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AF447 Thread No. 3

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AF447 Thread No. 3

Old 31st May 2011, 22:46
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mm43, graybeard;

The TCAS has numerous system inputs. One of the inputs is the stall warning system. I think the NAV TCAS FAULT message was triggered by a programmed inhibition of the TCAS warning.

When certain other systems require a higher priority in terms of pilot attention and aircraft systems/performance/energy, they inhibit warnings which would compromise such priorities. Here, the priority would be aircraft energy to recover from a stall, so a TCAS warning is set aside as the lesser danger and is inhibited during such an event. The AUTO FLT REAC W/S DET FAULT warning has the same source.

The BEA Second Report seems uncertain regarding the source. Even though the second reason, (altitude differences > viability of data) makes a bit more sense than the electrical notion, the above reason should be examined as possible or dismissable. The inhibition isn't strictly a fault and if the two messages, (stall/TCAS) were ever "in competition" for attention/energy, perhaps the TCAS would simply remain silent.

Anyway, just thinking...always hazardous!

Last edited by Jetdriver; 31st May 2011 at 23:26.
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Old 31st May 2011, 22:57
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Ignorant question. It has been surprising that the PF control input almost throughout this incident has been NU. Could it be related to the bank that he appeared to be offsetting pretty much throughout as well? The note in the basic control law that suggests keeping the nose up in a tight turn was interesting to this layman.
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Old 31st May 2011, 23:13
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Looks to me that the initial climb may have been due to a combo of flight through uplifting air, pilot induced pullup to avoid wx or possible a/c induced pullup due high speed, perhaps only flight director commanded if AP already OFF.

It's hard to see why else they would do that initial pullup and there seems to be a precedent in that other 'airprox' uncommanded pullup.

After that, when they ran out of energy, it seems clear that no-one on the FD realised that 'nose down' on the sidestick wouldnot be enough. They needed to trim.

Ah.....'trim' the basis of good piloting! Completely ABSENT in Airbus normal ops.

I mean, if you NEVER trim, how are you expected to realise that you are badly out of trim?
 
Old 31st May 2011, 23:17
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According to the victims association, the Ile de Sein has recovered 75 bodies, bringing the total bodies recovered to about 125.

Not clear whether this concludes this phase of the recovery process, or whether Ile de Sein has retrieved any parts of the plane (other than seats).

Also nothing said on whether there would be any future attempt (phase) to recover other parts of the plane.
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Old 31st May 2011, 23:22
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TCAS Fault

Good thought on the Stall Warn priority, PJ2, but Windshear Warn, GPWS Pull Up and GS Warn will merely silence the TCAS audio and put the TCAS in to TA, Traffic Advisory mode while the Warn is active.

IIRC, Stall Warn will not silence the TCAS, as they may go hand in hand. At any rate, it will not cause a TCAS Fault. Stall Warn could possibly take priority over the GPWS, but I'm not certain of that. I'll dig.
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Old 31st May 2011, 23:39
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Graybeard, yeah, I think you're right...the "fault" makes no sense. I'll dig too.
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Old 31st May 2011, 23:42
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Originally Posted by etudiant
Ignorant question. It has been surprising that the PF control input almost throughout this incident has been NU. Could it be related to the bank that he appeared to be offsetting pretty much throughout as well? The note in the basic control law that suggests keeping the nose up in a tight turn was interesting to this layman.
It doesn't look like if they attempted a "tight turn" in normal law. The bank oscillation was certainly due to AP going off with an induced right roll momentum that should have been trimmed by rudder corrections. The control law switch to alternate caused the roll axis to be direct (and sensitive) as the controls are powerfull (hence, stick moving left and right).

Read below, effect in roll direct and trimming the rudder:



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Old 31st May 2011, 23:47
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Takata.

What about trimming?

Was the trim wheel moved?
 
Old 31st May 2011, 23:51
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Trim Controls

Ah.....'trim' the basis of good piloting! Completely ABSENT in Airbus normal ops.
I mean, if you NEVER trim, how are you expected to realise that you are badly out of trim?
Do I understand this correctly:
1. Auto Trim continues to function even though the autopilot has disconnected?
2. There are no trim buttons on the sidesticks?
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Old 31st May 2011, 23:55
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Absence of "ICE DETECTED MESSAGE"

As in the BEA report is stated 'uneventfull' before 0210:05'
and then suddenly Pitot Probes clogged due to ice.

I'm wondering why the ice detection system didn't trigger an ICE DETECTED (0,5 mm ice aggretion within 60 sec.) WARNING MESSAGE?

Can accept that within the timeframe a SEVERE ICE DETECTED (7 times 60 sec.) is never shown.
I can also imagine that the visual ICE Indicator between the windshields is not in direct view during all the mess,
but the ICE DETECTED message should have been there!



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Old 31st May 2011, 23:59
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Hi BarbiesBoyfriend,
Originally Posted by BarbiesBoyfriend
Takata.
What about trimming?
Was the trim wheel moved?
Why should I bother to answer you after your very informative first post here. You obviously posted without even reading a couple of pages from this thread, don't you?
Read it.
All the questions you asked (airprox, trim, etc.) were already answered, some of them only a couple of post ago, some further back.
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Old 1st Jun 2011, 00:06
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Originally Posted by Smilin_Ed
Do I understand this correctly:
1. Auto Trim continues to function even though the autopilot has disconnected?
2. There are no trim buttons on the sidesticks?
1. Yes - Autotrim is part of the FBW systems as opposed to the A/P and A/THR systems.
2. No, but there's a big manual trim wheel just like on the other airliners in exactly the same place. The questions being raised involve training to use it.

Originally Posted by A33Zab
I'm wondering why the ice detection system didn't trigger an ICE DETECTED (0,5 mm ice aggretion within 60 sec.) WARNING MESSAGE?
In that part of the atmosphere what you're dealing with is not ice as it is generally considered, but supercooled water. This is water that is below freezing point, but still liquid because it has almost zero contaminants. Stick a big piece of metal into that water and it freezes into ice in less than a second. This was demonstrated in the BBC/NOVA documentary.
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Old 1st Jun 2011, 00:11
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Hi Dozy,
Originally Posted by DozyWannabe
In that part of the atmosphere what you're dealing with is not ice as it is generally considered, but supercooled water. This is water that is below freezing point, but still liquid because it has almost zero contaminants. Stick a big piece of metal into that water and it freezes into ice in less than a second. This was demonstrated in the BBC/NOVA documentary.
More likey, some very small ice crystals (which are not detectable by radar) and not supercooled water at this level flight (which is detectable).
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Old 1st Jun 2011, 00:14
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Takata

I've not seen much on how the Airbus normally trims for you. But I might have missed a bit here and there.

I think that while Airbusses design is great when it's all working , it's notso when in ''not normal' mode.

But hey, what do I know?

Sorry to disturb you.

Call me 'old fashioned' but I prefer to look after the trimming myself, and I'm used to doing so- unlike the AF447 pilots.

Frankly, I think the Airbus is the aircraft the erodes piloting skills more than any other. Anyone care to disagree?

Last edited by BarbiesBoyfriend; 1st Jun 2011 at 00:27.
 
Old 1st Jun 2011, 00:51
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Piloting skills

The MBA's that run commercial aviation to generate maximal shareholder value would rather not have any bodies on the flight deck. Silicon Valley assures us that cybernetics transcends human behavior in anomalous situations so that pilots are an unnecessary expense. Hull losses are a cost of doing business the bottom line impact of which is mitigated by aggressive legal action and publicists smoke and mirrors. How many airlines have failed because of accidents or flight crew errors? How many airlines have failed because of MBA incompetence? How many airlines were reborn under a different corporate name with the same MBAs managing them to carry on the pattern?
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Old 1st Jun 2011, 00:55
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Frankly, I think the Airbus is the aircraft the erodes piloting skills more than any other. Anyone care to disagree?
Please....can we just keep to the topic at hand and not launch yet one more 'eroding skills' discussion...it's been done to death and never resolves a thing.

Sorry, BBB, but dang, it gets a tad tiresome and will only produce another round of A vs B, Colgan vs the FAA and whatnot.

I flew (almost always manually to cruise, the descent, approach and landing) the A320, then A330/A340 for fifteen years. One doesn't lose one's skills, one permits flying skills to be lost, and THAT is a professional standards matter, not an airplane, airline, regulator or other matter. Disconnect the damn airplane and the autothrust and stay familiar with the airplane.

There's far too much blame about "loss of skill" directed elsewhere when the real one responsible for any loss of one's skills and professionalism is in the mirror. If your airline wont' let you hand-fly because they like automation, to hell with them and their MBAs, fight them on it!

Take a look at the stats: we've had far too many fatal accidents resulting from the most basic failure of all and which we're trained to avoid and prevent from Hour One in our first flight...stalling the airplane. If the training isn't there in the syllabus, demand it.

Sorry, but enough is enough.
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Old 1st Jun 2011, 01:00
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Takata
Originally Posted by BarbiesBoyFriend
I've not seen much on how the Airbus normally trims for you. But I might have missed a bit here and there.
I think that while Airbusses design is great when it's all working , it's notso when in ''not normal' mode.
Would you pull up to max deflection while trimming down your nose at the same time?
Certainly not.
If their THS was trimmed close to max (+13/14 deg), it was because autotrim followed their NU imputs. Once AoA overshoot +30 deg, autotrim was not working anymore: it could only be applied manually by the trim wheels (see my post above and parts about trimming manually in direct law).

Basically, it means that they didn't aknowledge to be in a developped stall at the first place, hence, trimming down was not their main issue: their lack of nose down imputs certainly was before they reached such an high AoA while falling from FL380.
Even so (without manual trim imputs), elevators (if not fully stalled) should have had enough power to recover below +30 deg AoA (due to low airspeed) and autotrim would then follow their nose down imputs. When and how much did they try? we still don't know yet from the release of informations.
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Old 1st Jun 2011, 01:17
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PJ.

OK. After this I'll never mention it again.....but...the trimless Airbus helps its pilots all the time trimwise, right up til when it stops. And then it leaves them precisely where?

I know you can practise 'manual flight' in an Airbus just like any other a/c, but please don't forget a bus ain't like a non-bus. In many ways.

Takata, to answer your first question, of course not, but the pilot held the stick back, the bus trimmed the tail 'nose up' (almost to max) and then stopped trimming.

So now, the pilot had to manually reverse, using his manual trim wheel that he never uses, a trim input that he never made!

Youre second point, that they ought to be able to push over even with the tail trimmed for full nose up I dispute (but only from experience of non-buses, so dismiss it if you like. These tails are really powerful though).

Third point, if implied, 'why not stick full forward til impact'. I'm as baffled as we all are.

I see you are from Toulouse.
I just think the bus rather isolates its pilots from what's actually happening. That's just an opinion.
 
Old 1st Jun 2011, 01:23
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Originally Posted by kilomikedelta
Silicon Valley assures us that cybernetics transcends human behavior in anomalous situations so that pilots are an unnecessary expense.
Uhh... No we don't.

(At least this Brit working for a Silicon Valley firm doesn't!)

PJ2 - Don't sweat it, they'll get to the bottom of this sooner or later, anything anyone says now is just conjecture.

BarbiesBoyfriend - The trim wheels are there and if airlines aren't training the pilots when and how to use them correctly that is not Airbus's fault. Old school "communion with man and machine" was lost as soon as the first widebodies came along, maybe even earlier - even the old 747 Classic, DC-10 and L-1011's feel was entirely artificial.
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Old 1st Jun 2011, 01:29
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Anyone,

Is "auto-trim" a feature of the B777? I think auto-trim is a function of Airbus' design which does not trim to hold a sped, but trims to maintain a set flight path. Nothing wrong with that, but different.

Gums

Any comments on the Viper's auto trim?

GF
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