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AF 447 Search to resume

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AF 447 Search to resume

Old 11th Apr 2011, 08:37
  #3281 (permalink)  
 
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ACLS65;

A little bit of research suggests that the "Ile de Sein" is engaged in carrying out a repair or repeater replacement to the Atlantis-2 submarine cable that links Argentina, Brazil, Canary Is and Portugal. There will be prior commitments to conclude before going on charter to the BEA, and in any case time will be required to position the ROV and all specialist personnel required for the AF447 recovery operation.
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Old 11th Apr 2011, 08:53
  #3282 (permalink)  
 
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ACARS

Would you get ACARS for major malfunctions of ailerons, flaps or rudder?
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Old 11th Apr 2011, 08:59
  #3283 (permalink)  
 
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Originally posted by auraflyer ...
... the wreckage could be on the abyssal plain. But it also suggests the pingers might have been disabled/destroyed on impact, unless there is some other reason they didn't activate.
We now have good reason to believe the pingers failed, and the Metron analysis consequently places the wreckage in the area of the Abyssal Plain.

The statistical analysis undertaken by Metron, methodically worked through the permutations, and now after the fact appears to to be valid. Irrespective, the BEA have chosen to fudge the outcome, as they do not want the site to become a tourist mecca; which is understandable. The debris field is in the Abyssal Plain somewhere in the north quadrant relative to the LKP. I don't believe the specific position is relevant at this time, as none of us has a need to plug it into a GPS.
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Old 11th Apr 2011, 10:24
  #3284 (permalink)  
 
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sd666, there is another reason I've not touched upon because it is so obvious for the ACARS transmissions to be blocked during some intervals.

Other aircraft are in the air. And they have position report messages to file. Several such could have taken place in the time window specified. I do not know the full ACARS protocol for transmission slots, transmission handshake, and who controls when aircraft send data packets are all unknown. However, two aircraft trying to send a message at the same time would interfere with each other.

Since ACARS is not an emergency sort of channel it is possible the protocol requires some form of wait between transmisson periods. During that wait other planes could request a slot. Then the satellite would designate the next plane to send a data packet. (The strategy after a packet's receipt acknowledgment would call for a small random delay with a very short time slot allocation request message being sent at the end of the delay. Planes heard would be serviced one at a time by the satellite granting them a transmission time slot.)

Regarding a spin maybe driving the satellite out of the antenna beam the satellite is geosynchronous. The antenna has a 40-45 degree cone to its 3dB or half power point judging from its claimed gain. The satellite use was probably the one just about over the coast of Africa. The plane was virtually under it in the N/S plane and well inside the satellites footprint E/W. If the plane spun fast antenna tracking would not work and it would probably go (barely) outside the beam. If the spin was a "leisurely" 2 minutes, as the gaps suggest, the beam COULD be automatically steered to maintain its aim at the satellite. (I was involved with a completely different use for Inmarsat satellites. And our antenna easily tracked something as leisurely as 2 minutes. I heard that some Arabs mounted antennas on top of their cars in Saudi Arabia and drove around using Inmarsat as their "cell phone" before there were cellphones. Cars turn. But the antenna tracked it.)

That's the basis for my doubting the transmission gaps are caused by the antenna aim being off the satellites.

On the other hand, the antenna is a patch antenna. So it's steering ability is somewhat limited to a cone about 75 degrees from vertical. A heavy bank could position the antenna so that communications was very marginal. A really severe bank could literally hide the satellite from the antenna.

One last observation I believe I noticed in the BEA report (English version) was that there were no indications of attempted ACARS transmissions that did not make it through. What I don't know is whether my mind is playing tricks on me or not. Bad aim would lead to partial messages with high error rates. That would cause them to be tossed. But the system would likely record the event as a lost message.

(Time for me to shut up. I'm getting into stuff to obscure to try to detail for probably no great purpose.)
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Old 11th Apr 2011, 10:42
  #3285 (permalink)  
 
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Here's a brief addendum inspired by a trip to Wikipedia (Inmarsat antenna locations) and PJ2's drawings.

Apparently the satellite likely in use is at about 15.5 degrees West. That means the antenna aim was on the order of 15 degrees off vertical. That means with its beamwidth if the antenna was aimed 15 degrees off vertical the opposite direction the satellite would still be well within the lobe perhaps at its 1dB or 1.5dB points ( 80% to 62% power points). Any transmissions would have been noticed.

(Visits to the Inmarsat site dug up pictures that were rather vague and no actual parking slot location. So I had thought the antenna was closer to 0 degrees via a really conservative guess.)
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Old 11th Apr 2011, 11:37
  #3286 (permalink)  
 
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JD-EE;

I seem to remember, but can't find the source right now, that:

- Somewhere in report #1 or #2, BEA says that all messages passed through the same satellite, and names that satellite. The Inmarsat site locates that satellite to the West of the aircraft.

- Somewhere else BEA says that during one of the 'breaks', the connection to the satellite was lost. Some considerable time ago, a poster on this thread disputed that, saying that BEA had misunderstood information provided by the satellite operator, and that in fact it was not established that communication had been lost in that period.

IIRC, ...
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Old 11th Apr 2011, 11:52
  #3287 (permalink)  
 
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Originally Posted by valvanuz
Would you get ACARS for major malfunctions of ailerons, flaps or rudder?
Sure, ACARS are triggered for any malfunction (minor, major) and cockpit alerts, including ACARS being inop... but nobody would receive it.
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Old 11th Apr 2011, 12:36
  #3288 (permalink)  
 
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Thanks TAkata,

If this is the case, is it safe to assume there were no malfunctions of rudder, flaps and ailerons at least until the last ACARS received (cabin vertical pressure i.e. +/- 6000ft)? If true, then no VS separation at high altitude?
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Old 11th Apr 2011, 12:48
  #3289 (permalink)  
 
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Drift below surface

Salute,
Originally Posted by sd666
In addition, you shouldn't assume that the aircraft hit the water directly above it's resting place on the sea-bed. Currents play a factor. Those current's could have caused a drift back towards the LKP completely by coincidence.
Well, a close look at the currents below surface will tell that it would be almost negligible for most of the heavy parts sinking right after impact (see, for example, this SHOM study about this spot hydrography available on the BEA site).

Consequently, the wreckage field should be pretty close from the actual crash site. Most wreckage would sink immediately with very little drift and only some of the parts with any remaining buoyancy would drift further away on the surface before sinking when its buoyancy will become negative.
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Old 11th Apr 2011, 13:21
  #3290 (permalink)  
 
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Salute,
Originally Posted by valvanuz
If this is the case, is it safe to assume there were no malfunctions of rudder, flaps and ailerons at least until the last ACARS received (cabin vertical pressure i.e. +/- 6000ft)? If true, then no VS separation at high altitude?
Well, it is safe to assume that what fault was not detected until 0214:26 was very unlikely.

But... this last advisory (cockpit ECAM signal) is about Cabin V/S (vertical speed) being +/- 1,800 ft/mn during 5 seconds.
It call for a reset/switch of the CPC (Cabin Pressure Controler).

From A330 FCOM:
To force a CPC changeover:
- Mode SEL.............MAN
. AFTER 3 seconds:
- Mode SEL............AUTO
The inactive CPC may then be reset
(check the CAB PRESS ECAM page).


What it means, then, is that the cabin pressure control was still in AUTO mode up to this point. As the CPC is also feeded by those ADIRUS (which faulted), I really don't know if any altitude may be safely deduced from this advisory alone without any following informations.

Nowhere did I read in the BEA report that this "fact" was established: that the aircraft altitude at this point was 7,350 ft (its cabin alt at cruise) or below. If it was a "fact", in my opinion, it would have been already mentioned as an evidence.
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Old 11th Apr 2011, 13:49
  #3291 (permalink)  
 
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Auraflyer

It will be interesting to see where the wreckage really is when the location is finally disclosed. I have long believed it is to the S of LKP based on drift analysis - although I am the first to admit that there are a lot of assumptions inherent in this. In the end however, the location really doesn't matter. Speculation as to the location of the wreckage was no more than a means to an end - examination of the wreckage and hopefully recovery of the boxes. The location alone can't tell us what is important - the events that led to this disaster.

One thing I am a bit puzzled about. The vessels involved in stage 3 had AIS (I remember mm43 giving us frequent updates). If phase 3 had been successful, we would learned of the location - unless of course they turned AIS off at that point. This time there is no AIS and they have not disclosed the location. Is it just coincidence, or did they make a conscious decision to deny the public this information in phase 4. If a conscious decision, why the change in policy?

I guess I can understand the reasons not to disclose the location. But then why is it they apparently didn't care in the earlier searches?

Although not searching for a conspiracy (and I really don't believe there is one), there are a few too many unusual things about the entire case.
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Old 11th Apr 2011, 14:08
  #3292 (permalink)  
 
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Yes, Olivier,

we discussed this at length some time ago. The options are:

- if the negative relief valve opened, it is irrelevant what the cabin pressure control was doing.

- if it did not open, then please come up with a mode of the CPC that would command the cabin to climb or descend at a rate greater than 1800 fpm. I believe that to be so improbable that it does not merit discussion on this thread.

PS:: In the earlier discussion you mentioned that the ATA code of the message points to the CPC. I believe the reason for that to be that the cabin pressure sensor is located in the CPC.

Last edited by Jetdriver; 11th Apr 2011 at 16:15.
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Old 11th Apr 2011, 15:45
  #3293 (permalink)  
 
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Originally Posted by tubby linton
The A332 will descend very rapidly with the speed brakes out.I remember flying into a Caribbean airfield and there was a very poor handover between the sector controllers. which kept us high.Once we were eventually cleared for descent the aircraft was descending in excess of the ASI v/s limit of 6000ft/min with the brakes out.
That's probably true for the initial pitch down when you intentionally let the speed to increase to VMO with idle thrust but soon the ROD will decrease and you certainly won't lose 36000 in 6 minutes that way.

The 330 is more known as a great glider that just wants to fly.
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Old 11th Apr 2011, 16:02
  #3294 (permalink)  
 
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mm43
in any case time will be required to position the ROV and all specialist personnel required for the AF447 recovery operation.

Yes, and in less than two months, the hurricane season starts and it will also be two years since the demise of AF447. I hope that they can recover everything they want before having to contend with the ITCZ seasonal weather. The French certainly like to takes things in a laid back manner.
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Old 11th Apr 2011, 16:06
  #3295 (permalink)  
 
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JD_EE; I agree with you in that I think there is evidence in the BEA report that the antenna was not blocked immediately prior to impact.

Therefore there is no evidence that there was a loss of hydraulics or VS prior to impact.

Takata; I don't disagree with you. My point is that there is no strong reason to suppose that an impact point close to the LKP is unlikely given that the 3D path of the aircraft between these points is unknown until the FDR is recovered and successfully read.
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Old 11th Apr 2011, 16:06
  #3296 (permalink)  
 
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Originally Posted by techgeek
A) a fully developed flat spin
B) a straight ahead "deep" stall

and why two experienced airline pilots couldn't recover from it.
Some colleagues in a 330 simulator, I say again, in the simulator, tried to exit from a full stall situation ... Very harsh, some managed, but most didn't. Slats out helped and one even used max thrust on one engine only ... Is the simulator representative of real life ?

For fuel economy, the 330 adopt an aft CG in cruise, and this does not help in case of stall.

Don't forget that a 330 is supposed to be protected from a stall, the most you usually do is to train up to stall entry and recover, or if in normal law, you watch how the protections work to avoid a stall and maintain alpha max.
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Old 11th Apr 2011, 16:20
  #3297 (permalink)  
 
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Cabin V/S message

Quote from HN39:
"...if it [the negative relief valve] did not open, then please come up with a mode of the CPC that would command the cabin to climb or descend at a rate greater than 1800 fpm. I believe that to be so improbable that it does not merit discussion on this thread."

takata and I have argued about this before, but I think there is one very remote possibility.

If at 0214z the aeroplane was still at medium-to-high altitude, a failure of both packs (or a double engine-failure) would cause a positive cabin VS (loss of cabin pressure) until the outflow valves had a chance to close. This might exceed +1800ft/min, falling (hopefully) to +500ft/min or less with the outflow valves closed (depending on the state of the door seals). Outflow valves closure might be automatic by a serviceable CPC, or by crew action if not (see the drill on takata's post).

However, I would have expected double pack failure and double engine-failure both to be ahead of cabin VS in the ACARS message hierarchy - they would be in ECAM hierarchy.
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Old 11th Apr 2011, 16:35
  #3298 (permalink)  
 
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Maybe I should elaborate on my earlier post on ACARS.

"MAINTENANCE STATUS ADR2" was transmitted at 2:14:14.

This should have been followed up by a Class 2 fault message between 2:15:00 and 2:15:14 (referring to BEA interim report). That Class 2 Fault message was not received. Since the Aircraft's orientation should have permitted sattellite communication prior to impact - that makes it likely that impact was within a minute post 2:14:14 - making it unlikely that the aircraft was at "medium/high" altitude at 2:14:14.
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Old 11th Apr 2011, 16:49
  #3299 (permalink)  
 
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Originally Posted by HazelNuts39
we discussed this at length some time ago. The options are:
- if the negative relief valve opened, it is irrelevant what the cabin pressure control was doing.
- if it did not open, then please come up with a mode of the CPC that would command the cabin to climb or descend at a rate greater than 1800 fpm. I believe that to be so improbable that it does not merit discussion on this thread.
PS:: In the earlier discussion you mentioned that the ATA code of the message points to the CPC. I believe the reason for that to be that the cabin pressure sensor is located in the CPC.
Salute,
If, if, if, hourah !
:-)
My point is that everything unproved by BEA analysis is worth mentioning. And so far, no analysis of this Cabin V/S adivisory will point at: there is only one explanation to this ACARS: the aircraft altitude had catched the cabin altitude at 0214:26 (less transmission protocole, less 5 seconds).

a) When the CPC is working in auto mode, some FMGC and ADIRUs imputs are needed (in this case, there is none and an upset would switch it to descent mode without any recovery altitude entered). Then, it is left in semi-auto mode (no FMGC/ADIRUs imput). Then, up to what speed may work the CPC in case of brutal and massive loss of altitude? (those working limits are for the full-auto mode).

b) In case of CPC problem (I'm mostly thinking about power supply due to on-going engine flameout issue); the CPC should switch to manual mode and use its built-in backup sensor (the one that you are refering at). In this case, the difference in sensitivity alone could produce an immediate altitude difference in cabin altitude of +/- 1,000 ft. While 5 seconds is enough to trigger such an advisory (+/- 150 ft difference = 30 ft/sec = 1,800 ft/mn).

So, I'm not as sure as you about its meaning, considering also that it is the last in the sequence and much more could have followed if more ACARS could be sent after this point in case, of course, that some power supply was still available for the SATCOM (or that the aircraft was not crashed).
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Old 11th Apr 2011, 16:57
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high sink rate

That's probably true for the initial pitch down when you intentionally let the speed to increase to VMO with idle thrust but soon the ROD will decrease and you certainly won't lose 36000 in 6 minutes that way.
On what ground are experts still thinking in terms of a normal descent from 36.000 feet down to the ocean?

There must have been a upset scenario pretty much from the beginning to loose that amount of height in the probable time frame. In itself its nothing more then loosing the potential energy. Itīs traded for speed and or distance in the normal flight regime, and its used up by a lot of drag and loss of altitude in a deep stall scenario nd airspeed below flying speed.

To regain the speed, the drag has to be reduced by flight control input, normaly the stabilator to reduce the AOA. For that you need a favorable CG and full stabilator effectiveness (no out of trim situation like full nose up trim).
That simplified basic probably applies to most aircraft designs. Canīt think of AB being totally different when it comes back to basic aerodynamics.

I think it is pretty sure that an upset occurred leading to low speed, high sink rate and that continued to prevail until the final end. Aircraft had been lost before for that reason and a descent rate of 6.000 feet / minute does nor look unbelievable in such a situation.

Do we know anything about the position of stabilator trim and the position of the CG? Couldīnt find it in the amount of posts.
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