Airbus A340 a FL350 attraversa zona di forte turbolenza.

[airplane]

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Airbus A340 a livello di crociera attraversa zona di forte turbolenza.

SECURITE DES VOLS Level bust en turbulences
Pôle Com SV - 26/07/2011 09:11

En croisière au FL 350, en IMC de nuit, un A340 en provenance de CCS traverse une zone de turbulences sévères, 10 nm au nord de la position 18N060W.

L'avion subit un fort gradient de vent (+22 kt de vent effectif en 5 s), avec une vitesse atteignant Mach 0.88 (MMO de 0.86) pour une CAS=304 kt avec déclenchement de l'alarme Overspeed. Simultanément, une déconnexion de l'AP se produit.
L'assiette de l'avion augmente ensuite progressivement vers 11°, avec un vario voisin de 5000 ft/min.

Moins d'une minute après la déconnexion de l'AP, l'avion atteint le FL380 avec une vitesse en diminution vers Mach 0.66 pour une CAS=205 kt (Mach GD =0.78, GD=276 kt).
La diminution de l'intensité des turbulences s'accompagne d'une réduction de l'assiette de l'avion, puis d'un retour à des paramètres de vol normaux.

La période de turbulences dure deux minutes avec une intensité plus prononcée lors des 30 premières secondes. Plusieurs pics d'accélération verticale sont enregistrés, les valeurs limites atteignant +1.7 g/+0.5 g.

Les informations météorologiques fournies à l'équipage n'indiquaient pas de turbulences dans cette zone du parcours. Le radar météo était en fonctionnement.
Aucun blessé n'est à déplorer parmi les passagers et 2 CRAT bénins sont rédigés par l'équipage commercial.

La rapidité de transmission de l'annonce «ici le poste de pilotage, PNC assis attachés, turbulences fortes », a contribué à limiter les dommages corporels en cabine.
Mise à jour 28/07/2011 : cet évènement fera l'objet d'une enquête du BEA à laquelle Air France sera associée.

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[JT8D]

Per completezza, dato che non tutti conoscono il francese, allego qui il link all'articolo relativo a questo evento in lingua inglese (tratto da AvHerald), così che tutti possano comprenderlo:

http://avherald.com/h?article=44280b2a&opt=0

Paolo

[airplane]

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>Airbusfamilydriver

Credo sia utile, ricordare il contenuto dello stralcio qui sotto:

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Airbus A330 C-GGWD, Airbus A340 TC-JDN
AAIB Bulletin No: 6/2001 Ref: EW/C2000/10/2 Category: 1.1


Background

The A340 was en-route from Istanbul to New York and the A330 was en-route from London to Ottawa.

Both aircraft were assigned to North Atlantic (NAT) Track E with an entry point into Oceanic Airspace of 58°North 10°West and a next reporting point of 59°N 20°W.
Both aircraft were cleared by the Scottish Oceanic Area Control Centre to cruise at Mach 0.82 with the A340 at Flight Level (FL) 360 and the A330 1,000 feet above at FL 370.

The vertical separation distance of 1000 feet was in accordance with RVSM (Reduced Vertical Separation Minima) used by approved aircraft within NAT MNPS (Minimum Navigation Performance Specification) Airspace....

Meteorological situation
A meteorological aftercast described the synoptic situation at 1400 hrs UTC as a low pressure area
centred to the west and south west of Iceland with an occluding front lying through 60° North and
16° West. Visible spectrum satellite pictures taken at 1400 hrs clearly showed the position of the
front. A change in the height of the tropopause was very likely at or near the incident position with
an associated change in air temperature across the frontal boundary. Moreover, NAT Track E lay
some 150 nm to the north of the core of a westerly Jetstream with a speed of 170 kt at FL 310. The
1200 hrs NAT Significant Weather Chart showed the position of the Jetstream and the occluded
front. At the incident location, NAT track E lay within the boundary of an area marked as likely to
contain clear air turbulence between FL 200 and FL 400. This area was associated with the
westerly flow of the Jetstream……….

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>>The A330 commander's report
Both aircraft were in clear air as the A330 was slowly overtaking the A340 below it. The A330
commander stated that his aircraft was slightly to the right of the A340 and almost abeam it when
he saw the A340's wings start to flex. At about that time he felt a bump, which he described as
similar to entering a mountain wave. Five to ten seconds later there was another bump during
which the A330's altimeter reading descreased by 200 feet. Immediately thereafter, the A330
commander heard a TCAS "climb climb" warning and he noted that the A340 TCAS symbol had
changed colour to red on his navigation display. He looked out and down at the A340 which was
some 200 to 300 feet to his left in a nose-up attitude and climbing steeply. The A340 passed
through the A330's level before the commander had time to react to the TCAS warning and the
TCAS was still issuing a "climb" instruction for a short while after the A340 had climbed above the
A330. The commander continued to minor the A340 visually and on TCAS. It appeared to reach an
apogee above FL380 although by this time it had fallen behind the A330. Nevertheless, it was still
laterally quite close to the A330's track so the commander altered copurse to the right to make
space for the A340 to descend back to FL 360. After a short discussion with the A340 crew on
VHF radio, the A330 commander broadcast a warning of severe turbulence on the common VHF
frequency and then reported both the turbulence and the aircraft proximity (AIRPROX) occurrence
to Shanwick on HF Radio. there were no injuries on board the A330 although there were spillages
in the cabin.

>>The A340 commander's report
At FL 360 the A340 was 1000 feet below the maximum cruising level displayed on the Flight
Management and Guidance System (FMGS). The commander was expecting a turbulence
encounter around 59°N 20°W and when the aircraft first entered light turbulence he made a cabin
announcement and switched on the seat belt signs. Shortly before the AIRPROX event he
experienced moderate turbulence and noticed outside air temperature changes. Suddenly the aircraft
began to climb, the Master Warning sounded and the autopilot self-disengaged as the aircraft
exceeded the speed limit of 0.86 Mach. The indicated airspeed dropped below VLS (the lowest
selectable) as the aircraft climbed and the commander took manual control of the aircraft because
neither autopilot would engage. The crew subsequently reported the incident to Shanwick on HF
radio and using their TCAS, they descended back to FL 360 in a safe area. At the time of the
AIRPROX the commander estimated the aircraft were one mile apart laterally. After landing at
New York the commander had the aircraft inspected by technical staff but no defects were found.
There were no injuries on board the aircraft.
The commander could not remember the sequence of warnings but he did recall being unable to reengage
either autopilot which prompted him to make manual control inputs. He also remembered
seeing an 'Alpha Lock' warning displayed on his Primary Flying Display.

Flight Data Recordings
The Cockpit Voice Recordings in both aircraft had over-run the event before they landed but digital
flight data readouts were obtained from the aircraft by the airlines involved. Both sets of data were
made available to the AAIB and subsequently to Airbus Industrie. However, since the aircraft
clocks were not synchronised, there was no accurate method of determining a coherent sequence of
events for both aircraft on one timescale. Therefore, a brief description of the salient data for each
aircraft follows.

A330 Data
Analysis by the AAIB showed that the aircraft first received a TCAS TA (Traffic Advisory) at
14:10:08 hrs (A330 clock time) which remained active for 12 minutes until the TCAS issued an RA
(Resolution Advisory) at 14:22:07 hrs. The RA persisted for about 19 seconds and the issue of a
verbal "climb climb" command was recorded. The aircraft remained under autopilot control and
within 150 feet pressure altitude of FL 370 throughout the event. Its Mach number stayed below
0.86 except for a momentary excursion to 0.87 which did not trigger an autopilot disconnect. The
angle of attack was generally about 2.5° and the highest recorded value in turbulence was 3.2°. The
derived wind direction remained within 10° of 240° but the wind speed varied between 68 kt and
98 kt in turbulence. In the same period the static air temperature fluctuated between -44°C and -
50°C. The first fluctuation was the most severe and there were five more cycles of decreasing
severity. The overall temperature change during the turbulence encounter was a 3°C increase at FL
370. An excerpt from the A330 Data is shown at Appendix A to this report.

A340 Data
The A340 crew received a TCAS TA at 14:09 hrs (A340 clock time) alerting them to the proximity
of the A330. At 14:20:40 hrs the aircraft entered a region of successive and increasing variations in
wind and air temperature, which in turn caused fluctuations in pitch angle, normal g, altitude,
calibrated airspeed, engine N1% and Mach number. One minute later in a particularly vigorous
fluctuation, the aircraft's Mach number briefly increased to 0.87. This speed excursion above the
Mach 0.86 limit triggered a Master Warning at 14:21:40 and automatically disengaged the
autopilot. One second later the TCAS issued an RA with a "descend, descend, descend" audio
warning. In the two second period after the initial speed excursion above Mach 0.86 the Mach
number decayed to 0.855 and then increased again to 0.882. It remained above 0.86 for two
seconds before decreasing and remaining below 0.86 for the remainder of the turbulence encounter.
Five seconds after the autopilot disengaged, the thrust levers were closed and then the autothrust
was disconnected, probably by the handling pilot in an effort to prevent another overspeed
condition. Ten seconds after the autopilot disengaged, the corrected or phase-advanced angle of
attack (a computed parameter which is not recorded but can be calculated by Airbus Industrie from
the DFDR data) reached the 'alpha prot' value. This angle of attack excursion beyond alpha prot
caused a change in the pitch flight control law from normal law (NZ law) to angle of attack
protection law (AoA law). If both sidesticks are at neutral, the AoA protection law seeks to hold the
angle of attack constant at alpha prot until a sidestick pitch command is made. If the stick is pulled
fully aft then the angle of attack increases to alpha max. If the sidestick is not moved aft, AoA
protection law remains active until a nose-down command greater than half forward travel is made
or until a nose down sidestick input has been applied for more than one second. The first recorded
sidestick input was made at 14:22:08 which was some 28 seconds after the commencement of the
Master Warning.
For 18 seconds after the autopilot disengaged the aircraft remained within 200 feet altitude of FL
360 but once AoA law was invoked at 14:21:50 hrs, the aircraft's attitude began to pitch nose-up.
The pitch-up trend continued for 17 seconds reaching a peak of 15° nose-up shortly before the first
nose-down sidestick command was applied. Throughout this phase the aircraft climbed rapidly
(reaching a peak rate of about 6,000 ft/min) due to the increase in lift created by the flight control
system's capture of alpha prot. The aircraft reached its apogee at FL 384 at 14:22:28 hrs where the
airspeed had decayed to 205 KIAS and 0.67 Mach even though full thrust had been applied.
Throughout the turbulence encounter, the normal g fluctuations were between 0.5g and 1.5g. The
recorded wind direction remained within 20° of the mean of 240° but the wind speed varied
between 67 kt and 108 kt and the static air temperature fluctuated between -42° C and -52°C. There
were 7 cycles of temperature change, the second cycle being the most severe. The mean air
temperature before the AIRPROX event was -46.5° C and afterwards it was -44.5°C. The crew
subsequently descended back to FL 360 and successfully re-engaged the autopilot and autothrust
systems.
The DFDR recorded a change from TCAS TA to RA at 14:21:41which was about one second after
the Master Warning started. The RA persisted in the aircraft logic for 27 seconds by which time the
aircraft was climbing rapidly through FL 372. The alert then changed to a TA which persisted for 8
seconds, ceasing as the aircraft climbed through FL 378. An excerpt from the A340 Data is shown
at Appendix B to this report……….


>>Analysis

General
Before the incident, both flight deck crews would have been aware of the presence of the other
aircraft because both had received at least one 'traffic traffic' synthetic voice message and they
would have seen the intruder aircraft symbol on their navigation displays about 10 minutes before
the turbulence encounter.
The incident began when both aircraft deviated from their assigned flight levels whilst the lateral
separation between them was less than nautical two miles triggering TCAS RA warnings in both
aircraft. Initially the risk was minimal because when TCAS RAs were issued, the aircraft were
about 800 feet vertically separated with transient variations in vertical speed due to the turbulence;
at that stage the A340 had not begun its 'zoom climb'.

The incident became serious about 10 seconds later when the A340's flight control system captured alpha prot and commenced a vigorous climb which resulted in the A340 climbing through the A330's assigned flight level whilst both aircraft were laterally separated by a few hundred feet.


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Ps.
purtroppo non ho sottomano il relativo link.


.

[airplane]

Per completezza, dato che non tutti conoscono il francese, allego qui il link all'articolo relativo a questo evento in lingua inglese (tratto da AvHerald), così che tutti possano comprenderlo:
http://avherald.com/h?article=44280b2a&opt=0
Paolo

JT8D,
Grazie, per la completezza...


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[Valerio Ricciardi]

Suddenly the aircraft
began to climb, the Master Warning sounded and the autopilot self-disengaged as the aircraft
exceeded the speed limit of 0.86 Mach.

E sin qui tutto bene

The indicated airspeed dropped below VLS (the lowest
selectable) as the aircraft climbed and the commander took manual control of the aircraft because
neither autopilot would engage. The crew subsequently reported the incident...

Questo invece lo trovo inquietante.
Da quando per proteggersi da un overspeed si deve ridurre la velocità a livelli simili?

once AoA law was invoked at 14:21:50 hrs, the aircraft's attitude began to pitch nose-up.
The pitch-up trend continued for 17 seconds reaching a peak of 15° nose-up shortly before the first
nose-down sidestick command was applied. Throughout this phase the aircraft climbed rapidly
(reaching a peak rate of about 6,000 ft/min) due to the increase in lift created by the flight control
system's capture of alpha prot. The aircraft reached its apogee at FL 384 at 14:22:28 hrs where the
airspeed had decayed to 205 KIAS and 0.67 Mach even though full thrust had been applied.

Può un sistema automatico essere affetto da eccesso di zelo?

Initially the risk was minimal because when TCAS RAs were issued, the aircraft were
about 800 feet vertically separated with transient variations in vertical speed due to the turbulence;
at that stage the A340 had not begun its 'zoom climb'.

The incident became serious about 10 seconds later when the A340's flight control system captured alpha prot and commenced a vigorous climb which resulted in the A340 climbing through the A330's assigned flight level whilst both aircraft were laterally separated by a few hundred feet.

Arrivo a comprendere persino io nella mia ignoranza, dopo averlo assaporato nei filmati delle acrobazie a motori spenti di Bob Hoover, il concetto che al netto delle perdite per attrito col fluido si può trasformare la velocità in quota e la quota in velocità; ma forse est modus in rebus...

Direi che forse potrebbero esserci le condizioni per inizare un serio ragionamento e vedere un po' dove rimettere le mani a livello di SW, da quelle parti, con freddezza ed umiltà, senza barricarsi in difese d'ufficio di una filosofia di automazione. Il concetto mi pare eccellente, forse qualcosa nelle moadalità di esecuzione è suscettibile di affinamenti.
E, nelle more, aumentare a livelli un poco meno ottimistici i livelli di separazione ammessi.
Il test di Touring non è ancora stato superato da alcuna elaboratore, a che mi risulti, dunque della nostra capacità di decisione ci si dovrebbe fidare un poco di più anche se la velocità di intervento di un sistema automatico è di norma concettualmente maggiore.

Su molte autovetture, non solo ammiraglie, è stato introdotto l'EBA (Electronic Brake Assist) che dovrebbe riconoscere dalla modalità di applicazione della pressione sul pedale del freno una situazione in cui il guidatore sta tentando una frenata di emergeza (panic stop). La taratura di questi sistemi è sempre in via di affinamento, per evitare che una frenata un po' più repentina all'inizio (ossia come modalità di inizio dell'abbassamento del pedale del freno) dovuta magari ad un semaforo giallo visto un pochino tardi con susseguente decisione un minimo tardiva di fermarsi e non attraversare l'incrocio, non venga puntualmente scambiata dal sistema per una frenata di emergenza tentata cercando di scongiurare un imminente impatto.
Perché se ciò avviene, la macchina esegue un brillante e lineare panic stop (assistita dall'EBD, ripartitore elettronico della frenata) e dall'ABS (antibloccaggio) elevando la decelerazione ai massimi livelli tecnicamente possibili su quel fondo... col brillante risultato di quasi garantire il tamponamento da parte della vettura che ci segue.

[vihai]

Il test di Touring non è ancora stato superato da alcuna elaboratore, a che mi risulti

CleverBot l'ha superato qualcosa tipo ieri

(Turing, non Touring.)

Ciao,

[Valerio Ricciardi]

...Alan Turing, certo, perdona il refuso, l'Alzheimer avanza.

E' una buona notizia, anche se sospetto che Turing fosse più esigente di quanto sarà stato consioderato sufficiente dagli "esaminatori"...

[airbusfamilydriver]

dal minuto 1:56 si parla di wake turbulence,severe turbulence,level burst e mid air collision risk

[AirGek]

Figata sto test di Turing.