Air France 447...stallo a d'alta quota...

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altri dettagli: in inglese.

An official investigative report confirms speculation that Air France 447, the flight that crashed into the Atlantic two years ago under then-mysterious circumstances, suffered a high-altitude stall before descending 38,000 feet in 3.5 minutes and crashing into the ocean

According to the preliminary accident report issued by the BEA, the captain had just relinquished control to the two co-pilots and left the cockpit when the first sign of a problem occurred, approximately two hours into the flight.

The Airbus 330 was flying at 35,000 feet and the co-pilots decided to make a slight turn to the left in an attempt to navigate around an area of turbulence. Just two minutes after executing the turn, the autopilot and auto-thrust disengaged.

As the airplane began to roll to the right, one of the co-pilots, left unnamed in the report, asserted control and made a left nose-up input. Seconds afterward the flight displays showed a sharp decrease in airspeed and the other co-pilot said, “so, we’ve lost the speeds.”

The co-pilot in control continued to make primarily nose-up inputs and the airplane climbed to a peak altitude of 38,000 feet, triggering the stall warning multiple times in less than a minute.

As the pilot at the controls struggled to regain control of the airplane, the other co-pilot attempted to call the captain back several times, according to the report.

When the captain returned to the cockpit, 1.5 minutes after the autopilot and auto-thrust had initially disengaged, the Airbus 330 was at 35,000 ft with an angle of attack greater than 40 degrees, losing altitude at 10,000 feet per minute, which is consistent with an aerodynamic condition known as deep stall in which the tail stalls, leaving the airplane in an aerodynamic state that may be a difficult or impossible from which to recover. Less than thirty seconds later, the co-pilot at the controls said, “I don’t have any more indications,” while the other co-pilot said, “we have no valid indications.”

The last data recordings, which showed the airplane still falling at 10,912 feet per minute, were captured less than 2.5 minutes later.

According to the BEA report, the speeds shown on the left primary flight display and the integrated standby instrument system (ISIS) were inconsistent for a period lasting under a minute during the string of events that led to the crash.

The BEA is expected to release a more developed interim analysis on the Air France 447 accident at the end of July. “Only after long and detailed investigative work will the causes of the accident be determined and safety recommendations issued,” the agency said in a statement released in conjunction with the accident report.

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aggiornamento ufficiale della BEA del 27 05 11 - forse quella a cui si riferiva Ayrton qualche post orsono.

http://www.bea.aero/fr/enquetes/vol.af.447/point.enquete.af447.27mai2011.en.pdf

Accident to the Airbus A330-203
flight Af 447 on 1
st
June 2009
updAte on investigAtion

https://www.bea.aero

27 May 2011
speciAl foreWord to english note
This note has been translated and published by the BEA to make its reading easier for Englishspeaking people. As accurate as the translation may be, the original text in French should be
considered as the work of reference.
history of flight
On Sunday 31 May 2009, the Airbus A330-203 registered F-GZCP operated by Air France was
programmed to perform scheduled flight AF447 between Rio de Janeiro Gale?o and Paris
Charles de Gaulle. Twelve crew members (3 flight crew, 9 cabin crew) and 216 passengers
were on board. Departure was planned for 22 h 00
(1)
.
At around 22 h 10, the crew was cleared to start the engines and to leave the parking space.
Take-off took place at 22 h 29. The Captain was PNF, one of the co-pilots was*PF.
The take-off weight was 232.8 t (for a MTOW of 233t), including 70.4 t of fuel.
At 1 h 35 min 15 , the crew informed the ATLANTICO controller that they had passed the
INTOL point then announced the following estimated times: SALPU at 1 h 48 then ORARO at
2*h*00. They also transmitted the SELCAL code and a test was undertaken successfully.
At 1 h 35 min 46, the controller asked the crew to maintain FL350 and to give their estimated
time at TASIL.
At 1 h 55, the Captain woke the second co-pilot and said "[…] he’s going to take my place".
Between 1 h 59 min 32 and 2 h 01 min 46 , the Captain attended the briefing between the
two co-pilots, during which the PF said, in particular "the little bit of turbulence that you just saw
[…] we should find the same ahead […] we’re in the cloud layer unfortunately we can’t climb much
for the moment because the temperature is falling more slowly than forecast" and that "the logon
with Dakar failed". The Captain left the cockpit.
The airplane approached the ORARO point. It was flying at flight level 350 and at Mach 0.82
and the pitch attitude was about 2.5 degrees. The weight and balance of the airplane were
around 205 tonnes and 29% respectively. Autopilot 2 and auto-thrust were engaged.
At 2 h 06 min 04, the PF called the cabin crew, telling them that "in two minutes we should enter
an area where it’ll move about a bit more than at the moment, you should watch out" and he
added "I’ll call you back as soon as we’re out of it".
(1)
All times
are*UTC.At 2 h 08 min 07 , the PNF said "you can maybe go a little to the left […]". The airplane began a
slight turn to the left, the change in relation to the initial route being about 12 degrees. The level
of turbulence increased slightly and the crew decided to reduce the speed to about Mach 0.8.
From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the
controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall
warning sounded twice in a row. The recorded parameters show a sharp fall from about 275*kt
to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments
later in the speed displayed on the integrated standby instrument system (ISIS).
Note 1: Only the speeds displayed on the left PFD and the ISIS are recorded on the FDR; the speed
displayed on the right side is not recorded.
Note 2: Autopilot and auto-thrust remained disengaged for the rest of the flight.
At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]".
Note 1: The angle of attack is the angle between the airflow and longitudinal axis of the airplane.
This information is not presented to pilots.
Note 2 : In alternate or direct law, the angle-of-attack protections are no longer available but a
stall warning is triggered when the greatest of the valid angle-of-attack values exceeds a certain
threshold.
The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started
to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The
vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied
between 12 degrees right and 10 degrees left. The speed displayed on the left side increased
sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the
recorded angle of attack was around 4 degrees.
From 2 h 10 min 50, the PNF tried several times to call the Captain back.
At 2 h 10 min 51 , the stall warning was triggered again. The thrust levers were positioned
in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of
around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable
horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and
remained in the latter position until the end of the flight.
Around fifteen seconds later, the speed displayed on the ISIS increased sharply towards 185*kt;
it was then consistent with the other recorded speed. The PF continued to make nose-up
inputs. The airplane’s altitude reached its maximum of about 38,000 ft, its pitch attitude and
angle of attack being 16 degrees.
Note: The inconsistency between the speeds displayed on the left side and on the ISIS lasted a little less
than one minute.
At around 2 h 11 min 40 , the Captain re-entered the cockpit. During the following seconds,
all of the recorded speeds became invalid and the stall warning stopped.
Note: When the measured speeds are below 60 kt, the measured angle of attack values are considered
invalid and are not taken into account by the systems. When they are below 30 kt, the speed values
themselves are considered invalid.The altitude was then about 35,000 ft, the angle of attack exceeded 40 degrees and the vertical
speed was about -10,000 ft/min. The airplane’s pitch attitude did not exceed 15 degrees
and the engines’ N1’s were close to 100%. The airplane was subject to roll oscillations that
sometimes reached 40 degrees. The PF made an input on the sidestick to the left and nose-up
stops, which lasted about 30 seconds.
At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have
no valid indications". At that moment, the thrust levers were in the IDLE detent and the
engines’*N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In
the following moments, the angle of attack decreased, the speeds became valid again and the
stall warning sounded again.
At 2 h 13 min 32, the PF said "we’re going to arrive at level one hundred". About fifteen seconds
later, simultaneous inputs by both pilots on the sidesticks were recorded and the PF said "go
ahead you have the controls".
The angle of attack, when it was valid, always remained above 35 degrees.
The recordings stopped at 2 h 14 min 28. The last recorded values were a vertical speed of
-10,912 ft/min, a ground speed of 107 kt, pitch attitude of 16.2 degrees nose-up, roll angle of
5.3 degrees left and a magnetic heading of 270 degrees.
neW findings
At this stage of the investigation, as an addition to the BEA interim reports of 2 July and 17
December 2009, the following new facts have been established:
ˆ The composition of the crew was in accordance with the operator’s procedures.
ˆ At the time of the event, the weight and balance of the airplane were within the operational limits.
ˆ At the time of the event, the two co-pilots were seated in the cockpit and the Captain was
resting. The latter returned to the cockpit about 1 min 30 after the disengagement of the
autopilot.
ˆ There was an inconsistency between the speeds displayed on the left side and the integrated standby instrument system (ISIS). This lasted for less than one minute.
ˆ After the autopilot disengagement:
„ the airplane climbed to 38,000 ft,
„ the stall warning was triggered and the airplane stalled,
„ the inputs made by the PF were mainly nose-up,
„ the descent lasted 3 min 30, during which the airplane remained stalled. The angle of
attack increased and remained above 35 degrees,
„ the engines were operating and always responded to crew commands.
ˆ The last recorded values were a pitch attitude of 16.2 degrees nose-up, a roll angle of
5.3*degrees left and a vertical speed of -10,912 ft/min.