AF 447 Search to resume (part2)

[grity]

One is a diagram of nine marker buoys and their drift paths, from an experiment made in June 2010. Look at those crazy loops! I guess that is what persuaded them to abandon any predictions about the crash site based on the location of floating debris.

the right answer is: it is impossible to extrapolate the direction of a turbulent flow....

but why they do not started this experiment one year earlier ?

[CONF iture]

Originally Posted by takata

a) this "someone" suggestion is very unlikely: autopilot can't re-engage until the flight parameters are restored to normal, neither ALTERNATE LAW (PROT LOST) would be changed back to NORMAL LAW (until after landing);

You are misinformed here : AP but also A/THR could be reengaged under alternate law.
But a RECENT OEB warns pilots not to do so, at least not instinctively ...

[noske]

the right answer is: it is impossible to extrapolate the direction of a turbulent flow....
but why they do not started this experiment one year earlier ?

Exactly. But they know and have already expressed their regrets. Second interim report, appendix 2, 1.5: "The dropping of drift-measurement buoys by the first aircraft to arrive over the zone would have made it possible to understand the drift better from the earliest hours".

[kit344]

Newspapers in France.

Would any of the Francophones like to comment on the relative levels of respect of various French newspapers?

I found two references List of newspapers in France - Wikipedia, the free encyclopedia and French dailies, the daily press in France but as a Brit I am aware that most (all?) papers have agendas determined by editorial policy and politics.

Personally I almost never buy papers, but prefer to read news online or listen to radio or TV news.

I am sure some sources are more sensational than others, and that ownership and major shareholders may also affect any un-biased reporting.

I use this thread as my primary reference followed by the official BEA website.

Hope this is not too far off-topic, this thread has drifted a long way from the original search for wreckage (now accomplished) and has moved on to various other parts of the investigation.

[SaturnV]

JPI, très certainement! Merci
____________

grity, as I recall they were trying to duplicate conditions at that time of year. During 2009, they were mostly relying on drifters, fishermen's buoys.

As I recall, the drift group did not use the 2010 buoy movement in preparing its June 30 2010 report. But Metron did in its January 2011 analysis.

[JPI33600]

kit344

Would any of the Francophones like to comment on the relative levels of respect of various French newspapers?

Well, among the biggest newspapers, I would recommend "Le Monde" as being the most serious one, and "Libération" is not that bad too. OTOH, I have been very disappointed/upset with "Le Figaro" on several occasions , and I prefer not to comment about "France Soir" .

This is only my personal opinion and YMMV obviously, so take it with a pinch of salt.

[cats_five]

Originally Posted by Lemurian

MATELO,

In this case, I apologize, but still, if we opened a thread on Capt Sullenberger's actions on that day, we'd discover that they were the results of an exceptionally disciplined mind.

They were also the actions of a glider pilot, which might have given him an extra way of thinking about the situation he was in. There was lucky as well - the incident occured in daylight, and the Hudson is a very busy stretch of river.

[takata]

Originally Posted by CONF iture

You are misinformed here : AP but also A/THR could be reengaged under alternate law. But a RECENT OEB warns pilots not to do so, at least not instinctively ...

This recent AD is for wording it more clearly: it is possible to (re)engage AP/FD if 2 ADRs are (re)displaying consistent, but erroneous, data (hence danger). I wrote it many times that it would be possible in such circumstances. But in AF 447 case, it seems very unlikely that they ever had such an opportunity due to the RTL settings still frozen at impact; a PRIM reset is also mandatory before doing it, but it was not made until very late in the sequence. In any case, it would be due to pilot's wrong choice of erroneous data as the computer will not activate AP/FD by itself.

[ChristiaanJ]

Re 'sûreté' and 'sécurité'....
The explanations in the earlier posts are fine, but there's one more point....

In French secondary schools, you are taught to avoid as much as possible using the same word twice in the same paragraph.
That's OK in literature, but it can be confusing, when authors of technical documentation try to apply the same rule at all cost.

It took me a few weeks (after moving to my first job in France) to understand that "tangage" and "profondeur" can be used interchangeably for "pitch" in an aeronautical context, until a French colleague explained this slightly odd habit.

So, while sûreté and sécurité are not true synonyms, don't be amazed if you discover them being used as such in the same paragraph.....

[CONF iture]

Originally Posted by HN39

I think you may have missed the point of my remark, which is that the following BEA explanation does not match the Air Caraibes occurrence

I see what you mean now.
I have just checked the French version and the English translation seems accurate. I believe there is a possibility the BEA text is inaccurate and should say :
''If none of the three Mach values is valid, a Mach value close to 0.8 is used. For example, it is of the order of 4° at Mach 0.8''
Such wording would better match the Air Caraibes occurrence.

Originally Posted by AGBagb

I'd be very interested to hear Airbus pilots' thoughts on what might have happened if the Air Caraibe pilots (for there were 2 almost identical incidents...) had *not* made the quick decision to ignore the stall warnings, when flying through high-level turbulence, with iced pitots, and in alternate law.....

It would have greatly complicated the all issue and probably bring more confusion to an already very confusing situation.
AT THE TIME the procedure was to simultaneously pitch down and apply full thrust. In other words it would have unnecessarily destabilized a situation that was under control.

Those Air Caraibes crews did so well under such confusing environment.

Shame on the BEA and others ... to not have treated adequately this valuable information.

[AlphaZuluRomeo]

@ kit344 : this webpage (i.e. your second reference) offers an honest & almost comprehensive look.

Why "almost" ?
1/ 20 minutes is missing as the 2nd free daily
2/ I don't read the economics press so frequently, but Les Echos deserves to be called a quality daily IMO.

As JPI33600, I've been disappointed/upset with "Le Figaro" on several occasions. But the same is true with "Le Monde", too (though perhaps a bit less often, or on less serious issues).

[Shadoko]

Hi,

@ kit344 and JPI33600, about French newspapers.About same advice as JPI, but have to said Le Monde seems less "above the others" than some years ago, and Le Figaro has often very interesting wording (verified by myself about domains where I have some knowledge), but is not politcally neutral.
And don't miss "Les Échos", a newspapers about economics, but with very trustable other news: Actualité économique et financière - Information économique et financière - Journal quotidien économique et financier - Les Echos.fr
If you are speaking about French language, Belgian papers have to be read: they are often more open minded than French ones. Try actu - lesoir.be as a "medium" example.

Just a word about "sécurité/sûreté": the meaning associated with "sûreté" is sure ("certain", same word in French). What is "sûr" has to happen, it is predictable, and by the way, safe because not hazardous.

[FlightSpanner]

Don't shoot me for asking (B1, B2 Engineer, non Airbus)

Is it at all possible for there to be a huge change in wind direction over a very short distance within this type of cloud, thinking head to tail wind, and if the probes are iced could this go unnoticed? and result in a real stall?

Also how do probes react to icing up, I know if the calibrated bleed hole blocks it will over read but if the opening becomes iced would the pressure inside remain constant due to sudden blockage or would the pressure decay as the opening gets smaller due to ice build up?

Just how large would the ice particles be? could they enter the pitot, build up and block within the hoses after the heated head?

Sorry if this has been discussed previously, taken me 5 hours to catch up with all the latest posts!

Thanks.

[JD-EE]

Originally Posted by Lonewolf_50

Vaguely, I should do a bit more homework to brush up on the basics. "Tumble" is the physical analogue (from old gyroscopes) I am trying to use to describe the function becoming unreliable, based perhaps on accelerometers going wrong, but I won't comment further as I think the l@ser ring gyro has been adapted due in part to its higher reliability. (Fault tolerance).

In theory (and I presume practice) if you rotate these essentially solid state no moving parts instruments fast enough or accelerate the rotation fast enough you may overrun some counter that is counting interference fringes. Then it becomes inaccurate. I would presume, probably safely, that this is outside the range of motions of even a military jet. The upset is quite different from tumbling a gyro with its reaction to forces perpendicular to its axis due to friction.

As to lost calibration, causes of that would, it seem, remain in the electrical, rather than physical motion, domain. Do I understand that correctly?

I would presume the most likely reason for lost calibration can be as simple as an electric power glitch that went beyond what its internal power supply can handle. As I mentioned above I don't think you can exceed its ability to count beat notes that come from the slightly different effective distances the light traveled clockwise and counter-clockwise (deiseal and widdershins if you will) around the "ring" of laser optics. Bang it hard enough and you might actually bend the optical bench destroying its accuracy and perhaps its ability to work. I'd expect that to require quite a bang, as with a serious attempt to break it with hammer or something like that.

Time will also cut its accuracy down. You measure rotation rate in steps. So if you remain rotating at not quite one full step from not rotating over time your heading will be different from what is reported by a significant margin. It works on the speed of light. So that would be a very small error that would require a very long time to add up to an accuracy loss.

Recovery after it's lost power or whatever requires a very accurate knowledge of the plane's exact geographic position (GPS), attitude, and heading relative to true North. That's easy on the ground, more or less. In the air it could be more than a slight bit difficult, especially when we get some vibration.

edit: auv-ee's description is excellent and in greater detail. Do consider it.

[Lonewolf_50]

Recovery after it's lost power or whatever requires a very accurate knowledge of the plane's exact geographic position (GPS), attitude, and heading relative to true North. That's easy on the ground, more or less. In the air it could be more than a slight bit difficult, especially when we get some vibration.

Given that ACARS didn't indicate a power supply loss, that scenario does not seem to fit this case, but ... to better understand recovery or lost capability ... if you had a power loss / or interruption (part of why there are 3 (do I have that right) in a given aircraft ???) ... then, not only do you need to reset location and direction, you have to establish wings level, nose pitch X, (zero, I assume) to re-establish correct attitude sensing from which the gyro can reference.

That is similar to "recaging" a gyroscopic Attitude Indicator if it has "tumbled" in flight, though from your description, a bit more complex.

[HazelNuts39]

Newspapers in France

kit344;

I would also recommend the website of the weekly Le Nouvel Observateur for factual, informative and timely news whenever there are new developments re: AF447.

[JD-EE]

Mr. deSitter, please understand IT professionals a little better.

If you are sitting in an airplane, push the button to start engine 1 and nothing happens do you sit and think before you push the next buttons? "Why did it do that? What will go wrong if I do X or Y or Z?" There is probably a procedure to follow. But IF (added) nothing will break if you sit there looking blank while you ponder the situation, check a few dials, and then proceed.

IT professionals are much like that. As a developer I am not strictly "IT person". But I often have what I just wrote do something completely wonkity. I'll sit and review what I did, what might have caused the error, and maybe even try to recreate it one or more times. (If it recreates easy it is easier to find.) But the first thing I do is sit there and exercise by brain instead of my brawn. It helps, before the next action, to have a half a notion what went wrong before making a total mess of things. (One of the REALLY critical questions is, "Was this the disk drive getting flakey?" If it is you want to get a backup before you mess with anything else. I am sure with the engine start scenario there are "co-symptoms" you look for and if they appear you try not to jump out the cockpit window and instead do your best to save the passengers then the plane then yourself from the engine that just caught fire. The disk drive is sort of the IT equivalent.

Think FIRST, then react. Otherwise you might turn something bad into a total disaster. (And for some operator errors on the keyboard all you can do is hit control-c, the command line stop the stupid program command, and pray. With the UNIX derived OSs if you accidentally misuse "rm -rf" you can clean off the entire hard disk if you don't stop it quickly. So the command issued is checked right away. Then you stare blankly looking at things and thinking. And of course that, too, involves thinking on what you did before you stop it. Sometimes stopping a command can do more damage than letting it complete.

Some people paraphrase this as "Don't just do something; sit there."

Edit - added back a word I'd been thinking and didn't type.

[JD-EE]

deSitter, there is a second issue that has me bemused. It's about the GIMME button. If it is supposed to give you an airplane to fly, and it is basically fly by wire, would you care to define what kind of aircraft it should mimic? It could drop you into a direct law that gave the controls the touchy feel of a P-38 configured for stunts or it could mimic a fully loaded C-130 or something in-between.

I'm thinking of the poor sods who get your demand and have to program it in. I tend to whine like that when asked to read minds by pointy haired bosses.

[CONF iture]

Originally Posted by takata

a PRIM reset is also mandatory before doing it

No, it is not.

it would be due to pilot's wrong choice of erroneous data as the computer will not activate AP/FD by itself

The AP not but the FD(s) absolutely.

[FlightSpanner]

if you had a power loss / or interruption (part of why there are 3 (do I have that right) in a given aircraft ???) ... then, not only do you need to reset location and direction, you have to establish wings level, nose pitch X, (zero, I assume) to re-establish correct attitude sensing from which the gyro can reference.

As well as 3 they should also have pri & sec power supplies, sec normally is an emergency battery. I also remember (training course a few years back) they have a degraded mode of operation, ATT mode, no position input needed and much quicker alignment, however i'm not an Airbus engineer so cannot confirm if they are the same.