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AF 447 Thread No. 7

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AF 447 Thread No. 7

Old 24th Nov 2011, 11:47
  #481 (permalink)  
 
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Sure looked like a lot more than 900' remaining to me based on runway markings. They may need their RAS database checked.
Metric callouts?
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Old 24th Nov 2011, 15:21
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Lately when I try a post, it fails to post and I am automatically (?) logged out. Not that I have that much to offer, but it is strange.

I prefer to think of HF as judgment and abstract process, not floormat under pedal sender. Also CRM.

I take your point re: LAW degrade ROLL, while remaining consistent in PITCH. The serious problem as I see it is retaining both in the same stick.

Try teaching yourself to reconsider the control as sensitive in one plane, and in the other, not so much. Unlike others here, I don't think PF had ham hands, or a "death grip" on the stick; I think he was focused on keeping 447 off her back. In doing so, he slid through fore/aft movements, and..........

BEA stated that after the a/c was commanded up, it was not immediately responsive. That does not mean she didn't climb. Also, AoA was well ahead of PITCH, consistent with a strong updraft. We'll have to see why the a/c commanded 5000fpm down for thirty seconds prior.
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Old 24th Nov 2011, 16:19
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Originally Posted by Lyman
The a/c was NOSE DOWN at handoff. It was also climbing at 1000fpm.
Again with the making stuff up. The nose pitched to a max of 1 degree down briefly for 3-5 seconds at 02:10:00 (still in autoflight). Disconnect happened at 02:10:05, at which point the pitch attitude was approximately zero. The climb starts at 02:10:15, because the PF has manually set the pitch attitude to about ten degrees.

The aircraft does not exceed 20 degrees of roll throughout the disconnect/zoom climb part of the sequence and only starts to approach 40 degrees of roll once the stall is well established. The protection limit of Airbus FBW is 67 degrees of roll. 40 degrees of bank is definitely out of the ordinary, but the notion that the PF was fighting to stop the aircraft from going on "her back" is nonsense.
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Old 24th Nov 2011, 17:42
  #484 (permalink)  
 
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Cruise: +3. Add 1 degree, FOUR degrees nose low. And CLIMBING.

The airframe is not Protected in ROLL in AL2, so your "67 Degrees" is meaningless.
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Old 24th Nov 2011, 18:33
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Machinbird Nice Depiction of the stick movements Grity! For a transport sized aircraft, this is very rapid. Mayonnaise stirring for sure when you consider the scale of what is happening with the aircraft. And look at the amplitudes of lateral stick travel!.
PF had to be all tensed up with his mitt firmly around the stick. Probably with his arm not properly supported as well.
in both of this videos is the speed of stick move maybe faster
(between 1:20 and 1:30.....)



ok both are landings with slower speed, and low altitude, and the first one is not an A330 but to stir one`s coffee is obviously not unusual....???

@ lyman exist the (very smal) possibility of a undiscovered worn or brocken rod-spring into the sidestick ???
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Old 24th Nov 2011, 19:26
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Originally Posted by Lyman
Cruise: +3. Add 1 degree, FOUR degrees nose low.
No - this is what we call "moving the goalposts" in the UK.

And CLIMBING.
No - even if you go by the vertical speed trace (which starts climbing before the altimeter trace), climb is not established until 02:10:11, at which point the pitch attitude is approximately seven degrees nose up and continuing in that direction.

The airframe is not Protected in ROLL in AL2, so your "67 Degrees" is meaningless.
You misunderstand me - I was not saying the aircraft was protected, I was saying that even with the aircraft at it's max bank angle in the stall, it was 27 degrees shallower than the absolute maximum the computers will allow when the protections *are* working, hence any idea that it was about to go inverted is complete hogwash.

I know you want to believe in a heroic PF that was wrestling a bad aircraft, but it simply is not borne out by the evidence. What we have is a relatively young pilot who was badly let down by his employer and was never trained for the situation in which he found himself. Having not been trained, he made the wrong choice when he raised the nose beyond five degrees. He compounded that by making another wrong choice and trying to keep the nose up and applied TOGA. He made a further wrong choice when he tried to deploy the speedbrakes. Bad move after bad move after bad move - but he'd never been told the right move.

@grity -
exist the (very smal) possibility of a undiscovered worn or brocken rod-spring into the sidestick ???
Very unlikely, or the BEA's simulated responses would not have tracked so closely. The videos you post show normal sidestick deflection during low-altitude operations, including takeoff, initial climb, approach and landing - but you shouldn't see those kind of deflections in cruise.
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Old 24th Nov 2011, 19:37
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Talking Impression from one who has no idea WTF he's talking about

@grity's videos:
Yi-yi-yi-yikes!!!
It certainly appears that the mayonnaise is well-blended.
(I do not want to fly in an elaborate video game!)
Thanks for these wonderful videos.

Something new occurred to me, although highly unlikely:
I wonder if the stick had a broken transducer. Perhaps that could explain all of these seemingly unexplainable inputs. Of, course, we hear no (as so far published) verbal feedback that would indicate such. Just another unsubstantiated thought to argue about.
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Old 24th Nov 2011, 19:47
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Grity,
The two videos are a bit of apples and oranges comparison with the AF447 initial PF control motions. Let me try to explain why:

First, the aircraft are landing, so the followng applies:
FLARE MODE
The flight mode changes to flare mode at landing, when passing 100 feet.
Flare mode is a direct stick-to-elevator relationship (with some damping provided by load
factor and pitch rate feedbacks). In addition, at 50 feet, a slight pitch down elevator order
is applied, so that the pilot has to move the stick rearwards to maintain a constant path,
so as to reproduce conventional aircraft aerodynamic characteristics.

Second, since the aircraft are landing, the aircraft must be in the proper location and attitude for "ground interface". This requires increasing attentiveness on the part of PF. It is a bit of a "crescendo" effect.




Third, There is a major difference in the control techniques displayed compared with the AF447 PF technique.
  • In the videos, the majority of the control inputs are pulses from neutral (Until Flare mode is activated).
  • On AF447, the control inputs were continuous.
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Old 24th Nov 2011, 19:53
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Couple of things to note about the 330 vid at JFK:

1. At 33 secs point, after A/P disconnect, "Flight Directors, OFF".

Not dealing with SS moves, but I think fair game for a Tech Log comment:

2. RAS info on final: "Approaching 22 Left." Well and good.

RAS info on the runway after NW touchdown: "One thousand, two hundred remaining."... "Nine hundred remaining." Sure looked like a lot more than 900' remaining to me based on runway markings. They may need their RAS database checked. 22L is 8400' & the double high speed taxiway they passed on the right is only half way down.

(BTW Mach' stated the above post very well)
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Old 24th Nov 2011, 20:06
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Mach', your post got shifted, but I think you're right about metric, it is a customer option.

The incompatibility with this on a US runway is that the callouts would not numerically coincide with the distance remaining markers.

And the RA callouts are in feet.....

(This random posting is like trying to talk to my wife.)

(And actually it's RAAS not RAS)

Last edited by OK465; 24th Nov 2011 at 21:01. Reason: Imperial v Metric
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Old 24th Nov 2011, 21:07
  #491 (permalink)  
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Board problems.

Re the comments about DTG and post ordering, as well as difficulty posting - I raised these with the hierarchy yesterday and the answer came back that we are experiencing the problems across all forums.

Both problems are ones we have had periodically in the past and it is a matter for the boffins to tweak a bit to fix things.

The delay on this occasion falls to the US holiday. Hopefully we will see the problems disappear shortly.

This random posting is like trying to talk to my wife

All of us married chaps have to let that one through to the keeper ...
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Old 24th Nov 2011, 21:15
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There will always be an England

@john_tullamarine
"...boffins.."

Isn't that some sort of a fish?
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Old 24th Nov 2011, 21:26
  #493 (permalink)  
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Guess I have to admit to being a boring old phart dinosaur of an engineer.
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Old 25th Nov 2011, 06:18
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Originally Posted by Dozy
He made a further wrong choice when he tried to deploy the speedbrakes. Bad move after bad move after bad move - but he'd never been told the right move.
Dozy, please tell me what was bad about deploying speedbrakes?

The mistake was not leaving them out long enough to realize that they had no effect on the aircraft. If PNF had not climbed all over him immediately for selecting the speedbrakes, they might have had a chance to realize that the aircraft had something other than "Some Crazy Speed."

PNF was so uneasy by then, the "emotional sparks" in the cockpit must have been a foot long. This interpersonal tension interfered with everyone in the cockpit's ability to reason.
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Old 25th Nov 2011, 09:31
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Originally Posted by DozyW
the BEA's simulated responses would not have tracked so closely
I would expect the PF to notice the different 'feel' of a stick with broken spring. The AB simulation is based on the recorded SS position, why would it be affected by 'feel'?
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Old 25th Nov 2011, 10:10
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Springs, force transducers, physical feedback, et al

Salute!

Looks like more efforts to blame the Bus versus the pilot, or a combo.

I have gone on record as feeling some Bus design features did not "help" the crew, but also feel most blame will still rest upon the shoulders of the crew and the mentality that the jet will "protect you".

Our physical feed back from motion/position of the stick is pretty decent if flying something as I did. Larger roll and pitch rates, and the inner ear sensors and the gee sensors in your butt helped. But the big heavies don't respond all that fast, so using visual cues ( like the instruments or outside the windshield) is the primary feedback, huh?

Spring failure is a red herring, IMHO.

About the only thing I would do is add force transducers to the grip as we had in the SLUF. That sucker had the same stick grip as the original Viper. So with "control augmentation" active, the first four pounds of stick pressure commanded control surface deflection with the angular position of the stick "frozen". Used to test this on test flights. Above the four pounds of pressure, you had to move the stick in an angular fashion, just like the "old" planes. If anything, the springs on the Bus stick may be too light. Maybe increase the pressure/force required to move that sucker a lot.

Just some thoughts from an old dino.
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Old 25th Nov 2011, 11:03
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Originally Posted by mm43
the nominal OAT was -43C and an updraft containing super-cooled droplets could have created an "ice-block" on the pitots and possibly other surfaces within a second.
Quite a jump from computer-simulated molecules. Clever molecules that avoided the ice detectors?
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Old 25th Nov 2011, 11:08
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Netstruggler, I am trying to explain to the non pilots on this forum just how difficult it would be to deal with varying control harmony.

When was the last time you flew an airbus at FL350 in roll direct? Does the roll response remain constant when roll rate degrades to roll direct?

A/P off. A/T off. F/D off. Thrust climb. What speed will it maintain?
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Old 25th Nov 2011, 11:34
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Originally Posted by Dozy
They were stalled, that's what was bad about it! They were mushing at that point, and slowing down further might have rendered the aircraft completely unrecoverable.
Dozy, they didn't know that. Since the speedbrakes were rising from the wings into the wake of the stalled wing-there was minimal incremental drag. The effect was minimal with regard to incremental AOA.

If they had really been going at some crazy speed, they would have been thrown forward in their seats and had that impression confirmed.

As it was, they felt no more deceleration sensation than if the aircraft were on the ground, parked. That lack of sensation should have been a big clue, but the crew were so keyed up by then, they did not recognize the significance of the brief 3 second activation and its lack of deceleration.

It was not an error to deploy the speed brakes when PF did so.
The error was letting PNF cow him into retracting them prematurely.
FCOM
SPEEDBRAKES
No Limitation

Last edited by Machinbird; 25th Nov 2011 at 11:35. Reason: TIME WARP NOTICE
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Old 25th Nov 2011, 11:59
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Cool

Hi,

Zorin_75
It didn't look much like a methodic attempt at troubleshooting though...
These pilots have behaved like small children
Indeed .. in presence of a toy (to awaken the sens of curiosity) with levers and buttons of all colors a child will operate them out of curiosity
If its action on a lever will give a result (eg music) it will start its work on the same lever for a while
If there is no immediate result .. it will handle quicly one after the other without interruption the levers and buttons and will be frustrated
This is exactly what makes these pilots
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