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AF447 Thread No. 3

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AF447 Thread No. 3

Old 29th May 2011, 11:17
  #541 (permalink)  
 
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I´m very disappointed from latest BEA report.
It is not what it tells. Its about what they actually know and dont want people (either public in general, or aviation experts not belonging to their investigation) to know at this moment.

At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%.
When,who and why the levers were retarded to IDLE?

Around fifteen seconds later, 2:12:17? the PF made pitch-down inputs. In
the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.

How long the pitch down inputs lasted? what effect was achieved?

At 2 h 13 min 32, the PF said "we’re going to arrive at level one hundred". About fifteen seconds later, simultaneous inputs by both pilots on the sidesticks were recorded and the PF said "go ahead you have the controls".
What inputs were being provided by each pilot?


The angle of attack, when it was valid, always remained above 35 degrees. The recordings stopped at 2 h 14 min 28.



We have to believe (faith based) their "new finding" "the inputs made by the PF were mainly nose-up", as BEA report doesnt provide the full sequence of pitch commands. It could even be pitch down input from 2:12:17 to impact, without being in contradiction with "history of flight" para.

I´m ashamed that they dont tell what dialogues were ongoing in the cabin, what diagnosis they achieved (either wrong or correct),...and lots ogf things BEA surely know and they hide.

Last edited by sirgawain123; 29th May 2011 at 12:19. Reason: correct myself: i meant pitch down where i initially wrote pitch up
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Old 29th May 2011, 11:21
  #542 (permalink)  
 
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bearfoil, #507

I have a bit of a problem understanding why others don't see this
handover as the "beginning" of things going rapidly pear.
So do I. The first two items in the timeline, page 2 of 4:

2hr, 08, 07, state normal, where the crew decide to detour and reduce
speed, then, a long two minutes later, autopilot and autotrim disengage. So
what happened during those 2 minutes to cause this and initiate the
deadly sequence of events ?.

Load of rubbish in the Sunday Times this morning about a "baby" pilot.
With that and other reports, looks like Air France and the crew are being
setup to take the fall for this one. Of course, the BEA are professional
and dedicated to the task of finding the truth, but may be withholding
data for many reasons. They are under no obligation to report
anything until the investigation is complete, but the latest report looks
as significant in terms of what it leaves out, as what's included. Imho,
of course.

In summary, not enough data and we must all be patient, yet again :-)...
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Old 29th May 2011, 11:37
  #543 (permalink)  
 
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Some rude articles come up in not so marginal media outlets..
As I stated earlier: and in turn the formation of "Public Opinion"

HE was one of Air France's "company babies": a dashing 32-year-old junior pilot - and a keen amateur yachtsman - who had been qualified to fly the airline's ultra-sophisticated Airbus A330 jet for barely a year.


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Old 29th May 2011, 11:41
  #544 (permalink)  
 
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As a total imbecile (Joe Public and a passenger) - I would have EQUAL confidence in a 'newbie' or a seasoned Pilot, purely on the fact that I assume by and large you do not have idiots flying aircraft, and in fact I might even say a less experienced aviator may be 'safer' as one would expect them to be relatively studious about wgat they were doing.

IMO Sirgawain123's question is VERY good: Why were the throttles closed? What would be the intention of such a control input?

Secondly: it the THS was at 13 degrees, what effect would this have on level flight? Would balancing inputs be needed on the control column/stick to prevent the aircraft getting too 'tail down'?

Are there any indications so far that after the Captain arrived there was any dramatic change in control inputs (as if the Captain spotted something?)

Once more with my halfwit goggles on, it does sometimes seem that people are reading too much into these things. G-ARPI crashed because the droops were retracted and the aircraft was pitched to hold an incorrect (too low) airspeed, and multiple stall warnings and pitch downs were ignored and countered until the aircraft stalled. The point being the investigation strived to reason why the crew did not notice the droop retraction: and this accident was a catalyst for CVR to be fitted.

This is not to say CVR is not a valuable tool: but rather CVR of itself does not prevent the 'cause' of accidents - it may prove that a crew was having a disco at the time, or snoring away, but may also prove that they simply did not foresee the 'main problem' - looking at what has been released so far does it not appear to be the case that this is the situation?

I do not know more than I read here: stall warning= push down - watch altitude and pitch. The command inputs we are seeing so far tell us that exactly the opposite was happening: therefore that is the cause of the accident is it not?
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Old 29th May 2011, 11:49
  #545 (permalink)  
 
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I may be missing something, but it seems to me it should be possible to write software that would calculate air speed without pitot tubes (and without direct reference to ground speed). INS (or GPS) should be able to provide the airplane's longitudinal acceleration at any point in time. From that and the airplane's mass you could calculate the longitudinal force. Subtract the thrust you know the engines are producing, and you'll have the aerodynamic drag.

The variables needed to calculate drag are air density, drag coefficient, and velocity (airspeed). It should be possible to calculate the drag coefficient from the airplane's configuration and attitude, and the density from altimeter and OAT. Plug those into the formula with the known drag, and out should pop the airspeed.

Much easier done than said, I'm sure. But a simulator takes control inputs and a number of other parameters (including airspeed) and calculates (I assume) an acceleration from which it determines the airspeed in the next "frame." The software I'm envisioning would be similar, except that instead of starting with airspeed and calculating acceleration, it would start with acceleration and calculate airspeed.

While I'm on a roll, there may be a simpler way: monitor the effectiveness of control inputs. If the pilot or FBW commands a certain rudder deflection (for example), gyros and accelerometers should detect the resulting angular acceleration. From that and the airplane's polar moment of inertia, you should be able to calculate the force (sideways lift) generated by that deflection. That force would correspond with an airspeed.
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Old 29th May 2011, 12:24
  #546 (permalink)  
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and calculates (I assume)
That looks the only possible statement in the above post..
 
Old 29th May 2011, 12:29
  #547 (permalink)  
 
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Speculations

The more I read, the more clear it gets: the poor guys failed to recognize they were flying a fully stalled plane, got absolutely scared by the bells and whistles blaring all the time, rocking wings, winding down altimeters, a panicked captain shouting instructions and simply frozen at the controls (or even worse, giving inputs that agravated the situation), failing to do the only thing that would have saved the day.
Pure lack of proper training, basic airmanship & situation awareness.
It's hard to admit that a lot of us could have reacted exactly the same way.

A perfectly flyable aircraft turned into a gigantic coffin.

Of course there'll be endless theories about A330 systems, speculations on Boeing x Airbus, if this, if that etc...
And of course BEA, Air France, Airbus and ultimately the government of France will, each one at their convenience, try to save their own a....s.
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Old 29th May 2011, 12:32
  #548 (permalink)  
 
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I may be missing something, but it seems to me it should be possible to write software..
Yep, this is the reaction to failed software - add more features that will ultimately fail.

The point is, if IAS goes south, you put the thrust at 80% and keep the nose at 3 degrees and then fly until you have visual reference and can sort it out. The last things needed are more and more complex layers of warez.
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Old 29th May 2011, 12:51
  #549 (permalink)  
 
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Originally Posted by Chu Chu
it should be possible to write software
http://www.pprune.org/tech-log/45283...ml#post6480647
I share this view : see my first post at http://www.pprune.org/tech-log/45283...ml#post6480478

Originally Posted by deSitter
Yep, this is the reaction to failed software - add more features that will ultimately fail.
Let's assume that there are better solutions than adding software on airliners. What is the best solution for unmanned flights, military drones ?
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Old 29th May 2011, 12:53
  #550 (permalink)  
 
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From post #290 on 28 May 11 ....
BEA Report – The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight.

The last recorded values were a pitch attitude of 16.2 degrees nose-up, a roll angle of 5.3 degrees left and a vertical speed of -10,912 ft/min.


Where is the BEA quoted (THS) trim nose-up angle measured?

Is it an internal computed value displayed on EICAS?

Is it 13.2º on the cockpit pedestal trim wheels?

Is it 13.2º as shown on some aircraft where the horizontal stabiliser (tailplane) leading edge fairing meets the vertical fin?

Or ..... ?
There were no replies to the above post so let the question be posed in a different form:

The iconic book 'Handling The Big Jets' by D P Davies was published in 1967 and revised in the 1977 edition. It has several pages of useful info and charts on pages 115 - 128 under the paragraph headed 'The Super Stall'.

Moreover, on page 122 there is an excellent diagram showing the 'lack of relationship between attitude and incidence'.

The recent BEA report 2 recorded the trimmable horizontal stabilizer (THS) at a 13 degrees nose-up value. Therefore the leading edge of the THS (depending on where measurements are taken) will be at a negative below horizontal datum angle of 13º).

Surely this huge displacement of 13º would be shown on the centre console manual trim wheels?

The trim wheels are visible to all 3 pilots on the flight deck. Also a true 13º is likely to have a much expanded arc on the trim wheel of perhaps double the true arc value to visually indicate this extreme displacement.
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Old 29th May 2011, 12:58
  #551 (permalink)  
 
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Is it Speed Over the Ground, or Velocity?

cogsim:
The last recorded values were a vertical speed of -10,912 ft/min, a ground speed of 107 kt, pitch attitude of 16.2 degrees nose-up, roll angle of 5.3 degrees left and a magnetic heading of 270 degrees.

ground speed: 107 kt
vertical speed: -10,912 ft/min = -107 kt

Coincidence? Maybe.
What speed does a skydiver's GPS read? It subtracts where you were from where you are to come up with Speed, so probably reads zero.

The Inertial Reference Units in expensive aircraft integrate accelerations in 3 dimensions to calculate Velocity. It's been a long time since I've been intimate with inertials, but seems to me the ground speed reported by BEA was in reality Vertical Velocity.

IOW, the plane dropped like a skydiver.

Good catch, cogsim.

Last edited by Graybeard; 29th May 2011 at 13:01. Reason: Change speed to velocity
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Old 29th May 2011, 12:58
  #552 (permalink)  
 
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Report contents

"They are under no obligation to report
anything until the investigation is complete, but the latest report looks
as significant in terms of what it leaves out, as what's included.
"

The BEA published facts to put an end to random speculations based on undocumented "leaks". It has no intent to release more raw data to self appointed "analysts".

Let's wait until end of June.
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Old 29th May 2011, 13:00
  #553 (permalink)  
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Keep in mind, also, that certification stalls start with a trim speed a little above the stall. I have no idea what THS setting would have been the target range during certification but I would opine that it certainly wasn't near full up .. this may have had adverse implications on this occasion.

Further we don't have much of a story relating to just what the guys up front were actually looking at ?

the poor guys failed to recognize ... (#548)

I don't really think that we have anywhere near enough information to suggest other than that your postulated circumstance may be one of a number of possible scenarios on this occasion ?

Time will tell what the CVR may have revealed to the BEA folk but I will be very surprised if there is any panic on the flightdeck until, perhaps, the last few seconds. It has been my observation that experienced flightcrew tend to hang in there in spite of what eventually becomes an obvious pending outcome.

We are talking a reasonable level of experience here, not ab initio student pilots with only a few hours under their belts ...
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Old 29th May 2011, 13:01
  #554 (permalink)  
 
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Let's assume that there are better solutions than adding software on airliners. What is the best solution for unmanned flights, military drones ?
This is implicitly very revealing of the software mentality - abstracting away the real world until all that's left is "flight", even though the missions and envelopes and hardware are completely different - as if there were just some abstract FlightStimulation 1.0 that could cover everything.
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Old 29th May 2011, 13:02
  #555 (permalink)  
 
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Yep, this is the reaction to failed software - add more features that will ultimately fail.

The point is, if IAS goes south, you put the thrust at 80% and keep the nose at 3 degrees and then fly until you have visual reference and can sort it out. The last things needed are more and more complex layers of warez.
Well said

However if after establishing 80% and 3 NU the descent rate remains virtually straight down, you need some serious nose down to get out of the stall (said from my armchair after several minutes of reflection).

While Attitude + Power = Performance holds true in stable flight, once in an upset you need recovery actions.
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Old 29th May 2011, 13:29
  #556 (permalink)  
 
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AF SOPs & stall, autotrim, situation awareness

Hi there
About the reasons why the PF initially pitched up the AC with a high thrust index: could it simply be the implementation of "manoeuvre d'urgence" in cruise phase ? (see the AF C/L "unreliable IAS / ADR check proc", the "manoeuvre d'urgence" is page 121 of http://www.bea.aero/docspa/2009/f-cp...cp090601e1.pdf)
But this "manoeuvre d'urgence" is CLB/5°... not TOGA/16°.
Will we know the procedures that were implemeted and the way they were through the CVR ?
Is the nearly saturated THS nose up angle of 13° a consequence of the autotrim and of the (integrated/lagged) repeated nose up orders ?
situation awareness:
- 13° THS nose up angle: were the pilots informed of this ? If so, a manual trimming back to lower angles would have been their only hope then ? (related SOP ?)
- altitude/vertical speed monitoring: the 1st response to the 1st stall alarms was to pitch up/climb (manoeuvre d'urgence ?), then pitch down orders reduced the VS and stabilized the altitude around FL370 (waiting for the CPT). Latter, the CVR shows that crew was aware that the AC was closing FL100, but no early mention (in the last BEA release) of a rapid descent rate (VS).
- attitude/thrust monitoring: the pitch & thrust procedure (AP/ATHR OFF) or the "manoeuvre d'urgence" are about setting these two fundamental parameters (even on CLB/5°), and the crew tried to compensate for the roll excursions, so the crew was presumably monitoring the artificial horizon ? Though the pitch angle reached 16° at FL380, and presumably remained high on the artificial horizon (one of the reliable parameters).
- stall alarms & pitching orders: at one point (CDB was back), pitch down orders were applied with a reduced thrust, and the AoA was reducing... but it restored the validity of the airspeeds and reactivated the stall alarms: a few contributors suggested that this might have been a highly misleading factor (among many others !) urging the crew to abord these nose down orders. But nothing is said by the BEA about the following pitching orders. The BEA does not yet tell whether the word "décrochage" (stall) was heard in the cockpit (CVR).
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Old 29th May 2011, 14:15
  #557 (permalink)  
 
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Flight Control Laws

With regard tot the control laws:

Both in normal and alternate law1 and 2, both elevator and THS are programmed to produce a certain G value. This would be 1G when the side-stick is in neutral. So when there is aft side-stick, both elevator and THS try to deliver more than 1G.

Only in direct law the THS is controlled manually through the trim wheels.

The clue of the THS position would be the scale next to the trim-wheel, but this is used only prior flight. In fact, the THS is not in the mind of an Airbus pilot during flight.

I absolutely don't know what I would have done in that situation, because my brain would be in overload and also blurred by all the natural drugs in my blood....

I suspect there will be increased focus worldwide on the training of 'loss of control', 'unreliable airspeed' and use of THS.

(A330 Cp/TRI/TRE)
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Old 29th May 2011, 14:42
  #558 (permalink)  
 
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It's very possible that my post #546 is as crazy as the reaction suggests. But on re-reading it, it looks like I was suggesting the replacement of pitot tubes with software. That seems completely nuts, even to me. I had in mind software that could provide a reasonable airspeed reference during a brief period in which the pitot tubes became unreliable.
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Old 29th May 2011, 14:47
  #559 (permalink)  
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Hyperveloce

Very welcome post. Well framed, the challenge to the PF (PNF).

- 13° THS nose up angle: were the pilots informed of this ? If so, a manual trimming back to lower angles would have been their only hope then ? (related SOP ?)
This is the salient concern? With a heavy tail and that large slab forcing down the aft hull, it is disturbing to consider the obstacles to regaining level flight.


- altitude/vertical speed monitoring: the 1st response to the 1st stall alarms was to pitch up/climb (manoeuvre d'urgence ?), then pitch down orders reduced the VS and stabilized the altitude around FL370 (waiting for the CPT). Latter, the CVR shows that crew was aware that the AC was closing FL100, but no early mention (in the last BEA release) of a rapid descent rate (VS).
I think the first two warnings of Stall were transient and not perceived as reliable, after all, the a/c had 0.80-0.82 M, and had response (Pull, Roll Left)? This also occurred prior to loss of speeds reads.

At the top of climb, an AoA of 4 degrees was established, consider this may have been the best obtainable (PF: "Why?"). In arresting the climb, the a/c may have already begun its Stall, with 13 degrees NU (THS), did the crew realize this? 4 degrees AoA, but a Pitch of something much greater? Was sufficient energy available to climb in less than aerodynamic fashion? If the Pilot, absent complete cueing, was lulled into thinking his airframe was behaving normally, the sudden loss of positive g would be alarming, and he may have reduced power to drop the nose, thinking it was the engines maintaining an improper AoA? With full Trim Tanks and a THS at near full NU, did the door slam shut? Can we eliminate a cg moving aft due to loading problems?

Last edited by bearfoil; 29th May 2011 at 15:18.
 
Old 29th May 2011, 14:57
  #560 (permalink)  
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Originally Posted by Hyper
(see the AF C/L "unreliable IAS / ADR check proc", the "manoeuvre d'urgence" is page 121 of http://www.bea.aero/docspa/2009/f-cp...cp090601e1.pdf)
- 11.5mb - please - anyone produce an English extract for us?

I again see "16 degrees of pitch" mentioned at FL380. Where is this published? I see only increasing through 10 in the climb. People again confusing pitch and AoA I fear. We do not know the pitch attitude at FL380. Garbage in = garbage out, as they say.

This thread is rapidly becoming the third farce in the history of threads on this accident. The BEA have released so little information it is impossible to understand what happened. Where is the CVR call of "what are you doing" by PNF as the pitch rises through 10 degrees and a heavy a/c climbs at 7000fpm at FL360 - from optimum altitude towards ceiling? Unreal. So much more must have been happening.
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