may 6 - 12 seach zone
 

I'm new here, and also not having any sonar experience, just some basics in acoustics. I overthought the may 6 - 12 "navy_search" and based on this drafted a small extended search zone, maybe someone more experienced comment on this. ( I think that the french navy's signal detection has more precise position compared to the backdrifted vertical stabilizer, just some interpretation is missing from the results ).

the following contains a lot of guesses:

- first guess ( may be ruled out by navy ): the navy used a signal processing which traded in directional sensitivity for signal to noise ratio, to rise the signal above background noise, this way the direction information was lost, they could only tell the location of Emeraude where the signal could be rised from background noise. Based on this, probably line shape, BEA made a search zone in the long axis of this position with a few nautical mile border. In this case the highest signal level probably was detected, with the Emeraude in the center of the navy_search_zone.

- the search in this zone found nothing, but if the navy could pesuade BEA to look there, then the detection had to be strong enough, but if nothing was there then the signal maybe travelled there on other ways. The attenuation of the pinger signal on this frequency doesn't allow direct detection from great distances sideways from the ocean bottom. my guess is: a natural amplifier had to amplify the signal to be detectable from greater distance.

- the vertical center of the sofar channel, based in the june 6 BEA celerity data, was in 700 - 900 m depth

- as far as I know sofar channel entered sound reaches specific depth in more or less circular patterns/spots, the attenuation in horizontal distance, and the max height reached during propagation depends on incident angle of the sound, a relatively shallow incident angle causes sound to propagate further, but not reaching high enough, a close to vertical incident angle enables reaching the surface but not propagating horizontally.

- there is an underwater mount ( red in bathymetry ) North-East from the supposed Emeraude position, if the color code is identical with the earlier published BEA bathymetry scale, then the top of the mountains are in the middle, middle-bottom of the sofar channel.

- the South-West side of this mountain is very steap, and three few nm sized parabolic like shapes may be identified on it.

- my guess is: a pinger located around the verical focal plane of these parabolas on the ocean bottom could concentrate the pinger signal into
the sofar channel, the incident angle beeing not horizontal, the signal travelled in the sofar channel with larger vertical swings, and one of these swings reached Emeraude.

Emeraude could detect it only at the place where the upper peaks in the channel were, and because swing length can be significant, maybe this was the first place from the mountain, or maybe further places can be identified with the same processing which was done with sonar data ( but if the Emeraude track distance was not enough fine, during the first search, then further refinement may not be made ).

I don't say that these shapes are perfectly formed parabolas, in the need of acoustic reflections ( if I estimate correctly then pinger wavelength is around 4 cm ) but may contain alligned surfaces wich concentrate waves.

I think I would take a look at S-W from the mountain, where the base of the perpendicular from the Emeraude highest detection position to the mountain is.

- if the wreck is there then the mountain blocked any signals into the direction of the largest part of the search zone
- there is a wide flat bottom area, between the Emeraude and the mountains, which may helped the propagation.
- if the pinger had been located on top of the mountain in 800 - 1000 m depth then it could also penetrate the sofar channel, but then it had to be heard from other positions also.
- if the pinger had been located further to the N-E direction then the mountain would block at least partially the sofar channel, preventing it to reach Emeraude in the middle of the navy_search area.
- the published diving depth for the french rubis class submarines are 300 m, and if the published rating is "low profile" then it could be in a depth of 400 - 500 m-s which made it possible to pick up the pinger signal.

Further bathimetry, west from the navy_search_zone was not done, but if similar sea mounts are present west of it but close to the navy search zone,
I would look there also.

http://i46.tinypic.com/352rxgp.jpg

I made this simple drawing based on the BEA bathymetry, I would search the yellow bordered area, and if I had time constraints I would take a look at least at the middle and the south-east one of the three parabolic shaped formations.

About time for the World's regulators to Start Thinking about this Type Measure
 

STAR NAVIGATION INTRODUCES THE WORLD'S FIRST REAL-TIME IN FLIGHT SAFETY MONITORING SYSTEM AND THE IDEAL COUNTERPART TO THE "BLACK BOX"


Star Navigation Systems Group Ltd., a recognized leader in the aerospace safety and monitoring industry, is proud and excited to announce the introduction of THE WORLD'S FIRST REAL-TIME IN FLIGHT SAFETY MONITORING SYSTEM ISMS™ the ideal counterpart to the "black box" and a quantum leap in aerospace safety technology!

Most people are familiar with the "black box", the near indestructible sealed recording device that assists investigators in determining the cause(s) of an aircraft accident. What isn't as well known is that not only are black boxes not the complete solution, by their very nature they are designed to indicate problems AFTER they have already occurred - much too late to help the pilots and passengers. In cases such as the Air France Flight 447 disaster earlier this year, the airplane's black boxes sank to the ocean floor and have never been recovered; despite a massive search the cause of that terrible tragedy remains somewhat of a mystery. It's obvious that a real-time counterpart to traditional black boxes is needed and Star Navigation has answered the call.

Star Navigation's In Flight Monitoring Service first introduced in 2005, was a quantum leap ahead in aerospace safety and monitoring technology. It performed all the functions of black boxes while providing current information to pilots and ground controllers, giving the ability to note any anomalies and to nip problems in the bud. The improved STAR-ISMS™ In Flight Safety Monitoring System provides both real-time and after-landing reports, intelligent flight data transmission, plus more detailed live flight data alerts through the efficient use of leading edge satellite-based technology.

One of the main features of the new STAR-ISMS™ is its built in GPS tracking software built-in GPS tracking software that enables more accurate tracking of an equipped airplane to the last known latitude, and longitude. It also boasts improved accuracy and the ability to instantly provide an aircraft's exact altitude, heading and airspeed.

The essential avionics and diagnostic information collected by the STAR-ISMS™ is transmitted at operator defined intervals or triggered events, via satellite, to ground-based installations in real time regardless of weather conditions. As well, Star's on-board hardware and software will independently analyze all selected incoming sensor & systems data and compare it with normal parameters - any deviation is noted and an alert is sent out if necessary. In the event of multiple failures, the automated "Mayday" feature commences an immediate “data dump”, sending as much information as bandwidth will allow. It can be said that STAR-ISMS™ opens a "virtual window" into the in-flight operation of a commercial aircraft.

The utility of the improved STAR-ISMS™ doesn't end once a plane has landed. All monitored in-flight data is recorded and stored for later review, and detailed reports are automatically generated, providing operators with useful information that can be used to streamline procedures and institute economies on future flights. These detailed reports are created mere minutes after an aircraft lands. One especially noteworthy feature of the STAR-ISMS™ is that the information it notes and records can be used by airline ground crews to plan maintenance scheduling, monitor aging equipment, even predict the possibility of hardcore failure due to material stress and fatigue. In effect, the STAR-ISMS™ acts as an "early warning system" for a host of potentially catastrophic equipment failures while reducing the frequency of expensive and time-consuming unscheduled maintenance and passenger delays.

Star Navigation has never been content to rest on its laurels and the Company continues to develop future applications for this valuable technology. With that in mind, the STAR-ISMS™ has been designed to be fully upgradable so that operators can improve their safety and monitoring capabilities while boosting operational efficiencies.

While the next-generation safety and monitoring technology featured in the STAR-ISMS™ In Flight Safety Monitoring System is not meant to replace airline black boxes, its use alongside them adds an extra level of safety that can be counted on to save time, money, and most importantly lives.

The STAR-ISMS™ In Flight Safety Monitoring System uses proprietary, patented Canadian technology and Star owns the exclusive world-wide license to this technology. Certified by Transport Canada and the Federal Aviation Administration, STAR-ISMS™ has been extensively tested and fully developed during normal commercial aviation settings and is now ready for deployment on the world's aviation fleets!

ABOUT STAR NAVIGATION

Star Navigation Systems Group Ltd. is a leading edge technology company focused on providing Aerospace Solutions - both hardware and software platforms - to assist aviation operators worldwide. Star has developed the STAR-ISMS™ In-Flight Safety Monitoring System - the first system in the world to feature in-flight data monitoring and diagnostics with a real-time, secure connection between aircraft and ground. The STAR-ISMS™ is the ideal counterpart to the "black box" and an essential safety feature for the world's passenger and commercial aircraft. For more information on Star Navigation, please visit the company website at Star Navigation Systems Group - Home

*based upon an original 1998 concept (Iridian-Roadshow) at http://tinyurl.com/kv2owv

Hello HN39. Indeed, if true, this "Le Figaro" article is very disturbing. I understand that the The BEA seems not very pleased by the discovery made by the Navy & Thales being made public (prematurely), interfering with its own communication/search, giving high hopes to the relatives of the AF 447 victims. Now, after the completion of the 3rd phase, we have the Navy/MoD claiming in the news that the BEA spent very little time to explore their estimates, ignoring some of them, and the BEA suggesting that the Navy mixed up with the AF 447 signals and signals measured in the Mediterranea to optimize the Emeraude sonar settings. :ugh:
Jeff
PS) The BEA seems to consider that there is no wreckage to the south of the LKP:
«Il n'y a jamais eu d'AF 447 au sud, nous avons perdu une semaine» (Le Figaro)
«Nous avions un choix à faire, nous l'assumons, le choix était d'utiliser les quelques jours qu'il nous restait pour suivre notre programme plutôt que de rester dans une zone où nous pensons que la probabilité de retrouver l'épave est relativement faible» (M. Le Troadec in "Le Point")

Reports about the end of the search are starting to appear:

Air France 447 Crash Hunt Ends With Areas Unexplored (Update1) - BusinessWeek

Quote from iabel:
"I would search the yellow bordered area, and if I had time constraints I would take a look at least at the middle and the south-east one of the three parabolic shaped formations."

As it's in the SW quadrant, and has not yet been covered (though very nearly), why not?
Parabolic reflecting faces are something even we simple mortals can understand.

But has the Seabed Worker already passed the area, perhaps, en-route Recife?

Chris

Out of curiosity, does anyone have any idea about how emphatic the BEA can be when they say that the Seabed Worker has not found anything? Presumably the side scan sonar recordings made by the AUVs will subject to further reviews onshore in case the initial viewings have missed something?

Hopefully before the next search phase in the autumn (Figaro article) the BEA and the french navy will get their acts together to better understand and interpret the Emeraud's recordings - if they really did "hear" the AF447 pingers then this should allow a better targetted search than the current crop spraying approach.

I have another concern - it is highly likely that several aspects of great significance related to the recordings, how they were made, and Emeraud's systems that are highly classified and consequentially greatly limit how much 'outside help' (i.e. non-French) can be used. Although Thales should be the best positioned to assist the Navy in decoding whatever mysteries the recordings contain, it would difficult to imagine that other input would not be useful.

I'm not sure who are the known underwater acoustics powerhouses are - but it would seem worthwhile having another set of experts analyze the data and see if they can independently come up with other suggestions - I'm suspicious though that would be prevented due to national security concerns. Thoughts?

- GY

What next?
 

Hyperveloce;

thanks for your reply #1161, and in particular to your PS referencing 'Le Point'. Some highlights of that article may interest others on this thread:

Phase 3 has ended without success. The ship is on its way to the port of Praia in the islands of Cabo Verde. Equipment and crew have to be demobilized may 27th. Decision regarding a new search phase has not been taken, and is not in the hands of BEA alone. BEA needs at least one or two months to take stock, together with its partners, of all search operations started almost a year ago, and eventually take a decision to continue the search.

Off-topic.

May I just say this is one of the most mature, enlightening and productive threads I have ever read on pprune.

Update: "Seabed Worker" - position
 

The Seabed Worker departed the Zone 2 search area for Praia, Cape Verde Islands at about 24/1930z and at 25/0635 was at 5°31'36''N 29°20'32''W Hdg 028.6°T Spd 13.0 knots.
---------------------
I think you may have misinterpreted what was going on. The Navy conducted tests using another Rubic class submarine to optimise the sensitivity of the sonar receiver to 37.5kHz. I seem to remember reading that the SNA fleets sonars operated at a nominal 18kHz, and following the adjustment, the mod details were relayed to the Emeraude, which from 01 July to 10 July operated in the optimised mode.

The Thales re-examination of the tapes recorded by the Emeraude used other techniques to extract 37.5kHz data hidden in the background noise.

mm43

I have read both threads since they began, but I do not remember seeing any comment regarding which and how many navy subs were used. GB, French, and US are probably givens. Were any Russia subs used. Some Russian boats, with their super tough titanium hulls (as opposed to the steel hulls of the US Navy boats and other Russian boats) can go deeper. How much deeper? The Russians are a little tight-lipped about that. Most think that depths in excess of 3,000 feet were easily accomplished, and one report suggested that 4,000 feet was within the reach of these vessels. If true, then if used at the onset, searching and listening at great depths, perhaps identification and location of the recorders might have been possible.

Not to throw a dart, but it just seems to me that the search effort was behind the power curve from the beginning.
ww

Not me, but Le Figaro's source 'proche du BEA', in the article posted by jcjeant:

translation: the (navy) would have mistaken the signals obtained in the mediterranean for those of AF 447

HN39

Apologies HN39! It appears I took what was there - out of context.

We are starting to get into the realms of Monty Python's Flying Circus, and it's best left to the waring factions to sort it out in some meaningful Gaelic way.http://images.ibsrv.net/ibsrv/res/sr...ilies/evil.gif

mm43

The Brazilian military were responsible for the initial search, and when working at a distance over the ocean, "tangents" are not easily avoided. Debris sighted from the air needs to be investigated at a seaborne level and that all takes time. It's that precious time in which a search gets misdirected that creates the difficulties in resolving what was where and when much later.

L'Emeraude was the only known sub operating in the search phase up to 10 July, and I don't think that they were operating at anywhere near their maximum [classified] depth.

mm43

As Phase Three spools down for the summer months, I thought I would pass on to you some indirect indication of this thread's world-wide interest. A few weeks ago I cobbled together a Google Earth KMZ file about the AF447 situation and posted it here, with gridlines and points of interest drawn at altitude and depth, hoping it might be useful in visualizing the search activities. As the file is linked only from PPRuNe, I was surprised to discover today that in the last week or two it has been downloaded from 165 unique IP addresses, from France to Hong Kong, Peru to Finland... So I parsed the data and built a small KMZ file showing who (by location) has visited the download page... a snapshot of the resulting view (over Europe) is below. When running this file in Google Earth, if you click on a location, a balloon includes country, region, city, and lat/long. The KMZ file is available here.

http://i958.photobucket.com/albums/a...KMZvisits1.jpg

GB

Hyperveloce made reference in a previous post to a couple of comments reported coming from the BEA and published in the French media. They were:-
This leads in nicely to Machinbird's observation that maybe they have been searching too far out, and the area closer in to the LKP needs investigation.

The above implies that the aircraft lost momentum quickly and was effectively stalled at or near FL350. Should that be the case, was icing of the pitots the problem?? It is possible the a/c encountered extreme turbulence suddenly, an updraft caught the starboard wing causing a left bank in excess of 45°, the A/P disconnected and the crew were left with lack of situational awareness and all hell breaking out around them. Was the nose pitched up and AOA moved beyond the CL limits and a deep stall resulted? We know the crew went looking for the "bird" - to no avail. The rotation of the a/c could account for the ADIRU disagreements over IAS, but one would have expected blanking of the engine intakes and flameouts. If that was the case, where were the ACARS WNG/FLT messages? The trim tank was probably full, which wouldn't have helped. Not unexpectedly, the final ACARS message is the Cabin Vertical Speed warning generated 5 secs after passing through 7,350 feet at a vertical speed greater than 1,800 ft/min. We don't positively know in what direction the cabin speed was moving, but it wouldn't be amiss at this time to conclude the cabin pressure was "high" and the a/c was descending.

Machinbird has made a point that needs looking at closely.

Finally, and I have asked before, does anyone know the format that Air France AOC positions are transmitted on ACARS. By that I mean, are there parameters other than the position sent? Probably a question to ask in the Tech Log. The BEA have made no comment on the LKP.

mm43

Au Sud?
 

So Seabed Worker has been stood-down, and is en-route north-eastwards to the Cape Verde islands. Dommage! How disappointing for everyone concerned. The BEA is quoted as saying that AF447 was never (to be found) "to the south". I wonder. Ignoring human influence, one would indeed expect the flight to continue roughly in the original direction. But the aeroplane was already about 3nm left of track at its last-known position, and that is unlikely to have been due to a position-error in the FMC.

Assuming the deviation at that instant was the result of crew intervention, there are many possible scenarios, perhaps the least likely being a deliberate track offset of 3nm to reduce the risk of colliding with opposite-direction traffic as they approached the Dakar UIR boundary. Most crews would choose to fly right of track. It is more likely that they had either been avoiding wx for about five minutes (might even have been regaining track); and/or they were just starting to make a turn to avoid a cell recently identified on wx radar, or perhaps to negotiate a passage they had identified between clusters of cells. Finally, they might have been caught unprepared, suddenly encountering precipitation/St-Elmo's-fire/lightning-strike/moderate-to-severe-turbulence.

Perhaps it is not inappropriate, at this pause in the search, to remind ourselves of some of what this crew was up against in the next minute or so. What we do know is that, whatever they were doing, they would have been aware of that fairly rare event in the cruise, an AP disconnect − even if they did it themselves (unlikely). It's a familiar but noisy one, with a suitably-loud audio-warning, aptly called the cavalry charge; quickly cancelled by pressing the AP disconnect button on either sidestick.

Zeroing our stopwatch at AP disconnect, here are the known problems during the next 71 seconds:
T+06 − ECAM warning of windshear-detection fault. Master Caution (i.e., amber W/L illuminates) plus single chime. ECAM drill (when time permits), but not in itself a worry.
T+13 − ECAM warning that flight-controls (FBW) have degraded to Alternate Law, with most flight-envelope protections lost (attitude displays annotated with amber crosses). Master Caution + single chime. ECAM drill (urgent). Sinister event, but normal control straightforward.
[By this time, it is likely that the crew would be aware of ASI anomalies, probably indicating serious loss of airspeed. Descent may be under way.]
T+19 − Speed Limit flag appears on captain's ASI, confirming loss of underspeed and overspeed protections, and removing certain (valuable) reference-speed annotations.
T+31 − Ditto on F/O's ASI.
T+37 − ECAM warning of A/THR failure. Master Caution + single chime. ECAM drill. If descending steeply at this stage, throttles can be closed to ensure idle thrust.
T+44 − ECAM warning of TCAS fault. Master Caution + single chime. ECAM drill (when time permits). Irrelevant.
T+50 − Flag on captain's FD. Flight Director has failed. Realistically, he cannot be using it.
T+65 − Ditto on F/O's FD.
T+71 − ECAM warning of rudder-travel-limiter fault. Master Caution + single chime + Systems Display switches to the F/CTL page. ECAM drill... Use rudder with care. Who would be using rudder in this situation?

Would the handling pilot have continued straight ahead into this developing hell, or tried to turn the aeroplane away from it? Could he have turned as much as, say, 180 degrees?

Chris

PS: mm43, why would the aeroplane be stalled early-on, when the ASIs were UNDER-reading?

Chris, why do you think under-read? Is it just because all the pitot tubes are blocked?
This could be a crucial point.

Hi,

That's a sad end of the third researches attempt.
Honestly I'm not surprised they don't find the black boxes.
But I'm surprised they don't find any substential elements of the plane .. who must not be the size of a shoes box.
Or the BEA theory of sea impact like described is false and instead .. the plane was partially or completely desintegrated in air .. or they had search at the wrong places.
With no more clues of what we have so far .. this must be the last one (wrong places) the most probable.
So .. another search campaign must be set.

Circles
 

Stepping off the distance traveled between ACARS reports every ten minutes from the coast of Brazil would indicate straight and level flight at a nicely constant speed right up to the very last report. Small variations in speed are likely an artifact of the minute-wide time stamps.

It would seem that the A/C was just about exactly where it should have been when it last reported at 0210 (although we don't know its altitude, and it was at the time 3 miles left of track). If it had initiated a steep bank leftward, that would have occurred within the minute prior to 0210. Earlier, the reported distance traveled between reports at 0200 and 0210 would have been measurably less.

Until 0209 it would seem there was no deviation from track nor WX avoidance. If they were precisely on track at 0209, at a GS of 7.8nm/min (0.13nm/sec) it would have taken maybe 30 to 45 seconds to bank steeply away from the track to a distance of 3nm. So banking left remains a possibility prior to AP Disconnect.

The situation went pear-shaped suddenly within seconds either way of the 0210 ACARS report. Put the location of that last report at the center of a circle (2.98º N x 39.59º W) and estimate how far the A/C might have been able to fly (glide ratio maybe 20:1 clean but we know it wasn't clean, with ACARS reporting a high sink rate implied by cabin altitude warnings) in about 4.5 minutes without overspeed (A/C reported intact at impact) while the cockpit attempted to regain control from underspeed/overspeed stall, catastrophic wind shear, or whatever caused the upset. An exercise for one of you A330 drivers. Draw the circumference. Shouldn't be far. Should find the hull inside.

http://i958.photobucket.com/albums/a...F447/track.jpg

Now GS could have been cranking up during the 10 minutes after 0200 as the pitots began reading lower and lower and thrust was automatically increased to compensate, and the A/C could have initiated a turn back from further up the track and been returning in reverse when the 0210 report was sent. In any event, we know where the A/C was at 0210 and we infer from the missing expected ACARS message that the A/C was in the water less than five minutes later.

Draw the circle.

GB

Machinbird has countered the question. In fact, I am just playing "devil's advocate" to draw out how the a/c could impact the way the BEA have reported, and within say 20NM of LKP.

In an area of 20NM radius from LKP, 40 percent of the northern semicircle has already by covered by sidescan sonar.

Regarding the ACARS messages, the timing is rounded to the nearest minute in which they were generated and is incorporated in each message prior to its identification groups. Check through them carefully and you will see that they are not necessarily in order, and those received in the first 95 seconds could have been initiated or causal to the A/P disconnect.

http://countjustonce.com/a330/af447-acars-1.png

The above list of warnings will be displayed in HTML format if you click on the image. Bookmark the new page for easy reference - its also interactive, allowing you to highlight a line or multiple lines by clicking on them. Clicking each line again will remove the yellow highlight.

mm43

Quote from Machinbird:
"Chris, why do you think under-read? Is it just because all the pitot tubes are blocked?
This could be a crucial point."

Yes. Simplistically, the only way I can think that ice could cause OVER-read would be the combination of blocked static ports, but pitots NOT blocked, AND then a descent. We know they descended (though not their initial reason for doing so), but the icing combination is improbable. Does that make any sense?

mm43,

Thanks for pointing out the ACARS timing uncertainties (lack of seconds in the labels). All the events I mentioned are labelled 0210z, I think? But the order and spacing are uncertain, and I hope no-one will take my piece as purporting precision.

Chris

It has been discussed before - Pitot tubes have a drain hole, to allow ingress of liquid to drain, their calibration assumes the leak. If the drain hole blocked they will over-read, not sure what percentage. If the pitot inlet then blocked you can imagine this high reading being locked in - until the heaters melt the trapped ice in the drain and speed reading drops to zero. If the a/c flies into a fine ice cloud, all sensors could be affected in a common-mode fault. If the auto-thrust reacts to the over-read before rejecting the readings - the pilots could be handed back control with insufficient thrust to maintain current true airspeed.

The drain holes are designed to cope with ingress of low altitude rain/hail storms, and their detail design will differentiate different manufacturers models.

I assume regular maintenance procedures do non-abrasively clean these drain holes - dimensions critical, but why do problems appear to have started to occur years into operation? Of course there's also climate change...

Rumours not news
 

Rumours descending from BEA 'circles' (... the Navy experts have mistaken mediterranean tests for signals from AF447):
Translation: we've lost a week for nothing
Counterrumours from Navy circles (not more than 24 hours):
BEA's Update 12/05/2010:The Navy again:Translation: We (Navy) gave BEA twenty locations, some of which have since been withdrawn, others remain valid but have not been explored.

Lost: The Mystery of Flight 447
 

BBC 30 May

BBC - BBC Two Programmes - Lost: The Mystery of Flight 447

Lost:The Mystery of Flight 447
BBC2 Sun 30 May 2010 22:00 &
Wed 2 Jun 2010 00:20

Thanks to the person who posted this..
For those of you outside the UK , you can watch British TV with this useful little program

WebTV Unleashed: Watch Free Live Web TV Online

It does not need installing, just run it.
BUT, you must have VLC player installed and it must be in its default location
C:\Program Files
It does not work here in Brazil if VLC is installed in C:\Arquivos de Programas
so, repeat, VLC MUST be installed in C:\Program Files

I was looking through the old AF447 thread for information and found a relevant post by Greybeard (#3399) which I will quote.
Prior incidents of A330 pitot icing have resulted in overspeed warnings as well as low airspeed warnings.

But look at this post by Jeff (Hyperveloce) on the 9th of July!! #3397.
Makes the hair on the back of my neck stand up!
Machinbird

ram port + drain blocked during climb means (almost) constant ram pressure together with decreasing static pressure, leading to overreading of airspeed. Experienced it once in a Piper Seneca (FIKI approved) with malfunction of pitot heat (it worked during ground check before and after, but heating power was obviously low).

If the French Navy really did confuse their own tests in the Mediterranean with the AF447 results, everyone involved would have had to overlook a difference in depth of several thousand feet, no, and of many degrees of longitude in all the locations? It's not even as if it's an obvious sort of mistake like a reciprocal or a decimal point error. Also, rather than providing "une zone qui n'etait pas la bonne", it would surely have provided invalid data.

I find this story unconvincing, and suspect the validity of Le Fig's source.

locating the ULB's
 

Just thinking aloud ...
The navy has said that it indicated twenty-odd locations where the pinger sounds might have come from, minus a few scrapped since.
The navy has also said that it identified two pingers, some distance apart.
Suppose the 20-odd locations mean different locations of the submarine, would the distance between the pingers and the difference between the distances of each pinger to the sub offer a means to locate them?

In other words, suppose a pulse from pinger A at distance sA from the sub is received at time tA, and that of pinger B at distance sB at time tB, would the difference (tA - tB) change as (sA - sB) changes for different locations of the sub?

HN39

SteamChicken: I doubt we will ever know many details about the Émeraude's data and collection methods: how they code location/depth/speed of the sub and other data within or alongside an acquired signal (like SMPTE time codes to sync audio to video/film frames); when/if analog/digital conversion takes place; what and what types of filters are in place, etc. etc. Maybe somebody simply threw the wrong mag tape into his briefcase before getting on the plane, and caused some confusion. Whatever the details, it seems the Navy is rightly pissed that after a great deal of post-processing work, they proposed several search areas that were blown off by the BEA. Would be nice if folks could get on the same page and move forward. Who is leading this effort, anyway? Seems in an earlier post here it was remarked that the fellow hasn't been heard from since... In another part of the ocean, BP's CEO is visibly on the front line, despite the heat.

GB

Machinbird, I think that the past Pitot freezing events (interim report #2) tend to show that the false stall alarm rate is far higher than the false overspeed alarm rate ? beyond AndiKunzi's mechanism, maybe another one leading to (peaks of) overestimated AS was put forward some time ago (I don't remember who suggested this): when the heater eventually takes over a weakening ice crystals event, the accumulated ice in the Pitot tubes could melt then approach boiling temp creating bubbles/overpressure peaks on the analog to digital measurement device ?
HN39, if the ranges (or the different times of arrival of the pings) cannot be measured (only the directions of arrival), it relies on several triangulations from several different positions of the sub ? If a doppler (relative speed of the sub versus target) could be measured, it would provide some other angular clues.
Jeff

Jeff, I've spun the airspeed completely around climbing over weather with a frozen up pitot in a Cessna back at the dawn of time. Aircraft climb may factor in to extend the duration or degree of overspeed indication.
The relative frequency of overspeed/underspeed indications during pitot freeze up is not the issue. The issue is that it can go either way and what happens when the airspeed indications increase significantly above actual. From last years posting, it would appear to be downright ugly. I really don't think this issue has been put to bed.

iabel; Thanks for your well thought-out analysis of the Emeraude's pinger detection possibilities. The locations you have indicated are ideal possibilities.

Hyperveloce; As the Navy have apparently reported that two pinger signals were detected, I wonder how they came to that conclusion. Consider that the Emeraude was moving at say 10 knots (I think its search speed is mentioned in one of the Interim Reports), then there are doppler shift events to be taken into account. These signals could possibly be indentified as separate entities if each had a detectable difference in their precise frequency and the sub's distance and speed in relation to each pinger was the same. But at this stage there is no way of knowing that, and one or both of the pinger signals detected could be multiple path. The fact that they have clearly indentified 37.5kHz pinger bursts is important, and though there is some current disagreement between the BEA and Ministry of Defence, I am sure that when Phase 4 is being drawn up, a prime area will be in the SW quadrant from West to a position WSW and between 30 to 40NM radius of the LKP.

mm43

The BBC blurb about the TV show says:

which sounds dubious, especially as the producer was ringing round the houses looking for a sim. Hope it's not going to be long on drama, short on sense. :(

I’m curious about this BEA position of not searching to the south.
Is there something in the ACAR’s transmissions that the BEA have not fully explained.
Now I have no expertise in this area, but is it possible that the transmit time and receive time get shorter (by milliseconds) assuming the satellite is to the relative north of transmission, so if the aircraft turned south the transmit/receive time would increase. Someone here must know the answer to this, if not shoot me down in flames for being naive.

Airspeed reading 300+ -- shades of Northwest B727 12/1/74

BTW, this accident to a feloow NW pilot got me started in the whole area of aviation human factors and accident investigation.


Goldfish

Forgive the slightly off-topic inquiry. Has there been any statement from Airbus or BAE regarding similar sequences of ACARS messages from other planes that might have suffered similar upsets?

The satellite is geostationary over the equator and in theory the the path length will get shorter when proceeding south toward the equator. However, without highly accurate timing markers in a transmitted stream of data, there is no way of measuring the path length. Even if the satellite had initiated timing, a return signal to it would have passed through indeterminable delays in the aircraft receive/transmit path.

Many moons ago, I did check which satellite was being used, but can't remember whether it was east or west (possibly a few degrees east) of the LKP.

A good thought, but not practical in this case.

mm43

Yes, and in recent times there was a QF72 upset that was determined not to be relevant, and others may have been similar, but deemed not to be the same.

mm43

Thanks for the reminder that I had not studied the post from iabel. It is an interesting analysis, pulling together aspects that we have discussed separately. I would caution that the distance from the center of the Navy search box to the mountain range is 12km; add to this the slant distance from the pinger to the mountains. 12-18km is a long way for a weak 37kHz signal, but perhaps not impossible with the "right" focusing and ducting.

I was thinking that reception of two pings per second would be sufficient evidence of two pingers, but I agree that the effect could be mimicked by multipath. I expect that frequency is the key.

The Doppler shift (if I have the math right), based on 10kt=5m/s, is 5(m/s) / 1500(m/s) * 37.5(kHz) = 125Hz. That is the maximum possible (not counting for currents) and the actual is likely much less if the sub only hears the pinger when the pinger is below or to the side of the sub (range-rate = speed * sin(angle from vertical) * cos(angle from bow)). However, if the sound was ducted or refracted to near horizontal, then the full Doppler could be detected if the target was ahead or astern.

Note, however, that the frequency of the pingers is badly controlled, likely by an RC timer. The spec says the frequency is 37.5 +/-1kHz. That leaves plenty of room to separate one pinger from another, even with Doppler obscuring the result, unless the two pingers happen to be close in frequency.

As for exploiting the Doppler shift for localization, that is certainly possible in principal, but may be difficult with the amount of data they have. The pulse length is only 10ms, which translates to 375 cycles. The maximum possible Doppler shift is 5/1500 = 1:300. Thus the Doppler has to be detected from about 1 cycle or less change in length of a signal buried in noise. If the aspect isn't favorable, that may be hard to do. Someone who has experience with Doppler measurements will know better. Doppler is routinely used to measure water current from the weak echos reflected from particles and turbulence in the water, but that is done at 10-50 times higher frequency, receiving with the same clock that was used to transmit, and averaging over multiple pings.