AF 447 Search to resume

[promani]

Many years ago I was taught that in any search exercise, you always start at the LKP and work outwards from there, allowing of course for any info that may direct the search in a particular direction. If this had been done last year, then maybe we would now know what really happened that fateful morning. It seems that it took the Russians to enlighten the French on a likely crash site. Also we can exclude the oil slick now, as I hinted awhile ago?

[Thermaller]

Considering that the released images appear to have been carefully selected so as not to show the remains of the deceased and not to reveal details that may either explain or lead to speculation about the cause of the crash, we should consider that the rear of the aircraft is in fact in the debris field and has been located.

Does anyone have knowledge of the French legal system? WHOI is contracted to BEA so presumably the recovered boxes will be handed to the BEA. Let's hope there are proper procedures in place on the recovery ship. Since there are criminal charges involved, would the French court order that the FDR and CVR be examined under court supervision, or will the BEA have exclusive control over what happens to them.

[Machinbird]

Also we can exclude the oil slick now, as I hinted awhile ago?

Promani, how did you reach that conclusion?

Thermaller, Alucia/WHOI, having just located the wreckage are mapping and documenting the site. The actual recovery will be by others under control of the French Government.

[CONF iture]

Originally Posted by HN39

What if the reference IAS is erroneous, i.e. 2 ADRs providing similar low airspeeds?

If 2 ADRs tell the same lie, the flight law will not degrade to ALT but remain to NORMAL. The low speed stability would not be part of the game, but the A\THR would try to compensate for the erroneous low IAS ... to MMO or beyond. I think.

[auv-ee]

Originally Posted by promani

Many years ago I was taught that in any search exercise, you always start at the LKP and work outwards from there, allowing of course for any info that may direct the search in a particular direction.

Seems to me that is exactly what was done. 15,000 km^2 is a lot of area to search, so BEA was very interested in any way to reduce that area (for Phase 3). The drift study seemed like a plausible way to do that, so they arranged for some people with drift experience to work on it. The result was the search box for Phase 3. In hindsight, the lack of detection in the search box made it likely (now clear) that the drift study was wrong (currents at this site are unpredictable), but at the time there were people who agreed with the decision to use this data to focus the initial search, while others believed (correctly, if confirmed by the FDR) that an upset A/C could never have made it that far from LKP.

If this had been done last year, then maybe we would now know what really happened that fateful morning. It seems that it took the Russians to enlighten the French on a likely crash site.

Hindsight is 20/20. I'm not sure how much influence the Russian experience had on the Phase 4 search. My understanding is that a brute force search of the remaining 10,000 km^2 was planned, starting with the part within 20nm of LKP. The rational for the 20nm is contained in the Metron analysis, and is based on the sort of aerodynamic considerations that have been much discussed here. I am sure that some will argue that the aerodynamics should have been given more weight at Phase 3.

http://www.bea.aero/fr/enquetes/vol....h.analysis.pdf

Also we can exclude the oil slick now, as I hinted awhile ago?

In the drift analysis, the pollution spot is discussed on pages 134-5. Here they explain how they backtracked the spot. Oil slicks are known to respond more strongly to wind than current, because they have no projection below a very thin surface layer that is wind driven. The report states that oil typically moves at 3-4% of wind speed, and that the wind was strong from the north. The backtracked position, based on wind and current, displayed in figure 27 (from yellow dot, back to orange dot), was based on down grading the motion to 2% of wind, as discussed on page 135. If they had stuck with 3-4%, I think the result would have been very close to the now known debris location. So, it's probably premature to say that the spot is unrelated.

http://www.bea.aero/en/enquetes/flig...oup.report.pdf

[Machinbird]

Machaca, That is a great picture. Lets use it for discussion.



Didn't an A340 lose its DFDR on a tail strike a couple of years ago? A recorder in this position may well be torn loose during an impact such as AF447 sustained. I would expect a skin strength discontinuity in the transition from the pressurized cabin to the unpressurized tail. Failure of the skin just aft of the pressure bulkhead is then quite possible, even with the plentiful stringers visible. The DFDR and some associated structure may well be lying by itself, separate from the wreckage.
The heavy vertical structure aft of the DFDR appears to be a support for the THS actuator. How does it tie in to the structure above? An item like this would be forced upward like a piston by the impact from below and could well account for how the VS was thrown. It appears to be pointed at the aft VS support structure. The forward VS support structure is above and forward of the aft bulkhead if I recall correctly
A very helpful view of an area most of us never get to see.

[promani]

Machinbird/auv-ee, the reason for my comment is that I understood that the BEA had consulted the Russians, who told the BEA that they normally found aircraft wreckage very near the LKP when searching for a crash site.
I have to admit that I find it difficult to accept that the oil slck had travelled south of the LKP, but the debris and bodies recovered in June 2009 went north. But I am willing to accept your expert opinions. I am just posting my thoughts, guys.

[Bobman84]

Can we please keep this thread about the search and recovery only. Start a new thread if you want to discuss stalls etc.

The debris is dispersed over "quite a compact area" of about 600 meters by 200 meters (1,960 feet by about 650 feet), he said.


All the wreckage will be brought to the surface and sent to France for study, said Jean-Paul Troadec, head of the French air accident investigation agency, the Bureau d'Enquêtes et d'Analyses, or BEA.


"We want to know what happened in this accident, most particularly so it never happens again," he said.


Three companies bidding to raise the wreck have until Thursday afternoon to submit proposals, he said.



The operation should take three weeks to a month, and will be paid for by the French government at an estimated cost of 5 million euros ($7.1 million), he said.

[PJ2]

Machinbird;

Yes, an Emirates A340-500 had a tailstrike at Melbourne. The preliminary report is here. The DFDR broke loose due to failed latches when the tail struck the runway (after a weight > speeds miscalculation). The report has a photograph of the DFDR mounting box and the DFDR, which fell rearwards, through an opening and below to the floor, (lower skin). It always remained with the aircraft.

Bobman84;

The operation should take three weeks to a month, and will be paid for by the French government at an estimated cost of 5 million euros ($7.1 million), he said.

To place in some perspective the costs of searches and estimated recovery, over the four years it took to complete the recovery and investigation of the Swissair 111 MD11 accident at Peggy's Cove, Halifax, the Canadian TSB spent approximately CAD$57m.

PJ2

[Machinbird]

Thank you for that clarification PJ2. The DFDR of that A340 ended up in an opening directly below the THS actuator, below the "floor" of the compartment.

That was a 'love tap' compared to the bash AF447 seems to have taken.
Unless the DFDR ended up wrapped in other structure, I would expect it is free of its mount simply in view of the forces involved and crash attitude.
That tail compartment is likely torn open.
Hopefully that bit of oarnge will not be too heavily silted or otherwise covered if it is lying free.
Then a good photo interpreter will have a fighting chance of picking it out.

[jcjeant]

Hi,

would the French court order that the FDR and CVR be examined under court supervision, or will the BEA have exclusive control over what happens to them.

A representative of the law will (should) be there to put seals on the black boxes

[mm43]

Hopefully that bit of orange will not be too heavily silted or otherwise covered if it is lying free.
Then a good photo interpreter will have a fighting chance of picking it out.

There is enough steel in the DFDR that someone out searching for gold using a $50 inductive loop detector would find it 600mm (2 ft) under.

In all seriousness, the technique may need to be used if the the orange brick has gone and buried itself.

Substitute the person for a towed magnetic anomaly detection (MAD) device.

[vanHorck]

mm43,

Welcome back to you! You have been dearly missed!

[PFR]

Extended Main Landing Gear.

Firstly....
Dutch wrote:-
"It has been and it is clear to me that neither Airbus, AF or the french government are ducking their responsibilities".Would agree Dutch. Lets give some credit where credit is due - there are a lot of professionals engaged in this.

Secondly...
As has been touched on in a number of earlier posts, including that running in Rumours & News, "AF447 wreckage found" (hopefully the moderators will merge the two) what of the significance of the Landing Gear being extended - as appears apparent in the photo's so far released.
Could that be a crew action in some effort to arrest speed/gain control of the descent? Or is it a reasonable post impact result?

[sensor_validation]

Originally Posted by takata

My understanding is that the system switched to "Alternate law 2" from the begining at 02.10. Then, "AOA protection" was lost from the start of the sequence anyway.

Why would they initiate such an "evasive action" at 02.10 while they had to keep flying "pitch and thrust"?... this would not be very smart without a real need to do so. During all the similar sequences documented so far (more than 36), not a single crew did take such an initiative to make an "evasive action" only due to unreliable airspeed data.

Nothing is telling us for sure that the aircraft impacted at the end of the ACARs transmition (02.15). In fact, without engine power, no more ACARs would be sent anyway.

Given the approx location of the debris, is the fact that the 02:10:30 (assume this is exact time of position acquisition, transmission 4s later) location was "slighty west 3NM" of track INTOL - TASIL now more significant.

Yes was discussed at length previously, and can only be answered for sure by the black boxes - but was the deviation deliberate or indicative of an earlier upset?

[HazelNuts39]

Extended Main Landing Gear

Originally Posted by PFR

what of the significance of the Landing Gear being extended

For those still interested in the causes of this accident (and we're still months away from the data we're hoping for), yes, I think it would be very significant if the gear had been extended by crew action. It is of course quite possible that the gear was released from its uplocks by impact forces. However, I would think that the duration of high vertical acceleration is no more than a small fraction of a second, and therefore consider it unlikely that the gear would reach the fully down position before being ripped out together with its back-up structure in the wing.

Perhaps someone could produce a picture of that gear as installed on an intact airplane?

Regards,
HN39

[takata]

Originally Posted by Bobman84

All the wreckage will be brought to the surface and sent to France for study, said Jean-Paul Troadec, head of the French air accident investigation agency, the Bureau d'Enquêtes et d'Analyses, or BEA.

Sorry, but it is not what Jean-Paul Troadec said. This is a bad translation of "All the wreckage brought to the surface will be sent to France", which is quite different: they will only brought to the surface what part is needed in order to fully understand the crash; they won't need the full aircraft if the recorders are recovered and are telling enough about the cause.

[Shadoko]

Hi,

First, thanks to all people giving so much interesting datas on this forum.

Second, as a newbie, three questions I did not find answers by reading some threads (too quicly?):

- if an engine flameout happened, was an ACARS to be transmitted?
- is a spinning "posture" making a stop to the satellite transmission (so, no more ACARS)?
- in the event of a vertical stabilizer rupture, is the cabin depressurization mandatory (and followed by an ACARS)?

Third, ... sorry for my frenchie English ...

Regards,
Sh

[hetfield]

I think it would be very significant if the gear had been extended by crew action.

Isn't there a blocking valve in the hydraulic system to prevent gear extention above a certain speed?

[SaturnV]

The following figures are from the Metron analysis that was done for BEA in January 2011.



^^^^ June 1 search grids. (low level only shown.) Brazil in yellow, France in blue.



^^^^ June 3 search grids.




^^^^ June 6 search grids. Voila.

Figures for the search grids flown on June 2, 4, and 5 are omitted in this post as these were over areas remote from the crash location.

On June 1, the Brazilian search grid was possibly/probably just to the right of the crash location, but the French clearly overflew the location. What are the possible explanations for this?

a.) the French were blind, or searched under poor observational conditions.
b.) any objects floating on the surface had already moved to the west, beyond the search grid, in the current and drift by the time the French searched.
c.) objects had not yet reached the surface when the French overflew the location.
d.) the French gave erroneous data to Metron as to the spatial area covered by their June 1 search.

The reasonable conclusion would be that if you overflew a possible crash location within 24 hours of the crash and observed nothing, then that is not where you will find the airplane.

The Metron analysis notes that the ship Douce France searched in the area of the LKP on June 1, but does not give the track of the ship.

All the current and drift reconstructions for June 1 and probably for the several days following, now appear to be badly flawed. But again these also presumed that evidence of the crash should have been spotted by the overflights on June 1 if that was within the area the plane crashed.

Here are links to the Metron analysis:
http://www.bea.aero/fr/enquetes/vol....h.analysis.pdf

And the analysis done by the drift group:
http://archimer.ifremer.fr/doc/00027/13777/10915.pdf