AF 447 Search to resume

[auv-ee]

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

[wes_wall]

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

[Chris Scott]

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.

[takata]

"Upset"

Originally Posted by sensor_validation

Of course many aircraft the same night did deviate, but given the likely weather pattern, to do so after 02:00 would surely have been too late?

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?

Originally Posted by sensor_validation

I didn't realize there was any doubt that AF447 departed from cruise altitude without a major incident - and I thought it was accepted that a '200Te falling leaf' would still take 4 mins to get to sea level? How long did the B-720 in 1963 take to fall from FL 370 before recovery at 14,000 ft, or the 1985 747 from FL410 to 11,000ft?

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.

Originally Posted by sensor_validation

No-one can explain why it would have occurred after 02:10 under effectively 'manual control' and before would presumably require a QF72 style flight computer 'glitch', perhaps the pitot tubes are innocent?

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.)

Originally Posted by sensor_validation

But surely the assumed proximity of the LKP to crash site suggests one major unrecoverable incident?

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.

[bearfoil]

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' (). 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.

[takata]

Originally Posted by Bearfoil

... 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)

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.

[bearfoil]

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.

[takata]

Originally Posted by Bearfoil

neither have I made a conclusion about this accident

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!

[Loose rivets]

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.

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?

[auv-ee]

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.

[Chris Scott]

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?

[wes_wall]

BEA Update

The vessel will leave the search area on Saturday 9 April

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.

[PJ2]

Originally Posted by Chris Scott 7th Apr 2011 05:55 Post #3143

The door underneath it is light and flimsy.

Not to put too fine a point on this aspect of the discussion...

Yes, agree with your comments. Further to your point in your response to BOAC, (who, I should acknowledge, has previously mentioned the notion that the gear may have free-fallen slowly, after impact, and during the slow descent to the bottom)...

The MLG doors are made from Carbon-Fiber Reinforced-Plastic (CFRP) with a NOMEX honeycomb core. The belly-fairings are similarly constructed,(the cabin material is the same NOMEX honeycomb structure but with a fibreglass surfaces and aluminum extruded edges/fastenings.) So while light and strong, they are indeed "flimsy" in the sense that direct, high-impact forces would break the material as we have seen in the recovered wreckage. IOW, this material will not "bend and conform" to the shape of the gear and so impede a free-fall, but would likely shatter, and provide no resistance whatsoever to the massively-heavy MLG structure. That the uplocks would break at impact has already been discussed.

Again, when the MLG actually free-fell is immaterial - it did, and it, and its dressings have remained attached to the rear spar and support structure. I think it is more important to rule-in/rule-out the crew extending the gear. It is a debate until the recorders tell us.

I mentioned the THS (#3129) not in relation to the Perpignan accident (AoA problem) but because I don't recall if/where in the three major AF447 threads, the failures of ADIRUs 1, 2 & 3, which provide input to the FCPCs which control the THS signals, have been discussed.

The aircraft went from M0.82 (or turb penetration speed of M0.78) to about M0.60/198kts (roughly the stall speed under the circumstances). I've tried that in an A330 simulator and it takes long time just to lose 80 to 90 kts in level flight with engines set to IDLE, (not suggesting that engine thrust was idle for AF447, I'm just describing the "loss of speed" experiment). So something else intervened to advance the loss of speed and approach to stall. What, and why?

There is always a causal path to a loss of control whether it resides primarily in human factors, (the known ones such as rule-breaking, distraction, overwhelmed, competence etc), or resides in technical/system causes or, (more likely) a blend of the two. As many have pointed out over the length of these threads, these have always been the primary questions.

PJ2

[ACLS65]

@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

[takata]

Originally Posted by wes_wall

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.

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...

[Chris Scott]

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.

[mm43]

Does this mean that the location of vital components have been identified and mapped, and therefore no further activity is required by them.

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.

[asc12]

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.]

[dufc]

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....?

[deSitter]

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