02:06:20 (flight attendant) OK.
The two copilots discuss the unusually elevated external temperature, which has prevented them from climbing to their desired altitude, and express happiness that they are flying an Airbus 330, which has better performance at altitude than an Airbus 340.
02:06:50 (Bonin) Va pour les anti-ice. C’est toujours ça de pris.
Let’s go for the anti-icing system. It’s better than nothing.
Because they are flying through clouds, the pilots turn on the anti-icing system to try to keep ice off the flight surfaces; ice reduces the plane’s aerodynamic efficiency, weighs it down, and in extreme cases, can cause it to crash.
02:07:00 (Bonin) On est apparemment à la limite de la couche, ça devrait aller.
We seem to be at the end of the cloud layer, it might be okay.
In the meantime Robert has been examining the radar system and has found that it has not been set up in the correct mode. Changing the settings, he scrutinizes the radar map and realizes that they are headed directly toward an area of intense activity.
02:08:03 (Robert) Tu peux éventuellement le tirer un peu à gauche.
You can possibly pull it a little to the left.
02:08:05 (Bonin) Excuse-moi?
02:08:07 (Robert) Tu peux éventuellement prendre un peu à gauche. On est d’accord qu’on est en manuel, hein?
You can possibly pull it a little to the left. We’re agreed that we’re in manual, yeah?
Bonin wordlessly banks the plane to the left. Suddenly, a strange aroma, like an electrical transformer, floods the cockpit, and the temperature suddenly increases. At first, the younger pilot thinks that something is wrong with the air-conditioning system, but Robert assures him that the effect is from the severe weather in the vicinity. Bonin seems ill at ease. Then the sound of slipstream suddenly becomes louder. This, presumably, is due to the accumulation of ice crystals on the exterior of the fuselage. Bonin announces that he is going to reduce the speed of the aircraft, and asks Robert if he should turn on a feature that will prevent the jet engines from flaming out in the event of severe icing.
Just then an alarm sounds for 2.2 seconds, indicating that the autopilot is disconnecting. The cause is the fact that the plane’s pitot tubes, externally mounted sensors that determine air speed, have iced over, so the human pilots will now have to fly the plane by hand.
Note, however, that the plane has suffered no mechanical malfunction. Aside from the loss of airspeed indication, everything is working fine. Otelli reports that many airline pilots (and, indeed, he himself) subsequently flew a simulation of the flight from this point and were able to do so without any trouble. But neither Bonin nor Roberts has ever received training in how to deal with an unreliable airspeed indicator at cruise altitude, or in flying the airplane by hand under such conditions.
02:10:06 (Bonin) J’ai les commandes.
I have the controls.
02:10:07 (Robert) D’accord.
Perhaps spooked by everything that has unfolded over the past few minutes—the turbulence, the strange electrical phenomena, his colleague’s failure to route around the potentially dangerous storm—Bonin reacts irrationally. He pulls back on the side stick to put the airplane into a steep climb, despite having recently discussed the fact that the plane could not safely ascend due to the unusually high external temperature.
Bonin’s behavior is difficult for professional aviators to understand. “If he’s going straight and level and he’s got no airspeed, I don’t know why he’d pull back,” says Chris Nutter, an airline pilot and flight instructor. “The logical thing to do would be to cross-check”—that is, compare the pilot’s airspeed indicator with the co-pilot’s and with other instrument readings, such as groundspeed, altitude, engine settings, and rate of climb. In such a situation, “we go through an iterative assessment and evaluation process,” Nutter explains, before engaging in any manipulation of the controls. “Apparently that didn’t happen.”
Almost as soon as Bonin pulls up into a climb, the plane’s computer reacts. A warning chime alerts the cockpit to the fact that they are leaving their programmed altitude. Then the stall warning sounds. This is a synthesized human voice that repeatedly calls out, “Stall!” in English, followed by a loud and intentionally annoying sound called a “cricket.” A stall is a potentially dangerous situation that can result from flying too slowly. At a critical speed, a wing suddenly becomes much less effective at generating lift, and a plane can plunge precipitously. All pilots are trained to push the controls forward when they’re at risk of a stall so the plane will dive and gain speed.
The Airbus’s stall alarm is designed to be impossible to ignore. Yet for the duration of the flight, none of the pilots will mention it, or acknowledge the possibility that the plane has indeed stalled – even though the word “Stall!” will blare through the cockpit 75 times. Throughout, Bonin will keep pulling back on the stick, the exact opposite of what he must do to recover from the stall.
02:10:07 (Robert) Qu’est-ce que c’est que ça?
02:10:15 (Bonin) On n’a pas une bonne… On n’a pas une bonne annonce de vitesse.
There’s no good… there’s no good speed indication.
02:10:16 (Robert) On a perdu les, les, les vitesses alors?
We’ve lost the, the, the speeds, then?
The plane is soon climbing at a blistering rate of 7000 feet per minute. While it is gaining altitude, it is losing speed, until it is crawling along at only 93 knots, a speed more typical of a small Cessna than an airliner. Robert notices Bonin’s error and tries to correct him.
02:10:27 (Robert) Faites attention à ta vitesse. Faites attention à ta vitesse.
Pay attention to your speed. Pay attention to your speed.
He is probably referring to the plane’s vertical speed. They are still climbing.
02:10:28 (Bonin) OK, OK, je redescends.
Okay, okay, I’m descending.
02:10:30 (Robert) Tu stabilises…
02:10:31 (Bonin) Ouais.
02:10:31 (Robert) Tu redescends… On est en train de monter selon lui… Selon lui, tu montes, donc tu redescends.
Descend… It says we’re going up… It says we’re going up, so descend.
02:10:35 (Bonin) D’accord.
Thanks to the effects of the anti-icing system, one of the pitot tubes begins to work again. The cockpit displays once again show valid speed information.
02:10:36 (Robert) Redescends!
02:10:37 (Bonin) C’est parti, on redescend.
Here we go, we’re descending.
02:10:38 (Robert) Doucement!