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AF 447 Search to resume

Old 11th Apr 2011, 22:37
  #3321 (permalink)  
 
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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.
Consider this ... let's say both engines are spooling down for whatever reason (supercooled water droplets accumulating in the engine core - read more here ... http://www.georgehatcher.com/Ice_Cry...To_Engines.pdf) - due to the simple fact that both engines were (potentially) exposed to the same weather effect they might be spooling down one after the other without too much delay. Now I would presume, that the ACARS error message for engine flameout would be triggered below a certain N1 value.

It remains to be calculated what would happen sooner - both engines failing (thereby shedding the AC1 electrical bus and cutting off ACARS) or cabin pressure loss (no clue how much pressure is lost due to imperfect seals and a "normal" outflow valve position) amounting to cabin alt rising those 150 ft that would trigger the CABIN ALT warning.

It would be very helpful if BEA would release the position of both MLGs and both engines in the debris field - might give a good clue if the east-west orientation of the debris field is significant. Why am I so hung up on this? Simply - if the aircraft was heading east-west (or west-east for that matter) at the point of impact, yet as the material analysis shows it hit the water near wing-level it would mean that the pilots were in control of the aircraft. Unfortunately that would open new questions again :/

PS: Apologies for typos ... half asleep :/
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Old 11th Apr 2011, 22:40
  #3322 (permalink)  
 
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All agreed, with the proviso that RAT in itself would not, I think, restore enough AC power to enable ACARS messages.
Just to clarify. The RAT would (as far as electrics go) only power the AC ESS and DC ESS buses, so the ACARS subsystem would remain unpowered.
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Old 11th Apr 2011, 22:41
  #3323 (permalink)  
 
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CPC

PJ2;

HN39 has already asked the question regarding valid ADR info to the CPCs. In the circumstances surrounding the various ACARS messages, e.g. NAV ADR DISAGREE, and it appears that at least PRIM 1 and PRIM 2 were switched off, possibly in an attempt to reset. Do you believe that in the probable circumstances at 0214, that the CPCs were receiving valid ADIRU data?

I'm thinking that in the fail safe situation that the pressure relief valves, once triggered could possibly be configured to also initiate the Cabin Vertical Speed Advisory. Any thoughts?
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Old 11th Apr 2011, 23:45
  #3324 (permalink)  
 
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Originally Posted by sd666
What evidence is there of a power supply failure?
The only evidence is the absence of a Class 2 status message. This would require the loss of both power sources within a 60 second window. It's possible (so BEA rightfully list it) but unlikely - there's redundancy in the power supply.
Evidences might only be found in the deep of the ocean; we'll only see some evidence once the recorders will be recovered and analysed. But it is exactly the same as for any other explanation so far (deep, spiral, flat, spin stall, vertical stab loss, one, two or three upsets, crew asleep, turbulences, updraft, downdraft...)

All we've got is very few facts and hints that we can try to put together:
a) attitude at impact.
This aircraft impacted the sea without any external sign of an upset attitude beside the loss of forward speed. If, at impact time, it was outside its flight enveloppe, it is mostly due to this lack of forward speed. Consequently, the lack of thrust can not be ruled out.

b) Impact time.
Determining the time at impact is only based on the probability of the ACARS sequence stopping between 0214:26 and not later than 0215:14; on the other hand, a dual-engine flameout after 0214:26 would have caused exactly the same effect: a dual-engine flameout = EMER ELEC re-configuration, and in this case, the SATCOM become inoperative and no more ACARS would be sent if the engines do not recover.

c) ACARS.
Something very serious was still in progress: F/CTL PRIM1 and SEC1 faults at 0213:45 and 0213:51, with a spacing of 6 seconds between both ACARS, mean that it happened simultaneously. Such a reset of both flight computers -primary and backup simultaneously- is not possible without an associated fault which was never transmitted. It certainly was not due to the crew manual reset as it is contrary to the basic safety rule: never reset both fligth computers at the same time => you'll be left with those mechanical flight control only (trim, not even direct law). Then I think it was likely due to some change in the power supply configuration, and those ACARS which should have followed in the later sequence might have been interrupted by the lack of SATCOM once in EMER ELEC.

d) Indirect ACARS hints.
There is plenty of ACARS linked to the ADRs faults but none about the engines state. If the aircraft departed and stalled during 5 minutes, this is very unlikely that none of the engine will suffer any failure, due to this (low speed?) stalled flight attitude, while none was ever transmitted all along the sequence. No flameout, no engine stall detected. Nothing about the powerplants which were running in manual thrust and were also feeded by the same corrupted air data.

e) Ice and rain.
At FL350, the presence of ice particules is clearly demonstrated by the pitot icing. If we still can not be sure of the real weather encountered at this level along F-GZCP path -she can fly above or between active cells like in many other cases of pitot icing recorded in tropical atomosphere- this is pretty sure that down below her, there was both ice and rain (beside any possible turbulence level). Now, her powerplants could also have encountered troubles with ice and rain, as demonstrated by many other events with similar engines mounted in various airframes.

Originally Posted by sd666
Good point, though I'd still argue you've got auto re-light and RAT as protection layers. All-in, I think dual-flameout is not a high probability.
The probability to lose an A330 from cruise level in the middle of the Atlantic was considered much more than pretty slim before this event. Nevertheless, one was lost.
Anyway, concerning a possible engine dual-flameout, see my post several pages back citing an Airbus to customers communication.
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Old 11th Apr 2011, 23:52
  #3325 (permalink)  
 
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1. French government monopoly 2. Captain in control

I am very surprised that there is not more concern in this forum about the fact that French government entities have control over the recovery and analysis of the wreckage. They have already been far too elusive about the mapping and identification of the debris field. I have only seen one rather oblique reference (sorry, can't recall where) to the tail section of the plane, and therefore the CVR and FDR, being in the debris field. If images of the tail section were released, it may create expectations about the condition of the recorders and the likelihood that their data will be intact. It concerns me that those images have not been released and that no statement has been made about the damage or lack of damage to that part of the plane. It leads me to wonder if the French government does not want there to be any expectation about the integrity of the data. In this forum it has been stated that the French court will have control of the recorders as sealed evidence. How do we know this?

Point 2: I have never piloted a powered aircraft but my issue here concerns commonsense rather than piloting skills. When there is an accident there is more often than not some sort of human error involved. As a regular paying passenger I have to say that I have faith in the technology but grave suspicions about the people up front. Many correspondents to this forum will be flight crew and may like to comment on my concerns, which are as follows: to me it is almost inconceivable that a captain would take a nap during the time at which the plane is traversing the tropical convergence zone, where it is known by all that there is elevated risk. Surely commonsense would dictate that the captain take the precaution of being in control at the time. If anyone believes that it is okay for the captain to take a nap during a period of the flight when there is a risk of an upset, doesn't that suggest that some pilots have become far too complacent about their responsibilities?
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Old 12th Apr 2011, 01:52
  #3326 (permalink)  
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HN39, you're welcome...as I say, some meandering thoughts which may strike chords with others and take us forward.
Would that information coming from the ADIRU's in ADR DISAGREE mode be considered valid by the CPC's?
I'm keeping in mind that the ADRs themselves haven't failed but are receiving erroneous pitot data which the ADRs are rejecting, and the SDAC (or FWC) is creating the disagreement message. I'm not sure if ADR data transmission stops because of this, or downstream users are "told" that the data is bad, or that any further error detection and use of data downstream would be made independent of the ADRs with the equipment responding with error messages of its own.

Without further research, I would have to say that the ADR static pressure data would still be valid and providing the ADR pushbuttons remained ON, available for use downstream of the ADRs, but it's a question I can't answer. I'll keep looking.


mm43,
I'm thinking that in the fail safe situation that the pressure relief valves, once triggered could possibly be configured to also initiate the Cabin Vertical Speed Advisory. Any thoughts?
Just to be sure, the PRIMs don't send data to the CPCs. I'm not sure if recycling the PRIMs would have any effect but I doubt it.

Understand the thinking on the safety valves. As I see them at the moment, they appear to be mechanically driven, (spring-loaded poppets) by differential pressure, (positive, and negative - the negative pressure relief valve mentioned earlier is additional, due to the volume of the fuselage), with electronics monitoring position for the CMC. There is no description of, nor does there appear to be any other mechanism which would drive the valves open through other means, (in either direction).

Last edited by PJ2; 12th Apr 2011 at 04:07.
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Old 12th Apr 2011, 02:35
  #3327 (permalink)  
 
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Translation of Update on 2010/04/11 meeting between BEA and family representatives

Good mmorning all,

With reference to post #3325/11 april by auv-ee pse find hereunder a revised translation of the french article published in "Tour Hebdo".

Thierry Mariani, Secretary of State for Transport and Jean-Paul Troadec, Director of the Enquiries and Analysis Office (BEA) for the safety of the civil aviation, met today with the AF 447 Rio-Paris victims families information commitee together with the representatives of the Gendarmerie's Air Transport section and the Gendarmerie Nationale's criminal investigation institute.

The families and the BEA were able to discuss the organisation of the recuperation of the wreckage, one week after having been located. The ship " Ile de Sein", belonging to the french Group Alacatel Lucent in charge of the recuperation of the wreckage, will depart Cap Verde on 21 April without any families representative on board so as to "not affect the judicial procedure".

The ship is due to come back mid-june. The priority will be given to the technical enquiry and, if found, the recuperation of the flight recorders. The families have also been advised that attempts will be carried out to recuperate some victims bodies in order to meet the judicial enquiries. If it is at all possible to recuperate them, they will be identified in France and given back to their families asap.

"The operator's schedule given today can be modified if the recuperation operation requires more time", said Thierry Mariani. During this meeting the Secretary of State presented Philippe Vinogradoff, new ambassador for the relations with families, appointed by the government in order to be the sole interlocutor between the victims families and the various authorities of the concerned countries.
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Old 12th Apr 2011, 03:01
  #3328 (permalink)  
 
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Re: Bleeding Speed Fast
I leave to your imagination why such an action would be taken.
Svarin, are you hinting at a Vmo/Mmo caused pitch up? I believe we discussed that a while back and came to the conclusion that we would need the black boxes to validate that concept. The information available presently is not sufficient to say yes or no, but the concept is not ruled out. At least it could account for some of the time before AF447 started down like a falling safe.
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Old 12th Apr 2011, 04:05
  #3329 (permalink)  
 
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It's been over five months since I've posted on pprune. Been regularly reading some forums and threads of course; this one for professional interest, and JB for therapy.

I shan't comment on any technical aspects regarding the upset and loss of AF447, as there are others who continue to do a much better job of that than I could. What I will advance is the postulate that the action (or inaction) of the flight crew likely had a great deal to do with the initial upset (as opposed to the intial upset being a direct result of technical factors).

There are certainly indications that the crew were (for reasons yet unknown) not being proactive during the 30 minutes or so leading up to the departure from controlled flight (lack of position reporting or other communications from the flightdeck, for instance). Human behaviour research tells us that if such was the case, then a reasonable assumptive progression from that goes one of two ways: 1, The crew were too busy with other duties, or 2, they were also not being proactive in other areas also for whatever reason(s).

There is no reason to suspect that the crew were overwhelmed with other activites in the half hour prior to the first ACARS, therefore postulate 2 is more likely. So, the suggestion that the crew did not take any action to address a deteriorating situation is worth discussion. Remember that the conditions that we are aware of on the flight deck (through ACARS) tell us there were significant events but none significant enough to explain the loss of the aircraft).

There is strong (circumstantial) reason to believe the Captain was not on the flight deck. Additionally, as all flight crew members know, there are a variety of reasons why:
1 There may have been only one flight crew member up front for ten minutes or more
2 There may have been two crew members up front but only one actually "in the loop".
3 There is even the possibility (documented in past occurrences) that there was no functioning crew member up front (nodding off, severe turbulence causing injury, etc).

I am not suggesting a specific reason for the lack of action (as there is clearly no evidence yet to do so) but I am suggesting that to be overwhelmed, such that the aircraft is lost, points to being caught way off guard. Which in turn points to an environment on the flight deck that was, shall we say "less than SOP".

Such a situation may also provide clues to why the passenger cabin seems to have been unprepared for whatever occurred.

Simply sharing thoughts...
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Old 12th Apr 2011, 05:03
  #3330 (permalink)  
 
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HazelNuts39, if it was the satellite to the west that would be the one at 53 West. That would increase the angles to maybe the 3dB or half power points on the antenna pattern. That might be enough to prevent a message getting through. But it'd leave footprints of the attempt.
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Old 12th Apr 2011, 05:22
  #3331 (permalink)  
 
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Chris Scott, I believe it's pretty clear the VS was with the plane until impact or very nearly to impact (15 seconds or less). The is no reason for the plane in a level attitude to lose contact with the satellite as long as it had power.

If the plane was in the last 15 seconds of its flight with the VS still attached, please describe how it came off before impact.

If the engines flamed out at altitude I suppose it is possible for the plane to sink in a power lost condition to the surface at that time. But, how does the CPC malfunction to provide the messages received BEFORE the engines flamed out? It seems messages would be a different order in that situation. (Recent discussion has me believing a double flame out would cause loss of power to the ACARS system. But, this would not be a total loss of power to the aircraft. I believe CPC and controls are the last items to go as power reserves and the aux generation capabilities on the aircraft die.)

Regardless, obsessing over VS falling off the plane because God swatted at it is not meaningful. That was not the beginning of the chain of events that ended AF447's flight prematurely. It would be an effect rather than a cause.

Note:
We may be able to establish a little bit more. If both engines flame out does that affect (or effect) oxygen mask deployment. (Would lack of power prevent deployment or would its loss cause automatic deployment?) Is there anything we can infer regarding presence or absence of power on the plane by the fact that the masks had not deployed?
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Old 12th Apr 2011, 05:31
  #3332 (permalink)  
 
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Quoth takata:
b) A power supply failure after 0214:28 could have stopped the ACARS transmission. Consequently, the crash time canot be acertained from the end of ACARS alone.
One can infer, however, that until the end of the ACARS transmissions less about 10 seconds or less the VS was still attached. Therefore one can also infer that a VS detachment did not doom the plane as it was already doomed at the earliest possible time for its departure form the plane.

That, in itself, says a lot, I believe.
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Old 12th Apr 2011, 06:29
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Hi Grizz. Good to see you again.

I agree that there the human factors are likely to have been very important. Possibly more important than the hardware.

At some stage, did both pilots drift off too sleep. We have all drifted off to sleep without meaning to. It shouldn't happen when flying a plane, but it has many times. Middle of the night, apparently routine flight, and disrupted circadian rhythm. All the ingredients are there.

If we get useful information from the CVR/FDR then all these questions will be answered. If we do not however, then we will be left with the following:
1. All the knowledge we had prior to discovery of the plane, which was inconclusive and fitted numerous theories
2. The location of the wreck. This is pretty close to the impact point. It would have sank fairly quickly and the subsurface currents are not that strong. The the wreckage is a very close approximation to the impact point.
3. The wreckage - which has already confirmed not a high speed impact with the water, which most people had accepted already.

So the only new piece of information to incorporate into existing theories will be the location.

Based on existing knowledge and an impact close to KNP, how does the following scenario sound?
1. Both pilots drifted off to sleep. Didn't avoid weather. And missed some radio calls (although there are other explanations for this, these explanations don't incorporate the failure to deviate around weather).
2. Pilots suddenly wake due to turbulence. Confusion about what has happened, concern about the present situation of the aircraft, and also concern about the implications for them. None of this makes for clear thinking in a hurry. Not difficult to imagine almost a panic situation.
3. Radar looks very threatening ahead.
4. Thinking "at least we came through what is behind us", and so a decision to perform major change in heading. 90 degrees or possibly even more.
5. Sudden upset, loss of control, and inability to recover.

This explains lack of preparation of cabin - CC seats not occupied, and lots of unrestrained pax.
A significant course deviation (reversal) may also explain the location close to LKP, and where all that energy (both kinetic and potential) went.

Again, we all hope the recorders will reveal all. If they can't be recovered (or if data can't be recovered from them), then we will be left with the best theory that fits all the knowns. And the location will be one of those knowns.
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Old 12th Apr 2011, 06:31
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Having recently experienced severe probe icing while avoiding CB at high altitude I can understand how the AF crew would be struggling to understand what was happening and might have been distracted from their avoidance of active CB tops. I would be interested to know more about the A330 radar control panel as fitted on this aircraft. Does it have an auto tilt function? If not, failure to reset the tilt manually to a cruise setting at top of climb might have meant that CB radar returns were not seen or correctly presented. An inadvertent CB penetration while coping with probe icing problems could easily lead to a big upset.
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Old 12th Apr 2011, 06:41
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Grizzled,

A330 fleet has logged 18.000.000 flight hours since its entry into service back in 1993 with only two hull losses (AF447 and the Afriqiyah one in Tripoli) with casualties.
Of course, it will have been better for all the poor souls on board those two flights that they did not occur.
Anyway, with such figures, we can surmise that this particular A/C type is basically safe.
We all know in this business that today accidents involve more and more human factors, including of course the interactions between pilots (one type of culture) and systems designed by engineers (one other and very different type of culture).

Therefore, it seems logical to come back (as other posters have done already) to the behaviour of the pilots during this flight.

Even if I am not as radical as you regarding this behaviour (I think they were alert due to the forthcoming crossing of the ITCZ), since some weeks after the accident, I have been musing over the following lines :
- either the pilots took the wrong decisions / actions as they were misled by corrupted data / information coming from the (in)famous iced pitots,
- or the pilots were overwhelmed by the volume of information to be dealt with (not lucky enough to have five brains in the cockpit as in the QFA A380 last November) and were not able to take the good decisions / actions on time.

Please bear in mind that none of these possibilities is from my point of view an attack on the professionalism / competencies of the two pilots in the cockpit (whether the Captain was there or not).

And that's why I am much more interested in the CVR than in the DFDR ... hoping anyhow that both will be found and decoded.
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Old 12th Apr 2011, 06:49
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Again with the fin!

Ok everyone seems convinced that the fin departed on impact with the water. I still ask - why? Most of the claimed evidence seems to be of the sort "nothing else could so tear up the supporting structure" - but do we know that? Composite materials fail explosively as the tremendous locked-in stress energy of the layered and bonded materials is released - so there is plenty of energy around to do a lot of damage. Also - there are no scores, scuffs, or other marks on the fin to indicate it collided with any of the rest of the disintegrating structure - why? We would have maybe the only case ever of complete destruction of an airframe without significant exterior damage to one of its largest members.

Perhaps I am being dense, but I fail to see how everyone can be so certain.

edit: yes I am aware of the notch taken out of the lower end of the rudder - something to be expected if the fin departed rearward in flight! Of course that will show on the tail cone should it be found.

Last edited by deSitter; 12th Apr 2011 at 07:18.
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Old 12th Apr 2011, 07:13
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Originally posted by deSitter ...
We would have maybe the only case ever of complete destruction of an airframe without significant exterior damage to one of its largest members.
Without getting into the examination of the damage done to the Vertical Stabilizer's mounting hardware, the rhetorical response is, "Please explain why the V/S would not suffer any exterior damage if it had fluttered down on its own from altitude?"
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Old 12th Apr 2011, 07:21
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That's easy, we have an example with AA587, whose fin was torn off by aero-forces and fluttered into Jamaica Bay. The rudder was lost, but otherwise the fin looks as good as new (from the attach points upward).

Indeed, the question arises in my physicist's muddled head, what is the maximum possible impact speed that will leave a fin in shiny new condition? And surely this speed will be gentler on the rest of the airframe than the evidence suggests.
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Old 12th Apr 2011, 07:30
  #3339 (permalink)  
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777fly;
I would be interested to know more about the A330 radar control panel as fitted on this aircraft. Does it have an auto tilt function? If not, failure to reset the tilt manually to a cruise setting at top of climb might have meant that CB radar returns were not seen or correctly presented.
A lot has been said on this and the other two AF447 threads on radar.

Information provided airline crews on radar systems and effective use is at best parsimonious and at worst, ineffective. I wrote about this on the now-locked thread a few days after the accident, wondering if it was as simple as that and all the rest were details.

I'm not sure what you mean by "auto-tilt". In all radar installations I'm familiar with, stabilization is provided by the ADIRS; -at zero tilt the antenna is always oriented to the horizon regardless of pitch attitude.

Typically for those new to it, understanding radar begins with the idea of a flashlight and it's beam width and what it will and won't light up at various distances.

Most FCOM's don't tell crews how to use radar. Many here will know this, but for those who haven't used radar, (from the manufacturer) the beam width for the A320 and A330 is typically 2.84deg, (1.42deg above, and below, center).

One uses the 1:60 rule to determine how far below or above one's FL the returns are and judges passage through a line such as the one seen that night, appropriately. The bottom of the beam at a two-degree down-tilt at 60nm is at 2 x 60 x 100 = 12,000ft below aircraft level, approximately!, (and the top is about 5000ft above the horizon!)

A 2.84deg beam is always 17,000ft wide at 60nm, (2.84 x 60 x 100), double that at 120nm, and remember the beam is weaker. At zero tilt, one is scanning about 8500ft above and below the horizon. So one has to scan up and down to learn what's ahead.

In other words, one doesn't leave the tilt set but, using the above simple information, scans up and down, using small tilt adjustments and even using manual gain for a few sweeps to understand what's ahead. One knows about blanking, about where turbulence will be found, about what does and does not show up in the returns, etc.

Unless things have changed in the last few years, none of this is taught or even mentioned formally. One has to seek the knowledge out and then put it to use and learn. Dave Gwinn (RIP) had a great course on radar at one time. I know there are others now.
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Old 12th Apr 2011, 07:45
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damirc:

"ust to clarify. The RAT would (as far as electrics go) only power the AC ESS and DC ESS buses, so the ACARS subsystem would remain unpowered."

I appreciate that a RAT wouldn't power ACARS - but it would provide hydraulic and electrical power to continue control of flight control surfaces.

To date; we don't have evidence of dual-flameout, but we do have evidence that the sensor system delivering airspeed, altitude and AoA data to the pilot suffered from icing and was unreliable.

Data so far points to it being it more likely that the aircraft was stalled into the water under power, rather than a scenario where both engines flame out almost simultaneously (without fuel starvation) and auto re-light also failed. We know it wasn't a planned ditching attempt, since lifejackets were found in their containers and flaps were retracted.
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