On June 1, 2009 Air France flight 447 from Rio de Janeiro to Paris crashed into the Atlantic Ocean killing all 228 people on board. While the Airbus 330 was flying on auto-pilot, the different speed indicators received by the on-board navigation computers started to give conflicting speeds, almost certainly because the pitot tubes responsible for measuring air speed had iced over. Since the auto-pilot could not resolve conflicting signals and hence did not know how fast the plane was actually going, it turned control of the plane over to the two first officers (the captain was out of the cockpit). Subsequent flight simulator trials replicating the conditions of the flight conclude that had the pilots done nothing at all everyone would have lived—nothing was actually wrong; only the indicators were faulty, not the actual speed. But, tragically, the pilots didn’t do nothing.

One of the co-pilots pulled up on his side stick, which raised the nose of the plane and put the plane, already at high altitude, into a sharp climb. The climb was too much for the plane to handle at this altitude, even with the engines at full power. The plane lost speed and eventually the air speed over the wings was too little to sustain lift and the plane went into a stall. The plane fell from the sky at about 10,000 vertical feet per minute with the nose too far up, an “angle of attack” of over 30 degrees (even in take-off this is only about 13 degrees).

My childhood friend learned to fly and got his first pilot’s license in high school and, since he needed flight hours, I would occasionally join him while he earned his qualifying hours. The very first time I flew with him in the passenger seat of a Cessna 152, which has dual controls, he explained the basics to me: “If you want to go up, pull back on the stick. If you want to go down, push the stick in. If you want to go down real fast, pull too far back on the stick.” I asked why this is so and he, a novice pilot, explained: “If a plane tries to go up too fast it stalls, loses lift, and then the craft acquires the aerodynamics of a rock.”

What is both tragic and disturbing is that the 2nd officer puts the stick into nose-up position two seconds after taking control (02:10:07) and four seconds later the first stall warning sounds (02:10:11) as the speed of the plane slows as it attempts the impossibly steep climb the pilot has asked for. Given the dangers of a stall, there is a loud stall warning (listen to it here). At 02:11:22, one minute and 15 seconds after the plane was put into nose-up position, the plane stalls and starts to fall from the sky. In the four minutes and 23 seconds between when the auto-pilot gave control to the pilots and the plane hit the water, killing all on board, the stall warning sounded over seventy times. Yet in the cockpit recording as the pilots attempt to control the plane, none of the three pilots (the captain returned to the cockpit at 02:11:43) mention the stall warning.

 

Report by Centre for Global Development