The correct link is as follows:
http://www.pprune.org/9387723-post759.html

Yes, to both questions.

I was aboard the first specialist responder work vessel which attended the wreckage of the Itavia DC9 in 1980. We had been working in the straights of Messina and as we had two manned submersibles and a crew of hydrographers we were immediately despatched by the Italian Admiralty to investigate the scene. Our gear was limited to 600m and the depth at the locus was much greater than that, so our onscene work was limited to surface recovery only.

At the time, there was no doubt in the minds of the two senior officers who we had on board from the charterer that the aircraft had been shot down accidentally by the usual suspect, mistaking it for a known Libyan MiG intruder. Subsequent investigation of the seabed wreckage cast some reasonable doubt on that and it's a bit of an open verdict as to how the aircraft was brought down.

One's first impression on arrival at the scene was the incredible number of bits of paper were among the more solid flotsam. Thousands of pieces of paper. Of the human remains, there were a hundred or so that we recovered and the local fishing boats who arrived a few hours before we did recovered many more, but mostly very small. The largest were recognisable parts of limbs, but most were really quite small.

From other work on the seabed in other cases, I've found quite intact remains of almost whole bodies within and very close to airframe parts.

When an aircraft comes apart at very high speed and high altitude, eg the shootdown of an Iranian Airbus by the usual suspect, ejected occupants tend to be stripped of clothing by the airstream during the deceleration to terminal velocity.

From personal experience in several such field investigations I expect that the condition of size of the remains on the seabed will be quite different to those found on the initial surface search.

I doubt that the lack of large body parts indicates anything definitive. I also doubt that a bomb is indictated by the skimpy evidence we have so far, but we need more data before we can analyse the three principal postulates.

Thank you for this post describing a horrifying and unique experience; our thoughts go out to first responders in such situations. I thought the Itavia DC9 was brought down by a bomb in the rear lavatory?

Cooperplace, you may be right.

At the time, the Rear Admiral and Captain of the Italian Navy who were our client reps were in no doubt that the aircraft had been shot down. They knew that the suspect navy had been trying to engage the Libyan MiG which we later learned had crashed unseen on Italian territory.

The official theory, for public consumption was, as usual, a conspiracy theory of a bomb. That's quite normal in these cases. It exonerates almost everybody in positions of public responsibility and it stops the public from thinking.

I don't know the true story behind the downing of that Itavia jet, but I entirely understand why the USN made the radar record of the salient time 'disappear'. Out of sight, out of mind. You don't need to know. It never happened. Move along. Nothing to see here. Do not discuss, especially publicly. Wait until you are officially told what to think. Most especially, wait until you are told what you can say about what happened.

The AIS plot shown above is very strongly indicative of the search vessel looking at a credible search datum.

They are clearly using Dynamic Positioning (DP) to manoeuvre the vessel on the search pattern and they are clearly using a deep tow sensor. They are not 'towing' the side-scan towfish or deep-tow pinger locator like a trawler tows a net. It's not astern of them, most of the time.

Sidescan sonar seems quite likely, but you would use a very similar pattern to 'box in' a suspected target with a deep tow hydrophone to locate a pinger signal.

A sensible searcher would concentrate his efforts, at this stage in time, to getting best data from the battery-limited pinger.

The way you do that is not by triangulation but by measuring the signal strength as you pass by the source. You plot that out with signal strength in the Y axis and the distance along track on the X axis. You get a parabolic curve, albeit a lumpy bumpy one which can sometimes be a bitch to interpolate. Maximum strength suggests that that is where your line reached closest point of approach (CPA). That gives you an LoP to/from the target, perpendicularly. By repeating that line perpendicularly you get a cross-cut of that LoP. By covering the other two sides you eliminate the baseline side confusion and further refine the position. Voila. You have a good approximation to the actual co-ords of your Dukane (or whatever) pinger.

I do, however, concur with those who have pointed out that the line-spacing is more consonant with a medium frequency sonar run, eg 125kHz, than what you would choose for a broad-brush pinger locator run in anything other than very shallow water. The reason why I think it's more likely to be a pinger locator on the end of the wire than a side-scan is that the speed over the ground is something like half a knot. That's Okay for a hydrophone but would not be enough water speed to keep a side-scan towfish on any kind of of sensible heading and would make sonar trace interpretation impossible.

I therefore conclude that they've got a pinger within earshot and are boxing it in before putting an ROV onto it.

The water depth at that locus, btw, is approx 3106m. The seabed sediment consistency in that area is like baby-poop. ROVs will have to be negatively ballasted, ie positively buoyant at bottom depths, so that they don't stir up the fluffy sediment and blind themselves during recovery of high value items such as the 'box(es)'.

ELT Signal Detected
 

Per the WSJ an ELT signal was picked up by satellite and that is why they have localized the search area to where they are now.

Capry -

The article was clear that it was an ELT, which floats, sends a radio frequency beacon, and is detectable by satellite, unlike a ULB.

They are using the ELT to focus the search for the ULB.

There was no indication of when the ELT beacon was detected, but the PMS Burullis made a bee-line to their search location immediately after the crash.

LKP-BURULLUS location
 

To note that distance from LKP (33.6757/28.79242) to last night's BURULLUS search location (33.5322/029.1371) is just under 20NM.

And perhaps more important (in view of the Greek Defense statement on their final radar images and the Egyptian denial of that) is that the BURULLUS location is on about a 100° course, East SE from LKP (noting that MS804 while at FL370 at LKP was heading 136°).

If MS804 is found around BURULLUS' location, this implies IMO that the claimed left turn after LKP indeed would have to have taken place, while that in turn gives further credence to the also claimed subsequent 360° right.

ELT's have changed since my flying days.
There is now a digital 406MHz signal that includes information registered to the aircraft or ELT owner.

Contact Approach...

I agree. If only it were that simple... The past few posts re ELTs and ULBs are a good example of why your perfectly sound idea doesn't work on these forums.

Somebody posts a quote from a newspaper (WSJ in this case), probably because they assume what is written in that article is "factual". A discussion then ensues based on completely wrong information about ELTs, first from the article itself, then made worse by answering another poster's question erroneously by citing that same article as a source of accurate info about ELTs and ULBs: where they are located on an aircraft, do they float, do ELTs transmit underwater, if so can the signal be received by a satellite, discreet ELT IDs (BTW... yes, one can tell what aircraft it's from) and on and on and on.

Which is why, with the utmost respect to the Mods whose job is so very difficult and frustrating, this should not be considered a "Professional Pilots Rumour Network" when reading this (Rumours and News) forum.

Sigh...

@grizzled: for the edification of the casual reader/lurker/ we could point them to the Tech Log forum,
where there's a thread with a discussion of ELT's with at least one good post. Summary from that (PPruNer avspook)

1. ELTs transmit on 121.5/243/406 MHz. (406 MHz contacts a satellite monitoring system. It uplinks messages to a Satellite that includes aircraft identifying information. Thanks to David Reid for the specifics in his post a few down from this one)
2. Some ELT's are tied into the Navigation system to uplink last position.
3. Many rely on the Satellite system to direction find the signal
4. An ELT (due to the frequencies involved) is not able to contact the satellite from underwater. It is also not a waterproofed box.
5. The aircraft hull mounted ELTs are typically set up to transmit when a G-load of a particular magnitude is detected (crash)

Sample product sheet (Honeywell; Thales and some other vendors also make products in this class).

FAA Spec TSO-C126A (Update: pages 9-16 of this link are TSO-C126b.
DO-204A, DO-160F are specs cited on some product sheets (DO-204b is pending based on some ICAO docs posted on line).

guara
Agree with you regarding the size of (or lack of) the debris field. Any one familiar with the foot print left by an airplane making contact with the ground, or water, would be thinking it strange that more objects would have been seen, and or, collected. Too many whys creep into the possibility the crew flew the airplane into the ocean. Large things which separate from the airplane after contact will float, and debris will bleed quickly from inside the interior.

For the love of god! don't show them the way to tech log it's the last bit bit of sanctuary I have on here.....

The ELT sends the (programmable) ICAO 24-bit address belonging to the aircraft (same as used for Mode S, TCAS, etc). That's sufficient to identify the aircraft without the need to maintain a separate database of unit serial numbers.

In post 808 it is implied that the country that shot down Itavia DC9 in 1980 is the same that shot down the Iranian Airbus which everybody knows who fired the missile. This is misleading because if somebody shot down the DC9 it was not the same suspect. It is a fact that the USN and the Italians and the French hid and destroyed evidence but the usual suspect did not shot the DC9.

It's generally accepted that nobody shot it down.

@FE Hoppy: apologies.
@David: Thank for the point on the ICAO 24-bit code.

I'm so sorry if was understood that I claim THE CREW sent the airplane against the Med Sea INTENTIONALLY. Now my post is deleted by mods, buy what I wanted to explain is that the crew INTENDED TO MAKE THINGS RIGHT to control but weren't able to success.
What I suppose (and many in my circle) is that once things came to be really BAD, the PiC or the FO took command of the a/c with the intention of a controlled/smooth splash-down but coudn't (possibly with serious electrical damage/smoke/etc and in full darkness this may be very difficult). The lack of rational debris for an A320 (in quantity) makes me think of a relatively quiet sinking. I don't forget the pieces of bodies and some objects really torn by strong forces, but those maybe cause of a localized break in fuselage, leaving the remaining of the hull in one piece (and possibly passengers caught by belts and in their seats).

There was a CNN report this evening (26th May) quoting the Egyptians as saying that some sort of beacon has been detected, enabling the search area to be shrunk to a few km2.
According to the reporter, the Egyptians are attributing this information to Airbus, yet the beacon in question only has a transmission life of 2 days, suggesting that the information is a few days old. One set of specs on the Technical forum seems to indicate that these beacons transmit for much longer than two days. I was perplexed by the CNN report -- thanks to the Technical Forum I am at least perplexed at a slightly more informed level.

In the US, ELT being reported located.

ELT?
 

Er, that's not quite what is being said.

This is what is currently on CNN for example:

I don't know if that is accurate, since I haven't seen anything directly from Al Ahram.

AFAIK, typical ELT is able to broadcast only for 50 hours from the time of activation...

According to the marinetraffic web site the PMS Burullus spent a day moving at a snail's speed in a classic zig zag course coverign an area about 1Km by 1Km. Its position has not been updated for nearly 24 hours - at least on the "free" version of the tracker I have used.

The lack of an update is most likely due to the Burullus being in exactly the same area of poor radio coverage, with the added problem of its antenna for the tracking system it uses, AIS, being just a few metres above sea level. In fact there was a loss of coverage for a hour or so yesterday. Some vessels use a satcom version of AIS, but you have to have a rather expensive subscription to see that data. Anyone have access to the Satcom version? I do not know if the PMS Burullus is using satcom to broadcast its position though.

It could be that the "authorities" do not want the vessel's movements to be tracked of course, and the vessel has simply turned its AIS transmitter off.

There is no suggestion that the vessel is stationary - the last update is time stamped nearly 24 hours ago, so it is simply the data is not available.

It is also notable that there seems to be a big empty space around the Burullus clear of other shipping, though that may just be coincidence, or a consequence of the particular location.

What was interesting is two days ago the Burullus moved on a relatively long "base line" (my interpretation) NE to SW many Km long at quite some speed, before retracing its steps to roughly halfway along that line, then moving very slowly 2Km SW, perpendicular to that line and then starting this 1Km by 200 odd metres zig zag back and forth (see posts 784 & 785).

Could the base line be the "pinger" being heard and triangulated, approximately, and then the fine zig zag be a sonar scan? Post 808 gives some very helpful information about sonar, but makes the point the Burullus was moving rather slowly for a sonar fish. My logic would say the pattern was more closely spaced than you would need to home in on a pinger, which I understand has a range of several Km not the hundred or so metres the pattern suggests. Would you not "just" make one pass in an arbitrary direction, looking for the peak sound level, then pass through that peak point at right angles looking for a peak again, and thus, with a bit of trigonometry, home in on the source?

But the fact that a vessel has swept an area just 1Km by 1Km (2 square Km or so if it has kept going at the same rate for the past 24 hours while its position has not been updated) may suggest they are hunting something down. The press "noise" would seem to support this.

We will know in due course.

not only that..., but ELT will not transmit through water...

CNN reporter seem to think the ELT was transmitting from the wreckage on the ocean floor.

It's amazing that with all the coverage of AF 447 and MH 370.., reporters still don't understand even the most _basic_ aspects of the technology about which they report.

anyway, this info apparently originated from Egypt and something about it is wrong - ELT signals are not being received from the ocean floor

Navire Hydrographique Laplace (A793)
 

The BEA just issued a communiqué tonight :
Marine Nationale Hydro. "Laplace" (A793) is sailing to the crash site with two BEA officers, in order to join the search for the CVR/FDR. She also boarded three pinger locators.
They are actually planning to send another vessel equiped with deep sea recovery assets.
The Egyptians authorities are still in charge of the search, assisted by the BEA.

A793 Laplace :
Laplace (A 793)

http://www.defense.gouv.fr/var/dicod...FR/laplace.jpg

BEA :
https://www.bea.aero/fr/les-enquetes...enu-le-190516/
http://takata1940.free.fr/BEA_Laplace.jpg

Alseamar DETECTOR 6000 System boarded on Laplace:
Underwater Detection Systems DETECTOR | ALSEAMAR
Black Boxes Relocation | ALSEAMAR

The other company contracted for next step might be DOS (Deep Ocean Search)
Deep Ocean Search - Home

The cost of operational search is actually shared by Egypt and France.

AT1's interpretation is pretty good.

The absence of nearby vessels is almost certainly a consequence of a day shape signal which either declares that the vessel is manoeuvring with difficulty or is "not under command". All ships will see that signal either by day, in the form of a ball over a double cone (diamond shape) over a ball, or by red/white/red vertically arranged lights at night and will give her a wide berth. There are variations on that theme, such as "engaged in underwater operations", but the message is pretty much the same: please push off out of my way. Furthermore the ships watchkeepers on the bridge will be watching any traffic within a dozen or more miles on radar and will call them on CH16 marine VHF (similar to 121.5) and request that they stay well away.

If the vessel appears to be almost stationary on AIS then one interpretation might be that she has deployed her ROV.

The way that works is that the ship maintains station on the ROV at a predetermined number of metres laterally and longitudinally from the ROV in "follow sub" mode and the ROV therefore controls the ship. It's quite cumbersome as the ROV is the size and weight of a Ford Transit or Galaxy and the ship weighs several thousand tons. The ROV therefore has to manoeuvre very gingerly and avoid making suddenly turns or accelerations. If the ship has to make very large thruster inputs to try to maintain station you can get aeration of the water under the ship which can cause loss of acoustic contact with the ROV and a massive muddle ensues. Angry words are exchanged on the intercom between the bridge and the ROV control shack. That's another reason why the bridge will want all other vessels to stay well away, preferably at least a mile or two.

It may perhaps interest Prooners unfamiliar with how these things work for me to explain a little about underwater nav.

There are two principal methods. Long baseline and (ultra) short baseline.

USBL works in one of two different modes. The first involves the ship sending out an interrogation pulse from a transducer which extends below the hull telescopically rather like a military submarine's periscope, only in the opposite direction. The ROV has a transponder which waits a known number of milliseconds and transmits a reply pulse. The ship's USBL transducer is a small cruciform affair and by measuring the phase difference at the four transducers you derive the angle at which the pulse arrived. Thus you get a 3-D position with respect to the ship. The other USBL mode involves sending the interrogation pulse electrically down the umbilical and a "flowerpot" responder on the ROV replies with a pulse just like a transponder. Advantage is that the interrogation is almost instant and not prone to raypath anomolies or acoustic noise on the outbound signal.

Long baseline is completely different. It involves setting out an array of seabed transponders and co-ordinating them. The ROV then self-navigates by doing what amounts to a DME/DME fix, using at least three and preferably four or five transponders. It then telemets its self computed position up the umbilical. Much more practical for deep water work like this job than USBL which will be slow and wooly. I'd be adversely surprised if these guys haven't deployed an LBL array around the locus by now.

Would the quality of the sea bed in this area (which you alluded to in an earlier post as being pretty bad) argue against the long baseline method, or do the transponders have mechanical means to mitigate issues with sea floor conditions? I'd guess that the state of the art has advanced to where you'd have kits optimized for differing conditions, and thus have some "muddy/silty" sea floor models for use in such conditions.

Bit of verbal diarrhea... but a bit more aint going to make a lot of difference...
During the mid nineties I was involved in bringing 5 ex-RCAF (CC-117) Falcon 20's onto the UK civil register. Three of these aircraft had previously been used for transport work and the other two for Electronic Warfare training. The transport variants were fitted with a detachable panel at the bottom of the fin. This panel carried a 121.5 / 243 /406(?) self powered Crash Locator Beacon; essential equipment given the RCAF operating environment in the wastes of the Arctic.
Deployment of the panel was initiated either by the crew and a switch in the cockpit, or in the event of a crash, by one of 5(?) Vacuum Crash switches, three along the lower fuselage and one in each wing tip. Operation of any one of these switches would deploy the panel and set the CLB to transmit. The boxes involved had been removed when the aircraft were retired but the activation mechanism was still in place...
As the Avionics Lead on the mod program, initially this and other role equipment wiring left me head scratching because the wiring diagrams for the said role equipment were 'not available'... but since we were going to remove all unidentifiable role equipment wiring it didn't matter too much. But the detective work was fun!
To the point however... I have often wondered why aircraft manufacturers don't design in something similar into modern airframes... an automatically deployable floating panel carrying a 406MHz ELT... ELT's are OK but once the aircraft submerges thats it... finito.
I always thought my former employers positioning of the required ELT was a bit stupid... the antenna was located forward of the tailcone at the base of the fin, but the ELT Transmitter was in the tail cone itself, the two connected by a length of RG-400 coax... in the case of a land crash the tailcone tends to separate from the rest of the airframe, thereby removing the Antenna from the transmitter... oops?

Wolf,

Good question.

What you do in soft sediment is deploy the beacon atop a long rope which is is attached to a bloody great big clumpweight and has a floatation collar on itself.

This keeps the beacon above the seabed, hopefully at a similar height above seabed level to that of its brethren in the array so that its depth does not vary much with the others in the array if the seabed current changes direction as a consequence of tidal or other current movements. If the current changes direction, the entire array sways and the resultant fix just goes with the flow, so to speak. They are generally five or so metres above the local seabed, but that depends on the planning of the array vis-a-vis intervisibility acoustically for the calibration of the array. They have to be able to 'talk' to eachother acoustically for them to to be able to self-calibrate trilaterally so that all of the baselines among the array are measurable.


The flot collar is there anyway to recover the beacon at the end of the job. There is an acoustically addressable release device at the base of the beacon. When you want to send the beacon up to the surface you send the command acoustically and the acoustic release releases the physical connection to the clump weight and the buoyancy of the transponder's flot collar sends it upwards. The flot collar is chamfered at its upper end so the the transponder floats nose down in the water at the surface and enables it to give ranging information to the recovering vessel. They cost several tens of thousands of Dollars/Pounds/Euros apiece and are not regarded as being expendable like the sonobouys that the military use with great abandon.

I've had a few rug-munching encounters with bean-counting bosses, without tea and biccies, when having to explain my failures to recover such beacons.

In the North Sea, they usually end up on the beaches of the Fresian islands. Rich rewards to be had by the cattlemen there!

Probably 10% Egypt and 90% French, if that.

http://i68.tinypic.com/9szeh4.jpg

http://i66.tinypic.com/2r2q79l.jpg

Hey Phalconphixer,

Your post regarding the detachable crash transmitter located in the base of the vertical fin, triggered electronically in the event of a crash, closely describes the system as fitted to the Lockheed P3C Orion, used widely by various navies throughout the world - great airplane!

Cazelet33

I didn't understand your reference to prop aeration muddling acoustic links between the ship and the ROV. The deep water installation vessels that I work with all have their ROVs powered and controlled via reeled umbilicals, I.e. the ROVs are physically connected to the ships and do not rely on acoustic signals between the two.

Even the AUVs (autonomous underwater vehicles) that I've worked with are pre-programmed, dumped in the water to do their sonar runs, then come back up at end of mission for recovery and data download - no acoustic comms during the scanning run.

@Cazalet33 At the time of my posts on Burullus early in the thread the message linked to the ship was something like "sub sea operations".

Early in the thread I also posted comments from a UK oceanographer who sketched specific sea floor shape and sediment issues which would make detection and search more complex than you might expect. Wonder if you can agree with his comments.

Just checked it - the label was “SUBSEA LOCATION”,

Was Dr Simon Boxall, an oceanographer from the Univ of Southampton ... see my post May 20th of around 10.20hrs

@Cazalet33 Burullus has been in the same spot at least since May 22nd, at the time it was in port, made a short move to Abu Qir (its home port), and then directly sailed to the spot at 9-10 knots. Quite early on there was a bit of an open 'circle' around it, but as i posted, quite a few ships still crossing close at between 10-16 knots. See Note *
As far as i can see B is supplied on station by a big French vessel. I have not detected a screen of navies vessels yet (like there was with AirAsia). But perhaps they have xpdrs off.

*Note: I checked the information that i have from the start of the surface search. Definition of "close" is when you look at it from the viewpoint of multiple ships making surface sweeps. When you look at it from the viewpoint of a single ship sounding around one specific location, then the 'circle' diameter was more than the 2 miles or so that Cazalet indicated.

Per CBS News:

FWIW it might be worth bearing in mind that if anybody quotes the likes of Reuters or AFP you can often cut out at least one middle man (in this case CBS) and do what most of the media do - go to the agency's own website. If you do that you often find subtle differences in wording and emphasis between what the relatively "raw" stuff the agencies often put out and what makes it into the more popular media output.

No new signal from EgyptAir jet since day of crash as search intensifies | Reuters

I phrased it badly. I meant that the USBL link, which is used by the ship's DP system when in follow-sub mode, gets corrupted and the ship starts overcontrolling and becomes more and more divergent.

An ROV can easily come to a dead stop, from a cruise speed of two or three knots in a matter of two or three metres. A 4,000 ton ship cannot. The DP system will command more and more thrust in an attempt to maintain station and that's when you get loss of acoustic link between the USBL and the sub. The ship can easily move out many tens of metres and start dragging the umbilical so much that the ROV itself can be jerked around. The tail starts wagging the dog and dogs don't like that. They bark and get quite snappy. The ROV crew blame the bridge crew and the bridge crew blames the ROV crew.

It can happen quite easily when, for example, the ROV suddenly encounters a snagged fishing net and has to make an emergency stop. It can also happen when the ROV suddenly finds an orange box on a job like this one!

@.Scott If true then:
a. surprising what Burullus is doing then ... certainly at this stage of the search ...
b. you would expect the search to 'spiral outward' then, say filling a circle of 25 nm diameter, perhaps Cazalet33 can say something about this,
c. the French research vessel referred to above and its patterns will tell us more later,

It is also not clear what kind of signals they are referring to ... was it a signal from the plane, from the radar, or a ULB (if not a spurious one) ...

Just thinking. Authorities could also decide that in modern times it is better to clearly state the main points of what they know, what they dont know, and what assumptions are the basis for the activities that are ongoing. This could also indicate and educate people on the complexity of these searches and investigations. All this leaking and anonymous stuff ... makes a bad impression on the general public.

An illustration of this could be the find of another probable MH370 fragment today. It was found by a guy who by chance had just seen a few photos of earlier finds. During the MH370 search an Australian SAR official was quoted who said that his experience was that people could not recognize such fragments as being from an aircraft - especially when they had been in the water for (even) a (short) while. After the fact other officials say that this find is a prove of the accuracy of the drift predictions. That also surprises me, if these predictions were so good as claimed, why did they not publish them as soon as possible with a request to the public to report possible finds. And the give the public (and seafarers) a number of examples of what they might expect to find and see.