AF 447 Search to resume (part2)

[JD-EE]

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.)

[ChristiaanJ]

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....

[kilomikedelta]

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.

[mmciau]

Machinbird,

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

[kilomikedelta]

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.

[JD-EE]

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.

[JD-EE]

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.)

[Chu Chu]

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.

[aterpster]

JD-EE:

I do figure God will have more important things for me to be concerned about than where my body lies.

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.

[Centrosphere]

Kilomikedelta,

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.

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...]

[mm43]

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

[Razoray]

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?

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

[gums]

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.



then the graphic:



then the vertical velocity and description of the descent:



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.

[Bizman]

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"

[rh200]

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.

[mm43]

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.

[Machinbird]

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.

[snowfalcon2]

CONFiture

Originally Posted by snowfalcon2
I don't really understand this fuss about independent power supply.

Here is what the report mentioned :
..... the lack of data following the power loss on both engines could have severely affected the ability of the investigation to make findings as to the causes and contributing factors to this occurrence.

It is not the only one, the Portuguese had also made an explicit recommendation :

As a matter of fact, I can now read from the FCOM :
The recording system is automatically active in flight (whether the engines are running or not).

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

[OleOle]

Originally Posted by rh200

..., whilst holding the wings level with rudder. We did this for a not insignifigant amount of time.

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 ?

[fizz57]

If you didn't actively stabilize the plane with rudder.....

How effective would the yaw damper be in this situation?