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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 11th May 2011, 23:23
  #1181 (permalink)  
 
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From article linked above:

"Only 50 bodies floating on the surface were recovered when the plane crashed 1,500 miles off the coast of northern Brazil on June 1, 2009.
Another 178 are still missing and up to 100 of those are thought to be inside or around the wreckage itself."

78 passengers unaccounted for in the wreckage or recovered. Is there another portion of the wreckage somewhere else than the main field??

It will be interesting to see if they report that the entire wreckage is indeed accounted for, or if there are some significant fuselage sections missing... Could shine some light on the not-intact at impact theories...
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Old 11th May 2011, 23:32
  #1182 (permalink)  
 
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Machinbird

Thanks for that Turbine D. Can that be interpreted that you consider it improbable that AF447's engines would become stalled, even at high Angle of Attack? I know that engine technology has come a long way since Davies described an aircraft flaming out both engines while locked in a deep stall.
Yes, I would say it is improbable the engines stalled. Today's digital electronic engine controls enable more variables to be controlled to prevent stalls verses engines that do not have this type of control system.

From the BEA Interim Report # 1, Page 20:
The engines were subject to real-time monitoring in the framework of the engine condition monitoring program. Examination of the data recorded, including the data transmitted on the day of the accident, shows that both engines were functioning normally.
I don't think they would report this if there any suspicion the engines were a part of the high altitude scenario that took place. BAE has been very cautious to report only confirmed factual items.

TD
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Old 12th May 2011, 00:21
  #1183 (permalink)  
 
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TurbineD

Yes, I would say it is improbable the engines stalled. Today's digital electronic engine controls enable more variables to be controlled to prevent stalls verses engines that do not have this type of control system.

From the BEA Interim Report # 1, Page 20:
Quote:
The engines were subject to real-time monitoring in the framework of the engine condition monitoring program. Examination of the data recorded, including the data transmitted on the day of the accident, shows that both engines were functioning normally.
I don't think they would report this if there any suspicion the engines were a part of the high altitude scenario that took place. BAE has been very cautious to report only confirmed factual items.
It takes some reading between the lines to interpret this.

Does the comment about "monitoring data transmitted the day of the accident" include every minute of the flight or just periodic sampling?

Modern engines have been reported to have stalled even with the aircraft operating normally at high altitudes, from ice pellets associated with the tops of storm activity.


While the engines may not have been part of the high altitude scenario, were they operating when the aircraft hit the water and therfore would have been part of the crews attempts at recovery?
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Old 12th May 2011, 00:37
  #1184 (permalink)  
 
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"Only 50 bodies floating on the surface were recovered when the plane crashed 1,500 miles off the coast of northern Brazil on June 1, 2009.
Another 178 are still missing and up to 100 of those are thought to be inside or around the wreckage itself."

78 passengers unaccounted for in the wreckage or recovered. Is there another portion of the wreckage somewhere else than the main field??
You can be pretty sure they had found all the wreckage at the conclusion of phase 4. They located the wreckage very quickly and certainly had the time and the budget to keep looking if there was a major piece missing.

They would not have found all the bodies on the surface. Remember it was a huge search area, and it was out in the middle of the ocean so they were searching by ships and fixed wing only. A body is not that easy to see from a fast moving aircraft, and you can only see a couple of hundred metres at best from a ship.

This is yet another good reason to leave the remaining bodies undisturbed. Were they to recover all bodies, there would be angst among the relatives while waiting to see if their loved one was recovered. Better to avoid that scenario.
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Old 12th May 2011, 00:42
  #1185 (permalink)  
 
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jcjeant
Other than an academic point of view .. what is the importance of the "trajectory" when a/c hit water or a/c heading for the investigation of the accident ?
At this point in time it is becoming less important since many of the "high value" items have been located, however the aircraft heading at impact is preserved in the wreckage trail, and once known can be used with some success to infer locations of specific items of the wreckage, even those items not visible in the mapping of the wreckage. If DFDR data is not available, then many seemingly inconsequential portions of the wreckage will be needed to infer what happened.
Once (as we all hope) the data is read successfully, they may be looking for specific items to further define what happened. Until the data collection phase of the investigation is over at the wreckage site, the more known about the impact conditions, the better.
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Old 12th May 2011, 01:00
  #1186 (permalink)  
 
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It could be the c.g. I tellya!!! If that plane had a c.g. further back than it normally used, the thing could easily settle into a fairly stable deep stall if its pitch attitude was steep and then it ran outta air molecules for the tail to work with - just like the Viper.
Indeed, this was discussed as a possibility that the (somewhat) aft (cruise) c.g may have played a part in any instability, in early posts to the original R&N AF447 thread

The c.g. was not further back than it normally used though, it would have been a normal aft c.g. for trim drag reduction, achieved using the tail trim tank.
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Old 12th May 2011, 01:05
  #1187 (permalink)  
 
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Machinbird is right: it is perverse to suggest that the aircraft heading and track (and from them, allowing for the surface wind, the degree of sideslip) at impact are irrelevant.

It is also presumptuous at this stage to assert that the heading was necessarily random, wandering, and completely outside the control of the PF. In the absence of FDR data, it might give some indication of the minimum track-mileage from LKP to impact, and hence an idea of the mean angle of descent.
 

Quote from HeathrowAirport:
"There are two flights from Cayennes tonight. SOCA-LFPO...
...Does anybody know which flight they are going to be on?"
Preferably not the same one. Presume the QAR cassette/card, if found among the retrieved avionics-rack, would not have been sent to Cayennes yet?

Quote from The Telegraph (London):
"Robotic underwater cameras have shown many victims still intact in their seats in the smashed fuselage of the Airbus A330 jet from Rio de Janeiro to Paris.
But both those bodies recovered had disintegrated while being raised through warmer water and stronger currents to the surface, rescue officials said.
Now two Paris judges overseeing the recovery operation have said more decomposing bodies should not be brought up from the wreckage."

I wonder if loose bodies could be placed in an open-topped tank
say, 2m x 0.7m x 0.7m (weight 1 tonne plus the weight of the tank itself)
to bring them aboard ship in cold water.
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Old 12th May 2011, 01:20
  #1188 (permalink)  
 
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HN39
Quote:
Originally Posted by Machinbird
For a mental picture, imagine dumping a bucket of dirty water into a clear lake. The initial interface between the two would look something like an inverted mushroom.

Your intriguing model kept lingering in my mind. If your bucket was filled with pebblestones instead of dirty water, would they 'mushroom'?
Yes, but not to the same extent. What is necessary is to "entrain" water between the stones to begin the process of distributing the energy to the adjacent "uninvolved" liquid.
Without entraining-you effectively have a solid object (like a spear or torpedo).
In a high speed impact, the entraining process goes on for a longer time and at higher energies and results in more wreckage to wreckage impacts. The level of destruction is impressive in these situations.
HN39, With regard to your 8.5 meter radius around the engines. How did you choose that particular figure? Your transverse line concept should be fairly accurate.
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Old 12th May 2011, 01:32
  #1189 (permalink)  
 
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Chris
But both those bodies recovered had disintegrated while being raised through warmer water and stronger currents to the surface, rescue officials said.
Now two Paris judges overseeing the recovery operation have said more decomposing bodies should not be brought up from the wreckage."

I wonder if loose bodies could be placed in an open-topped tank
say, 2m x 0.7m x 0.7m (weight 1 tonne plus the weight of the tank itself)
to bring them aboard ship in cold water.
I really think that what is likely happening is that evolved gasses in solution inside the bodies is literally blowing them apart on their way up. Sort of like a terrible case of the bends.
All that the people on the ship know is that the bodies look one way on the bottom and quite differently on the surface.
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Old 12th May 2011, 01:41
  #1190 (permalink)  
 
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Hi,

I am very ignorant about flying, but a little less about physiology. Imho, THE problem with recovering people is about pressure. Even around 4C, there are some chimical processes. And many decaying processes involve gases* formation. The only way to recover bodies without inconvenients would be to pull them up very, very slowly to give time to gasses to dissolve. May be days, perhaps weeks: dive computers don't give time for this kind of depth!

*and perhaps even solids as methan ice, which will sublimate at low pressure.
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Old 12th May 2011, 01:56
  #1191 (permalink)  
 
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Shark bites

EE: I'm not convinced. The word etrange is an adjective, directly following the noun (requin) that it modifies. The french is clear "unknown shark" (and the French language does not tend to suffer from the zillions of grammatical 'exceptions to the rule' that we live with in English).

The original French is written in the singular 'un requin etrange' (an unknown shark). However, it is also possible that the author intended this to be read along the lines of 'an unknown shark species. In this case, probably not because there is a mystery species out there, but more likely because there was not sufficiently strong evidence to implicate one species or another...

Enough on the sharks. Back to the fascinating technical theorizing that draws this SLF (and pilot wannabee) to PPRuNe every day....
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Old 12th May 2011, 01:56
  #1192 (permalink)  
 
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The c.g. was not further back than it normally used though, it would have been a normal aft c.g. for trim drag reduction, achieved using the tail trim tank
However that assumes parameters expected in a cruise regime.

If that normally stable attitude is upset for anyone of the various reasons already suggested, and we now have an a/c with a much higher angle of attack and a much lower airspeed than was ever reasonably envisaged in that trim configuration, then the influence of a rearward C of G may have a much greater effect on what the aircraft does and whether it is able to respond to corrective control inputs.

I'm out of my field here, but I do work with aircraft where C of G can be critical, especially in the aft region. That's all I wish to say other than to congratulate all contributors on the quality of depth of their discussions. I feel privileged to look on, and I apologize for my comments if they are inappropriate.

FOR

Last edited by FullOppositeRudder; 12th May 2011 at 03:55. Reason: clarification
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Old 12th May 2011, 02:17
  #1193 (permalink)  
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Center of gravity and control effectiveness

Salute!

Well, Harry, I joined the forums soon as I could when the plane was lost. Long time FBW pilot, and I was "interested".

The planes with the relaxed static stability can easily tread where no other planes and pilots have dared to tread.

I have a problem with "certification" of such a beast unless I am assured that there are mechanisms to keep the c.g. within the capabilities of the basic aerodynamics that may be encountered and the available pilot/crew inputs when things turn to worms.

The jet I flew only had one such fall back mechanism, and we couldn't even use the switch unless our AoA was far beyond the normal limits of the flight control computers.

Flying about with an aft c.g. that previous designs could not handle without a FBW system is inherently risky. I fully realize that mission determined my jet's control laws, as it did for the Airbus. OTOH, there comes a point where the pilot/crew must use the system in a way that is not allowed for when things go beyond the design spec. As I said, I am against manual override except for one or two conditions where the computers get bad data or the plane is in a condition not envisioned for "normal" flight control laws.

I would not rule out an out of limit aft c.g. as a contributing factor. Hell, the "normal" aft c.g. scares me.

I would like to see the pitch moment graph that I put out for the Viper compared to that of the Airbus. Anybody here has such a graph?

respectfully,

Gums sends...
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Old 12th May 2011, 03:08
  #1194 (permalink)  
 
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Lets leave it there

both those bodies recovered had disintegrated while being raised through warmer water and stronger currents to the surface
Without going into detail, there were a number of cautions raised in this forum and doubtless elsewhere about retrieving bodies underwater for two years. I suspect the judicial authorities in charge have now seen the validity of these cautions.

Retrieval of bodies in this state can be very hard on those involved, and it's likely completely impossible to treat such remains in a dignified manner.
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Old 12th May 2011, 03:37
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Cool

Hi,

Chris Scott

In the absence of FDR data, it might give some indication of the minimum track-mileage from LKP to impact, and hence an idea of the mean angle of descent.
I must be dumb .. lol .. as I don't understand ..
If the "heading" of the plane at sea contact is the same (or like) of the one of the normal route .. or if the "heading" is reverse of the normal route .. or even perpendicular of the normal route ... what this would indicate about angle of descent .... or track-mileage
Before the impact (at any "heading") the plane can (in the time running from altitude LKP to sea) had take many different headings .. and many different rates of descent .... and many different angles of descent ...
I don't see how find the track of the plane if I know the altitude LKP and the time to impact and the heading at impact ...
With these 3 data only .. the equation cannot be solved
There are many more unknowns

Last edited by jcjeant; 12th May 2011 at 03:54.
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Old 12th May 2011, 04:17
  #1196 (permalink)  
 
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With these 3 data only .. the equation cannot be solved
There are many more unknowns
Bingo! [how do ya say that in German?]
More data soon to come.... that's all we can hope for.

Last edited by 3holelover; 12th May 2011 at 05:30.
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Old 12th May 2011, 04:57
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Originally Posted by JD-EE
What are the noise power characteristics vs frequency for 100Hz through 100kHz. (I understand 100kHz is basically down to thermal noise levels.) And I'd LOVE to know some transducer sensitivity characteristics. Alas, I don't know where to look for this data.
I assume you are asking about the ambient noise of the ocean in the 100Hz-100kHz range. I don't have a copy handy of "Principles of Underwater Sound", Robert J. Urick. Over that wide a range the answer is complicated, because different effects and sources dominate the noise in different bands. Generally the noise decreases from low frequencies to high, and then above 100-200kHz, it starts to rise again as the thermal noise of the water becomes dominant. I have a chart at work, but I have not memorized it.

Of course, transducer sensitivity is important in system design, but in the range that I have worked 10Hz-30kHz, it is possible to design transducer/pre-amp combinations that have less noise than the ocean ambient. Thus the ocean noise is measurable and the transducer parameters are not critical for determining detectability. I could find some numbers when I'm at work, or you could look at data sheets from vendors like Benthos, Teledyne, EDO (if they're still in that business), ITC, Massa (I think I'm showing my age, so I'll stop...).

I'm sure the various contributors are aware, but I want to clarify that we are mixing two separate discussions: how to best detect existing pingers, and how to design a replacement pinger that is more detectable.

With regard to the latter, and without addressing every point that has been raised in the past couple of days, I offer that all REMUS vehicles operate with digitally coded transponders (transponders ping in response to interrogation). This greatly improves the ability to operate in a multipath environment, because the chip time is much shorter than the transmission length, which is still on the order of the traditional 10ms. I'm not sure that we get much improvement in detection range.

The receivers operate continuously, running 4 simultaneous auto-correlations (to detect any of 4 different codes) for an expense of about 50mW, including the preamp. That's about 3 alkaline D-cells for 30 days. If that is changed to lithium primary, the size probably becomes similar to what's in the existing pingers, though of course it would need still more energy so that it can transmit as well as receive.

Last edited by auv-ee; 12th May 2011 at 14:09.
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Old 12th May 2011, 05:38
  #1198 (permalink)  
 
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GarageYears I work A LOT with aircraft sounds, no need to explain more, but the MOST powerful signal extraction technique I use to isolate specific discrete noise sources from the composite is what I can "profile subtraction" - I suspect there is a "real name" for this but the general process is to sample a long period of baseline noise (for example the cockpit ambient noise in steady cruise, no changing parameters - speed constant, alt constant, etc). This is then 'saved' as the profile. Then I take my wanted sample and "subtract" the profile from the sample... the result is the residual
visa verse non freezing speed?

if you need stady cruise for your intresting experiments, did you think it can be possible to create a system which can read the birds noise and extract the speed (or altitude)(or even the change of this parameters) while it compared the currend sound profil with a databank of sounds ?

gums I would like to see the pitch moment graph that I put out for the Viper compared to that of the Airbus. Anybody here has such a graph?
figure 6 in the third paper from BJ-ENG #944

but it is not very cleare abaut which point this moment is operating, because stable is the system if the changing of the moment is lower than the movement of the pressure-point, who will move up to 50% until the AoA reach 90 deg.....
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Old 12th May 2011, 08:19
  #1199 (permalink)  
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Two points which may calm down these wild directions the thread is tramping:

1) It is to be hoped that heading v time will be recoverable from the FDR, and then all will be revealed

2) Without wishing to cause extra distress to the bereaved, the main value to the enquiry of body recovery from the sea bed will lie in examining the damage to the skeleton to try and ascertain the nature of the impact with the sea (and seating state) if that cannot be determined from the FDR. Thus the 'condition' is secondary, and I would hope that after a sufficient 'sample' has been recovered the wishes of some of the bereaved can be observed.
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Old 12th May 2011, 08:24
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Cool

Hi,

They have had plenty of time to design, build, test and certify such a system if they were half way serious. You have to ask, why haven't they ?
Well .. seem's a simple ... good plan and designs
Indeed they have now pleeeeeenty time for build and certify this genious design .... for the next crash at sea....
For the AF447 crash ... methink they had no fogiest idea of what they will find at the bottom ....
In fact ... they think they would never find the AF447 .....
Nevertheless I doubt any torpedo tube will be modified in the future .. for this kind of operation
BTW .. the FDR and CVR must be already on the metropolitan french soil now ......

Last edited by jcjeant; 12th May 2011 at 16:53.
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