Or perhaps attempting to regain control after the flying machine did something "off the wall" while iron mike was in control.
I wouldn't be surprised if the accident was found to be beyond the aircrew's control and experience.
(Other than by not flying into the weather in the first place, but we just do not know what they saw up ahead in their radar at this point.)

There's a P in PIO... the meat as some of you call it. It took a pilot to rapidly deflect alternating full rudder until it snapped off, in the case of AA587, that was no autopilot causing it.

In fact, I don't think there has ever been an incident where an autoflight/autopilot system was ultimately responsible for the crash of an airplane, so if this system caused departure into an unsalvageable state, that would be a first.

Except, it's not a first for pilots to fly into the top end of a (major!) CB and losing it.

So, when you hear a stampede, think cows, not zebras (for those of us living where there predominantly are cows)...

Yes, and autoPILOT has a 'Pilot' in it.
As I stated earlier, it relates to PIO (but is not strictly PIO since no human hand is on the control.)

The human pilot uses variable gain strategies that can be unexpected or inconsistent, but an autopilot must follow its program.

A fly by wire aircraft is being flown by the autopilot essentially until it degrades to a flight law that is strictly pilot directed. Direct law on Airbus is such a pilot directed mode if I recall the system correctly.

Some of you may also be surprised to learn that the A320 aircraft has encountered lateral PIO on a line flight.

PIO is essentially a cliff like change in aircraft behavior that can be brought on by a number of factors. but incorrect gain in the control loop or excessive time lags at the effectors (control surfaces to you) often set it off.

For those that are curious about the subject, find a copy of "Aviation Safety and Pilot Control" published by National Academy Press, ISBN 0-309-05688-8. It is probably more understandable than the textbooks and is moderately priced.

- Clive - your profile does not say much, but I guess you are looking at this from an engineering pov?

As others have said, it is more than possible that there was no 'planned' ditching. From a piloting pov, gear is sometimes lowered to try to control speed, and we do not yet know if this happened. It is useful to me to see if we can establish, from what we can see so far, the likelihood of the gear breaking free after impact rather than being extended AT impact. As with others, I believe the intial impact would have firmly 'trapped' the gear in the up position - whether inertia would have been sufficient to force it through the distorted doors and the uplocks is for physicists/engineers to say. I would hope that someone can see from the pics whether various jacks/angles etc indicate a simple 'free-fall' extension in the water or a planned one? Have we seen both main gear (and nose) yet?

Thank you for the information on gear stressing.

CONF iture;
To answer your questions directly, the slats are not mentioned in either preliminary report, and it's not possible to determine the position of the slats from the photographs available on the BEA site. The wreckage and/or the DFDR will tell us soon enough but there is one possibility although it may be looking too deeply.

If the CAS is higher than 100kts, only the slats are available with a selection of Config 1. So for normal operation in flight, the position of the flap drive does not tell us anything about the slats.

If the CAS is below 100kts, selecting Config 1 will bring out the slats and also bring out the flaps to "1", (8.5deg), which is a normal takeoff configuration in, (Config 2 and 3 can also be used for takeoff).

Since the SFCC [for others not familiar, Slat - Flap Control Computer] gets its speed information from the three ADIRUs, [Air Data and Inertial Reference Units] and we know that there was a loss of airspeed data in the three ADRs we don't know how the SFCC would respond to a crew selection of flap 1.

When recovered, I think it will also be interesting to see what the THS [Trim Horizontal Stabilizer] or screwjack position is.

BOAC, we have seen both main gears but not the nosewheel.

PJ2

Sadly, when it's all said and done, I think we might discover that the THS was at or close to the full NU position and in the "Use Manual Trim Only" mode at impact. This THS flight control degraded mode freezes the THS (trim wheel control only) and thus overpowers the pitching moment of the elevator control power via the sidestick for pitch changes.

I would suggest that at CG positions of say 34-38% which are typical of this type in cruise, that if the THS attained a position of full NU (or close to full NU), that it would cause the a/c to stall and furthermore not allow any chance of stall recovery...unless manual use of the pitch trim is used to reposition the THS in the ND sense.

Just speculation and my humble opinion of course...

Hi,

isn't there a gear safety valve on A330 (I'm not current on 330)?
If so, where does it get the speed from?
What happens if no valid data signal?

Thx

Shear pin
 

The rear attachment of the pylon of wing-mounted engines incorporates a shear pin. It is designed to break when the engine is hit from below in a crash, and allows the pylon and engine to pitch up and depart over the wing, so as to avoid rupturing the fuel tank. I have difficulty imagining a similar function of a shear pin in the main gear support structure. Could you explain that in more detail?

Automatic trim
 

I believe you are referring to the A320 accident at Perpignan. In that accident the condition you describe developed because the AoA vanes were inoperative. If those vanes are free to move, automatic trim stops short of the stall AoA. I believe that at that point it is still possible to recover by normal use of the elevator.

Inertia (Momentum) of MLG assembly
 

Quote from BOAC:
As with others, I believe the intial impact would have firmly 'trapped' the gear in the up position - whether inertia would have been sufficient to force it through the distorted doors and the uplocks is for physicists/engineers to say.

Just a reminder that each A330 MLG is a massive (heavy) structure - one of the biggest in the business - whereas the main door you are considering is suitably large, but made of a composite material about as light as fibreglass. I'm also not convinced that this material could wrap itself around the bogie (wheel truck) without shattering.

It is true that pilots occasionally use the gear as an airbrake, and - in extremis - even to provide lateral stability. A double-engine failure would probably prevent the gear being subsequently retracted for a ditching, due to the effect on hydraulics, even if the APU could be started in good time. Once down, therefore, it would probably have remained down. So: was it?

CliveL's 9g longitudinal shear-pin - or something equivalent - must prevent an extended MLG from compromising the rear spar (or my "Bermuda Triangle"). The fact that the rear spar and MLG are still visible ensemble in the BEA photo convinces me that the gear was not in the extended position at the end of the flight.

Quote from Machinbird:
Some of you may also be surprised to learn that the A320 aircraft has encountered lateral PIO on a line flight.

Not uncommon, in my line-checking experience, due to what I have referred to (on another thread) as "sidestick abuse".

That it would do that is not in dispute, nor that the extended gear would separate at high enough forward speed. (Some "deep stall" or "flat spin" adepts postulate near-zero forward speed). What I find difficult to believe is that, if the gear was separated from the wing in more or less retracted position, taking large parts of its support structure with it, that it would end up in fully extended position relative to its support structure. Wouldn't the longitudinal 9g forces referred to by CliveL hinder its 'gravity extension'?

Regards,
HN39

http://s7.directupload.net/images/11...p/dm8hdjdd.jpg
if this strukture was part of the fuselage, then we mayby have a look of the middle seats, row 4 to 7
grity

MLG pushed up or down
 

I guess in case of a retracted gear, it would depend on the A/Cs attitude during impact if upward or downward forces on the gear prevailed: the inertia forcing the gear down or the water pushing the main door an the gear up. The main door of the MLG would be one of the first parts of the A/C to hit the water.

HN - I do not see it so clearly - the water, which is providing the retardation force is 'retarding' the gear also and may balance the 'inertia' of that. Only if you slowed the rest of the a/c leaving the gear unaffected by entry into the water would what you say be a 'definite'. I am sure the only certain way to know is to look at the various bits of the assembly in terms of what goes where on a 'normal' extension and what has sheared from what in line with CliveL's post. We could well just be looking a slow 'gravity' drop from a broken airframe as it made its way down 3900m.

Regarding lack of occupant preparation...

If it were primarily a deep stall with not much rotation, I would expect the 'g' forces to actually be fractionally less than 1g for most occupants.

I tend to think there was 'total suprise and shock' in the cockpit of loss of control (on top of loss of everything else that had already happened). Furthermore there was some understanding that the situation was priority#1, absolutely all effort must be applied to deal with it as quickly as possible, everything and anything else was totally moot until it was resolved.

tt

a quick off-topic
 

CONF iture, what about building 7? The NIST team has studied WTC7 quite thoroughly, and the study only confirms that the 9/11 conspiracy nuts are just that — conspiracy nuts.

[end of off-topic]

ttcse, the data from Pulkovo 612 confirm your expectations — the RPM were too low to produce any noticeable Gs.

Quote from BOAC:
HN - I do not see it so clearly - the water, which is providing the retardation force is 'retarding' the gear also and may balance the 'inertia' of that. Only if you slowed the rest of the a/c leaving the gear unaffected by entry into the water would what you say be a 'definite'.

I wonder if you may be missing the point, BOAC, re the inertia of the heavy MLG; in particular the bogie/wheel-truck part (furthest from the pivot point). At the extreme VS thought likely, the deceleration of the belly, or centre-section, as it struck the water would be great, due to its large surface area and relatively low mass. The bogie has a high mass and small surface area, relatively speaking. The door underneath it is light and flimsy.

Chris

Machinbird,

I happen to be intimately familiar with a number of PIO incidents on A3XX aircraft, and there are two factors that have been most important in these:

1. The A3XX sidestick (control) philosophy is not rate but attitude based, i.e. you move the sidestick to the side (and with it a caret on the PFD), and the bus will keep the attitude you demand by pointing that caret. So, for example, you move the caret in the right hand side of the PFD and the bus will maintain an attitude to follow that caret. Unlike an analog system, where you bank the airplane and it will maintain most of the bank on its own while you just keep the bank angle with what's essentially neutral controls.

2. When in direct law (i.e. the proverbial has hit the fan and you're one failure short of MAN PITCH TRIM ONLY), it'll start behaving like an airplane you learnt to fly on... and you're in effect flying a rate based control system, where your inputs have to be given differently.

While I have great respect for the beautiful autoflight systems airbus has developed, this very basic control philosophy is flawed in my opinion and could have been part of what unfolded in the middle of the night over the atlantic, inside a CB. Don't go there. We teach that at basic levels...

A BBC update from this morning claims that there will be a meeting with families in "two weeks".

BBC News - Conflicting emotions of Air France crash relatives

Are any further photos expected. Lack of additional information regarding the site or discovery is loudly silent. A sign of things to come?

Airbus FBW Sidestick
 

Quote from ZeeDoktor:
The A3XX sidestick (control) philosophy is not rate but attitude based, i.e. you move the sidestick to the side (and with it a caret on the PFD), and the bus will keep the attitude you demand by pointing that caret. So, for example, you move the caret in the right hand side of the PFD and the bus will maintain an attitude to follow that caret.

I'm afraid that is all incorrect!

If you move the sidestick to the side in the air, you are requesting a roll-rate proportional to the displacement. If you then centralise the stick, the bank will be maintained.

This does not apply, however, on the ground. On take-off, it is stick-to-surfaces until about one second after lift-off, when the white cross (that you call a 'caret') disappears from the PFD for the duration of the flight.

(Pitch control is a bit more complicated to explain, but intuitive.)

In the air, PIO is the result of the pilot impatiently or nervously changing the stick position before his/her previous selection (stick-position) has had the time to be effected. In that respect only, it's not so different from conventional aeroplanes. The trick is to use thumb-tip and index-fingertip for roll control; thumb-tip and middle-fingertip for pitch.

Chris

PS (by Edit)
You are right to say that, in Direct Law, it's a bit like "an airplane you learnt to fly on", i.e, roughly stick-to-surface. That does not mean "a rate-based control system", however. You are right that it feels very different from the higher laws, and is rarely practised except for short periods in the simulator.

"Upset"
 

0200 and 0210 are the only two positions transmitted during this time window, it doesn't tell much about the flight.
Who know, today, her route and what exactly F-GZCP radar pictured on her path?

The real question is how and when she departed from altitude, not that she actually departed.
My point is that other factors can't be ruled out at this point as there is absolutely no certaincy about the time and nature of the "upset" causing the crash. Many ACARS were sent from 0210 and it is very likely the start of a following sequence leading to one or more catastrophic events... but it doesn't mean an immediate unrecoverable upset!

See below about an aicraft falling from the sky like a "leaf" in 5 minutes (or more). One can make his own opinion.

No-one can so far explain why switching at 0210 to ALT2, due to unreliable airspeed, would cause an immediate upset as none of the similar events ever caused one! After being switched to manual control, any manual imput could cause one in relation with other unknown factors (workload, weather, technical, etc.)

Yes: one upset... or more than one!
In my opinion, the attitude at impact and the rate of descent is not ruling out more than one incident!

9 unrecovered upsets from cruise level (data Metron Inc., BEA study):
Date.........ft/mn..Level..Dur....Dist..Type....-> Cause
07.12.1995..32,000..FL310...57s...8 NM..TU-154B -> Spiral / roll upset
19.12.1997..29,000..FL350...75s...5 NM..B-737.. -> Unknown
21.12.2002..27,000..FL180...40s...2 NM..ATR 72. -> Stall / icing
19.11.2001..26,000..FL260...59s...4 NM..IL-18V. -> Spiral / diving
01.01.2007..20,000..FL350..105s...9 NM..B-737.. -> Roll upset
15.07.2009..16,000..FL240...90s...5 NM..TU-154M -> Spiral / roll upset
22.08.2006..14,000..FL390..166s...3 NM..TU-154M -> Stall-spin
23.03.1994..12,000..FL310..156s...3 NM..A-310.. -> Spiral-spin / roll upset
16.08.2005..12,000..FL310..210s..17 NM..MD-82.. -> Stall

AF447 - timed cases for one upset from cruise level:
01.06.2009..35,000..FL350...60s..~5 NM..A-330 (1 mn)
01.06.2009..23,000..FL350...90s..~5 NM..A-330 (1.5 mn)
01.06.2009..17,500..FL350..120s..~5 NM..A-330 (2 mn)
01.06.2009..12,000..FL350..180s..~5 NM..A-330 (3 mn)
01.06.2009...9,000..FL350..240s..~5 NM..A-330 (4 mn)
01.06.2009...7,000..FL350..300s..~5 NM..A-330 (5 mn)
01.06.2009...6,000..FL350..360s..~5 NM..A-330 (6 mn)


Recovered upset: B747 China Airlines (17.02.1985)
1. 1014:50 -> 40,442 ft -> roll upset (4.8 G pull up)
2. 1015:23 -> 30,132 ft -> unreliable attitude data (5.1G pull up)
3. 1017:15 -> 9,577 ft -> recovery & climb

Total upset duration: 145 sec.
1..10,310 ft lost...33 sec..18,700 ft/mn
2..21,155 ft lost..112 sec..11,300 ft/mn
3..31,465 ft lost..145 sec..13,000 ft/mn (average)


"Upset" definition (from “2008 - Airplane Upset Recovery Training Aid Revision 2”):
An airplane upset is defined as an airplane in flight unintentionally exceeding the parameters normally experienced in line operations or training. In other words, the airplane is not doing what it was commanded to do and is approaching unsafe parameters.

While specific values may vary among airplane models, the following unintentional conditions generally describe an airplane upset:
• Pitch attitude greater than 25 deg, nose up.
• Pitch attitude greater than 10 deg, nose down.
• Bank angle greater than 45 deg.
• Within the above parameters, but flying at airspeeds inappropriate for the conditions.

Given the 'lenient' limits granted the Autopilot in cruise, and bunk weather, it is reasonable to assume the pilots were established in "acceptable" autoflight until sometime just before the stream of ACARS signalled what is likely an already upset aircraft. The mechanical (A/P) limit having been breached, the pilots were left with a rapidly manouvering airframe with which they had not had time to acommodate their 'meat-think' (:ugh:). As per ZeeDoktor, the transition between a docile machine and one that requires a stable set of anticipatory thinking only, the conclusion is quite apparent. (That this is a flaw in AB philosophy)

If impact was 6.5nm away from last known position, it would need a bit more forward travel past LKP to avoid considering the a/c dropped like a stone at an average AOD of 45 degrees. This means a turn (back) of some description, and most likely pilot input. This excuses to some extent the searches assumption of distance away from LKP.

A "flat impact" is concluded, but this is not to say that she wasn't in some Pitch extremis just prior to impact. If a tail-first hit, the VS driving downward in its aft spar axis explains the lower corner (Rudder) damage, and could allow for the reasoning that concluded the VS landed away from the crash site.

This also allows for some 'time' for the Mains to sever their stowed position downward, just prior to contacting the sea essentially vertically, and perhaps without a horizontal vector to speak of.

Well, Bearfoil... maybe?
But, at this point, finding only such an (obvious) conclusion is much more telling about what you will find very relevant in support of your own theories rather than giving a single hint about this manufacturer philosophy.
Everything opposed to your pre-fabricated opinion should otherwise being considered as a "cover-up" as you already mentioned many times this very same obvious and single conclusion (I remember that you even mentioned that Airbus/BEA would not try to recover this aircraft as they already know pretty well what caused this loss).

Nothing very new.
:)

Do not put words down I have not said. At no time did I suggest the authority would not search, neither have I made a conclusion about this accident. I have a strong opinion, but am ready to accept any evidence that shows other than that. I resent your attempt to make a personal judgment outside the context.

Then, no offense. I'm very sorry: my very poor English is certainly not able to cope with your high syntax level that everybody can perfectly read in your post just above. But forgive me if I won't search into the hundreds of posts about this crash to find out what I mentioned myself. I certainly can be wrong or I just confused you with someone else who expressed, post after post, exactly the same view ("strong opinion") as you!
:}

That just made me mindful of a time just north of the Pyrenees when I was trying to tell the guy on the ground that we had little idea of our position. We were on a 22min beacon-to-beacon leg, and 47 mins later we finally passed that beacon. For a lot of the time, our progress had a high vertical component - it was nothing short of chaotic for well over an hour, but there was never a time we turned intentionally off course.

If, as it seems is the case, this poor crew found themselves inside a vicious CB, only a second by second analysis of their exact position will throw much light on those terrible minutes. I'm not sure even the FDR will reveal that much detail as only inertial summing could reveal the details of the decent.

Is it hoped there will be that kind of detail in the FDRs?

BEA Update
 

This just posted at:

Sea Search Operations, phase 4

Information, 7 April 2011
The team on board the Alucia will complete vehicle operations on Friday. The vessel will leave the search area on Saturday 9 April and should reach the port of Suape (Brazil) on the morning of Tuesday 12 April.

Does this mean they have decided that all the wreckage has been found, I wonder, or that they have located all they need - including all three recorders?

BEA Update
 

Does this mean that the location of vital components have been identified and mapped, and therefore no further activity is required by them. Seems there is an abundent of information known but not released.

@wes_wall:

It sounds like they are just switching gears from localization to recovery, not that they are done yet.

From the same BEA site:

"The operation would thus be divided into two phases:

• a localisation phase (phase 4) financed by the industry, which will use a relatively small and thus less expensive vessel;
• a phase of detailed observation and recovery if the wreckage is discovered (phase 5), financed by the French State."

"Phase 4 will come to an end upon detection and identification of the wreckage by the BEA, and at the latest, at the end of the third stage in July. If the wreckage is found, the BEA will immediately launch phase 5, involving detailed observation and recovery, by calling on one of the three vessels pre-selected in the meantime, which will be chosen on the basis of their availability at the time of the discovery."


The New Undersea Search Campaign

No surprise. The area is small, flat and sandy and they've got 3 UAVs available for the mapping... But no ROV.
They will need the ROV to go further and for looking inside the wreckage.

You are right about the "rumors" from those sources "close to the investigation" (Governement, BEA, Justice, experts, families, journalists...)
One sample (all unverified):
. the wreckage is very close to LKP (straight down);
. there is still large parts of the cabin well preserved;
. some corpses still attached to their seat;
. some corpses lying around the wreckage;
. the BEA is incompetent, having searched mostly at the wrong place...
:ugh:

ACLS65,

The only news here is how early they will have been able to complete Phase 4, and one must assume that the rest of today (Thursday) and tomorrow will be spent completing routine photography and the inventory of items in the debris field (or fields) already discovered.

They must have located the DFDR and CVR, and presumably the QAR (although the latter is not designed or located to be crash-resistant).

But their announcements certainly are, err..., somewhat restrained.

They will have completed high resolution sidescan sonar flights over the area, then reverted to camera fly-by of the debris field, probably taking shots from all four quadrants. They are obviously confident that all major components of the aircraft have been accounted for and that they have sufficient information to allow the recovery operation (Phase 5) to proceed in due course.

This operation has certainly proved the operational capability of the REMUS 6000 AUVs provided by the Waitt Institute for Discovery (2) and the Geomar Oceanographic Institute, Germany (1), and operated by the Woods Hole Oceanographic Institution's REMUS team.

Resolution of sonar images
 

Can anyone enlighten us about the resolution of sidescan sonars? The BEA images show that the Remus AUV was using 120kHz. What sort of spatial resolution could one expect at this frequency? And how is the data displayed?

In other words, what are we really looking at in this image? Are the redder parts colored to represent things that are physically located higher, or have a stronger return, or something else? What causes objects to have a stronger return with sonar? At 120kHz, how small an object could one expect to pick out?

[sorry-- this was posted in another thread but is more relevant here, I hope.]

Is it conceivable that the vessel would leave the area without having located the structures likely to contain the various recorders?

I would have thought that this was one of the main aims of the project and the return to port to me indicates either location of the recorders or a high certainty that they are within whatever sections of the fuselage have been found on the bottom of the ocean.

If this was not the case would the search not continue....?

VS loss
 

Thanks for this extremely interesting thread. Remember the first thing found floating some distance from the main site was the neatly severed fin. There was much talk about the merits of composite materials and AA587 in New York (an A300).

All the talk about stalling and loss of stability brings me back to one of the first points made - did the airplane lose its VS and then go out of control, did it lose it from aero-forces during a spin/dive, or from impact with the water? Could the fin have been knocked off by an encounter with a huge up/downdraft?

-drl