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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 8th May 2011, 22:20
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Originally Posted by Machinbird
The reason for a very long LOC event is fairly obvious, the Airbus FBW system was still in control.
There is not so much left of the FBW to control in ALT2 Law. Wasn't it one of the first events to be triggered at 0210?
Or you'll have to start your sequence even earlier, which is even worst considering this timming issue at stake.

Originally Posted by Machinbird
But how was the airspeed lost so quickly? Logically the aircraft departed controlled flight with a strong upward vector.
Now if someone can match up these endpoints, we will likely come very close to the cause of the loss of AF447 without even using the recorder data
I'm believing that those end points can only be matched if every starting assumptions made is basically correct. If one discard something, like ALT2 law, one will certainly end with two fairly unmatchable end points.

Originally Posted by grity
henra theoretical: if the bird is without any control but starts with an extrem climb mayby 60 deg, this (~balistic) path will reach a maximal high of ~12700m (full change the kinetic horizontal energie into potencial energie), while reducing the speed to very low untill it will deap stall and if it then fall with a stable AOA of 50-60 deg. back to 10500m and afterwards down to zero.....

this path could need ~100 sec longer than yours and can end within a range of 8000
When this "zoom & boom scenario" is considered, it will seem obvious that those fully monitored engines (from Brazil take off to 0214:26) will trigger at least "ENG STALL" ECAM warnings and all related ACARS.

Remember that F-GZCP engines were working "fine" during all the sequence covered - dixit the BEA as well.
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Old 8th May 2011, 22:38
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When this "zoom & boom scenario" is considered, it will seem obvious that those fully monitored engines (from Brazil take off to 0214:26) will trigger at least "ENG STALL" ECAM warnings and all related ACARS.
But all very dependent on power setting. If my aircraft had just lofted me to the edge of space, I would put the throttles wherever the engines seemed happiest just to keep them running and the lights and hydraulics available.

Do you have specific data on engine operating envelope-Olivier? I wouldn't be surprised if the engine authorized envelope would be exceeded, but the stall margin envelope is typically very dependent on power setting.

And without Direct Law, I don't think a deeply stalled Airbus has a hope of recovery. It is a THS thing.
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Old 8th May 2011, 22:40
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SaturnV, as a woman with pierced ears I didn't think of the screw on type that would, indeed, probably come off.
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Old 8th May 2011, 22:43
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Mr. Optimistic, "Any clues as to what the northerly outlier is ?"

Not that I know of. But it if is the bare APU it might give a solid hint of what direction the plane is going.
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Old 8th May 2011, 22:46
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Post-Stall and Spin Dynamics of Large Transport Aircraft

@mm43 et el

Recent NASA papers:

https://engineering.purdue.edu/~andr...2007005369.pdf

http://ntrs.nasa.gov/archive/nasa/ca...2008034489.pdf

http://ntrs.nasa.gov/archive/nasa/ca...2005208658.pdf

http://ntrs.nasa.gov/archive/nasa/ca...2008033763.pdf
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Old 8th May 2011, 22:46
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Thanks. If they are going to put up videos wish they would make them legible ! Probably says 'a rock'.
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Old 8th May 2011, 22:48
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Engines during upset

Takata,

those fully monitored engines (from Brazil take off to 0214:26) will trigger at least "ENG STALL" ECAM
Remember:

2:13:16 ~ 2:13:41 Possible "Loss of Signal" with satellite
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Old 8th May 2011, 22:50
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bearfoil, most of the debris is pretty random. There is a good chance that the heavy stuff (engines and maybe APU) dissipated its horizontal velocity component fairly quickly in water. So they will fall fairly straight down with little dispersion from current or anything else.

If that is true, the Northerly outlier is the APU, AND the plane hit tail first then left wing, then we MIGHT be able to say the plane was heading more or less SSE to SE. That's a lot of ifs. So as noted I'm sticking to relatively random debris field modified by underseas currents as most likely. But I am putting in my one cent's worth that AF 447 may have been heading generally SE-ish.
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Old 8th May 2011, 22:59
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Also, it's worth remembering that sections that sank relatively intact at the surface will have imploded on the way down (or possibly even exploded if they sank with trapped air inside), further complicating the picture.
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Old 8th May 2011, 23:10
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woodvale, a few decades ago Amateur radio equipment was infected by this make it stupid simple philosophy. It (cough) missed a great deal in the assumptions it made. With older equipment and experience found I could dig out signals others didn't dream were there. (One fellow had to redesign a piece of a black world project because I could drag out and recite to him the unencrypted speech being sent. That was a MAJOR oops.)

The Amateur radio world got over this affliction. Military radio as a general rule has not. Aircraft radios are also minimal user interaction and control as well. This applies to the flight controls as hope that the airliner manufacturers may get over the make it stupid simple philosophy, too. If you are going to design an aircraft that gives up control when the automation gets confused but not before then you need the pilots to have the most wide open control possible. Maybe that will be a takeaway from AF-447.

Meantime, lobby for a switch on the radar front panel that may involve an "ARE YOU REALLY SURE?" interaction with the pilot that enables full control of the display including any raw mode that could exist. Maybe that MISS will be fixed. The pilots are being offloaded for other flight controls. So they have time to operate the radar in detail modes; and, they have time to learn how.

(And off hand I find it a little unsettling that airliners are working to become so simple to fly even al Qaeda militants can do it with minimal training.)

{^_^}
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Old 8th May 2011, 23:15
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post #925, captplaystation, excuse the presumption, but perhaps this will be the one that redefined the whole approach to automation.
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Old 8th May 2011, 23:16
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Originally Posted by RR_NDB
Remember:
2:13:16 ~ 2:13:41 Possible "Loss of Signal" with satellite
The system doesn't eat ACARS. This quote is to explain a possible delay in the time stampings, but not a message disapearance.

If the statellite link is lost, ACARS in the pipe are kept until the link is restablished. The protocole takes 6s with full aknowledgments at both end.
As the satellite was obviously working until 02:14:26 with no ACARS processing interrupted up to this point (it is known from the Sat operator), only very late ACARS in the maintenance system (not already processed) was kept by it until the end of transmissions.
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Old 8th May 2011, 23:34
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henra - stopping from 470nm/h in 4 nm is a fairly modest (by automotive standards) 1/3g. Now, for a plane that wants to fly that's an absurd horizontal deceleration. For a plane in an upset condition that may be entirely within what could be expected. A very sharp pullup might do it, at least to my untutored visualization.

This does hint strongly that the upset happened a very short time before the LKP report. A very sharp pull-up followed by a fast drop may explain nobody managed to get to their life vests and people were still out of their seats perhaps queued at the potties. Once the upset started they'd be tossed around the cabin and not able to get back to their seats.

This does favor delta92's scenario, I suspect.
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Old 8th May 2011, 23:36
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Originally Posted by mm43
The boot wouldn't have helped that much! Low IAS and only 7.9 of rudder allowed by the RTLU!
Um, the MISS, Make It Stupid Simple, philosophy may have struck again.
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Old 8th May 2011, 23:38
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takata, think the point being made was that there was a loss of link integrity for a short while as per Svarin which may correlate to a manoeuvre

Interesting ?

Now more : both PRIM1 and SEC1 messages appear right after the "possible loss of signal" window.

Interesting ?

On another point, if the last position report was at 2:10.x when the a/c was already 3nm west of track then since there is at least another 4 minutes of flight based on acars, and at cruise speed this translates to a lot of ground, the a/c must either already be decelerating or the timeline for height and speed loss gets tighter AND the ground covered has to be negated in a subsequent manoeuvre.
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Old 8th May 2011, 23:40
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Originally Posted by Machinbird
But all very dependent on power setting. If my aircraft had just lofted me to the edge of space, I would put the throttles wherever the engines seemed happiest just to keep them running and the lights and hydraulics available.
I understand that this is for the zoom part of your scenario.
But what about the boom part of it?
Would you keep full throttles, once having already a very large AOA exceedance , and all your way down during about four minutes?
from, say 40,000+ feet down to sea level?

Originally Posted by Machinbird
Do you have specific data on engine operating envelope-Olivier? I wouldn't be surprised if the engine authorized envelope would be exceeded, but the stall margin envelope is typically very dependent on power setting.
Not at hand.
But say 50-60 degrees AOA without much forward speed remaining at all (in order to stay into your 8000 m zone) will make such an angle for the airfoil to bypass in order to reach the compressors that I really doubt of the tolerance. I'm not even talking about all the tropical storm ice/water you will ingest at lower than cruise levels in the process.

Originally Posted by Machinbird
And without Direct Law, I don't think a deeply stalled Airbus has a hope of recovery. It is a THS thing.
What make you think Direct Law may be lost?
The rudder would be still limited (could be an issue at low speed for stall recovery) but other surface control would still move freely.
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Old 8th May 2011, 23:49
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Originally Posted by takata
When this "zoom & boom scenario" is considered, it will seem obvious that those fully monitored engines (from Brazil take off to 0214:26) will trigger at least "ENG STALL" ECAM warnings and all related ACARS.
That is what troubles me with the simple scenario of pitch to a fatal point and actually slide down backwards at least part of the way. Wouldn't that put the candles out? And isn't a tail down stall recoverable using the elevators? Maybe they were in the middle of recovery when they hit?

{^_^}
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Old 9th May 2011, 00:00
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Old article here giving some general details about GE engine monitoring

MRO USA: Engine diagnostics: GE opens the envelope

It is highly likely that everything was OK when the engines last 'phoned home'. Interesting to note that the data packet sent to GE must include basic flight information

..."normalising" the data based on Mach number, altitude, pressure and inlet temperature...
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Old 9th May 2011, 00:19
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Originally Posted by mm43
RetiredF4;

Thanks for that "Airplane Upset Recovery" link.

Wainwright dealt in general terms with the issues, but seems to have ignored some of the FBW limitations that are inserted into the equation when not in Normal Law - see below.
I think you missed a bit of the intro:
It is not aimed at protected Fly-by-Wire aircraft.
There is no need for this type of continuation
training on protected aircraft, although a
general knowledge of the principles involved is
useful for every pilot.
Now, the document is 10+ yrs old, the work that went into it, 15yrs or more, since then we've had crashes like Perpignan and we know that it's perfectly possible to stall these a/c when things aren't working right, so maybe it's time to disagree with "There is no need...".
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Old 9th May 2011, 00:23
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Crash QTR

Before boxes info, one may ask:

Among the recovered bodies may be BEA or else one has the crash time?

An old mechanical clock would be nice;

Would simplify our current discussion
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