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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 22nd May 2011, 13:36
  #2081 (permalink)  
 
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Cool

Hi,

Hi,
This is no news, a bulletin inserted in each A330 flight manual (3.08.09). Note that this bulletin was published 10 years before AF 447:
This is a Airbus issued procedure.
Was this one used by AF before AF447 problem ?
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Old 22nd May 2011, 13:36
  #2082 (permalink)  
 
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Dozy, it's more of a cost benefit issue. For newer aircraft right off the production line fancier CVRs might come automatically. But retrofitting them would cost way more than the benefit when you consider the probability of the accident happening again given the record of the plane's reliability. Retrofitting for a fancy experiment in sound is "right out."
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Old 22nd May 2011, 13:51
  #2083 (permalink)  
 
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Hi,
Originally Posted by jcjeant
This is a Airbus issued procedure.
Was this one used by AF before AF447 problem ?
What am I supposed to say about that?
Better go in court for asking them to publish their manuals, drills and control procedures. But I'm quite sure that the lawyers won't refrain from doing it. Hence, you'll know about their findings and, not before, you will then be able to make educated comments because they would be based on something.
But until then, what would be the point for speculating about what happened in circumstances we are still not even aware of: like how the deck was manned by whom, what they did once in trouble, what procedure was applied, was it sound or not, etc..
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Old 22nd May 2011, 13:54
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John Tulla said:

one of the first skills that is lost is what is known as "fine motor control," especially in the hands

gums has made some comments on the F16 stick. I recall from a course years ago (so it might be scratchy) that the initial test article had a zero break out stick arrangement which was unflyable due to low level muscular tremors. If I recall correctly, the initial mod was to introduce a 4lb break out load to get rid of the non-commanded small perturbations.
My memory of the F-16 development (not hands on) is rather hazy as well. But, I seem to remember that the change to the initial fixed-stick force-control only was to incorporate a 1/16 inch backlash movement and include a breakout force measured in mere ounces...just enough feedback to let the pilot know that he had made a control input. Any more would have caused major problems in formation flying and sight corrections during weapons delivery.

I can't remember the stickforce per g for the F-16 (but I am sure someone will jump in). However, the force used in typical fighters at the time such as the F-18, was one lbf per additional g (with also one inch aft stick movement for the F-18) in pitch. The F-18 break-out force was very low.

With regards the Airbus series with sidestick control I seem to remember a 3 lbf breakout force being required to cause the AP to disengage if the instinctive disengage button was not used. The breakout force in manual flight is tiny but noticeable without being objectionable.

Again with regards the Airbus series, in normal flight, the fore and aft movement of the stick in pitch is a g command system (not pitch angle or rate)...ie, back stick commanded an increase in g above 1.0g and vice versa for a forward stick command.

If impending overspeed was sensed, the flight controls would automatically pitch the aircraft up at up the +1g additional (to reduce pitch angle and speed) but stayed in the g command mode.

On the other hand, if impending stall was sensed, the flight controls would go into the alpha mode where fore and aft stick controlled AOA (not g) until such time that the actual AOA reduced below a set value.

These control modes described rely on air data from the ADRs. Any wrong data from the ADRs is quickly detected but, in the meantime the erroneous data can cause the flight controls to revert to degraded flight modes and trip FCS computers off line.

I think that one of the most insidious effects of the degraded modes is when the THS "freezes". In this case the THS MUST be controlled manually using the pitch trim wheel.

I have seen many students completely caught off guard in the simulator when this happens as they try to control the aircraft in pitch using sidestick alone. Of course the THS completely overpowers the sidestick which is only controlling the elevators in this case.

There is an appropriate warning, but in the excitement this seems to be easily overlooked. Manually reset the THS to zero trim and all is OK.

Simulator training is essential to instill the importance of manual THS control and should be conducted regularly during "Jet Upset" sessions.
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Old 22nd May 2011, 13:54
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Originally Posted by syseng68k
Once this was complete, the modules were linked to final code image and tested to the original product spec, again with normal and bad input data and with a variety of hardware failures injected for good
measure
.
Didn't work too well in QF72's case, where one dud ADIRU brought the whole show to it's knees and completely out of the control of the pilots for some time...
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Old 22nd May 2011, 13:58
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Have AF made any change to their procedure for crew rostering/rest since the accident (ie who should be in LHS at ITCZ ) ?
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Old 22nd May 2011, 14:13
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gums, I am starting to wonder if the leaks are from BEA or people reading this stuff and thinking, "Oh, that sounds like it will sell newspapers!"
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Old 22nd May 2011, 14:23
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Dunno, that DS article seems plausible (why steer into Cb - didn't, one puzzle down, no turbulence -CC not seated, second puzzle gone, Capt could be on rest, confirmed). The Capt return to FD could also be the basis of the insinuation about who was on FD.
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Old 22nd May 2011, 14:25
  #2089 (permalink)  
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Stick force per gee

Salute!

Sorry, Flex, but the old mil-specs required approx 4 pounds per gee. The Viper approximates that very well due to the computers. Older jets had springs, dashpots, bobweights and bellows to "stiffen" the stick.

Actual control surface movement for most of the older fighters were directly related to control stick displacement as you have stated. The "artificial" feel techniques varied by aircraft, but the gee doofer seemed the best, as a bobweight exerted more opposing force the more gees you pulled. Planes like the F-4 had audio beepers to let you know about AoA, but I don't think gee - ask 'bird.
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Old 22nd May 2011, 14:30
  #2090 (permalink)  
 
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Mr Optimistic;

Too plausible perhaps? Who would look at a pitch attitude trace, and not look at sidestick positions?
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Old 22nd May 2011, 14:32
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HN39, hmmm, true, but I was thinking it was based only on CVR.
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Old 22nd May 2011, 14:45
  #2092 (permalink)  
 
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I think you are reading too much into the press article.

It didn't say there was no bad weather it said they tried to plot a smooth path through. (they failed)

So we did have turbulence. At the moment the puzzle still indicates an aircraft flying where it probably shouldn't have (still need to know why).

The rest is unfortunately the normal consequences to be expected when you hit the type of weather reported in that area. You know, the weather the others avoided. There is no need to make this unnecessarily complicated just because the truth is uncomfortable.

And please do not take that as blaming the crew. It is just a statement that we need to know why they didn't properly avoid that storm. There may reasons other than wrong call.
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Old 22nd May 2011, 15:18
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Pitot Static

Thank you, Takata for the diagrams and pages of info.

The info as presented tries to pack too much into a page, mixing pitot and static pressures together. AFAIK, all the prior events were airspeed errors alone, and did not have altitude errors. Airspeed and altitude are separate and unique functions within the ADR, except at low speeds, and their output data bus words are separate and unique. An ADR may flag or put out erroneous airspeed without affecting altitude output.

The FCOM Bulletin #009 page 3 gives the case for total pitot obstruction, not just drain hole obstruction, although it is known that Thales pitot were prone to drain hole obstruction due to roughness in the holes. Drain hole obstruction without impact air obstruction will give an erroneous higher than correct airspeed.

Total pitot obstruction, per page 3, puts the plane into an unstable situation. Increase of altitude cause increase of IAS. The A/P will try to increase pitch to reduce the IAS, causing even higher erroneous IAS. This is in accordance with Der Spiegel story.
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Old 22nd May 2011, 15:36
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where do you people get your imagination from?

Try engaging an autopilot with those fault messages. Oh ye. it won't.

And speed and altitude functions are not unique at all. Yes if the pitot probes only are affected then you will only suffer speed problems however if your static ports have a problem you will witness both altitude and speed issues.

All BEA are trying to do now is ensure a professional release of the information because it has been established that the a/c was technically fine. Now that doesn't leave many options.

Until we know why the crew didn't avoid that weather front we won't know why this happened. We already know what happened.
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Old 22nd May 2011, 15:41
  #2095 (permalink)  
 
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Safety Concerns:
Try engaging an autopilot with those fault messages. Oh ye. it won't.
Do we know how long the pitots were iced and in what manner before the A/P disconnected?
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Old 22nd May 2011, 15:48
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Pitot total

I've followed this complete tread and have nothing to add really but now I was wondering the following: I've had many discussions about the result of a blocked pitot and all people I've spoken to think the same so I gave up!
But I'll give it one more go!

Although with an open pitot head the effect is minimum but I was thinking that with a blocked pitothead the buildup press inside will slowly "leak" away through the drainhole???

The result off this would be a slowly decreasing speed reading staying at fltlevel and same real ias???

Pls. You proffesional idea about this?
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Old 22nd May 2011, 15:51
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I have been a lurker on this board and have to say that I really appreciate the comments here by professionals. It has helped me realize how much it actually takes to fly such an aircraft. Something one usually does not think about when traveling as a passenger (as am I).

jcjeant:
Having said the above, I am unsure where your comments are coming from. In the interest of full disclosure, so I can make an informed opinion: are you a pilot, passenger, lawyer, associated with one of the family on AF447? Or just somebody with some hatred? What exactly is your expertise?

Thank you
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Old 22nd May 2011, 15:51
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JD-EE

gums, I am starting to wonder if the leaks are from BEA or people reading this stuff and thinking, "Oh, that sounds like it will sell newspapers!"
I concur, see #1820.
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Old 22nd May 2011, 15:55
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takata & Graybeard,

Lets assume for a minute (I say assume), the scenario that Graybeard has proposed is correct, e.g., the AP is attempting to correct for an erroneous reading of higher speed by pitch up. Would, at the same time, the AT functions begin to roll back thrust (N1)? I assume the ECU or FADEC would be receiving the same erroneous speed data and react accordingly. Once out of AP & AT and without correct knowledge of airspeed, one would have to reset both pitch and engine speed manually using the tables for a 35K altitude, wherever those table might be in the cockpit at the time. So then, I wonder how long one has, without correction, to reach a stall point from which recovery becomes difficult or problematic.

Just some curious questions. takata, thanks for all the charts and data you posted.
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Old 22nd May 2011, 15:59
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Safety Concerns

"...All BEA are trying to do now is ensure a professional release of the information because it has been established that the a/c was technically fine. Now that doesn't leave many options.

Until we know why the crew didn't avoid that weather front we won't know why this happened. We already know what happened...."

Not sure how you in fact know what "All BEA are trying to do"

How do you know they were in weather?

You already know what happened?

I think you are basing conclusions on the Leaks.

At this point, "technically fine" is in play. The "Leaks" almost certainly derived from BEA data, though the "provider" identity is in doubt.

If BEA spill the beans this quickly, it will be surprising. If they do, they will have made a rapid fire finding of fact(s). Indicative of an unusually clear chain of failure, the data must have been remarkably straightforward

I am still intrigued by the method by which the a/c stalled. Was it AoA creep, was it inattention, the fact remains it occurred prior to, or consequent to a/p, a/thr loss. How steep was the incline Captain DuBois had to climb towards the Flight Deck?

If his voice is on the CVR, shouting, then one suspects loud ambient noise, which he felt he had to overcome, or did he take exception to the crew's lack of response?

All in all, even to this day, nothing new, whether airframe or crew related. I've been yelled at, but I deserved it.
 

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