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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 19th Dec 2014, 18:24
  #861 (permalink)  
 
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Hi A33Zab,

Apologize for posting slightly off-topic, but since you're here (and the subject has been touchhed in posts above),

Is the Flare Law in the A330 similar to the A320? The FCOM wording seems to differ a bit between the two. I wonder if it's just a wording issue, or the A330 Flare Law is implemented differently, due to size of the a/c or other reasons...
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Old 19th Dec 2014, 19:09
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Airbus has Laws, Boeing has Modes....
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Old 20th Dec 2014, 03:12
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From Airbus FCTM and from instructor support :

FLIGHT MODE ANNUNCIATOR
The FMA is located at the top of the PFD screens. It is divided into 5 columns
which indicate the operational modes of the AP, A/THR and FD. The columns
are numbered from the left and indicate the following:

The relation between the pilot input on the stick and the aircraft response is called the CONTROL LAW which determines the HANDLING CHARACTERISTICS of the A/C.
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Old 20th Dec 2014, 07:11
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FLARE LAW

@C_Star:

BPalmers explanation is extensive and correct if all works as advertised.
In ALTERNATE - if due to multiple ADIRUs faults - do not rely on Hi AoA protection/Vc protection (ALT1) to kick in.

@Winnerhofer:

C_Star is correct: it is FLARE LAW not FLARE MODE.
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Old 20th Dec 2014, 08:21
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Winnerhofer
Basically Law is manner of flight controls response to side stick input. It uses the word mode as ground mode, flight mode and flare mode to define different laws in operation during that phase. Also it uses word mode to define phase of FMGC like Take off, Descent cruise etc. For instance in one document it says Thrust levers are also mode selectors meaning they can change the phase. It is used loosely.
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Old 20th Dec 2014, 17:47
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After five+ years of discussion about AF447 flight laws we start to search the definition of the words "law" and "mode" ...

Last edited by roulishollandais; 4th Jan 2015 at 17:02. Reason: franglais
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Old 20th Dec 2014, 17:54
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Quote:
Originally Posted by Winnerhofer
Once the plane is in ALT, it remains in ALT until overseen by maintenance.

Not exactly - Alternate Law is only "latched" (as in cannot revert to Normal) if the divergent conditions last for more than 10 seconds. A transient condition of less than 10 seconds will allow for a return to Normal Law in flight.

In this case the pitot tubes were blocked for too long and Alt2B was latched.
Thank you both.

I have been lurking on the forums a while, but left the discussion to the experts. So with the big disclaimer that this is all coming from a non-pilot, there is one aspect that has been standing out for me:

It is astounding how much into a 'tunnel visoned' Bonin must have been to miss that he was having the plane in climb for a total minute. It was night outside and it seems he left all the ECAM trouble shooting to his partner, so his eyes must have been on the PFD. Yet he seemed to ignore the altitude display, with the numbers constantly changing, aswell as the the climb/sink rate rate gauge.

After around 25 seconds in, at FL 368 Robert tells him to mind his height, and Bonin explicitly acknowledges it ("Ok ok je redescends"). Some nose-down inputs on the stick follow, but, for a lack of better phrase, the stress must have pushed "height awareness" out of his mind again, as he continued climbing up to finally FL 378.

It seems during those 60 seconds pre-stall a simple realisation like "My supposed FL is 350. I am 2000 feet above my FL, I must descend!" never materialised.

In this thread and in the BEA report the term "startle effect" is brought up several times and it feels to be spot on. It's very hard to read the transcript and not think "If only Robert had been more insisting after he noticed the wrong attitude".

Last edited by Calapine; 20th Dec 2014 at 21:31. Reason: spelling correction
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Old 20th Dec 2014, 18:48
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Originally Posted by A33Zab
it is FLARE LAW not FLARE MODE
FLARE MODE does exist too.
Actually Airbus is not too sure how to name it ...
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Old 20th Dec 2014, 23:07
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BEA Video

The official BEA video representation of the recorded flight data is meant for professionals.
So, how does it look for a professional?

First of all, of course, a professional had already read all the available reports, interim and final. From the data, presented in those reports, a professional had already understood fully what had transpired on the flight deck of AF447.
Still, reading data from graphs, spread out over several pages, makes it somewhat awkward to integrate, for instance, the stick movements with the aircraft attitude variations.
The video does this information integration very nicely.

Earlier in the whole discussion about AF447, somebody made a remark about the steering commands of the PF as if he was stirring mayonnaise in a mixing bowl. The video nicely illustrates that concept. The wild left / right gyrations of the sidestick do not seem to be justified by aircraft roll behavior.

The total lack of situational awareness is illustrated by the useless slam forward / slam backward movements with the thrust levers and by the utter disregard for the pitch attitude.

One can understand the tendency to initially start a correction in the upward direction, because the altimeter did dip down a couple hundred feet at the start of the event. However, there seems to be no target at all to strive towards resettling at FL350. It is all just blind panic to yank on the stick.

An airliner at optimum cruise level has a pitch attitude of about 2.5 degrees nose up. The usual climb rate when optimum cruise level is reached, is 1.000 to 1.500 ft/minute. When a step climb is made, the engine thrust is sufficient only to sustain an increase in pitch attitude of about 1 degree!
In normal words, an airliner at cruise level is as fit as an old geezer. There is no way that an airliner at cruise level can sustain 10 or 15 degrees pitch up attitude without massive loss of airspeed.
Still, the video shows that just before the apex of the pull-up, there is a pull movement of the sidestick that shortly yanks the nose up to a whopping 18 degrees.

The only reasonable explanation for the steering behavior is a panic mode, right from the start – but, the text from the CVR transcript had already shown that, the hapless comments, …. .

Secondly, the video opens up again the hamster wheel of arguments about, if this had been different in Airbus, or that had been different in Air France - Baloney!

Judging from accidents worldwide and on all types of aircraft, a certain percentage of pilots has no clue about real flying, no matter how many hours they have cruised airliners through the sky. Would stick shakers, interconnected yokes or simple old fashioned flight control systems have made any difference? NO.

Look at West Carribean MD-82, 16 august 2005, over Venezuela, stick shaker ON, stall and yoke fully back all the way from FL330 into the ground. Besides the rattling stick shaker, there was also the call from the First officer, "Captain, this is full stall, full stall!"

Look at Swiftair MD-83, 24 july 2014, yes, this year, over Mali, stick shaker ON, stall, wingdip over left and guess what were the yoke inputs all the way down from FL310 until just before impact? Full backstick and right roll!

Especially in that latest case, there is no excuse possible along the lines of – how could we know? Well, by soaking up aviation knowledge perhaps, after all that has been discussed in the aviation world since 1 june 2009, the fatal date for AF447.

Last edited by EMIT; 21st Dec 2014 at 17:03.
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Old 21st Dec 2014, 06:41
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@ CONF iture

Actually Airbus is not too sure how to name it ...
True,

AMM is more consequent about naming:
FLARE LAW if as a function of EFCS
FLARE MODE if as a function of AP/FD.
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Old 21st Dec 2014, 10:46
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A33Zab
As I said these terms are used loosely. Following is from A330 and A320 FCOM respectively where it says MODE. There is a little bit of difference between A330 and A320.


FLARE MODE


Ident.: DSC-27-20-10-20-00000273.0001001 / 23 JUL 12


Applicable to: ALL


When the aircraft passes 100 ft RA, the THS is frozen and the normal flight mode changes to flare mode as the aircraft descends to land. Flare mode is essentially a direct stick-to-elevator relationship (with some damping provided by the load factor and the pitch rate feedbacks). At 50 ft, a slight pitch down elevator order is applied. Consequently, to flare the aircraft, a gentle nose-up action by the pilot is required.


FLARE MODE


Ident.: DSC-27-20-10-20-00001071.0001001 / 23 JUL 12


Applicable to: ALL


When the aircraft passes 50 ft RA, the THS is frozen and the normal flight mode changes to flare mode as the aircraft descends to land. Flare mode is essentially a direct stick-to-elevator relationship (with some damping provided by the load factor and the pitch rate feedbacks).
The system memorizes the aircraft's attitude at 50 ft, and it becomes the initial reference for pitch attitude control.
As the aircraft descends through 30 ft, the system begins to reduce the pitch attitude to -2 °nose down over a period of 8 s. Consequently, to flare the aircraft, a gentle nose-up action by the pilot is required.
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Old 21st Dec 2014, 13:33
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@vilas:

You have convinced me,
They should change MODE here into LAW (like in FCTM/ISD/AMM) to prevent confusion with AP/FD Flare Mode.
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Old 22nd Dec 2014, 15:15
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EMIT
Judging from accidents worldwide and on all types of aircraft, a certain percentage of pilots has no clue about real flying, no matter how many hours they have cruised airliners through the sky. Would stick shakers, interconnected yokes or simple old fashioned flight control systems have made any difference? NO.
However Air France through his spokesman E. Schramm said maximum competence was present in the person of the 3 pilots in the cockpit of AF447
It just remains to explain why these 3 pilots have not practiced these skill during the decisive 4 minutes of the flight Rio Paris
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Old 23rd Dec 2014, 21:54
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Emit

Would stick shakers, interconnected yokes or simple old fashioned flight control systems have made any difference?
How much difference do the side sticks, detents, laws, sub laws, modes, conditions that only occur if the plane above a certain speed, hight, wheels down etc etc etc etc etc etc make? Im not saying these things are totally useless but a modern western commercial plane with significantly less of these complexities does not have a noticably higher accident rate? Does does the extra complexity counter their potenial benifit. Genuine question.
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Old 29th Dec 2014, 22:20
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OZ8501

It would appear at this stage to be related to the thunderstorm activity along the flight path.

We all thought that we wouldn't see pilots pulling up into a stall again repeatedly but it happened in the swift air MD-83 accident this year.


If this turns out to be a stall/weather related accident that will be the 5th in the last 10 years (West Carribean, Colgan, AF447 & Swift Air so far).


Perhaps it is time to install stick/yoke pushers that automatically push the nose down upon repeated Stall Warnings?
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Old 29th Dec 2014, 23:07
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Originally Posted by Winnerhofer
Why didn't the BEA do this filmed just as TSB did?
Presumably because it was a different scenario. As I've said before, with SR111 the most glaring outcome regarding procedure was that the cockpit smoke procedures were not fit for purpose because the procedures took too long to follow and did not take into account the possibility of an immediate need to land. With AF447, the crew did not follow any published procedures, so there was no need for that kind of experiment.

Originally Posted by Qantas_A380
Perhaps it is time to install stick/yoke pushers that automatically push the nose down upon repeated Stall Warnings?
The problem with that is that in the event of sensor/air data failure, there's always the possibility that the sensors could return a false Stall Warning. Airbus (and presumably Boeing, MD et al.) made a design decision that in the event of such failures, the presumption should be that the pilot knows more than the systems, and that the systems should therefore defer to the pilot.
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Old 30th Dec 2014, 22:06
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Originally posted by Winnerhofer:
Club 410, Club 430 and QZ's QRH
What, if anything, does this have to do with this thread, AF 447? We need to be told…
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Old 31st Dec 2014, 13:39
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Originally Posted by Turbine D
Originally Posted by Winnerhofer
Club 410, Club 430 and QZ's QRH
What, if anything, does this have to do with this thread, AF 447? We need to be told…
Regarding Club 410, the connection would be that the Pinnacle crash was mentioned in the AF447 report, since it involved a stall at cruise altitude. Other than that, there are more differences than similarities.
  • The Pinnacle crew were quite aware that they were pushing the performance limits of their aircraft, and they had already made a request to descend. The stall occured after ATC had told them to stand by, and apparently they feared the stall less than a descent without clearance (which would have drawn more attention to the foolishness of their little joyride).
  • The Pinnacle crew recovered from the stall at first, losing only about 3000 feet, if I recall correctly. That would somehow fit with the description of the accident Captain by one of his colleagues as "the best stick-and-rudder pilot" he could think of.
  • Anyway, while the stall was an essential part of that accident sequence, too, it was not the immediate cause of the crash.

Last edited by noske; 31st Dec 2014 at 16:47. Reason: oops, last sentence was incomplete
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Old 31st Dec 2014, 14:41
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Originally Posted by Winnerhofer:
Here, for instance, is a Brazilian A330 crew dealing with a similar airspeed malfunction in 2003, according to a BEA report:
36 incidents of UAS on A-330/A-340 aircraft were tabulated prior to the BEA issuing Interim Report #2 on AF 447. The Brazilian incident was one of them. All 36 crews managed to recover safely by recognizing and executing recoveries by one method or another.
What I would like to point out to you is the fact that there is a wealth of information about AF 447 contained in the previous 11 Threads. Going through the threads would save you internet surfing time and repeating AF 447 information that has been already covered and discussed.
Below is a chart that was presented and discussed in AF 447, Thread #8…


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Old 1st Jan 2015, 23:36
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Pitot Tube Icing

Looks like nearly all those events occurred in tropical regions. These days it may pay to be on extra alert when traversing tropical thunderstorms (especially if you cannot divert upwind) and be ready for either iced pitot tubes or iced AOA vanes.

Surprising how many events triggered stall warnings. I assume they were generated because of pilots pulling back on the stick upon autopilot disconnection. Baffling why Bonin was the only pilot who didn't drop the nose upon stall warning though.

Last edited by Qantas_A380; 2nd Jan 2015 at 02:38.
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