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AF447

Old 2nd Jul 2009, 18:15
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Flat Landing

Most of the a/c damage was compressional - horizontal components in cabinets pancaked and vertical components survived intact if not in perfect condition. Also the large sections have multiple cracks much like when a plate is dropped as an analogy. Also the deck being bent upward would require a huge vertical pressure load - e.g. water. I agree with the French engineers of the type of damage versus impact mode.
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Old 2nd Jul 2009, 18:16
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SLF here and I have a few 'common sense' questions because I do not see a problem with the VS having come off with forward movement:

1. Would it be correct to assume that the plane did not fall quite like a brick, i.e. at a right angle, into the ocean?

2. That some forward momentum sheared the VS's attachments, these emerging as weak points at the moment of impact because of uncommon forces acting on it?

Thank you
1. BEA are, effectively, saying she went in "flat". So she could have flown like a "Branson Balloon", but not in a vertical alignment. They say she went in hard so certain things do make sense (and other "theories" disproven).

2. No, I'm questioning the report saying the VS came off in a forward direction based on the rear and centre mounts "existing". Surely, if the force was "forward", the rear mounting point would fail first as it would pull beyond it's stress point as it would be being stressed the most first. Maybe whoever typed up the report had brain fade for a minute?
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Old 2nd Jul 2009, 18:47
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No surprise paxs were without life preservers. This was not a prepared emergency. The airplane was not attempting to ditch.
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Old 2nd Jul 2009, 18:59
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If the VS failed due to rapid forward deceleration I would expect to see more damage at the leading edge adjacent to the tail cone - there is virtually none, just a missing fairing.

A forward deceleration would cause the VS to 'cart wheel'; its C of G is some distance above the attachment points.

Perhaps I misunderstand the report ...
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Old 2nd Jul 2009, 18:59
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Alain Bouillard of the investigating team said the plane probably hit the water belly-first.
They're not sure?

They think the plane was intact upon impact because the debris and bodies have been located within 100nm or more of each other after days at drift and they've found parts from different parts of the plane. Reverse drift charts would show if that range collaspes at ground zero.

The state of the vertical tail is what I've been saying all along, the afterbody broke from around it. The tail didn't break off in the forward direction, the afterbody broke away in the aft direction upon water impact in this case. Until they quit saying 'probably hit the water water belly-first', and say that all damage from front to back of the plane shows consistant orientation of failure, then I'm not ruling out inflight breakup.

Yes, airliners will flat spin with aft cg, and they'll regular spin just fine too.
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Old 2nd Jul 2009, 19:01
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gonebutnotforgotten:
The preliminary report says (note on page 54):

Note : la loi de commande alternate 2 est une loi en facteur de charge en tangage et loi directe en roulis. Seule la protection en facteur de charge reste disponible. Dans certains cas, les stabilités haute et basse vitesses peuvent également être disponibles.

As I understand it there is no way for the crew to revert to direct law at FL350 (though I gather there are some at low speed). So my previous comments still stand, I wouldn't be confident that my basic handling skills, such as they were, acquired on conventional aircraft, would have served me well on that night. To judge from this thread, not many AB pilots have thought through how they would control the aircraft in this condition, and it looks as if the FCOM doesn't help a lot either.
Hi,
Ok. My understanding of what you say is that you are totally confused about how those Airbus are flying and what people are saying. The direct law is what is left when all computer assisted protections are gone. The only one remaining when going to Alternate Law 2 (with an airspeed disagreement triggered) is the load factor airframe protection on pitch axis as all other computer assisted protections are derived from various speed vectors (high speed, low speed, alpha prot, etc.).

loi alternate 2:
- "facteur de charge en tangage" (pitch, full deflection limited to +30/-15 deg and imputs are corrected in order to not exceed the load factor limited to +2.5g/-1.0g).
- "directe en roulis" (roll = direct, stick imputs = aileron moving, 20 deg/sec)
- "directe en lacet" (rudder = direct, stick imputs = rudder moving, full deflection is still limited to a function of speed depending on the last accurate speed until slats are deployed).

What some people do understand by reversion is that the flight controls are being degraded when, in fact, it is the computer various protections which are degraded depending on what data the computer is still able to process.

And yes, direct law is the mode used to test fly any new aircraft going off the assembly lines at which every basic pilot is trained... and all your "basic handling skills, such as they were, acquired on conventional aircraft" would have served you very well because you would have a conventional aircraft to fly.

S~
Olivier
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Old 2nd Jul 2009, 19:01
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The BEA may be like the FAA: upon discovery of a problem, they don't reveal it until they have a solution available. Just speculating..
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Old 2nd Jul 2009, 19:04
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Didn't Pulkovo 612, a TU-154, purely mechanical aircraft, not impact in a flat spin after an attempt to out climb a CB with insufficient power over Donetsk, Ukraine ?

YouTube - PULKOVO 612 Tupolev Tu-154 85185 crash simulation 08/22/06 WEATHER RADAR ATTENUATION EFFECT
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Old 2nd Jul 2009, 19:08
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I don't know how you can speculate on the failure mode of the VS with any credibility. The way it would fail in the circumstances described would depend on a number of factors that we are simply not privy to.

e.g
Failure mode/structural configuration of the surface to which it is mounted.
Centre of gravity (typically quite near the root in fact).
Any air loads on it.
Configuration/relative strength of the mountings.
Relative angle to impact acceleration.
etc
etc

Pure speculation
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Old 2nd Jul 2009, 19:10
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I find it sad with todays technology that the control centres along the route had no idea what was going on. I'm glad that I now operate in areas of good communication & radar coverage. There is no excuse......apart from penny pinching.

Although the BEA seem to be very insistent on proving that no expense is being spared in making things right with all those shiny ships being pictured in the report.
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Old 2nd Jul 2009, 19:11
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The slight torquing they mentioned may have sent the VS straight into the water to the side of the airframe and past the wing. Speculation can lead to facts if something comes up as a theory and the facts are looked at with a new view that may be confirmable.
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Old 2nd Jul 2009, 19:11
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An observation

At time 01:35:15 AFR447 calls ACC-AO with a position report giving time at INTOL, FL and estimates for SALPU and ORARO and requesting a SELCALL check.

At time 01:35:38 ACC-AO: "Acionamento do código SELCALL" [SELCALL check confirmed].

At time 01:35:43 AFR447 transmits: "AIR FRANCE FOUR FOUR SEVEN, thank you" (for SELCALL check).

At time 01:35:46 ACC-AO welcomes AFR447 and requests estimate for TASIL.

During the following 28 seconds ACC-AO requests estimate from AFR447 for TASIL 3 additional times without any reply from AFR 447.

At this time AFR447 was well within the approx. 200nm VHF range from Fernando de Noronha and even if VHF communications were lost, providing that AFR447 heard ACC-AO's estimate request for TASIL would a professional crew such as the AFR447's one not have made contact by HF providing the requested TASIL estimate?

What event at or around time 01:35:46 could have prevented the AFR447's crew from responding to the reiterated request from ACC-AO?

It has been mentioned that three other flightcrew were interviewed flying within 30 minutes of AFR447 (+ - 30 min. or + - 15 min.?) and that these deviated from tract by 10 to 80 kilometres whereas AFR447 appears to have flown on track (see PDF page 11 of the French BEA Prelim. Report) placing the aircraft in the middle of severe CB surroundings from which the other three aircraft had deviated.

Could the 02:10 event be secondary to an earlier event leaving the crew incapacitated at that time?
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Old 2nd Jul 2009, 19:17
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Blue Amber: An interesting thought but a more likely explanation would be that after receiving a SELCAL check the crew simply went straight off comms monitoring. After all thats the whole point of having SELCAL.
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Old 2nd Jul 2009, 19:23
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Blue Amber:
Could the 02:10 event be secondary to an earlier event leaving the crew incapacitated at that time?
Hi,
Maybe you missed the part where AF447 tried to log on (three times 0133, 0135, 0201) to DAKAR ATC but the call was rejected because of the flight plan which wasn't duely recorded:

1.16.2.1 Messages ATC
Aucun message ATC n’a été reçu ou émis par le F-GZCP. Seules trois tentatives de connexion au système ADS-C du centre de Dakar ont été enregistrées le 1er juin à 1 h 33, 1 h 35 et à 2 h 01. Les trois demandes ont été refusées avec un code FAK4, signifiant que le système de contrôle avait constaté une absence de plan de vol pour cet avion ou une inadéquation entre le plan de vol déposé et l’immatriculation, le numéro de vol et la position reportée.
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Old 2nd Jul 2009, 19:27
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Another question from this SLF. I've noted a lot of questioning about whether or not AF447's flight crew deviated from their assigned flight path. Whereas several other a/c in their vicinity did so. Not being at all familiar with protocol if the flight crew of AF447 did attempt to deviate wouldn't they have needed permission to do so, and from whom? I'm quite sure that one does not simply deviate from one's assigned flight path without asking for permission first, correct? My thinking is if they did indeed deviate then that decision would have been made well before TASIL when we know they still had comms?
So why no mention of AF447 asking for a deviation?
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Old 2nd Jul 2009, 19:30
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Further observations.

The following re. the ADS-C (Automatic Dependent Surveillance-Contact) system if from Eurocontrol's website:

ADS-C : Automatic Dependent Surveillance-Contract


The basic concept of the ADS application is that the ground system will set up a contract with the aircraft such that the aircraft will automatically provide information obtained from its own on-board sensors, and pass this information to the ground system under specific circumstances dictated by the ground system (except in emergencies).
Contracts are INITIATED BY THE GROUND and CAN NOT be modified by the pilot.
Note that the contract is a 'dynamic agreement' between the ground system and the aircraft. It is not (as one could think) a piece of paper that has some legal value.
RTCA DO-212 : Minimum Operational Performance Standard (MOPS) for Airborne ADS equipment : Compliance with this standard is recommended as one means of ensuring that the equipment will perform its intended functions satisfactorily under all conditions normally encountered in routine aeronautical operations.



_____________


Thus the aircrew may not have been a "manual" participant.
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Old 2nd Jul 2009, 19:31
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The VS remains a point of discussion.

In post # 725 I had ventured the following, based on the damage to the rudder base and the impression that the rear VS attachements had not "failed" and the damage pattern to the Mobile Crew Rest Area:

"tail end first impact of intact a/c ?
I would concur with those posters theorising that the VS broke off in its entirety on impact and I would add: of a by and large intact a/c.

Looking at the VS photo's, I dare to argue that the a/c impacted more or less level flight, but at a very high AOA, making the very end of the tail section hit the water first, crunching the tail section upwards and in the process damaging the lower-edge of the rudder and unsettling the VS attachment. Subsequent impact of the main, more forward a/c sections would then arrest the forward movement of the VS to the point that it separates from the tail-section alltogether.

Just theorising on what material is available at present."


For the VS to fail aft first and to break forward (left) one presupposes at least some forward speed (in addition to considerable vertical speed).

In that connection I wouldn't mind having further information on whether "belly first" in the definition used by BEA means underside in general, i.e. contrary to sideways or upside down. Such definition would not exclude underside tail first and could (with at least some fwd velocity) explain the VS breakaway.

DB
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Old 2nd Jul 2009, 19:32
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rgbrock1:
My thinking is if they did indeed deviate then that decision would have been made well before TASIL when we know they still had comms?
So why no mention of AF447 asking for a deviation?
See post just above, maybe they tried to ask DAKAR (3 times). There is obviously something wrong with this flight communications.
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Old 2nd Jul 2009, 19:36
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I agree that we do not have all the facts ... accident investigation is about looking at the damage, speculating about a cause of that damage and confirming that that fits the evidence.

Yes, I agree that the C of G would be nearer the root than the tip, look at the location of the slings as the VS was lifted out of the water and you will have a good idea where the C of G is (or isn't).

Looking at the location of wreckage/bodies (1.12.1 in the report), spread over 200 km; that doesn't look like a totally intact impact with the ocean to me.
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Old 2nd Jul 2009, 19:50
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To the SLF:

Generally, one would obtain approval for a deviation. However, if the need becomes critical, ATC comms are poor, or one is in an uncongested area then it is, in my opinion, better to analyse the risk and deviate anyway if necessary. With modern TCAS systems the risk of conflicting with other traffic are greatly reduced.
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