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AF 447 Thread No. 7

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AF 447 Thread No. 7

Old 9th Dec 2011, 19:17
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Originally posted by Lyman ...

Still looking for direct evidence of ICE, not unsubstantiated opinion.
The following may help your search for evidence:-

Then review the CAS trace in BEA's IR#3 - second from top on page 112. I'm sure you will note the increasing CAS during the climb
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Old 9th Dec 2011, 19:25
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447 entered an updraft, it is on record. after exerting its influence on her, she started to climb, and reached a VS of 500fpm. What was the velocity of the updraft? 500fpm? Hardly. let's be conservative and call it 60 knots, vertical. Before the airframe rises, the pitots are sampling the airflow. If 60 knots on the nose, the IAS is 60 knots increased. If on the tail, 60 knots reduced. How about straight up? 30 knots less, and sampled simultaneously by all three probes. This is enough to cause the a/c to reject NORMAL LAW, and degrade to ALTERNATE. It also explains some Mach deviations reported in the DFDR. After sufficient time to outwait a possible anomalous loss of AS, the A/P is commanded to quit, after the RTLU locks.

Now this does not solve the problem of what happened, but it does suggest that perhaps an obsession with ICE may want a look. It may also call to question the reliance on this autoflight system in a cell.
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Old 10th Dec 2011, 03:45
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Air France 447 Flight-Data Recorder Transcript - What Really Happened Aboard Air France 447 - Popular Mechanics

The best so far and probably a synthesis of what the final BEA report will say. So helplessly sad.
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Old 10th Dec 2011, 05:03
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The comments reading is interesting
I notice that many are pointing to the dual input system and again yoke versus side stick and also the lack of CRM
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Old 10th Dec 2011, 10:12
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Updraft/downdraft velocities

The vertical wind speeds in this graph have been derived from the recorded AoA, pitch attitude and the aircraft horizontal and vertical speed components. The calculation is very sensitive to small errors in AoA and pitch attitude, and should therefore perhaps not be taken too seriously.

Last edited by HazelNuts39; 11th Dec 2011 at 10:41. Reason: Change of image hosting service
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Old 10th Dec 2011, 15:56
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HazelNuts39

I take your point re: sensitivity. Such vulnerability to errors of small magnitude is out of context (sic) for any graph of windspeed. One is tempted to say that the nomenclature is reversed, and that the airmass is the line "Aircraft". However, to claim the airmass line as the a/c would involve a belief that the v/s of this airframe is ridiculously responsive to airmass, let alone controls.

So the graph is essentially useless, imo. A response of airframe of even 500fpm to an updraft of 2500fpm is to stretch, especially when considering the a/c is in sensitive airspace, and in autoflight. Also consider the airframe, per graph, is responding far too quickly to light forces, and reversing out of all sense of Physics.

Do you take my point? The airframe is climbing at a rate completely inconsistent with the data. No updraft of 2500fpm will cause this aircraft to leave its cruise level with a functional (sic) autopilot latched. Nor will it cause said autopilot to command 4.5 degrees nose down (-1 degree PITCH) from cruise (+3.5 degrees) at Mach .80.

All this well before disconnect, no PF touching anything.

mm43

I am not saying there was no ICE. I am proposing that the loss of autopilot and the degrade to AL was caused by loss of AS, actual, as a result of Updraft. Once in the climb, in warm wet air, the airframe, including Pitot Probes and Statics, may well have ICED. I believe that it was likely, even. I also think that it was not consequential, since Airspeeds returned quickly. At that point, however, the Airspeed was remarkably lower, due Updraft, AoA, and climb gobbling up energy.
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Old 10th Dec 2011, 16:03
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Rates versus gee versus "q" and Ps

Excellent post, Retired. And coming from an old stick-and-rudder-and-AoA dude, heh heh.

- As with the 'bus, our Viper control inputs resulted in close to "absolute" rates and gee, and were not "additive". The 'bus has some attitude and roll values added that we didn't employ. e.g. Pitch gee is biased for pitch attitude up to "x" degrees of pitch in Normal law. Gee is also adjusted for bank angles up to "x", so making a level turn and keeping the jet level is easier than what we had in our little jet. This aspect of the Nz laws helped us enter the dreaded deep stall at extreme pitch attitudes, as relaxing stick pressure resulted in a continuous one gee pitch command and the jet didn't go over the top in a ballistic trajectory at zero AoA or gee.

- The discussion about blending pitch rates with the gee command is a good one. Our laws reflected that, especially in landing configuration when rate dominated gee command. We also biased the AoA curves to provide us the "feel" of a conventional jet where you trimmed/commanded for an AoA. In other words, the neutral speed stability had to be overcome.

- Both of the above made the Viper feel like a much larger jet. Going thru turbulence and thermals at low altitude/high speed was very smooth. Was like an old Cadillac with the "soft" suspension versus the teeth-splintering up and down ride.

- The dynamic and static pressure inputs influence body rates due to the "gains" that are used for control surface deflections in magnitude and rate. As I have pointed out before, the Viper used fixed values for the gains when the air data was deemed unreliable. Seems the 'bus gives up and tells the pilot - "you have the controls". Heh heh.

MM43's input on handling the frozen sensors hits home for this old dinosaur. Had the static ports freeze up once in the SLUF and was descending for the approach in weather. Hmmmmm... I am not going down and speed is building up. Since we had an inertially-derived vertical velocity in the HUD, it was obvious I was going down and I checked groundspeed ( also inertially-derived), Clue light comes on and I realize I had frozen static pressure. BFD and waited for the radar altimiter to kick in at 5,000 feet and then the ice on the ports finally melted, so things were back to normal.
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Old 10th Dec 2011, 16:10
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gums

And certainly without PAR, eh?
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Old 10th Dec 2011, 19:18
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Originally Posted by Lyman
So the graph is essentially useless, imo.
I'm really relieved to read that.
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Old 10th Dec 2011, 20:02
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It is apparent that HazelNuts39's graph is based on sound method and best available data.

To dismiss it because it does not support a theory, seemingly based on numbers that have been pulled out of a hat at random, is foolish.
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Old 10th Dec 2011, 20:28
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@ Lyman

No PAR, just ol' Gums and the ILS radio stuff and some skill and cunning. Oh yeah, no PNF to worry about.

OTOH, worst WX I ever landed in was a PAR, and a crusty Navy Chief talked me down in 100 and a quarter official, but more like 50 and an eighth. Call it WOXOF, if you will.
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Old 10th Dec 2011, 21:08
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I might be making a totally stupid remark, but the "wind chart", even though it's not reliable, made my mind think "physics of flight".

Don't know the A330, neither how silent/loud it is and how loud changing airplane velocity is. These "speed of airflow" changes are not always created by changes in airplane speed, but also by violent up- or downdrafts. I wonder if, even when the airplane reduces its speed in reality, the sound of increasing violent updrafts could've created a false sense of speed.

On the other hand you have the physical characteristics of low speed stall (low speed because the "stall" protection is here primarily a low speed protection), which in my brain has always been a "silent" maneuver because of low speed. Yes buffet will be there, but it can also be a characteristic of higher speed flight.

If that is the case the "initial pull" seems logical because the physical environment gives you the impression of being in an airplane that increases speed. Add a "stall" warning on top, and confusion can be total. Sense and computers give totally opposite impressions to the pilot and it is only the "wind sound level". We all know the problem of visual illusions, however they can also be physical.
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Old 10th Dec 2011, 22:19
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Originally Posted by RetiredF4
The rear lateral Turbulence Damping command is computed by the FCPC1
What is FCPC1 and which aeroplane has it installed?

Originally Posted by Gums
our Viper control inputs resulted in close to "absolute" rates and gee, and were not "additive".
Because you had G-trim, very useful feature for tactical fighter, absolutely unnecessary for aeroplane that spends 90% of its time in straight and level.
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Old 10th Dec 2011, 23:34
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Clandestino
What is FCPC1 and which aeroplane has it installed?A330 /340
You ask for others or you are testing?


GENERAL DESCRIPTION A330/340 Flight Controls

The surfaces are controlled by three types of computers, depending on their
functions:
- the Flight Control Primary Computers ( FCPCs ) ( 3 per A/C ),
- the Flight Control Secondary Computers ( FCSCs ) ( 2 per A/C ),
- the Slat and Flap Control Computers ( SFCCs ) ( 2 per A/C ).
The FCPCs and FCSCs enable to control the aircraft in the roll, yaw and pitch
axes.

and so on....

As said before, it is useless to discuss matters without having basic knowledge of the systems.
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Old 11th Dec 2011, 00:53
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@Lyman

I know you have "pulled" a post where you accepted that ICE was a factor, though stated again the inability of the A/P to maintain altitude in what appears to have been a fairly steady updraft (+/- turb) for about 25 seconds prior to A/P disconnect.

The A/P was pitching the aircraft ND in an attempt to maintain assigned ALT, and clearly from the graphics, the RVSM parameters were being exceeded. Perhaps the A/P disconnect was for that cause, and the UAS just happened along with the rising "warm/wet" air. The RTLU "latch" could only have been caused by the "speeds", and coincidentally the RVSM and UAS issues collided - time wise.
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Old 11th Dec 2011, 01:17
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After reading the "talk in the cockpit" I thought why are the hand control sticks not linked together mechanicly-So each pilot can feel & see the input of BOTH controls, Not, One pulling to climb-One pushing for Air speed. With HAL 5000 on the fritz with frozzen petots ,Looks like a major design screw up in anyones book.
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Old 11th Dec 2011, 17:42
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Originally Posted by Hamburt Spinkleman
To dismiss it because it does not support a theory, seemingly based on numbers that have been pulled out of a hat at random, is foolish.
That's our Lyman! (ba-dum-tish!)

In all seriousness though, what Lyman is not taking into account is the time factor of the calcuations for those readings and traces. One of the things I noticed on my A320 sim trip was that when an altitude capture is selected, the V/S display on the FCU module will initially display a surprisingly high value before it settles - I believe this is because the value is computed in real time and relates to what the V/S *will be* if the current pitch and thrust commands are maintained - of course, when the autopilot stabilises pitch after the initial pitch-up or -down, this value becomes something more realistic.

My theory is that the values on the trace are also calculated in real-time and those large bumps just before disconnect are a result of what the V/S *will be* if the current trajectory is continued, the pitch is retained and/or corrections are not made. The autopilot was engaged long enough to ride out the bump but did not have enough time to return the pitch attitude to 4 degrees nose-up, eventually coming to rest around 1.5 degrees nose-up. The aircraft would have regained cruise level on it's own, but slightly more slowly. Everything that happens after then (including the elevator movements that command the zoom climb) are a result of the PF's overcontrol of the sidestick.

I suspect that what may have spooked the PF was not something he saw that we don't know about, but something we do know about - namely this "bump" just before disconnect, which briefly brought the pitch attitude below 0 degrees. The residual autopilot command was enough to bring the nose back above zero, but I think he mentally programmed himself to correct it manually and unfortunately overcooked it. From then on they were in the zoom climb and things quickly stopped making sense for him.

@hillberg - read the thread from the beginning, it's always going to divide people but it has already been covered to death here and elsewhere.
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Old 11th Dec 2011, 19:14
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TSB reports over threads ,A **** load of "Computers" & No "pilots" and control "Inputs" that have no feed back from PIC & SIC, A flawed approch to innovation in flying.
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Old 11th Dec 2011, 20:11
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A330 AP/FD & A/THR Conditions

Assembled from separate logical snippets.......(could be not complete!)

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Old 12th Dec 2011, 09:51
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Originally Posted by DozyW
My theory is that the values on the trace are also calculated in real-time and those large bumps just before disconnect are a result of what the V/S *will be* if the current trajectory is continued, the pitch is retained and/or corrections are not made.
Based on the close correlation of normal acceleration, V/S and altitude (each being either the time-derivative or the integral function of one of the others), I don't think the traces support that theory.

According to FCOM 1.31.40 p.15 description of indications on PFD:
The displayed vertical speed information is normally based on both inertial and barometric data.
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