis is correct, they were simply towed in the wrong place.

"Le Figaro" reports that the two data recorders are probably not colocated but separated by a 1.5 to 4 NM range.
Le Figaro - France : Le vol AF 447 livre ses premiers secrets
Jeff
PS) on the bathymetric maps, red is ~ -1000m deep (slightly above), blue is ~ -4000 m (slightly below)

The "turn back" was broached quite some time ago. Engine(s) loss was discussed as well. Early separation of the VS seemed problematic due to antenna location. If the black boxes are indeed 8 km apart, disintegration in flight looms back into view. Then again, Figaro tells me the Muslim "problem" is overblown, and 7 kilos of Heroin were intercepted, not a gold standard of journalism, imo.

Chris Scott reminds us of the Cabin P alert and loss of the pressure vessel seems a possibility. Since it was (ACARS) last, a descent to and through 8000 feet seems supportable (with cabin integrity), and the alert also could be saying "We're lower than the Cabin, and can't keep up." The alert also suggests that pressure inside was way low, and 8000 feet cannot be maintained, something that could happen at any altitude (seemingly) from 37k down to 8000, if indeed the warning was genuine and based on true sensing.

Although PJ2 didn't agree that a turnaround was done "Immediately", it is conceivable that had the Pilots turned to miss the Wx and experienced an uAS in concert with the turn, they may have made it into a 180 rather than a 30.

For keeping the thread going with brilliant data and graphics, much is owed to mm43 and others. It is a good thing that plenty of folks are keeping up with the investigation, for many reasons, not the least of which regards mitigating the factors that caused this tragedy.

bear

location of pingers
 

The uncertainty comes from : the sub's navigation uncertainty added to the bias on sound propoagation. Considering that reckoning the actual sound velocity profile in such environmental conditions proves rather difficult, the expected detection range will greatly vary. therefore, when eventually you have something on your sonars, you never know whether your are at the limit detection range or whether you just happened to cross a specific sound ray. Most of the time, you'll assume that you were at the limit detection range, which increases the uncertainty.
Also, if you want your position record to match your recordings, in order to be able to determine where you were sailing when the detection occured, you need a very accurate time measurment on both logs. This adds too to the final estimation.

Hi Chris,

Quote:

---

Originally Posted by Chris Scott

Can you explain what “external pressure” has to do with cabin pressure (cabin altitude) and cabin VS? What am I overlooking?

---

Maybe the controller schematic. What ADIRU 1+2+3 are used for?

It is not ECAM warning. It's an ADVISORY (controller to be set on manual).
S~
Olivier

Well not really:
"Six mois après, la «Musulin mania» s'est essouflée"
read: mu -su- lin
It is someone's name (a money convoyer), and nothing to do with "Muslim problems".
But the beacon possible range of separation is 1.5 to 8 km, will certainly be the smaller range and might be simply due to area relief.
Sub's undersea navigation is quite accurate and signal was picked during some time along this zone exploration. Signal propagation is certainly the main factor but as sub moved, it would be possible to make corrections.

Using this false post to answer Savu post below:
Sub navigation (SNA) had to be precise at any time to cover assigned search area. This was a systematic search, controled by surface vessels and all military navigational systems.
Here are BEA maps from today presentation: SNA search zone assigned (until 10 July) is the left zone while TPL searched the right zone.
http://takata1940.free.fr/zone01
http://takata1940.free.fr/zone06
http://takata1940.free.fr/zone10

Just like when we're flying, submarine inertial navigation accuracy depends on many factors such as the length of time since the sub had a positive fix on an external reference (whether visual - not easy in that place- or sattelite or radionav). However accurate inertail plant may be, there always comes a time when the estimated position has been drifting a bit. My guess is, would that sub have detected some signal, they would have soon fixed their position, but at that time, the inacurracy was not a big deal as long they had nothing to report.

Takata, do you mean that the pingers signal separation (1.5 to 4 NM) could be spurious and due to multipath (like echoes, delayed replicas) induced by the rough seafloor ?
Jeff

This will give the incertitude range but it is not the only factor. Sinking down to 3,000-4,000 depth in mountainous terrain might give separations even if both were close in surface. One piece may sink and hit one sloped face of a mountain, roll down into one valley while another may sink and hit the other face and roll down into a different valley.

Update: "Seabed Worker" - positions
 

The "Seabed Worker" has been moved a little more to the east. Limited position information makes it difficult to judge what she is doing, but currently my guess is that she is still running her two Remus AUVs.

10 May 2010 12:14z Hdg 319.2 Spd 02.3 2°43'05"N 31°06'26"W
10 May 2010 10:22z Hdg 318.3 Spd 02.2 2°40'00"N 31°03'44"W
09 May 2010 23:50z Hdg 281.4 Spd 00.9 2°41'59"N 31°08'03"W
09 May 2010 22:06z Hdg 120.8 Spd 01.0 2°41'52"N 31°07'45"W

An updated bathymetric chart which includes an added colour spectrum scale along with a lat/long grid as a reference. Remember the spectrum colors are only a guide and that the contour relief of the bathymetry will change the saturation.

http://i41.tinypic.com/34zwu4n.jpg
mm43

Possible implications of CABIN VERTICAL SPEED ADVISORY (cont’d)
 

Bon soir takata,

Quote:
“Maybe the controller schematic. What ADIRU 1+2+3 are used for?”

To do its whole job, a CPC obviously needs to know the aircraft altitude (external static pressure), which it obtains from the AD part of the ADIRUs. It is also interested in the aircraft VS, and during aircraft climb and descent will adjust the cabin VS − for example if the aircraft VS is higher than expected − to keep the differential pressure at manageable values. These are the data it obtains from the ADIRUs. Their accuracy would be affected in the unlikely event of icing of one or more static ports.

Unfortunately, the schematic does not show where the CPC obtains the cabin altitude and cabin VS from. But these require, by definition, a sensor or sensors within the pressure hull. These presumably communicate data to the CPC and the FWC electronically. A loss of power could interrupt receipt, but received data should be valid.

Again unfortunately, I don’t have the exact criteria for the production of this advisory by the FWC, so am relying on other’s posts. These indicate that it is triggered by excessive cabin VS for at least 5 seconds, no other data being considered.

So I repeat my question: why do you dismiss this ECAM warning (sorry − advisory) as being spurious, or irrelevant?

Chris

Hyperveloce;

There is always the possibility that the 37.5kHz pinger bursts ducted between salinity inversion layers, and when detected by the sonar their source wasn't necessarily in the immediate vicinity. A reason why the BEA wants the ULB frequency lowered to a nominal 9kHz.

mm43

Further examination leads me to believe that should barometric data not be available from ADIRUs 1, 2 or 3, then the Captains static baro is supplied via the FMGC.

mm43

Cabin Vertical Speed Advisory
 

thinking to this last ACARS at 02:14Z, we can bear in mind that all the past Pitot freezing events duration was less than 4 mn (typically 3mn): even if the static ports were compromised during the cruise phase at high altitude at 02:10Z (during these past events, it induced a slight barometric altitude bias: a few 100ft), after more than 4 mn and probably, in the AF447 case, a large loss of altitude (external temp. increase), isn't it probable that the air data (ADR) had recovered/de-iced ? beside the BEA reports have raised the possibility that the PRIM were manually reset at 02:13Z (to explain ACARS that were not seen during the other past Pitot freezing events): if true, this could only have happened because the air data was back at 02:13, prompting the crew to try to regain the normal law, don't you think ?
Jeff

True, and let's not overlook that one piece may go straight down, while another may be attached to a structure with some buoyancy and therefore drift due to currents a considerate distance before it settles on the seabed.

Maybe someone who knows how the black box and CVR are attached to the airframe can shed some light on this possibility.

Cabin Vertical Speed Advisory
 

RE: hyperveloce #989

Hi hyperveloce;

your observations are correct and relevant. However the main contention seems to be whether the advisory was necessarily generated below 7350 ft aircraft altitude, or that it could have been generated at cruise altitude.
EDIT:: By the way, freezing level was at 16350 ft according to Tim Vasquez.

regards
HN39

The vessel is still working in the zone in which the SNA "Emeraude" is believed to have recorded very low level ULB pinger signals. The BEA have said that should debris not be located in this zone by 12 May, the search area will be extended. Should that occur, then the ducting theory will have been correct, but the path loss is such that the search zone would normally have taken that into account.

10 May 2010 22:40z Hdg 262.6 Spd 07.0 2°41'07"N 31°10'28"W
10 May 2010 20:54z Hdg 260.9 Spd 00.4 2°42'28"N 31°05'45"W

Weather is wind 090/5-10KT, swell 090/1.5m period 8/9 sec. with little change expected over next 3 days.

mm43

If the sound does become ducted, then from that point on, spherical spreading no longer applies, so the amplitude would not drop as much with increasing range. The closest model may be circular spreading (if the sound is trapped in planar layers), or some other depending on the boundary constraints. If this happens, the detection range, as measured along the ray path can be extended. The attenuation loss continues to apply, but is a function of temperature, salinity and pressure, and thus will be somewhat different for a near-surface path than for the deep ocean path. Within a duct, there are usually multi-paths, and these interfere in ways that can decrease or increase the sound level at various points in the duct. This scenario assumes the receiver is also in the duct or is at a point where previously ducted sound is escaping the duct.. I have no idea if any such duct existed at the place and depth that Emeraude recorded the signals. A local sound speed profile would shed light on that, but one likely does not exist close enough to place and time.

I'm not sure what conditions have to exist for sound from a deep water source to enter a duct. It seems like the angle of incidence would have to be far from vertical, which would increase the path length (slant range) making for an already weak signal at entry. I was assuming previously that useful ducting was unlikely on that basis, but who knows.

My assumption was based on the angle of incidence having changed when transitioning a deepwater inversion (4,000m) and subsequently becoming entrapped on encountering another layer in the 300 - 500m range. If that was the case, it would explain the apparently low signal/noise levels that have been recorded.

As you say, we don't know at what depth the sub was operating, though on examination of some bathymetry I believe she obtained, I'd make a guess and say in the 150 - 200m range.

mm43

To auv-ee:

Thank you for your detailed and informative reply. Seems Thales worked a miracle to find ways to identify the pings from the background noise. Let's hope there's news of a find soon.

While we wait (with the highest of hopes) for news, and in between mm43’s –and others – amazing and informative contributions, I would like to bring up a matter raised a few days ago by machinbird.
His post related to accident remains, and it got me thinking again about the issue of the autopsy reports. Sadly, like machinbird, I too have some experience with accident remains (meaning the aircraft and its contents). In that regard I agree with his comments about the nature of damage and injury in different scenarios. For that reason I find it amazing that it’s almost a year since the accident and yet the autopsy reports have not yet been shared with the BEA.
Though it’s of course not a pleasant subject, it must be said that much can (and would) be learned by the BEA from the autopsy information (assuming of course that the autopsies were professionally performed. I have seen nothing that casts doubt upon that notion.)
One small example: The information we do have (from the BEA) suggests that the bodies that were recovered were identifiable and intact. That in turn strongly suggests an impact that was not as catastrophic as some have surmised. Indeed, to me it suggests the possibility that some semblance of control may have been present until impact, or until shortly before impact. This scenario seems even more plausible as the now presumed location hints at the possibility of a longer flight time than was previously envisioned by some.
CAVEAT: I have gone to great pains to use terms such as “may have, possible, plausible, and suggest” extensively. I am NOT putting forth an explanation; I’m simply pondering.

grizz

Hello mm43,
Thank you for keeping updated the Seabed Explorer positions.

FMGC doesn't supply air data to the controller but only flight plan related data: altitude at departure, altitude at landing, altitude at cruise, etc. in order to calculate the various cabin altitude regulation adjusted in time with the flight plan. On the other hand, what is mentioned is that the controller will use Captain ADIRS (ADIRU 1). "Captains static baro" is displayed by ADIRU 1 which is either ON or OFF (no separation is made from the components of Air Data (AD) part of each ADIRU, only Inertial Reference (IR) part may be separated if AD part fails.

Hi,
Well, there is no rule saying that, because previous documented freezing events at such high altitude lasted from few seconds to 2 mn, this one would be over after 3 mn. Also, none of the previous events caused an aircraft to crash. Going lower may in fact add much more to the problem rather than resolving it as we might suppose that they were flying above thunderstorms. In fact, much more water particules would be encountered below AF447 actual cruise level before going out of the "freezing zone".
The only reason (beside other problems) why they would have to initiate a descent is that they couldn't climb above this level while turbulences would make their current flying altitude dangerous.

Furthermore, going back to "Normal Law" was certainly not an option as they would have to land first before it could be restored. Once ALT2 is triggered by such faults, they would be struck into this mode until landing and maintenance performed on the Air Data systems.

S~
Olivier