The controller asked the crew to maintain FL350 and to give their estimated time at TASIL.
Flight AF447 is told to keep cruising at 35,000ft and inform Brazilian air traffic control when it expects to reach the waypoint 'TASIL' - the entry point into Senegalese airspace, where responsibility for watching over the flight will transfer to the control centre in Dakar.
01:55
The Captain woke the second co-pilot and said "[...] he's going to take my place".
On a long flight it is normal practice to carry an extra pilot to allow one of the crew - the captain in this case - to rest. Of the two pilots left in charge, one had 4,479h on A330/340s, and was the most experienced of the three on the A330 in terms of flight time, although all of the captain's time on the type had been in command.
01:59:32-02:01:46
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 pilot flying the A330 highlights the relatively high air temperature outside the aircraft. Higher temperatures mean the air is less dense and reduces the ability of the wing to generate lift, meaning the aircraft would be unable to sustain flight at a higher altitude.
The pilot also mentions that the aircraft has been unable to connect with Dakar air traffic control ahead of crossing the airspace boundary between Brazil and Senegal. This absence of contact, close to the transfer point, may be significant in the context of the subsequent failure to realise that AF447 had gone missing.
02:08:07
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.
Probably to avoid an area of heavier turbulence, about which they were aware, the crew deviated from the flightpath. The A330 nevertheless encountered turbulence and the crew chose to slow the aircraft from Mach 0.82 to Mach 0.8. This is normal practice when penetrating storm clouds, in order to prevent the aircraft's speed from slipping outside of design limits in rough air.
02:10:05
The autopilot then auto-thrust disengaged and the PF said "I have the controls".
Investigators have not confirmed why the autopilot and autothrust disengaged, although this is a normal response of the A330 if its computers detect inconsistency in the airspeed data received from the pitot tubes on the nose.
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.
While the pilot appears to have rolled the aircraft to the left, to counter a roll to the right, he also pulled the aircraft's nose upwards - for reasons yet to be explained. This would have put the A330 into a climb, but the aircraft already had little flexibility to climb higher, because of the temperature, and the slower speed would have further reduced the lift available from the wings. The stall warning was the first indication that the A330 was struggling to maintain lift.
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).
On the captain's side of the aircraft - his seat occupied by a relief pilot - the airspeed on the cockpit display suddenly appeared to fall. This also occurred to the backup, or standby, display. These readings did not necessarily mean the aircraft had actually slowed to 60kt; the displays are fed information from the pitot tubes on the nose, and a blockage in the tubes - from ice, for example - could have generated useless data in the airspeed computers.
02:10:16
The PNF said "so, we've lost the speeds" then "alternate law [...]".
The non-flying pilot realises that the airspeed information is unreliable and that the aircraft has switched, as designed, to following less rigid flight control laws. Critically these laws no longer automatically protect the aircraft from reaching high angles of attack, at which it risks stalling.
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.
Positioned increasingly nose-up, the A330 climbs rapidly by 2,500ft - the investigators have not clarified whether the climb was intentional - but the pilot then reduces the climb by pushing the control sidestick nose-down.
The captain's displayed airspeed suddenly leaps to 215kt. It is unclear whether this figure is reliable; if it is, the aircraft has slowed dramatically.
02:10:50
The PNF tried several times to call the Captain back.
The non-flying pilot appears to consider the situation serious enough to warrant recalling the captain.
02:10:51
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 A330's angle of attack is too high, and the aircraft is losing the battle to sustain lift, as demonstrated by the stall alarm, yet the pilot is still keeping the nose pointing upwards - in apparent contradiction to a basic principle of flight: escaping a stall requires the nose to be pushed down, in order to regain a smooth, fast airflow over the wings.
Even though the crew pushes the engines to full power, the high altitude probably renders this ineffective. The resulting thrust is still not enough for the heavy aircraft to generate enough lift in the thinner air.
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.
The aircraft automatically trims itself to correspond with the nose-up attitude. In the meantime the standby airspeed indicator's reading suddenly rises, bringing it into line with the reading on the captain's display; the two speeds have been inconsistent for less than a minute.
Despite the stall condition the flying pilot still holds the nose of the aircraft upwards.
02:11:40
The Captain re-entered the cockpit. During the following seconds, all of the recorded speeds became invalid and the stall warning stopped.
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.
All of its lift having been sapped, the aircraft virtually free-falls from its peak altitude of 38,000ft. With its nose still pitched up, and the pilot still giving nose-up commands, it drops at 180km/h on a steep trajectory downwards. Although the A330's engines are operating at high power, the stall attitude prevents restoration of smooth airflow over the wings. The stall warning had only stopped because the system ignored the extreme readings being generated by the aircraft's predicament.
02:12:02
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 this point, shortly after the captain re-entered the cockpit, comes the first indication of an attempt to unstall the aircraft, as the pilot starts pushing the nose down. The engines are throttled back to idle power, possibly to aid the rescue by reducing the tendency for thrust at lower altitude to pitch the aircraft up. The decrease in angle of attack and the return of valid speeds - which in turn bring back the stall warning - suggest the beginning of a recovery.
02:13:32
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 A330 descends towards 10,000ft. The pilot surrenders control to another member of the crew - not necessarily the captain - but the angle of attack is still excessive and the aircraft is still falling rapidly.
02:14:28
AF447 runs out of altitude and time. Having failed to recover from the stall, it pancakes onto the ocean surface at 200km/h and disintegrates.
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