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AF 447 Search to resume

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AF 447 Search to resume

Old 22nd Apr 2011, 23:48
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AUV-EE Drag & terminal fall speed

AUV-EE After my drag and terminal velocity theoresing (thats all it was, but should be valid for any fluid)

Water Viscosity at High Pressure and Temperature

We have documented a two-fold increase in the viscosity of water from 0.1 MPa (1 bar) to 1 GPa at room temperature
Given the importance of water in planetary geophysics, it is surprising that almost no measurements of viscosity are available above 1 GPa.
400bar about 40 MPa

Conclusion So yes, even at 2 x viscosity unlikely to be any substantial change in drag

Last edited by HarryMann; 22nd Apr 2011 at 23:50. Reason: Change!
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Old 22nd Apr 2011, 23:52
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wing design

I haven't seen much discussion above about low-level aerodynamics issues - like how does wing design on Airbus affect the problems that might be encountered? I know the wing design must be very different in practice to that of Boeing - you can see this if you watch a lot of comparable landings, say a 777 vs. an A330, and the Boeing is much more stable during windy approaches, seems in all cases to land and roll. The Airbus has a definite tendency to loft down the runway. Something in their wing design favors low speed flight. So what does this say about flight when getting near the "corner"? I know these Airbuses are quite happy at 37,000 feet, but do perhaps these wings have a less forgiving performance envelope at cruise altitudes? I'm just curious, I know nothing really about commercial wing design.
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Old 22nd Apr 2011, 23:56
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Originally Posted by JD-EE
The simplest answer to this dilemma is that the problem began, probably not long after 01:35 and finally brought the plane down.
What about the connection attempt to the Dakar center ADS-C system at 02:01 (Interim Report n°1, p. 48)? The report (p. 66) says, that this "first connection with the system is made by the crew". Would they have bothered with something like that if they were already in serious trouble at that time?

Last edited by wozzo; 22nd Apr 2011 at 23:59. Reason: Quotation Marks
 
Old 23rd Apr 2011, 00:00
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Originally Posted by JD-EE
auv-ee, I'd expect more time spent looking and less time snapping pictures of everything in sight (or site.) 100,000 pictures stored in a 10 bit HD raw format would be quite a lot of data. Now, I am aware that finding computers with 207 gigabytes of spare storage is easy these days if you purchase new they might have decided to save storage and only preserved the pictures that showed something interesting.
With an AUV there is no such thing as looking at something that has not been recorded. There is no significant bandwidth between the bottom and the surface, so everything is recorded blind and sifted through after recovery.

The camera is 2k x 2k, B&W, reported recently in a commercial article. Images are likely stored in an uncompressed format, because images of the bottom are noisy (sand/silt looks like noise) and so do not compress effectively. Dynamic range is the key factor in UW photography, because the contrast is low and the lighting is uneven, so the images would be stored with at least 16 bits/pixel. So each image should be about 2-4Mbytes (depending on bits/pixel). Not a lot of storage by today's standards. Also, the data would be dumped to a larger disk after each dive. No problem acquiring 100,000 or more pictures.
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Old 23rd Apr 2011, 00:45
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De Sitter Wing Design

There is (or always was) a fundamental difference between approaches... Airbus went a bit more for minimal area with very high lift devices and Boeing (usually) adopted a 'big wing', lower wing-loading philosophy.

Anotther way of saying this, that might make more sense to some, is that the 'low drag cruise bucket' is (or should be) a bit wider on the Boeing than Airbus.

However, that was a few decades ago, I imagine now, as we find with many cars for instance, that optimum design from different mfrs eventually tends to merge to a common theme and standard.

I can't really comment much on your view on low level and approach flight behaviour. I would doubt whether, effects observed were dependent on wing design.
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Old 23rd Apr 2011, 00:54
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Originally Posted by jcjeant
Hi,

Post reread .. and can you reread mine
Suppose IF
You are responsable of a plane (and so .. directly of all people aboard)
Someone came to you with a bad news:
We have lost contact with our plane.
What you will do ? by all means find what happened to the plane ...
Read the comms timelines in the earlier reports, eg. http://www.bea.aero/docspa/2009/f-cp...90601e1.en.pdf [sections 1.9.1 and 1.15]. If anyone was negligent in the delay in searching for this flight, it was ATC. First a failed handover seems to have got the flight "lost" for some hours, then by around 4.30, other flights asked to try contact (AF459) and AF is alerted to try and contact. At this point this is just a lost-contact.

But ATC seems to think all is fine, because at 5.09:
the ATLANTICO controller requested confirmation that the flight was already in the SAL FIR. The DAKAR controller replied: "yes, no worry".


By 6am., AF is onto SARSAT looking for ELT transmissions (none - normally that would be good...) and talking to all the ATCs, and then ...
At 6 h 35, the MADRID centre told the BREST centre that the flight was at that time in contact with CASABLANCA FIR and would enter the LISBOA FIR within a quarter of an hour. The BREST centre transmitted this information to the Air France Operations Control Centre and to the Cinq Mars La Pile Regional Control Centre.
So ATC told AF all is well (4+hrs after the crash!), and we are talking to your plane.

It then takes a further 1-2hrs (with AF reporting further concerns about lack of contact with base) before the various ATCs seem to agree that actually no one is talking to the plane, and maybe someone ought to raise an alert, but can't decide which zone the event is in and therefore who should raise alert.

Finally Dakar decides something might be wrong at7.41, 5+hrs after the plane should have contacted them...
At 7 h 41, the DAKAR shift supervisor informed the Dakar Rescue Control Centre that flight AF447 should have passed the TASIL point at 2 h 20 but that it had not had any contact with the plane.
From that point, it looks like SAR starts and I guess ACARS is used to refine LKP from radio comms to direct the search.

Reminder: ACARS checked ONE HOUR before ETA !! (astonishing fact)


Reminder:
shortly before this, AF OCC were told that the plane was in contact with ATC over Morroco. Why would they therefore be looking at ACARS other than normal review for maintenance (probably shortly before ETA) ?

Reminder2
: you (and some other posters) seem to have an idea that ACARS is some kind of aircraft tracking system, crash alert system, crash locator system, or black box subsititute. ACARS is none of those things. It's basically a messaging system for maintenance so that they know before they get the the a/c that they need the tools to unblock the aft loo, rather than having to get onto the a/c, download the messages and realise the tools they need are half a mile away on the other side of security.

AFAIK, there is noone (human or automaton) supposed to be watching the ACARS streams looking for nasty fault messages followed by loss of transmission that taken together might possibly indicate that a plane just fell out of the sky. NOone was "asleep at the switch" as someone else put it.

Could ACARS be used in this way (given hindsight of this event) ?? I'd guess possibly. But it isn't designed for it, and I think you'd have to be really clever (or lucky) about how you do the analysis (would need to be automated alert system of some sort) to get the false alarm rate acceptably low.
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Old 23rd Apr 2011, 00:57
  #3827 (permalink)  
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JD-EE;

After the crew acknowledged the SELCAL check, only a few seconds had elapsed when ATLANTICO requested their TASIL estimate but the crew did not respond.

I don't think this in itself is an indication of "trouble" at that moment, anyway (but I think it began to unfold shortly after and well before 0210).

After the P2 thanked ATLANTICO for the check, I think the P2, (who I believe was the F/O, with the RP as P1) pushed the HF radio button down, turning off the volume to the #1HF before hearing ATLANTICO's request. The request was necessary because TASIL is the FIR boundary and AF447 did not provide ATLANTICO with the TASIL estimate on first contact, which is when it's normally done. It happens and it's no big deal. And turning off the volume to get rid of the HF static noise is also normal. That's what SELCAL is for. Yet while ATLANTICO verbally requested the estimate three times, the SELCAL was never used to call the crew back.

I think AF459's experience is germane. AF459 was "37 minutes" later at ORARO than AF447. I think the phrase "at the level of" is a translation for "abeam" ORARO, as they were on a wx deviation (east of track) at that point.

The information on page 68 of the first BEA Report discusses AF459's experience with weather deviation and what they saw on the radar and what the radar settings were, such as antenna tilt, varying the gain from MAX to CAL, and which in my view were exactly correct. they were about 160nm away from the weather which is described as a "vast squall line". The animation of the tracks of all relevant aircraft is interesting - one can see AF459's deviation while AF447 neither communicated nor deviated, (as you say), yet they must have seen the same radar returns as AF459.

It's why the CVR is as important to recover as the SSFDR.
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Old 23rd Apr 2011, 01:22
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wozzo, "What about the connection attempt to the Dakar center ADS-C system at 02:01..."

Good point. I'd forgotten about that. And that would be pretty close to when the pickle fry had to have started. They had at least a few minutes to get into communications and at least tell nearby planes they were deviating.
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Old 23rd Apr 2011, 01:35
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auv-ee, arithmetic redo.

2k by 2k by 16 bits is 8 megabytes. That times 100,000 is 800 gigabytes. That is a LARGE disk to take home. (2e3 * 2e3 * 2 * 1e5 = 800e9)
Of course, that would not be one AUV taking 800GiB of pictures. That's a different storage problem. A 32G solid state drive would hold a fair amount, maybe enough to be worth a trip back to the surface. I figure I'd not put a regular hard disk in an AUV environment?

I'm not sure the ship would have had the spare terabyte drive to store the
images. (1024 vs 1000 factor plus file system overhead.)

Somebody else remarked about 15,000 images. That sounds like a reasonable number to take home. But I'm just guessing.
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Old 23rd Apr 2011, 02:23
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Originally Posted by SLFguy
Quote:
[snip] Every movement of the vessel at the surface is translated to the Remora's umbilical cable with a delay, said Brennan Phillips, manager of ROV operations at the University of Rhode Island in the U.S.

"If the ship moves, it takes half an hour for the vehicle to feel it," he said. "You need an extremely stable ship."
[end quote]

I wonder why they don't use a compensating system (hydraulic-air) like used on the drill rigs (semi) or DS for the risers tensionners and on the derrick travelling block

This is odd. Why no Tether Management System?
The quote from Phillips refers to the horizontal movement of the ship. The delay is related to the depth of the operation (and various cable parameters), but the half-hour figure is applicable at 4000m.

The heave of the ship, or payin/payout of cable, is transmitted down the cable quickly (at a speed determined by the elastic and mass properties of the cable). That is where, as you suggest, heave compensation can be applied. There are various methods possible:

Gas or active hydraulic rams/sheaves, of the sort you suggest,
Active winch (constant tension),
Bobbing crane (active or passive),
Attachment of floats to the lower tether to form an "S" section for (partial) decoupling,
Two-body deployment: depressor weight, with shorter neutral tether to the ROV,

And probably others. The latter two also decouple horizontal movement of the ship; and the last is sometimes implemented with a free length of tether, and sometimes from a second, smaller tether management system (reel) as part of the clump weight (what you referred to, right?). One reason not to use the first three methods for this job is that the constant flexing, under tension, of the same part of the cable, while deployed at a near-constant depth, can weaken the cable or damage the conductors or fibers.

I don't see any place where Phoenix says they won't use one of these methods, but I agree that their standard data sheet for the Remora 6000 does not show or claim any. Their web site does list an available ram-type motion compensator. I have no clue as to what they plan to use, and agree that delicate work with no decoupling of wave motion would be tricky.
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Old 23rd Apr 2011, 02:48
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Originally Posted by JD-EE
2k by 2k by 16 bits is 8 megabytes. That times 100,000 is 800 gigabytes.
Oops, I got very little sleep last night.

The REMUS vehicles have several nx100GB hard drives for the camera, SS sonar and other data. There is little problem with HDs in AUVs, though 250GB solid state drives are also available for more $$.

I can buy a 1TB laptop drive at our local office supply store. No one would go to sea for this work without adequate media for storing the data to be acquired. I expect they have a RAID array to hold the data from the many missions.

For reference, I am just reading a book (Project Azorian) about the location and attempted salvage of the Soviet K-129 submarine at a depth of about 5700m. In 1968 the US Navy took 20,000 film pictures of the site, with 9000 showing parts of the wreck.
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Old 23rd Apr 2011, 02:52
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Translation of Figaro article

The investigators have located the part of the aircraft where the recorders are placed. Reading them remains uncertain.

The mystèry of flight AF 447 could be unveiled in early May. The investigators chargéd with recovering the black boxes of Rio-Paris, which crashed June 1 2009 with 228 people on board, flew from Roissy pour to Dakar Thusrday. They have Ils met the câble ship Ile de Sein, which belongs to Alcatel-Lucent and Louis Dreyfus Armateurs and have headed off to the accident zone which they will reach in four days.

Their mission is first to raise the black boxes from the aircraft. The investigators hope to have that done in 24 hour, worse case in a few days". The Remus submersibles used by the previous expediton - which discovered the wreck - has effectively gridded the débris field and taken 15 000 photos. Remains of the nose and tail pf the aircraft , the motor[s], parts of the fuselage have been geolocated and will allow a more rapid deployment of the submersible used in this last campaign.

[from Squawk Ident

"Among the debris photographed, no trace of the black boxes but the part of the aircraft which shelters them has been formally identified and located. It is the pressure bulkhead, the wall that separates the pressurized part of the aircraft and its nonpressurized one, at the back (of the plane). On the Airbus A330, the two black boxes are fixed on each side of this pressure bulkhead."
]

"It's 50/50"

The cockpit voice recorder ( CVR) placed in front could give the investigators all the conversations in the cockpit and will allow the determination of who was at the controles and how the crew dealt with the accident. Le flight data recorder (FDR) should furnish all the paramèters of flight and will determine the scénario of the drama. If, as the investigators hope, the flight recorders are retrieved in 24 hours, a frigate of the French Navy will come from Cayenne to retrieve them, then send them to the facilities of BEA at Bourget. The investigators will remain at the site to concentrate on raising bodies. "Several dozen bodies" have been found and photographed by the Remus submersible.

It remains to find out if the black boxes can be read and have not been totally damaged by the accident. Black boxes have already been retrieved several months after an accident. They résist à shocl de 3,400 g on aircraft impact, à température of 1,100 °C for an hour in case of fire and àn undersea pressure of 6,000 mètres for six months.

In the case of AF 447, they will have been over two years at a depth of 4,000 mètres. "It's 50/50", estimates somebody close to the investigation. If the recorders can no lomnger be read, the investigators will have to raise parts of the aircraft that can help the BEA in its investigation: calculators, the position of the controls or even the maintenance recorder, situated in the hold, which contains considerable information on the flight.
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Old 23rd Apr 2011, 02:54
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PJ2 quote:
I would not want to criticize theories if they are developing and/or promising, but if someone believes something strongly, in this context there is the requirement for substantiation.
PJ2, I appreciate your desire to be dispassionate and even-handed. I thought long and hard before deciding to criticize the "Loss of VS at altitude as a causal factor" approach to this accident. I don't see this line of thought as developing anymore, it only operates in a 'restatement' mode in my view. The same old concepts are paraded out and restated. More jello nailed to the wall.
Determining that the VS was attached at impact takes the examination of this accident in one direction, and assuming the VS was lost at altitude takes it in another. That is why it has been a constant source of discussion between contributors.
So true. But if one of these branches can be effectively discounted, then attention can go to the other branch. New thoughts can be developed.
Too often we look at things in terms of what we already know. Pilots look at questions of how could the crew have done things differently or how the airline may have put the crew in a box? Systems Engineers look at things like how the types of systems they have worked on in the past can cause such an accident? Maintenance 'Engineers' look at how particular types of systems they have had problems with might have contributed to this accident? We all have our unique viewpoints. Only when knowledge from new disciplines is added do we seem to find new corners of the AF447 puzzle.
If the problems with the VS-loss theory were addressed such that the evidence of the recovered wreckage and the photographs were accounted for, I don't think anyone would resist the notion.
However, a number of contributors have provided sufficient opportunity to demonstrate the validity of the theory against specific objections, and have found no response.
As I stated yesterday;
Loss of the VS in-flight is probably the most discussed concept in this thread.
This single-mindedness is not an asset and detracts from other explorations.
I for one have delayed opening up new areas for discussions because there was an active discussion going on about how the VS might have been lost. I strongly suspect others are in this same boat.

BEA may be an agency of the French government and as such can receive political "direction" from on high, but they have their own credibility to preserve.
Their reports on the accident have been conservative, and only very recently has there been significant evidence that some of their early conclusions will have to be re-thought and corrected. (Accident location actually near LKP and possibly, the significance of ADR related ACARS messages). Their statements regarding the VS condition and their conclusions regarding how the VS came off the aircraft have not yet been disproved despite many attempts to do so and several attempts to besmirch the BEA's reputation.
If one of the proponents of the 'VS was lost at altitude' concept will provide a succinct, bulleted summary, of their points, then I am sure that the other viewpoint holders (VS was lost at impact) will have no trouble discussing them appropriately.
The problem has been that too often, the points have not been stated succinctly and instead are stated in general terms along with a variety of irrelevant cat and dog subjects. This causes many of us to tune this part of the discussion out.
VS was off at altitude proponents, please conspire among yourselves and pick a spokesperson or team to present your key points.
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Old 23rd Apr 2011, 03:41
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Why so few photos of the wreckage

Actually, there is probably a very simple answer.
Suppose BEA picked several interesting photos from those taken and released them to the world primarily for the purpose of showing that they had indeed found the wreckage.
Suppose then that a sharp eyed individual examining one of the pictures said "That shape over there, I think it is human remains" and then publishes that statement online. Whether or not the item was correctly identified by the poster, there would be an embarrassing and distressing scandal.

Each picture released has the potential for causing such incidents. You can bet that those photos that were released were carefully screened to be easily identified and non controversial. With the workload the BEA staff has now that data is starting to flow in, they will be in no hurry to release any other pictures.
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Old 23rd Apr 2011, 03:51
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Cool

Hi,

infrequentflyer789
Read about ATC sequences.
So we have there a suite of ATC error .. made by incompetents or lazy controllers.
They have (if all exact) a responsability of the delayed researches...
I hope those particulars will be cited at the court and punished.
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Old 23rd Apr 2011, 04:33
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The animation of the tracks of all relevant aircraft is interesting - one can see AF459's deviation while AF447 neither communicated nor deviated, (as you say), yet they must have seen the same radar returns as AF459.
That is interesting. How was the track for AF447 obtained? Im assuming the tracks from other aircraft were also from the same source. We can also see AF459 going around what must have been phantom returns on their radar. What this animation tells me is that none of the flights there had the complete picture of whats ahead. It could very easily have been any one of them in the position AF447 ended up in. (that is to say in the middle of what looks like a very active cell.) It seems to me we are tempted to question the track of AF447 simply because they were unlucky enough to not make it to the other side...
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Old 23rd Apr 2011, 04:39
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ACARS as an alerter?

There has much recent discussion regarding why ACARS was not referenced earlier re the loss of AF-447. Also, much discussion early in the thread on better design of DFDR/CVR boxes and pingers.

While acknowledging that ACARS is not designed to be anything other than an automated maintenance events log transmitter (and not necessarily exactly sequenced), one result I look forward to out of BEA's final report will be a recommendation that a new feature be implemented in airborne ACARs software and ground receiving computer systems:

1. Airborne ACARS to transmit a simple short standardised "I-am-alive-and this is my gps position altitude and heading" message every say 5 or 10 minutes. If the traffic overhead is low, it could perhaps be done every minute.
2. Ground based receiving computer systems to implement an automatic message parsing function to look for the I-am-alive message and trigger an alert if the next expected one or several messages are missing. The trigger could have a relaxed timing window to allow for the I-am-alive message to be pre-empted by routine maintenance messages taking priority.

This seems such a simple thing to do in software. May take months to years to certificate of course (on the airborne side, but not on the ground systems, particularly as ACARS likely does not have raw heading, position and altitude data routed to it), but would have the effect of:

a). Aiding airline dispatchers to raise an early initial alarm, rather than wait for ATC to coordinate of reports of missing scheduled communications.
b). Ensuring search resources can be mobilised faster, with greater certainty to a smaller search area.

ACARS is not designed for this function, but it is the one reliable system we have on board today that could be readily adapted to include this capability, having continuous immediate access to reliable global communications.
The ground based message parsing and triggering would be relatively trivial to implement.

Such a capability, could be relatively easily developed, requires no more boxes or systems in the aircraft, and may not even require any wiring changes if the (optional, preferably desirable,) gps position, altitude and heading data are available on any of the data buses brought to the ACARS system.

NB: This concept is much much different from suggestions way back early in this thread that FDR data be transmitted over ACARS. This would require high bandwidth, which ACARS does not support.

What I am suggesting is an ESSENTIAL requirement for ONLY for a standardised, very terse, I-AM-ALIVE code. Loss of one or several sequential messages is what would trigger an alert.

Any other data transmitted could be optional, depending on aircraft configuration and data availability to ACARS. I am suggesting only position, heading and altitude as minimally desirable, as together they enable a reasonably accurate estimate of LKP. VS/TAS/GS could be roughly and sufficiently interpolated from this, particularly if transmissions at the one minute or so level could be supported.
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Old 23rd Apr 2011, 04:41
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The problem started on AF447 and finished there!

Folks,

I think it is time to reverse the time machine and go back and take a closer look at what actually transpired between AF447 and ATLANTICO at INTOL.

Refer to the AF447 thread where many moons ago I laid out the obvious discrepancy in the waypoint timings provided to ATLANTICO for SALPU and ORARO. ATLANTICO had good reason to query the aircraft and at the same time request the ETO TASIL at the FIR boundary.

Now why were the timings so obviously incorrect???

When DAKAR requested a FP for AF447, the Virtual FP information provided to DAKAR by ATLANTICO was an estimate for TASIL that they (ATLANTICO) had created. Were ATLANTICO too busy to pursue AF447 using SELCAL and check with DAKAR that the a/c had made contact with them at the FIR boundary? I doubt it. They just assumed that DAKAR OCEANIC would get comms with the a/c at some stage of its transit through the DAKAR FIR.
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Old 23rd Apr 2011, 06:45
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Machinbird;
I thought long and hard before deciding to criticize the "Loss of VS at altitude as a causal factor" approach to this accident. I don't see this line of thought as developing anymore, it only operates in a 'restatement' mode in my view. The same old concepts are paraded out and restated. More jello nailed to the wall.
Yes, understand. No criticism intended of your post because I believe the view expressed is on the right track, not because "I" don't like the other theory, but because the evidence has not led us to that conclusion.

If the evidence for loss of the VS sometime before impact, (and if not at altitude as the precipitating event, why is any other scenario important short of 'attached at impact' ?), were incontrovertible and argued as such, no problem, but it has not and the pursuit is, as you state, no longer productive in terms of finding out what happened and how the aircraft actually hit the water.

What is the simplest explanation for the seeds of this accident? Where did the series begin? What failed and where in the series to intervene in the causal paths and permitted "the next step" to proceed to completion?
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Old 23rd Apr 2011, 06:53
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mm43;
They just assumed that DAKAR OCEANIC would get comms with the a/c at some stage of its transit through the DAKAR FIR.
Yes, I think so. Missing comms is initially, not that big a deal on the Pacific, Atlantic or Arctic. It is slowly changing as ADS and CPDLC installations grow.

But this is the sense of "normal" I was meaning to convey about comms; - when no scent of something wrong is sensed by anyone, at that point.
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