The Air France flight from Rio de Janeiro to Paris plunged into the Atlantic because the aircraft's speed sensors gave invalid readings, France's Bureau of Investigation and Analysis (BEA) said Friday.
But findings are mixed and some are doubting some of the official findings.
Most surprising of the findings came the news that at the very start of the incident, the captain was NOT in the cockpit.
The report findings said the aircraft climbed to 38,000 ft when "the stall warning was triggered and the airplane stalled."
The investigation, an interim report, raises the question of why the pilots responded to the stall by pulling the nose up instead of pushing it down to recover from the stall, says CNN's aviation expert Richard Quest.
The report said the speed displayed on the left primary flight display were "inconsistent" with those on the integrated standby instrument system (ISIS).
The aircraft experienced some "rolling" before stalling and then descending rapidly into the ocean. The descent lasted 3 minutes and 30 seconds and the engines remained operational, said the report. It plunged at 10,912 feet (3,300 meters) per minute.
At the time of the descent, the two co-pilots and captain were in the aircraft cockpit.
Quest said: "For whatever reason the aircraft speed sensors failed and the A330 went into a high altitude stall. The pilot's actions were unable to recover the aircraft and some might say, made the bad situation worse.
"The actual falling from the sky will have been horrific. This plane fell out of the sky."
All 228 people aboard the Airbus A330 Flight 447 from Rio de Janeiro to Paris were killed on June 1, 2009.
Air crash investigators at the Paris-based BEA have been working on the theory that the speed sensors, known as pitot tubes or probes, malfunctioned because of ice at high altitude.
Since the accident, Air France has replaced the pitots on its Airbus fleet with a newer model.
The report quotes some of the pilot's conversation -- who were not named -- and reveals that they were aware of the upcoming turbulence and storm.
Four hours and six minutes into the flight, one of the co-pilots, referred to as 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... I'll call you back as soon as we're out of it."
The report said that four hours and 10 minutes into the flight, "The autopilot [and] then auto-thrust disengaged," and co-pilot PF said: "I have the controls." The report said the stall warning sounded twice in a row.
At four hours and 10 minutes into the flight the other co-pilot, referred to as PNF said: "So, we've lost the speeds." A second later the stall warnings sounded again the report said.
At about this time, "The speed displayed on the left side increased sharply," the report said. The aircraft was then at an altitude of about 37,500 ft.
The report said that at this time co-pilot PNF tried several times to call the captain back to the cockpit.
The aircraft then climbed to 38,000 ft and at around four hours 11 minutes and 40 seconds into the flight, the captain re-entered the cockpit. During the following seconds all of the recorded speeds became invalid and the stall warning stopped, the report said.
Co-pilot PF said "I don't have any more indications", and the co-pilot PNF said "we have no valid indications".
About a minute later co-pilot the PF said "We're going to arrive at level one hundred." This is a height of 10,000ft. About fifteen seconds later, the data recorder indicate "simultaneous inputs by both pilots on the sidesticks."
The recordings stopped at 4 hours 14 minutes and 28 seconds into the flight. A full investigation into the crash is expected next year.
Earlier this week French air crash investigators said they would be able to identify two bodies recovered this month from the crash site.
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 Galeão 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 angle of attack 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.
