HN39, I always took the in line of flight phrase to mean the plane's horizontal velocity component was chiefly in the direction the plane was pointing. In that sense the phrase both appears accurate and sensible. (Damage on recovered components and bodies would have been different with a significant tailward motion or a side-slip motion.)

Machinbird,
Without going into all the macabre details.... the temperature at 4000m down is only a few degrees Celsius above zero, much like a fridge.
But I agree, recovery of the bodies is not going to be an easy, or pleasant, task....

Machinbird;

Difficult to know. The environment is probably 4 deg. C. (maximum density of water), anaerobic and at a very high pressure on an abyssal plain. There would probably be very little biochemical activity going on, either from human tissue or local fauna.

I suspect that some find it difficult to accept that learning from forensics is too ickky for them.

Machinbird,

Wouldn't the pressure at the AF447 site expel any gases from tissue?

Tissue gases (CO2, N2, O2) would be forced into solution at the thousands whatever bar pressure at this depth. Biochemically produced gases (CO2), if produced (unlikely), would be similarly solublized. Only when brought to the surface would the expected decomposition processes be operative.

KMD and 3holelover, the term "black box" went further back than the "black finish", I believe. In electronics one of the users was a hypothetical box with an unknown function and unknown contents. All you had were the various gozintas and gozoutas on the box to manipulate and discover what was inside. On the other hand it MAY have started with the original WW-II military equipment that was typically black for airborne Army equipment. But Navy equipment tended to be a sort of light gray while Army radios tended to be olive drab. ALL tended to be referred to as black boxes from time to time.

Machinbird, if a piece of aircraft structure necessary for analysis is being raised that has bodies attached to it, what should they do? Scraping the bodies off is likely to be a worse disturbance of their peace than bringing them up as whole as possible and dealing with them with dignity as they are detached from the plane's structure.

Bringing up an unattached body may be a sociologically iffy measure. I hear reports that some want the bodies left at the bottom and some want their loved ones returned for proper burial and "closure". (And, of course, from my own standpoint, I figure I'll be in no state to be particularly concerned about the disposition of my body. I'll have other concerns, either learning to play a harp and sing or greeting all my predeceased friends in that other place. Erm, more seriously I do figure God will have more important things for me to be concerned about than where my body lies. It's up to what my survivors want for their own personal closure.)

My dictionary gives 1945 as the date of first use for "black box." If it's right, a WWII origin seems like a good bet.

JD-EE:

I am happy for you that you have God figured out.

Of all the families so concerned about the remains on 447, some share your views, some are more of the faith, some are not of the faith at all.

In the latter class lay some of the most caring individuals of all, for they view this only life we have as being of utmost importance.

Sorry, back to the technical aspects at hand.

Kilomikedelta,

Sorry for being WAAAY off-topic, but...

Wouldn´t this mean that the bottom of the sea at abyssal deeps should be teeming with dead, but conserved, carcasses of the many sea creatures dying for some reason other than being eaten?

[on the other hand maybe not many sea creatures can enjoy a quiet death...]

Organic matter decays or is "recycled". Really no different to being "six feet under".

The marine population at that depth is limited, although it is not uncommon to find underwater geysers at great depths that harbor many forms of life. 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...

Underwater Geysers Warm Flowing Sea Water - Science News - redOrbit

Back to impact
 

Salute!

Well, after discussing this with another member here, I shall make another post that deals with the impact.

The French prolly have it right about a low forward velocity, fairly level attitude impact. I offer some excerpts from the LM Code One magazine that discusses the deep stall we had in the Viper.

One thing to look at is the statement that the jet was descending about 300 feet per second!! So it is entirely possible for impact to have taken place within 2 minutes or so from entering a deep stall at cruise altitude. This also provides an explanation for serious, deadly forces on the pax.

http://http://i120.photobucket.com/a.../verbiage1.jpghttp://i120.photobucket.com/albums/o.../verbiage1.jpg

then the graphic:

http://http://i120.photobucket.com/a...tch-moment.jpghttp://i120.photobucket.com/albums/o...tch-moment.jpg

then the vertical velocity and description of the descent:

http://http://i120.photobucket.com/a.../verbiage2.jpghttp://i120.photobucket.com/albums/o.../verbiage2.jpg

Let's make this clear..... I NEVER got into a deep stall!.. I did a tail slide once, but the pitch rate after starting back down was so high that the flight control computer and control surfaces could handle it.

After looking at some of the control laws for the "bus", I can see the same thing happening as with the Viper. Computers try to limit gee and AoA and speed, but the c.g. and aero characteristics of the plane allow the thing to "settle" into the deep stall. The "bus" didn't have the MPO ( manual pitch override) that gave us direct movement of the stabilators with zero "help" from the computers. Closest the "bus' has is manual elevator trim wheel.

Woods Hole explains how they found AF447
 

An excellent 14 minute interview with Mike Purcell of the Woods Hole Oceanographic Institute. Purcell was chief of sea search operations for the mission that this May found and retrieved the aircraft's critical voice and flight data recorders.

The URL is here:
Podcast: Air France 447 — Finding the "Black Box"

Not sure how relavent it is, and whether its possible in a large jet, but an interesting thing happened to me in relation to stalls. Many moons ago, like a lot of young people when doing flight tests, I was always in a rush to get out of the stall in the tests or in practise, usually making the whole thing messy in the process.

One day I was at a small country town being tried out on their aircraft by their CFI, and he noticed my "sloppyness" in the stall recovery, which he took as being "frightened of the stall". He basically got me to hold it in the stall and not recover, whilst holding the wings level with rudder. We did this for a not insignifigant amount of time. I could imagine some scenario where if we hit the ground the vertical speed was large and the horizontal low.

Phase 4 Search and Phase 5 Recovery - clarification
 

WHOI lead the REMUS 6000 Autonomous Underwater Vehicle search which used three of these vehicles operating from the Dive Support Vessel "ALUCIA". The AUV's using sidescan sonar detected the presence of debris which was confirmed when further dives by AUVs using cameras photographed (85,000) the whole debris field from a height of 10m above the sea floor.

The photographs allowed the BEA to localize parts of the debris field, and a different vessel - "Ile de Sein" using a REMORA 6000 ROV operated by Phoenix International is currently undertaking recovery operations. The recorders have been recovered and ancillary recovery work is still proceeding.

I have to admit chatting with Gums a bit (A fellow fighter pilot).
First, note one important fact. The F-16 is a FBW aircraft that can become locked in a deep stall (if unlucky), and it doesn't have a T tail. The pitching moment curve shows two white marked areas that independent of stabilator position, act to trap an aircraft at high angle of attack. One curve for the upright situation, and one for the inverted situation. The moment curves are pretty symmetric about the center which includes the normal flying envelope. You should note that a stabilator is a much more effective pitch control than the elevator & THS combination typically found on airline type aircraft. (This has implications for stall recovery)

I think people are missing the significance of another highly relevant fact:
AF447 was deliberately flying with an extremely aft CG. Almost 39% MAC. The aircraft is certified to fly in that envelope, but there is an important element in that certification. The flight control system has to perform properly.

My favorite flying machine, the F-4 was allowed to approach 36% MAC assuming it was not carrying too much in the way of external hardware. If you were to disable the stability augmentation system though, that nice flying aircraft became not so nice. It wobbled around in a loose semblance of controlled flight, and this was with a CG in the lower 30% MAC range. (But not so wobbly as that recent TU-154 on Rumors & News). :}

Now, Gums' F-16 chart is listed for 35% MAC, also fairly aft as CG goes. The F-16 is actually unstable in the subsonic portion of its flight envelope which helps its maneuverabilty, but makes the flight control system an essential element for controlled flight. It won't fly long without it!

The F-16 pitching moment chart is probably a fair model for A330 pitch authority at extended AOA ranges. Until Airbus publishes a pitching moment curve for the A330 over an extended AOA range, we can probably assume that the F-16 chart is fairly representative of what might happen with the transport as far as shape of the curves, but not the same numbers.

The A330 is a relaxed stability aircraft. This means that the certifying authorities are allowing it to fly with a CG that ordinarily wouldn't be allowed, but is allowed because the A330 has reliable systems that make this a non-event, but in the event of a loss of the normal control systems, it has enough inherent stability (say in Mechanical Law) that it can be brought back home.
I am not however proposing that AF447 lost its flight control system
(Normal Law) until the ACARS sequence but merely noting that if something interfered with the proper functioning of the system, and if the turbulent environment that the aircraft found itself in was not conducive to continued stability, then we might have an explanation for an early loss of control at the beginning of the sequence. The aircraft has to be extremely dependent on proper functioning of its flight control system near aft CG. limits. This area could probably use more discussion.

CONFiture
 

Thanks for the information.
It surprised me that (at least in the past) power supply to recorders was apparently dependent on an engine running. I would have thought powering the recorders would be equally important as powering the essential flight instruments and flight controls. Hence my skepticism re. adding a special independent recorder power supply.

The FCOM remark suggests the issue has been addressed. Good :ok:

This is what a pilot of benign equipment would expect. If you didn't actively stabilize the plane with rudder, it would dip over a wing sooner rather than later, much more so in turbulent air. AF447 apparently didn't dip over the wing, otherwise it would have crashed differently into the ocean.

The further aft the CG the less benign an airframe becomes. There was already an interesting discussion in this forum concerning CG and the A330: http://www.pprune.org/tech-log/37719...stability.html

As an adolescent boy I flew single-seated gliderplanes. Pilot weight is the most significant contribution to the trim sheet in those planes. Because I hadn't yet reached the weight of an adult I made some hands on experience with aft CG.

Considering the importance of CG within the flight envelope, outside the flight envelope and during the transition, I was wondering if it would be feasible to make pumping of fuel from the tailplane trim tanks to the mainplane tanks part of the unreliable airspeed procedure ?

How effective would the yaw damper be in this situation?

mm43,

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,

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.

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.

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?

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

@3hl ; JD-EE ask the sharks: this was published the first one June 8, 2009

http://farm4.static.flickr.com/3629/...5d96e1.jpg?v=0

- 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?

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...

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" ??

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.

Yeager discovered? ........ Didn't he already know that from the Miles M52

Miles M.52 - Wikipedia, the free encyclopedia

Another good interview with Mike Purcell appears in print here:

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

Weather!
 

Hi,

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.

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

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:
http://takata1940.free.fr/graphic_03_1_lg.jpg
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:
Overall, most of the conditions described by the researchers were present during AF 447 flight:
http://www.boeing.com/commercial/aer...aphic_03_4.gif
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

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

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.

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.

Of course decomposition is still possible - it just takes place much slower than at higher temperatures.

All very macabre and sad.

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.

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.

New video from the BEA
 

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