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AF447

Old 18th Jul 2009, 10:49
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Hyperveloce,
PS) is there an explanation for the 3 Atlantico requests (for TASIL estimates) that remained unanswered by the AF 447 at 01:36Z ?
Having successfully tested the Selcal, the crew left the audio HF watch, relying on Atlantico -or others on the same frequencies- to contact them via Selcal.

Fly400,
What we do not know is if AF447 attempted to contact DAKAR on HF. And we will not know until the CVR is recovered. It is possible that any attempts to contact DAKAR may have been recorded on the ATLANTICO tapes, but we don't have those either.
The calls to Dakar would have been made on 6535 and Atlantico was on the 6649 family. Had Atlantico picked-up some transmissions, they would have reported it.

Last edited by Lemurian; 18th Jul 2009 at 11:01.
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Old 18th Jul 2009, 13:52
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Where are the antennas?

HF must be longer than a meter or so; just idly wondering on what part of the a/c it / they are deployed..
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Old 18th Jul 2009, 15:17
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FLY400

I see from ATC DL News Home that
"Once a periodic contract is established, it remains in place until it is cancelled or replaced by another periodic contract."

So when one wants to switch from one ground station to another do you cancel the first station and then try to logon to the next one?

When it cannot logon what happens then? Does it keep trying at intervals or does the operator have to initiate a retry?
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Old 18th Jul 2009, 15:42
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Having successfully tested the Selcal, the crew left the audio HF watch, relying on Atlantico -or others on the same frequencies- to contact them via Selcal.
Did ATC tell them to do that? Did they tell ATC they were going to switch to SELCAL?
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Old 18th Jul 2009, 15:53
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Did ATC tell them to do that? Did they tell ATC they were going to switch to SELCAL?
It would be a hell of lot easier if people knew what they are talking about.
ATC doesn't tell you to. It's just standard procedure. One doesn't swithch to SELCAL, one IS on SELCAL watch unless the test proved negative.
Since the dark age of aviation in this area, radio contact remains flimsy, always have always will. ADS is supposed to be the magic bullet and it is when it's working, which is most of the time.
No radio contact would have prevented the loss of this aircraft and as far as mayday call goes, they had thousands of other things to to do like try to save the aircraft, be afraid and stressed like most of you won't ever be in 3 life times.

I think this thread should be closed until the BEA comes up with something new. It is getting both boring and repetitive.
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Old 18th Jul 2009, 16:23
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In both Boeing and Airbus airplanes there is one HF antenna shared between 2 HF transceivers. It is located just behind the leading edge of the Vertical Stabiliser.

There are 2 other components between the HF transceivers and the antenna. One is a coupler that connects the transmitting HF to the antenna. The other is an antenna tuner that optimises the antenna to the transmitting frquency.

While only one HF is able to transmit at a time, both HFs are able to receive simultaneously.

You are correct. The physical antenna is about a metre long.
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Old 18th Jul 2009, 19:44
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Originally Posted by cribbagepeg
HF must be longer than a meter or so; just idly wondering on what part of the a/c it / they are deployed..
I believe it's mounted on the VS, but it's an active antenna, so it doesn't need to be long.

See post 984 on page 50 for diagram.

Last edited by Lightning6; 18th Jul 2009 at 20:24.
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Old 19th Jul 2009, 09:02
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Just Found This Item

I've only copied the first three paragraphs; to post more would be to patronize most everyone here.


Guyana fisherman finds possible debris from Air France crash; officials contact Brazil
July 18, 2009 - 11:34
THE ASSOCIATED PRESS
GEORGETOWN, Guyana - A fisherman in Guyana apparently has found a large piece of a plane that authorities suspect might belong to the Air France jet that crashed in the Atlantic Ocean, an aviation official said Saturday.
The 30-foot-long piece of what appears to be aircraft fuselage washed up on a beach in the South American country this week, said Paula McAdam, deputy director of Guyana's Civil Aviation Authority.
The Brazilian Embassy said it would send experts to examine the debris, she said.
Pasted from <Guyana fisherman finds possible debris from Air France crash; officials contact Brazil | Macleans.ca - Canada - Features>


There is also Bruno at CRASH-AERIEN.COM - Le Site Français des Accidents et Incidents Aériens who says there are 3 MLA accelerometers on the A330, all of which come in square casings and none of which are made by Sensorex. See full posting below:


bruno7
Principicule de Taxiway

Inscrit le: 21 Mar 2009
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Localisation: ILE DE FRANCE

Posté le: Ven 17 Juil 2009 23:36 Sujet du message:

Il y a 3 acceleromètres sur A330 pour la fonction Maneuver Load Alleviation (MLA) et Turbulance Damping.
Ces accelero Nz et Ny sont logés en soute avionique (juste devant le logement de TAV) pour les deux concernant la fonction verticale et au plafond du fuselage tout à fait au fond de l'avion c'est à dire sous la dérive.

Ils n'ont pas cette allure là,le boitier est carré et le fabricant n'est pas Sensorex.



Pasted from <WWW.CRASH-AERIEN.COM :: Voir le sujet - Air France AF447 : Après l'arrêt des recherches (Partie 2)>

Last edited by ArthurBorges; 19th Jul 2009 at 10:03.
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Old 19th Jul 2009, 10:26
  #3769 (permalink)  
 
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re: AurthurBorges "Just Found This Item"

Covered in posts # 3742 & # 3751 - compare the paint job on the Ariane nose fairing with the wreckage.
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Old 19th Jul 2009, 15:20
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ACARS interruption & rain attenuation

Art Deco, what are the rain attenuation values you have used for your estimation ? Do you make use of a cloud model (a spatial distribution of water, ice,...) ?
Jeff
PS) this article maybe of interest:
A prediction model that combines rain attenuation and other propagation impairments along Earth-satellite paths, Dissanayake, A.; Allnutt, J.; Haidara, F., Antennas and Propagation, IEEE Transactions on Volume 45, Issue 10, Oct 1997 Page(s):1546 - 1558 Digital Object Identifier 10.1109/8.633864
but there also may also be attenuation from the a low gain LOS due to the antenna itself (partially masked by the airframe, LOS in a low gain direction of the radiation pattern, rotating plane & antenna axis)

Last edited by Hyperveloce; 19th Jul 2009 at 15:36.
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Old 19th Jul 2009, 22:37
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At the beginning of the Air Caraibes (ACA) incident that happened last fall, the situation looks rather close to that of AF447, at least with regard to these elements: same FL (350), about same gross weight (206 t), ADR disagree, Alternate law.
As you know, during the incident the ACA crew experienced two stall warnings which the PF considered spurious and disregarded. That probably saved his day.
The analysis of this incident, which was published earlier, states that given the configuration, the threshold to trigger a stall warning is AoA = 4.2°.

Question: do you people with flying experience on A330 think that at 4.2° AoA this airplane is so close to max AoA that it is reasonable to throw a stall alarm, especially in the situation at hand ?
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Old 20th Jul 2009, 01:59
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DJ77

Surely that's a question for the aerod and systems dept at AI. This wouldn't be a matter of 'stall' as much as initial buffet onset. Pilots wouldn't have much if any experience of flying into that AoA regime during cruise, surely, to be able to assert 4.2 is too early, 4.5 is about right. These things are figured out from detailed consultation of test-flight crew/flight-test engineers and examination of buffet/maneouvre limits of the wing from plotted Lift~Drag~PM/Mach boundaries.
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Old 20th Jul 2009, 09:42
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AF908 CDG-TNR AUG/2008 Air Safety Report

Radiocokpit has published an ASR. AF908 CDG-TNR (Antananarivo) FGNIH A340-303X
F-GNIH was on her way at FL370 between OBD 13°06'40.5 E 30°13'53.3 and MLK N09° 33' 47.4 E31° 39'11.4 on the UB612 (Khartoum FIR) when this incident occured.
There are a lot of similiraties with the chain of events of the 447.
The report is in French and I have unfortunately not enough time to translate in English but most of you should easily understand or use automated translation tools.
RCC editors have "translated" the report in plain French (blue color).
Please note:
CDB= Captain
OPL = F/O
PF Pilote en Fonction (left seat)
PNF Pilote Non en Fontion (right seat)
At the time of the incident the Captain was in command at the left seat and one F/O at the right seat. The second F/O was at rest.

Link :

Eurocockpit - Archives

Scroll down to
AIR SAFETY REPORT - 1/6

FGNIH AF908 CDG - TNR - ALARME STALL ET PERTE DES INDICATIONS DE VITESSE SUR LES PFD
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Old 20th Jul 2009, 15:54
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How a pilot would react to stall alarms ?

Isn't there a past case, on an A340 in cruising phase (at FL370) between Paris and Antananarivo (F-GNIH) during which the pilot decided a nose down when stall alarms were sounded ?
Eurocockpit - Archives
added after reedition__________________________________________
before the problems with the airspeeds, the PF had reduced the speed to Mach 0.80 ("a little bit over the green dot") after the plane had entered turbulences not detected by the radar. So that when the stall alarms sounded (due to rolling back airspeeds due to Pitot freezing), maybe it was logical that he thought that they were justified (being just "a little bit over the green dot") and reacted accordingly ? (nose down & descent)
____________________________________________________________
I am also trying to see whether the A/THR could have had a similar reaction just before its disengagement (increasing thrust level to correct a spurious airspeed decrease just before being put off line), diminishing the upper aerodynamic margin. And also at A/P level (disengagement => an ongoing phenomenon compensated by the A/P before its disengagement is let free to drift/amplify when the A/P goes off).
Jeff
PS)
-these stall alarms occured approx. 30 s after the sequence of fault reports incl. AP & A/THR off in the Air Caraïbe case, a critical phase during which the crew are already busy to understand/isolate the faults, to apply the check lists/procedures and to pilot manually.
-the stall alarms immediatly follow the AP & A/THR off for the flight FGNIH AF908 CDG - TNR

Last edited by Hyperveloce; 21st Jul 2009 at 18:49. Reason: elapsed time between A/P off & stall alarms
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Old 20th Jul 2009, 18:06
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New theory

Regard one little piece of all of this, something occured to me. I wonder.

I'm thinking the 'twist to the left' component indicated for the fin-failure in the preliminary report might simply result from a deflected rudder at the moment of impact. A deflected rudder would impose a twisting force on the base. A deflected rudder could also be one of the factors in where the freed fin traveled after impact. Of course there are definitely other possibilities for the twist.

frequency change(i.e., not fishing for dialog, i'll just drop-off the card and go do my other things)

Last edited by ttcse; 20th Jul 2009 at 18:20.
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Old 20th Jul 2009, 20:24
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Stall warning

RE: HarryMann (#3774)

These things are figured out from detailed consultation of test-flight crew/flight-test engineers
Actually, these things are governed by airworthiness requirements, e.g.:

FAR/JAR 25.207 Stall warning (a)Stall warning with sufficient margin to prevent inadvertent stalling (...) must be clear and distinctive to the pilot in straight and turning flight.

Subparagraphs (b) through (f) of this section define the required margin in more detail.

regards,
HN39
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Old 20th Jul 2009, 20:35
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A "clear" and "distinctive" alarm ?

HazelNuts39
Then add flight safety engineers to the investigation pool.
Because the alarm can be "clear" and "distinctive" (meaning a signal you can not miss ?), but if there can be "undue stall alarms" (see ECAM messages) or due stall alarms (see SOPs), a variable meaning/interpretation according to a situation which is very difficult to assess in a few sec. or even min., then the alarm signal and more importantly the reaction it should induce is not so much "clear" and "distinctive"
Jeff
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Old 20th Jul 2009, 21:17
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Stall warning

RE: Hyperveloce #3779

I am quoting from a requirement that must be met by all large (transport category) airplanes. Before the FBW age, the requirement was met by natural pre-stall buffet or, if the airplane didn't have that, by a stick shaker triggered at a certain AoA. I assume that the aural warning "STALL STALL STALL" meets that requirement for the A-330. Quoting from the ASR FGNIH AF908:


Suivi immédiatement de l'alarme STALL STALL STALL (sans l'alarme cricket associée) avec indication de TOGA LK.
Any system in the airplane should be designed to prevent "undue" stall warnings.

I would be interested to know if the A-330 stall warning, for any given configuration, is triggered solely by the AoA signal, or that it depends on the airspeed (pitot) -signal.

Regards,
HN39

PS: I should have added that other requirements specify that operational speeds, i.e. the minimum speeds flown intentionally by the pilot during takeoff, enroute and landing must have sufficient margin above the stall warning speed to prevent interference during normal maneuvering.

Last edited by HazelNuts39; 20th Jul 2009 at 21:29. Reason: text added
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Old 21st Jul 2009, 00:25
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Hazelnuts39

From a July 8 posting at Eurocockpit:

UPDATE: We're getting lots of emails telling us stall warnings are only triggered by the AOA windows. There are numerous documented cases of stall warnings caused by icing of Pitot tubes. Moreover, "risk of undue warning" is cited in cases of ADR DISAGREE.
It seems the AOA threshold for triggering a stall warning depends not only on SLATS/FLAPS position, piloting law but also speed (or Mach number).
As a reminder, the ACA crew had already applied severe turbulenece procedure, which consists of disengaging A/THR and displaying thrust appropriate to flight level, but they nonetheless faced a stall warning when trying to maintain flight level despite altitude variations due to speed adjustments.

ORIGINAL TEXT

UPDATE : Nous recevons un abondant courrier nous indiquant que l'alarme de décrochage n'est générée que par les palettes AOA (Angle Of Attack, sondes d'incidence). L'alarme décrochage apparaît dans de nombreux cas documentés de givrage des sondes Pitot. La mention "risk of undue stall warning" apparaît d'ailleurs en cas d'ADR DISAGREE.
Il semble que le seuil d'AOA de déclenchement de l'alarme Stall soit fonction de la position des SLATS / FLAPS, de la loi de pilotage, mais aussi de la vitesse ou du Mach.
Pour rappel, l'équipage ACA avait préalablement appliqué la procédure "severe turbulence" consistant à débrayer l'A/THR et à afficher une poussée correspondant au niveau de vol, mais a pourtant été confronté à l'alarme Stall en essayant de maintenir le niveau de vol compte tenu de la variation d'altitude (liée à la correction de Mach).

Pasted from <Eurocockpit - Accueil>
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Old 21st Jul 2009, 01:08
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How is the stall alarm computed ?

Originally Posted by HazelNuts39
I would be interested to know if the A-330 stall warning, for any given configuration, is triggered solely by the AoA signal, or that it depends on the airspeed (pitot) -signal.
So would I.
If this stall alarm is computed from AoA only (and not also the airspeed, the altitude, the aerodynamic configuration: flap ext.,...), maybe it is linked to the AoA law (the alpha prot) ? And then the next question is: how is the alpha prot computed ? Wouldn't the threshold "alpha prot" be a table depending on the flap configuration, airspeed and altitude ?
And if there is an indirect link between stall alarms & airspeeds (via the alpha prot values), in the Air Caraïbe case, there is a lag of 30 sec. between the CAS drop+sequence of FLRs and the stall alarm: maybe an underlying filtering process ?
Jeff
PS) Increasing Pilot's authority over automated systems via the AoA law:
http://www.pn.ewi.tudelft.nl/educati.../notes/loc.pdf

Last edited by Hyperveloce; 21st Jul 2009 at 01:24.
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