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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 6th May 2011, 12:02
  #781 (permalink)  
 
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mm43,

Organic matter decays or is "recycled". Really no different to being "six feet under".
What we are discussing is precisely the lack of any kind of biological activity at the bottom, so the corpses don´t "decay" or are "recycled".

Razoray,

But the location of AF447 is similar to a barren plain....as we can see by the lifeless bottom....so dead sea life never makes it to the bottom...
I´m not quite sure of what you´re implying here, but...I ´m not referring to life at the bottom, just to the marine life just passing above. THEIR carcasses must fall (per gravity) to the bottom; that´s what I was talking about.

You´re right about the extremophyles living at the hydrotermal vents, but these ecossystems probably constitute only a small percentage of the sea bottom.
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Old 6th May 2011, 12:21
  #782 (permalink)  
 
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gums, Machinbird, and OleOle,

If this thread is supposed to be about the search, I guess you could be regarded as straying off-topic. But, in the increasing tedium above (without wishing to detract from some notable exceptions), you've got my vote. Not sure I've much useful to contribute with my level of aerodynamics, save just a few comments.

Yes, the A330/A340, like the A320, are referred to as "relaxed (longitudinal) stability" aircraft. Unlike the A320 family, they increase this relaxation at cruise altitudes by despatching fuel aft. In the "A330 Longitudinal Stability" thread (see OleOle's link) Brian Abraham quoted some static-margin (longitudinal stability) figures for a range of types. (The P-51 Mustang's was surprisingly low for a long-range fighter, I thought.) Presumably these are for a typical CG? We don't have comparable figures for the A330-200 in the cruise, but I suspect it is very different from gums's F-16. So, even though they share a low-mounted horizontal stabiliser, I'm not convinced that the characteristics at high AoA are comparable.

There seems to be a presumption that AF447 became stabilised in a deep stall. gums's graph of pitching-moment versus AoA for the F-16 shows a very unfortunate situation at around +50 (and -50) degrees AoA, where full forward (back) stick is unable to create a useful corrective pitching moment. The question is: would the "relaxed stability" of the cruising A330 still have sufficed for AF447 to drop its nose at the normal-stall AoA? If so, how would a deep stall have been achieved?

Then there is the question of dynamic stability, raised by john tullamarine on that thread. I think many of us have managed to achieve mild phugoid oscillations, hand-flying in normal line flying, without necessarily recognising same. Perhaps we could have avoided them with the benefit of an AoA indicator. AF447 not only lacked that, but also any reliable ASI.
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Old 6th May 2011, 13:48
  #783 (permalink)  
 
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Perhaps we could have avoided them with the benefit of an AoA indicator. AF447 not only lacked that, but also any reliable ASI.
If AoA is used for various control law functions, but is not available to the crew for their scan (if I understand you, there isn't an AoA gage in the A330 cockpit) then it appears that any flight deck crew is set up for a curious struggle with the robot when increasing AoA is in play.

What you suggest, however, is scary to me. With quite likely an unusable airspeed indicating system, lack of an AoA indication leaves the flight deck crew without a back up/input into their situation within the airmass, beyond their knowing "something isn't right" and perhaps the VSI indication of "we are falling" as their point of departure for corrective action.

Did I understand you correctly?
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Old 6th May 2011, 14:15
  #784 (permalink)  
 
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What to do when trapped at AoA

This discussion of envelope is very interesting! I have two questions..

1) Machinbird, the F-16 has more thrust that weight, so if you get stuck in this band where you can't pitch your airplane, can't you just firewall the engine and gain speed until you're out of it?

2) On the A330, is it possible that the crew got into a regime where they felt that the only solution was to apply max thrust and this pitched them up and over into a dive? I thought power applied to a large transport 2-engine plane would always tend to pitch up.

thanks
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Old 6th May 2011, 14:15
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@3hl ; JD-EE ask the sharks: this was published the first one June 8, 2009

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Old 6th May 2011, 14:47
  #786 (permalink)  
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Originally Posted by deSitter
Machinbird, the F-16 has more thrust that weight
- a gross over-simplification taken from a sales brochure? It has a high thrust to weight ratio, greater than 1:1 at lower weights.

Likewise HAD the thrust-pitch couple taken them 'up and over' as you imply there was little likelihood of impact with the sea 'en ligne de vol'.

Lonewolf - AoA is useful, but unless the 3 x IRS failed the crew would have had all they needed to fly - pitch and power. Admittedly a narrow band of pitch attitudes available, but easier to select than a fluctuating AoA

Back to some sort of reality while we wait?
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Old 6th May 2011, 15:07
  #787 (permalink)  
 
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You´re right about the extremophyles living at the hydrotermal vents, but these ecossystems probably constitute only a small percentage of the sea bottom.
Sorry for not being clear. Yes, Hydrothermal Vents only occupy a small percentage of the deep ocean floor, but support the largest percentage of marine life at those depths. Also, the marine life in the Hydrothermal zones is not necessarily extremophilic, because the vents create a more normal living environment (nutrients, temperature etc...) even at those great depths (this is what shocked scientists when they where discovered).

So most marine life lives in relative "shallow" waters, and than at depth with help from vents.... In the case of A447, they were basically in between, in a dead zone....like out in the middle of some desert, or on the top of a mountain. Keep in mind most of Earth is ocean, so there is plenty of empty space....furthermore, at that depth, with no added heat, the temperatures are low, which inhibits bacteria growth and decay.

Not much there...
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Old 6th May 2011, 15:11
  #788 (permalink)  
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I think Pitch and Power has been discussed a good deal in these threads. Intuitively, Pitch and Power must flow from a 'stable' (recoverable, manually) platform to begin with; it isn't a "recovery" technique? Certainly not without the instrumentation to support a recovery with AoA and thrust ?? It was determined that this A330 is not equipped with the most basic gauges to support handflying from upset "into" P/P ??? The 10,500 Pounds of fuel in the HS tanks is allowed only in 'normal' flight, so certification does not require minimum tools to recover from upset, which is "impossible" to enter, driving the elimination of these tools from the cockpit; a very logical, albeit deadly error. A circle of illogic that "looks logical" ??
 
Old 6th May 2011, 15:35
  #789 (permalink)  
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Salute!

TNX for the support, Chris, and I was "buying time", as you suggest, until we see the data resulting from the successful search.

Perhaps we wait a bit, OTOH, the new thread we shall soon have when the data becomes available will require some background concerning the stability issue, ya think? So before I shut up and wait some more.....

There must be a reason that the French claimed early on that the plane hit the water in a fairly level attitude without a high forward vector. The only scenario this old pilot can envision is a deep stall, not a conventional stall/spin.

- There is no requirement to enter a deep stall by pointing the nose up at a 70 or 80 deg angle and "waiting" until speed gets so low that you lose pitch authority. In the Viper's case, you can get "parked" if you are already slow and then do something stupid and/or have an external loadout that interferes with "normal" aerodynamic characteristics that the flight control computers were designed to handle. The "bus" would not likely be rolling or skidding as the fighters do at low speed, but abnormal flight conditions could certainly conflict with all the control laws the "bus" "normally" applies.

- The test pilot commentary shows he was at 100% mil power ( no 'burner/reheat/augmentation). So power won't get you out of a deep stall. The drag at high AoA is significantly higher than the thrust available. Further, you are risking an engine stall if you monkey about with the power under those conditions.

- The comment by another pilot about "sitting in a stall" for a bit until things stabilize or get worse is a good point. The test pilot talks about this, and the Viper control laws were verified when the yaw/roll moments were brought under control by the computers and the jet just sat there in the stall and things seemed benign other than extreme vertical velocity and basic "loss of control", heh heh.

- The Viper's "stabilators" were called that because they acted like the basic horizontal stab and the elevator. As Yeager discovered, moving the whole surface is a good thing, maybe even necessary, when supersonic. It's akin to moving the basic stab with the jackscrew or other mechanism for the commercial jets. Additionally, the Viper stabilators moved independently and were used to help roll under certain conditions ( good example to be provided when we get the "final" thread going). In fact, all of our control surfaces moved independently.

- It will be interesting to see the AoA data plot, and I did not realize the plane did not have a cockpit display. If the speed sensors were FUBAR, then all the thing had working for it were AoA and the attitude sensors.
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Old 6th May 2011, 15:47
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As Yeager discovered, moving the whole surface is a good thing, maybe even necessary, when supersonic.
Yeager discovered? ........ Didn't he already know that from the Miles M52

Miles M.52 - Wikipedia, the free encyclopedia
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Old 6th May 2011, 16:44
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Another good interview with Mike Purcell appears in print here:

Air France 447: How scientists found a needle in a haystack - Boing Boing
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Old 6th May 2011, 16:47
  #792 (permalink)  
 
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Weather!

Hi,

Originally Posted by HazelNuts39
The engines don't normally stall when the airplane stalls. The engines may stall or surge when the intake is exposed to extreme angles of attack or sideslip. The airplane in cruise configuration stalls at an angle of attack that varies between 14 - 15 degrees at low altitude, and 6 - 7 degrees at high altitude. I wouldn't expect the engines to stall at angles below 30 - 35 degrees, depending somewhat on power setting.
which is someway conforting my point.
Stall is a function of AOA, altitude and speed. She may have gently stalled at cruise level but should have recovered "naturally" while losing altitude and speed... unless her AOA would have also increased all her way down without ever exceeding the limits where the power plants would have also experienced any trouble with that.

Which process in itself is fairly unlikely without a very large AOA exceedance, in range of some "deep stall" attitude (50 degrees?), which will imply troubles for her power plants airfoil all her way down.

Next come the distance covered: four full minutes elapsed between last position (02:10:30) and end of ACARS (02:14:30) while less than two is needed to bring her down (at an average rate of about 300 ft/second).

This would mean two more minutes of level cruise flight before entering such a stall (02:12:30), then more than 16 Nautic Miles covered: consequently a crash site somewhere about 20+ NM from LKP.

Originally Posted by HazelNuts39
And if they stall, they don't usually flame out immediately, more likely they will surge and overtemperature.
Not systematically, and certainly not when external/environmental factors like ingestion of ice, rain or foreign objects are concerned, not only standard "airfoil" related troubles. This is something about what I already posted several times in this thread or the previous ones.

You can look, for example, at this study published in Boeing's AERO Quaterly 4.07
AERO - Engine Power Loss in Ice Crystal Conditions

by Jeanne Mason,
Senior Specialist Engineer,
Engine Performance and Operability,
Propulsion Systems Division

Originally Posted by Jeanne Mason
High-altitude ice crystals in convective weather are now recognized as a cause of engine damage and engine power loss that affects multiple models of commercial airplanes and engines. These events typically have occurred in conditions that appear benign to pilots, including an absence of airframe icing and only light turbulence. The engines in all events have recovered to normal thrust response quickly. Research is being conducted to further understand these events. Normal thunderstorm avoidance procedures may help pilots avoid regions of high ice crystal content.
I also posted, several pages back, an article about CFM-56 engines related problems with dual flameouts at cruise level in certain conditions (tropical weather, ice particles and no alert).

Lets have a look at this NASA picture showing what a convective storm really looks like above the standard 22,000 ft freezing level:

This NASA Tropical Rainfall Measurement Mission (TRMM) combined satellite radar image shows a vertical cross-section of a convective storm. The image shows the freezing level clearly by the "bright band" where ice particles become coated with melted water and are excellent reflectors of radar energy. Below the freezing level, liquid water is highly reflective. Above the freezing level, while the concentration of moisture may still be high, the cloud is mostly composed of frozen ice particles with radar reflectivity below 20dBZ (units of radar energy). Small ice crystals are irregular in shape and poor reflectors of radar energy. These small ice crystals are believed to be associated with engine power-loss events.
Strikingly, this may also answer the main question why AF 447 did not take another path accross the weather as its radar could have been blind at this flight level:
Originally Posted by Jeanne Mason
On-board weather radar can detect large particles such as hail, rain, and large ice crystal masses (snowflakes). Small particles, such as ice crystals in high concentrations near thunderstorms, are invisible to on-board weather radar, even though they may comprise the majority of the total mass of a cloud
Overall, most of the conditions described by the researchers were present during AF 447 flight:
Originally Posted by Jeanne Mason
Researchers have identified several conditions that are connected to engine ice crystal icing events. The most important factors are:
* High altitudes and cold temperatures. Commercial airplane power-loss events associated with ice crystals have occurred at altitudes of 9,000 to 39,000 feet, with a median of 26,800 feet, and at ambient temperatures of -5 to -55 degrees C with a median of -27 degrees C. The engine power-loss events generally occur on days when the ambient temperature is warmer than the standard atmosphere (see fig. 4).

* The presence of convective clouds. Convective weather of all sizes, from isolated cumulo*nimbus or thunderstorms to squall lines and tropical storms, can contain ice crystals. Convective clouds can contain deep updraft cores that can lift high concentrations of water thousands of feet into the atmosphere, during which water vapor is continually condensed and frozen as the temperature drops. In doing so, these updraft cores may produce localized regions of high ice water content which spread downwind. Researchers believe these clouds can contain up to 8 grams per cubic meter of ice water content; by contrast, the design standard for supercooled liquid water for engines is 2 grams per cubic meter.

* Areas of visible moisture above the altitudes typically associated with icing conditions. This is indicated by an absence of significant airframe icing and the ice detector (when installed) not detecting ice, due to its ability to detect only supercooled liquid, not ice crystals.

These additional conditions are also typically found during engine ice crystal power-loss events.
* No pilot reports of weather radar returns at the event location.
* Temperature significantly warmer than standard atmosphere.
* Light-to-moderate turbulence.
* Areas of heavy rain below the freezing level.
* The appearance of precipitation on heated windshield, often reported as rain, due to tiny ice crystals melting.
* Airplane total air temperature (TAT) anomaly-reading zero, or in error, due to ice crystal buildup at the sensing element (see case study on following page).
* Lack of observations of significant airframe icing.

Graph Legend:
--- graph tiret (above standard) = Standard Atmosphere +10C events
___ graph plain trait = Standard Atmosphere events
... graph dots (below standard) = Standard Atmosphere –10C events

S~
Olivier
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Old 6th May 2011, 17:13
  #793 (permalink)  
 
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Razoray,

I just discovered that the idea I was referring to already exists as a technical term:

Marine snow - Wikipedia, the free encyclopedia

It is indeed a source of food for benthic life.

My interest in this, concerning this thread, is that "marine snow" somewhat defines the kind and volume of native life at the bottom, and by consequence probably the degree of conservation of the bodies of the dead pax and crew.

Thank you for your time.

=================================================

This is just fascinating:

Whale fall - Wikipedia, the free encyclopedia

Last edited by Centrosphere; 6th May 2011 at 17:18. Reason: complementing the post
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Old 6th May 2011, 17:22
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A report I have read states that the body recovered is the skeletal remains of a passenger still strapped in their seat. So maybe someone can tell me how this is possible when it appears many of the posts state it should not be possible to decompose at the depth of AF447. And just to inform, there are bacteria in the human body, in the mouth and stomach for example.
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Old 6th May 2011, 17:30
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Originally Posted by promani
A report I have read states that the body recovered is the skeletal remains of a passenger still strapped in their seat.
Maybe you should first ask yourself what kind of "source" was used in this "report" you read. "Skeletal" doesn't fit with most leaked informations (from family members) about the curent state of the victims.
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Old 6th May 2011, 17:43
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Of course decomposition is still possible - it just takes place much slower than at higher temperatures.

All very macabre and sad.
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Old 6th May 2011, 17:47
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Lonewolf - AoA is useful, but unless the 3 x IRS failed the crew would have had all they needed to fly - pitch and power. Admittedly a narrow band of pitch attitudes available, but easier to select than a fluctuating AoA
BOAC: I understand that. In the upset training I am familiar with, AoA is a primary scan item. I asked the question under the assumption that the problem is an upset, and a recovery of that upset under instrument scan (crosscheck?) which typically calls for a scan (crosscheck?) on critical instruments.

I recall the pitch and power discussions from a year ago and more. I was among those wondering why that fundemantal would not have been a solution set were the problem confined to the airspeed going unreliable. A/S unrealiable and upset takes us into a different problem to solve, depending upon the nature of the upset.

It will be interesting and enlightening (if the transcripts of CVR are ever in the public domain) to see if the "stall" audio warning was on, and for how long, during the upset in this case. I am operating under the assumption that were there not a stall at some point, plane would not have hit the ocean. The old "death spiral from vertigo" model in a multi place cockpit with experienced pilots seems an extremely remote, almost nil, possibility.
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Old 6th May 2011, 17:49
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Skeletal


I could bring up something I wrote earlier in the thread. "Flail" injuries, 200 knot impact, and chaotic cabin contents suggest a type of injury that is consistent with extreme trauma, and would prompt a rescuer to describe "skeletal" (bone exposed) trauma. Degloving. Originally, when considering ejection at altitude and great velocity, I thought degloving was a way to describe what Brazilians may have sussed as "Skeletal" (Flail). Just because one considers skeletal remains as being the result of decomposition, does not make it so. Osmotics and decomposition of connective tissue due breakdown of protein does not require bacteriostatic action necessarily.

So in short, a suggestion is made that includes both possibilities, without rejecting either. From Trauma during the crash, or degradation in situ. Or both.

Last edited by bearfoil; 6th May 2011 at 19:21.
 
Old 6th May 2011, 17:58
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New video from the BEA

http://www.bea.aero/fr/enquetes/vol....montee.fdr.mp4
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Old 6th May 2011, 18:58
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Interview with Woods Hole senior engineer

Lurker and SLF, but this may be of interest to some, an interview with Mike Purcell from Woods Hole, chief of the search operations.

Air France 447: How scientists found a needle in a haystack - Boing Boing
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