DenisG;
If you read the BEA's interim reports, you will discover -

At the time of A/P disconnect, the a/c appears to still have been at FL350. What happened after that is still purely speculation.

The injuries attributed to bodies speak of significant spinal injuries consistent with a high vertical moment on impact.

Regarding entering the 2nd mesoscale event NNW of ORARO, I wouldn't have expected any different response to the situation as that encountered in the first event. It seems that they were not aware of what they were flying into.

There were well over 4,000 posts to the original AF447 thread now in the Tech Log, and approaching 900 in this thread. The questions you are asking have already been posed and debated.

mm43

Takata;
For my understanding of your views and given this statement, are you claiming that the static ports were also iced?

HN39, just read from the FCOM, the cabin altitude is limited to 7350' for flights over 2hrs; under 2 hrs it goes to 8000'.

PJ2

Cabin V/S Advisory
 

takata,

thank you for your elaborate reply. Let me first clear up a possible misunderstanding. I'm not ignoring the ICE issue. At the origin of the ACARS messages is an airspeed 'discrepancy'. The only and almost universally accepted explanation for that is blockage of the pitot tubes by icing.

However, cabin pressure is not affected in any way by pitot pressures. The cabin pressuration systems uses aircraft altitude, which is derived from the pressure measured at the static ports. These are flush with the skin, and do not collect ice in the way that the pitots do. Nothing in the ACARS messages indicates a problem with the static pressure. The pressure measured at the static port is normally corrected for 'position error'. BEA's 2nd interim report explains that this correction is not correctly applied when airspeed is corrupted. However, the resulting error in the indicated altitude is so small (300 ft) that it does not in itself cause a problem with any system.

Here I respectfully disagree. The message means that at this point the airplane was below 7350 ft, descending rapidly, and at least one engine was operating.

If total engine failure occurred, it must have occurred between 2:14:26 and 2:15:14, below 7350 ft, at temperatures above freezing.

HN39

EDIT:: 8000 ft changed to 7350 ft. My thanks to PJ2 for info in #920. I don't have access to the FCOM.

EDIT 2:: Further to my post #909, some selected quotes from the applicable regulations:
EDIT 3:: "less than 50 ft" corrected to 300 ft

I've been following this Thread and its predecessor closely from first post on.
@mm43:
When I look at the likely crash location you determined last September and comparing it to the location they are now searching in detail it is absolutely striking how good that matches !!!:ok:

It seems your research bettered all the experts of BEA and those directly involved in the Search. Amazing !
Maybe they should have listened more to pprune and especially to you!

What remains a bit of a mystery to me is how they could have come that far from the last known position and hit the surface with very little forward speed. And all that after a hard 180° turn.
Normally such a hard turn would cause speed bleed.

If you calculate the time/distance between last known position and actual search location this would require ~ 500kts average speed point to point even without considering turn (speed loss and longer actual flight path) and deep stall (forward airspeed <<100 kts).
Maybe there is indeed some merit to the flameout scenario...

Hi HazelNuts39,
Well, I know that static ports are not supposed to fail... but, directly from AIRBUS specifications, in case of UNRELIABLE AIRSPEED (caused by Pitots failure) SPEED as well as ALTITUDE are both to be considered unreliable. Check it yourself!
Furthermore, I studied last summer the various UNRELIABLE AIRSPEED events reports, and in several cases lasting for more than few seconds ALTITUDE was also directly affected (if I remember correctly, during Air Caraibes event, variations were in the range of 300 ft). Which point to the fact that whatever pressure could be "correctly" measured by static ports, Pitots failure would affect the data processing.
This may be due to ADIRUs, as I think that total pressure is used to correct static pressure at some point during the process. But the question is what data will then be used to supply the CABIN pressure controler when all ADIRUs are rejected or turned off-line ?

May I respectfully ask: how are you jumping to this somewhat dodgy conclusion?
S~
Olivier

Cabin V/S Advisory
 

Hi takata;
you are quite correct. "less than 50 ft" should read 300 ft. BEA's analysis shows the same value.

HN39

EDIT:: In the Air Caraibes case, or any other reported UAS event, there is no mention of a cabin v/s advisory.

Hi there.
@02:10Z, the crew is submerged by alarms & ECAM messages, possibly false alarms (those are not transmitted in the ACARS) like in the other past cases of Pitot failures (stall alarms most of the time, overspeed alarms occasionally), airspeeds are unreliable, no more A/P or A/T, alternate mode 2 (loss of many flight protections), no visual clues (night with bad visibility), possibly turbulent atmosphere... and lengthy/tricky procedures to implement... The anemometric failure is detected @02:10 but the failure of the 3 anemometric chains may have begun some tens of seconds before, beginning with the exclusion of a 1st ADIRU against the two others (which may have diverged in a similar/agreement fashion) ending with the disagreement between the two ADIRU remaining.
Some others have pointed out the plausibility of a crew rotation just before (@02:00Z), CPT going to rest.
At this point (@02:10-02:11), taking in account the large route variation of the AF447, wouldn't the worrying possibilities be: a bad reaction of automation (A/P) to the erroneous airspeeds before their unreliability can be detected (for example A/P & A/THR OFF with TOGA LK which would remain locked: overspeed risk) and/or drifts induced by A/P OFF (a growing bank angle, since the automation did not control it any longer), and/or the risk of overloaded attentions of the crew, stretched between procedures implementation and manual flight: as I see it, a first risk would be to badly react to a false stall alarm (frequent) meaning taking it for real and following the procedures accordingly (risk of overspeed), another risk would be not to pay attention to the growing bank angle, and let it drift in excess (say over 60°-70°) before trying to regain control. The high altitude overspeed/mach buffet has been somewhat debated on pprune, the other is similar to the Adams Air case (but less extreme: for AF 447 the roll would be controlled and the control of altitude close to be regained). Maybe there are other early (@02:10-02:11Z) risks in the chain of events ?
We now know that the crash area could be such that it imply a large route deviation (more than 135°), and a rapid descent (35000 ft over 40-50NM in less than 4mn45sec: -9° of average slope or ~7500 fpm in average). Beyond the high altitude stall/mach buffet, there are also the fully developped flat spin hypothesis, and the engine flame out. Apart the high altitude mach buffet or stall, could the terminal trajectory be explainable by a large initial roll/bank perturbation in cruise at high altitude like the Adam Air ? (possible causes: bank drift that remains unoticed due to task overload & spatial disorientation, only a wing stalls in overspeed, turbulences,...). The time needed to control the large initial bank perturbation would induce a large route deviation and loss of altitude. Maybe also that attempting to control the altitude before having controlled the excess of bank angle would be a bad reaction and would worsen the situation (Adams Air case I think). The terminal conditions described by the BEA reports (A/C en ligne de vol so 0° roll/bank, nose up/tail impact first, vertical compression) suggest that, in the vertical plane, there may have been a rapid loss of altitude initially (much larger than the average 7500 fpm, combined with the large roll pertubation, to control first) followed by a ressource (route stabilized toward E-34) in an attempt to control the altitude, close to its lowest point (vertical speed much lower than the average 7500 fpm), with an incidence (nose up) at the impact/pancacking with the surface. I think that the trajectory would pretty much look (horizontally) like the MM43's illustration (a blunt/short radius turn (with a rapid loss of altitude) and a rectilinear end (which would be the ressource attempt).
Jeff
Adams Air case: Aircraft Accident Report AdamAir PK-KKW (see page 28, the bank angle exceeded 90°, the variations of altitude -35000 ft & route: +250° in ~1min)

Scenario
 

RE: mm43 #911

mm43;
I concur with your trajectory and events, except no.5: -
If the cabin v/s condition followed engine flameout, the corresponding ACARS message would not have been sent. In my opinion flameout is a dispensable element in this chain of events.

regards,
HN39

Yes, flameout optional and not yet a given requirement, but possible?
But an excellent overall synopsis agreeing that a deteriorating lateral stability situation could have played a major part, particularly in an early and rapid course change... one also wonders whether we should postulate that the shorn-off spoilers as consequence of airborne rather than impact related stresses...

I do hope contributors will avoid trying to connect (tie-together) the actual BEA sea-surface impact conclusions with the prior (LOC) trajectory.. there is really no need to assume that partial or full control was not regained prior to impact (i.e. that flight problems at cruise can be realted to impact attitude/speed). There are many other ways the descent and the actual crash into the sea could have been connected together, without one continuous event, surely?

Also still reminding myself that this was a terrifying few minutes for so many on board and a very bad night for civil aviation generally... many lessons must be learned, and as usual, no doubt it will be found that so many should have been learnt before and lessons implemented properly so many years ago - I am sure that 'basics' are involved here that people died for long ago!

Somewhere in one of the AF447 threads, I tried to explain away the SATCOM loss of signal, and came to the conclusion that there had been a 2 x flameout. However, I am open to other opinion, and the resumption of the SATCOM link could also be explained by the APU having been started, or a start achieved on #1. The BEA's comment regarding the tail rotating to port on impact could be related to the wings level, small positive attitude and TOGA on #1 with the RTLU locked at 7.9 degrees.

If the APU had been started, would the Cabin Pressure controller have been active? I haven't seen any data on this, and have assumed that should there be no electrical supply from the prime sources that the controller would operate below 8000/7350 feet to equalize the cabin pressure.

mm43

The vessel appears to be operating in a fairly confined area, and my suspicion is that the ROV is being used at the following location:-

8 May 2010 23:18z Hdg 157.5 Spd 00.5 2°42'04"N 31°13'39"W

Refer to Post #904 for the supporting graphic.

mm43

mm43, in your graphic showing the 50 degree bank how does the time for that event compare with the loss of signal period for the ACARS data? (Sorry, I don't have the BEA report at my fingertips. I do note a sudden 50 degree bank would move the ACARS antenna off the satellite during the event. It likely would not be able to reestablish it for the turn shown until the plane leveled out again.)

{^_^}

Google Earth .KMZ Overlay
 

With the hope that a summary of known positions placed into 3D space in Google Earth might be of help, I have built a .KMZ file containing the known track of the aircraft drawn at altitude FL350 (10668 meters) and the location of the search vessel SEABED WORKER on May 8, 2010 placed at sea level. Concentric rings at 10 nautical mile increments radiate from the Last Known Position of AF447 at 0210. The area of interest (Seabed Worker) is 42.11 NM, heading 246.20 deg., from the Last Known Position. For reference, I included the excellent, if not stunning, chart by mm43 created April 2, 2010 and posted to PPRuNe (#650), scaled and overlaid onto the ocean surface:

http://i958.photobucket.com/albums/a...7/geScreen.jpg

Download the Google Earth .KMZ file here. [720KB]

Load the .KMZ file into Google Earth (Version 5). Use the Places Panel to check or uncheck the visibility of various layers:

http://i958.photobucket.com/albums/a...7/gePlaces.jpg

I will update this .KMZ file with new information after the BEA press conference tomorrow.

Good luck to all!

GB

Thanks to all and specially 'mm43' for this very interesting thread. Here goes with a very small contribution.
Day before yesterday there was an interesting article in the Spanish press, namely the 'El Pais' newspaper. Just like many other newspapers they have also used the word 'located' in their headline, which raised my hopes that the 'black boxes' had been found but the article nonetheless offers other news that has not appeared in previous posts, so here goes with a translation:

Air France Rio-Paris airplane black boxes located
The black boxes of the Airbus flying from Rio de Janeiro with destination Paris belonging to the company Air France have been located nearly a year after the accident, when it crashed into the Atlantic on 1 June with 228 persons on board. They are to be found, according to the French Ministry of Defence, somewhere at a depth of 3,000 metres in an area of about 100 square kilometres at about 1,000 kilometres from the Brasilian coast. It will not be easy to find them. "It will be like looking for a shoe box in an area as big as Paris and with a mountainous area similar to the alps." said the French Navy Spokesman, Hurgues du Plessis. The find had been given up as lost, since the black boxes only had batteries that lasted two months to emit a signal in order to be located. The delimitation of the area has come about thanks to the investigators who have newly examined the recordings of a submarine that weeks after the accident combed the area blindly (blindly=randomly?)and at the time no signals were detected. Thanks to software developed by the industrial group THALES, it has been possible to isolate the toc-toc-toc signals from the boxes. But that sound no longer exists that would serve as a guide and finding the boxes will be a miracle.
The causes of the accident are still unknown. The official French organisation in charge of the investigation maintains that the aircraft crashed into the sea and that it did not disintigrate in the air, and that Pitot tubes, curiously also manufactured by the THALES group, that measured it's speed were giving contradictory inputs. This was one of the causes for the accident. But on its own would not explain the reasons for the accident.

First, it is difficult to imagine that a highly sofisticated and modern nuclear submarine would miss 'hearing' the signals from the black boxes but much more so to accept, that while they were recording sound, they did not record their position relative to the sound recording. Perhaps they did and for military reasons this information has been restricted. If then there is a record of the submarine's position that can be related to the sound recording, then finding the boxes becomes a real possibility in a fairly short space of time and perhaps the reason why the "Seabed Worker" is maintaining a position in a limited area, according to "mm43".
The other interesting bit of news is that the pitot tube manufacturers THALES are actively assisting in the search and developed the software to 'clean' the submarine's sound recordings and be able to identify the signals from the black boxes. Obviously THALES have an interest in finding the black boxes which might assist in establishing to what extent the pitot tubes were to blame for the accident and if there were other factors that contributed to the crash.

JD-EE; 2:13:08 was ground station receipt time = 2:13:10 on handshake, and 2:13:45 is ground station receipt of next message = 2:13:41 on initiation. Known LOS equals 31 seconds. They were in low latitudes (3N) and a 50 degree bank when using the 6dB omni shouldn't have caused a drop-out. I believe the SAT was about 15 degrees east of them.

mm43

Hi MM43. One way to achieve a tight ground referenced turn radius is to accomplish the majority of the turn in the vertical. This may be indicative of a LOC incident early on.
Gimbal angle limits on a satellite antenna could well explain a drop out, but the satellite data drop out seems to be much later than the initial deviation, so perhaps a second unusual attitude at that time??? I'm still trying to make some sense of the information at hand without too much luck.
:ugh:

Tracer buoys?
 

The charts by mm43 and greatbear made me think about the role of the currents transporting debris from the impact point.

What if the first search planes on scene would as a standard practice drop, say, twenty tracer buoys (with GPS and a location transmitter) over the search area in order to map out the surface currents as accurately as possible? Then when debris is subsequently found, this "current map" would enable much more accurate pinpointing of the actual impact point.

What do you think, would this be a) useful, b) feasible for future similar crashes ? According to Wikipedia, a Brazilian SAR aircraft spotted debris about 35 hours after the crash. It is not clear if there were other search aircraft in the area before, but even so I'd assume that the more accurate picture is collected about the surface currents, the bigger likelihood of locating the wreckage.

PS: Sorry if this has been mentioned before... I had no time to scan the large number of previous messages.

High speed impact???
 

Looking in BEA's reports for information on the forward speed at impact, the closest thing I was able to locate is based on detail examination of fuselage frame segments attached to the base of the vertical stabilizer, from page 28 of BEA's 2nd Interim Report:
This led me to question the widely held assumption of 'low' forward speed at impact.

Based on the cL-AoA data posted earlier (ignoring ground effect), the following entirely hypothetical but mutually consistent numbers might be of interest for the purpose of recent scenario discussions:
Airspeed 300 kt CAS (M=0.453); vertical speed 40 fps (2400 fpm); loadfactor 2.5 g.
FPA (airdata) -4.5 deg., AoA 10.5 deg., pitch attitude 6 degrees.

HN39

Satcom info
 

The satcom on aircraft is an electonically steerable phased array antenna with nominal gain 12dB (type CMA2102). The info in BEA report re a satcom drop out is, I am reliably informed, a misunderstanding by BEA and there is no conclusive evidence of a dropout.

snowfalcon2;
Undoubtedly there will be lessons learned from this incident. Your suggestion is not new to this forum, and will obviously be borne in mind for the future - one hopes.

Bear in mind that the accident happened in a rather unpredictable part of the Equatorial North Atlantic, and even though there is satellite surface current and wind data available, the reliability of the data has not been sufficiently tested. My experience suggests that the surface current vectors - comprising both direction and speed were erroneous, and reference to other drifter data is not much help either. At low latitudes a coriolis correction may not have been needed in the smoothed data supplied. In fact, subtracting around 20 degrees from the vector angle and in creasing the velocity by 50 percent will have improved my original backtrack position enormously. I had, when arriving at that position, increased the velocity by a factor of 50 percent, and it was just the vector angle(s) that let me down.

Hindsight is a wonderful thing!

machinbird;
From Andy Tracy's A340/A330 Control: Flight Laws

Alternate 2 Pitch control laws are identical to Alternate 1. Lateral control law in roll is a direct law with a direct stick to surface position relationship. The gains are automatically set according to slats/flaps CONF. Yaw control law provides a Dutch roll damping function and damper authority is limited to +/4 rudder at CONF 0 and +/-15 in all other CONF. Turn coordination is provided with flat/slat extended. Protections are as in Alternate 1 except that there is no bank angle protection in ALT 2 and in the case of failure of 2 ADRs, no VSW prot and in the case of failure of 3 ADRs, no high speed protection. V/Mmo is reduced to 330/.82.

No turn coordination, RTLU locked, other distractions and the outcome could have been anything!

mm43

Gualala;

I note from the CMA-2102 specs that the beam switch speed is less than 50uSec and the nominal 12dBi gain should be good provided the aircraft does not get in the way. I wonder why the BEA decided that there was LOS in the times they mentioned. Perhaps one day they will correct that error.

mm43

snowfalcon2, the initial search was a long, narrow, rectangular box from the last reported position almost to Tasil, favoring the right of the expected track. A second search box was flown that day in a more square-shaped rectangle from the last known position to about half-way to Tasil.

Searches on the days following were made to the right of the track, and south of the last known position, even south of the St Peter & St Paul islands. Various sightings of possible debris led in part to searches in these areas. I believe no debris from AF 447 was actually found in the searches from June 1 through June 5.

Once a search was again done that covered the area that was left of the track, the first bodies were discovered on June 6, approximately halfway between the last reported position and Tasil. These bodies were left of the track. If the bodies had been in that location on June 1, I believe that they would have been within the boundaries of the two search boxes of June 1.

By being outside the boundaries of the initial search, they were missed.

Hindsight is always 20/20, but it is unfortunate that the search on subsequent days was devoted to areas to the right of the track. If the search boxes of day 2, which were run basically perpendicular to the right of the track (as if the aircraft had deviated right) had been mirrored by searches to the left of the track, its quite likely bodies and floating wreckage from AF447 would have been found on June 2nd or 3rd. That would have fixed the impact position a lot more precisely.

Having limited resources, a long distance to fly to the search region, the Brazilian military made the judgment of where, given the currents and meteorology, the impact was more likely to be, and focused their efforts there. In a more perfect world, they would have looked as earnestly at the area to the left of the track as they did on the right.

Update: "Seabed Worker" - position
 

Here are the latest available positions for the vessel:-

9 May 2010 11:59z Hdg 050.0 Spd 01.5 2°42'12"N 31°08'07"W
9 May 2010 09:50z Hdg 166.1 Spd 02.9 2°42'17"N 31°08'18"W

http://i42.tinypic.com/1z6y6nd.jpg

The ROV appears to be down, and hopefully the recovery of the DFDR and CVR is underway.

mm43

Sounds good, mm43. Bon courage à tous. May all our speculations soon face the moment of truth. In the meantime… ;)

Quote from mm43:
“If the APU had been started, would the Cabin Pressure controller have been active? I haven't seen any data on this, and have assumed that should there be no electrical supply from the prime sources that the controller would operate below 8000/7350 feet to equalize the cabin pressure.”

Don’t have an A330 Tech Manual, and no doubt the Cabin Pressure controller employs data from many sources, including the Air Data elements of the ADIRUs. As I think HazelNuts39 has said somewhere above, however, aircraft cabins are not designed to withstand a negative differential pressure, i.e., a lower pressure inside than out. In an unusually rapid descent to sea level from normal cruising altitude, the controller will do its best to keep the cabin altitude below aircraft altitude, by increasing the cabin VS; but may eventually be unsuccessful. In a rapid descent, we call that “catching up with the cabin”, don’t we? That’s why there has to be an inward relief valve, which is purely mechanical.

As for the readings of cabin altitude, I don’t see why even (improbable) icing of the static ports, as postulated by takata, should invalidate cabin altitude (or VS). If I was a passenger on the aeroplane, and was carrying on my lap a good old-fashioned altimeter and similar VSI, their readings would be little different from those used by the Cabin Pressure controller. Cabin pressure is cabin pressure, and is measured somewhere inside the cabin or pressure hull; nothing to do with static ports.

Unless I’m missing something, the readings should be valid, and their interesting implications follow.

Chris

Thanks mm43,

So the sharp turn at 2:10:34 or so did NOT cause a communications blackout. That came later. Communications should have blocked out during the postulated 50 degree bank for the 135 degree turn. Apparently it didn't, which is strange. And then it did blank out when the plan was apparently straight and level.

This gets more puzzling each time we get a little more data.
{^_^}

Machinbird, the ACARS antenna is, apparently, a patch style antenna with no "gimbles" as such. It's electronically steered with a very wide beamwidth. (50 to 90 degrees) It can probably be steered to within 15 degrees to 20 degrees of the antenna's plane and, of course, all the way up to normal to the antenna's plane.

What I don't know is whether the antenna is operated open loop off aircraft navigation data or closed loop with a servo. Given the wide beamwidth I suspect the antenna is simply steered off basic aircraft navigation data and the (fairly well) known satellite position.

We discussed this back in the old thread. I don't remember enough of it off the top of my head to be sure on details. But I do believe a 50 degree bank would have put the aircraft between the antenna and the satellite which was off to the West of the aircraft by a significant amount. Digging back to the original discussion should dig out the details of the antenna. I remember a posting that pointed to the manufacturer's data sheet.

{^_^}

mm43;
The #1 CPC is powered by the DC ESSential bus, the #2 CPC is powered by the DC1 bus and CPC Manual Control is provided by the DC BATtery bus.

So yes, the control of cabin pressure would have been fully available with APU and even with with no APU with manual control from the DC BAT bus.

Chris Scott is correct regarding negative pressure relief; the single valve is installed aft of the L1 door.

Takata;

Just for info....it is not possible to say without very detailed examinations and perhaps simulator investigations, that the CPCs would be affected by loss of just the 3 ADRs due to iced pitots only. I wondered about this but cannot determine it from the FCOM.

Some data may still be provided to the CPCs or it may not - the FCOM is very simplified and geared towards the flight crew "need-to-know" level. It is not entirely possible to confirm the effects of loss of just the static ports either, without a similar investigation.

Chris Scott;

Thanks for answering the question. Reference to the Cabin Pressure Controller schematic shows that in Automatic Mode the barometric reference comes from the ADIRUs, but my take is that should that reference fail, then it selects Manual and the Safety and Relief valves will attempt to keep Cabin Pressure equal to the outside when descending below 8000/7350 feet. Here's the schematic for good measure -

http://i40.tinypic.com/2iu6rex.jpg

mm43

Good to hear about the progress of the search.

What are the chances of larger fuselage pieces being found as well considering some bulky pieces were found in the initial search. Hope to hear more news soon.

Just another theory.....
 

and as HarryMann said:
Astute .... unless there were onboard electrical disruptions....

All logical and tends to point to a structural failure (i.e. a partial loss of fuselage integrity causing a pressurization loss) following the high altitude loss of control - an overstress event that would not be a surprising outcome of a high-speed loss of control and tightening spiral.

Neither would it be inconceivable that the FBW flight control's circuitry (i.e. vice designed "graceful" degradation) may have been affected physically by any loss of fuselage integrity or bus loss (==> loss of roll or pitch axis control). But partial/limited control might have been regained latterly, sufficient to enable an erect attitude at impact.That theory of two "follow-on" event scenarios, broken by a brief interlude of partial control, ties in with the loss and later regain of signal period for the ACARS data.

I tend to favour the theory that something beyond normally allowable RTL-limited rudder deflections were permitted during their unusual attitude recovery, following the airspeed anomaly and ADIRU compromise. Large unintended rudder deflections during a high-speed LoC event may have partly detached the vertical stabilizer from its mounts, or even locked the rudder at a significant deflection.

Following the LoC recovery, with a rudder stuck at a significant deflection, the yawing roll may have been able to be countered by aileron control to achieve a wings level attitude, but the overall drag, limited controllability and descending trajectory may have quickly forced a ditching solution, notwithstanding that some power may have been available. A higher speed ditching may have been predicated by the limited controllability.
.
.
Just another theory.....

Higher Speed Impact
 

Some time ago, I offered the opinion that the evidence presented by the recovered debris and reports of injuries to passengers indicated a low speed impact. BEA hasn't yet come out with much on the horizontal velocity of the aircraft on touchdown but indicated a high vertical velocity existed.
My accident scene experience is limited to tactical jet aircraft and may not apply strictly to much larger aircraft, however let me share some mental data points I used to form my initial assessment.
Situation 1. An aircraft flying into the sea in near level flight at 300 knots. Data point: A piece of a crewman's boot, specifically the heel, torn away, complete with insole, and sheared in half lengthwise leaving only the starboard side of the heel. The few pieces of wreckage recovered were generally in the 18" to 24" size range.
Situation 2. An aircraft, departed from controlled flight <250 kt, with very high sink rate impacting the earth on the leading edge of the stbd (swept) wing. Data point: Every element of the forward fuselage was shattered to small pieces and most washed out of the crater by the fuel load. The after quarter of the fuselage did not shatter and retained its characteristic shape.
Situation 3. An aircraft impacting the water at 550 kt, 50 degrees nose down. Data point: Pieces of the crew were extruded into the instruments, some instruments were shattered some just crushed. Engine shells were converted into bent pieces of sheet metal.
I cannot convince myself that an airliner sized aircraft, impacting the sea at 300 knots with a high sink rate (even if in a level attitude) would not result in damage comparable to situation 1. The large size of the recovered cabin components indicates a significantly slower touch down.
It will certainly be interesting to see what the aircraft actually did assuming the DFDR is found and contains data all the way to touchdown.

Hello everybody,
I agree with that, and like many here, I don't have access to A330 simulator and can't say a lot more about it.

Nonetheless, as a recapitulation of my point: (1) cabin pressure controler need to be feeded by external data and those data are known corrupted by (at least) pitot probes freezing with a verified error range well above 1,800 ft per min. in absolute value = 30 ft per second. (2) ADIRUs 1, 2, 3 are used to feed the controler, and all three are supposed rejected. (3) this alert (at this point) is minor, only informing the crew that cabin pressure is to be controled manually.

Consequently, it is not possible at this point of the flight (02.13) to deduct anything from this ACAR about:
1) Flight altitude;
2) Rate of descent/climb;
3) Depressurization issue.
i.e. This alert may be related to purely sensor/ADIRUs errors; it may be related to a real aircraft descent rate above 1,800 ft/mn from whatever altitude (in case external pressure is still feeded to the controler by another circuit - but whilch one?); it may be related to crew actions during troubleshooting...

But it doesn't mean that the controler was trying to regulate the cabin pressure at 7,350 ft or below. It is alerting the crew that the controler would be unable to regulate it automatically..

S~
Olivier

Pinger Range
 

DjerbaDevil:

"First, it is difficult to imagine that a highly sophisticated and modern nuclear submarine would miss 'hearing' the signals from the black boxes but much more so to accept, that while they were recording sound, they did not record their position relative to the sound recording. "

Actually, detecting these pingers under the conditions encountered in the search is not so simple. Judging from the typical characteristics of the pingers used: (see Dukane model DK120 and DK100 Underwater acoustic locating beacons), 37kHz and 30 day duration, they are most useful when a plane goes down in shallow water and/or close to shore. After all, most aircraft accidents occur in the takeoff or landing phase, and thus happen in the vicinity of airports. What is needed for deep water recovery are larger/heavier transducers at 9-15kHz (lower attenuation), and transponders (rather than pingers), which only ping when interrogated, so that they don't waste power when no one is listening. This is the usual weight/cost tradeoff that aircraft are so sensitive to.

In this case, the a/c went down in deep water far from shore. This affects the search in two ways: the mid-ocean location takes time to reach, using up part of the 30 days, and the deep water consumes much of the limited range afforded by a high frequency pinger (unless you can deploy a deep receiver).

Consider this calculation:

The source level of the pinger is 160db re 1uPascal @ 1meter.

The deep ocean ambient noise, in a calm sea-state 2-3 (4-10kt wind) at 37kHz is about 37db re 1uPa/sqrt(Hz). The pinger has a 10ms pulse length, giving it roughly a 100Hz bandwidth, so the noise is effectively summed over a 100Hz band: sqrt(100Hz) = 10 times = 20db; so, the total noise in-band is about 57db re 1uPa.

Thus the loss budget is 160-57 = 103db.

Spherical spreading from the source, in db, is 20*log10(R in meters) (because the source level is specified at 1m), and the attenuation loss at 37kHz is greater than 6db/km.

At 5km, the spreading loss is 20*log10(5000) = 74db, and the attenuation is 5km * 6db/km = 30db for a total of 104db. Thus at 5km, the signal power is about equal to the noise power. This ignores other sources of noise, such as higher sea-state, ship self-noise, receiver thermal noise, etc. Normally, a 20db signal-to-noise ratio is required for simple detection, resulting in the commonly quoted 2-3km detectable range.

Now the pingers may be at 4km depth, and the sub can only descend to some classified depth, but a published value for Emeraude of only 300m. That difference may (depending on actual pinger depth) consume over 3km of the detection range.

As for the ambiguity in location, I doubt that it is due to navigational uncertainty, but rather due to acoustic localization uncertainty. I have no idea what signal processing was done to actually extract the signal from the noise, but it would likely have involved integration over long periods of time: as long as the sub, traveling at, say, 3-6knts to minimize self-noise, would have been within a few of km of the pinger. After a long integration, one would only be able to guess the location with a resolution of roughly that integration "distance" (time, times the sensor transit speed), i.e a few km.

Hi Denis,
Sorry Denis, I missed your post. I cited the distance from memory without verifying it and from the BEA flightplan and positions (below), you are correct, speed between 0200-0210 was about 468 knots (not 473)

AF447 positions:
0210: 02°58'47"N 30°35'23"W (LKP)
0200: 01°48'00"N 31°08'59"W
0150: 00°38'23"N 31°45'36"W
0140: 00°29'23"S 32°22'11"W
0130: 01°38'59"S 32°58'47"W
0120: 02°49'11"S 33°36'35"W
0110: 04°01'11"S 34°14'24"W
0100: 05°12'35"S 34°52'11"W

So, you can make all your calculations from that.
S~
Olivier

BEA press conference
 

BEA will hold a press conference today, Monday, at 14:00 Paris time.

Good guess, but how would the controller know "outside" pressure without ADIRUs providing "oustide" pressure?
That's the bug and what might have caused this alert.
S~
Olivier

@PJ2
A320 CVR was recording Sully's cockpit conversation during their dual flameout and Hudson ditching. They were under APU, but there is no precision about FDR data. It should be the same for A330.
S~
Olivier

auv-ee;
Many thanks for the path loss calculations. I am in agreement with what you say, the only additional problem in deep water searches is the salinity inversion layers - one at 250 - 350m and if deep enough another near 4,500m.

I suspect, and it would appear to be the BEA's position, that the upper inversion layer was the barrier to the Emeraude recovering something useful above the S/N. Whatever technique has been used to to extract viable data, probably had to make use of some analogue techniques to mix something out of the noise. As I mentioned in a previous post, playing with digital analysis in a playpen of noise, is a bit of a no go area.

You might like to share your ideas on what form the Thales analysis probably took. On the otherhand, as the data was obtained by the military, we will probably never know what was actually done!

mm43

From Seabed Worker positions provided by mm43, I retrieved the ocean depth searched between 6 May and 9 May and it doesn't look to be the best place as it is fairly rugged and deep near to -4,135 m at lowest point. I'm not sure that something has been already located as the zone is still about 8 x 8 NM:

http://takata1940.free.fr/images1/search10.jpg

06 May 2010 22:18 -3,028
06 May 2010 23:54 -3,746
07 May 2010 10:33 -3,362
07 May 2010 12:12 -3,362
07 May 2010 21:08 -3,726
07 May 2010 22:44 -3,800
08 May 2010 00:30 -3,575
08 May 2010 09:19 -3,827
08 May 2010 11:01 -4,003
08 May 2010 12:45 -3,839
08 May 2010 23:18 -3,571
09 May 2010 11:59 -2,769
09 May 2010 09:50 -2,816

Cabin v/s advisory
 

takata;

as shown in the diagram produced by mm43 #946 (my thanks to mm43 for that) the negative relief valve is not controlled by the CPC. Intended as an 'emergency' backup, it is often no more than a simple mechanical device that requires no more than a negative pressure differential to open. As explained by Chris Scott, that happens when the aircraft overtakes (catches up with) the cabin, which is unlikely to occur above 7350 ft aircraft altitude.

HN39