Earlier we described the final minutes of Air France flight 447, which crashed in the Atlantic two years ago.We speculated that, based on the account, it sounded as though the co-pilot of the plane–who was at the controls at the time the plane’s airspeed indicator failed–had screwed up.
We also asked a jumbo jet captain to read the report and weigh in. Below is his response.
The captain explains that we still have too little information to know precisely what happened, but he makes clear that the pilots faced an extraordinarily challenging situation.
I read your article with interest. Obviously I can only surmise based on the report. But let’s see if we can parse through the events as they transpired.
1. The plane began at 35,000 feet and was at .82 mach. This would probably be pretty typical but we need to know what the max altitude would be for the plane’s gross weight and speed at the time. Was 35,000 feet pushing the limit sort to speak? This is important because as we max perform the wing the airspeed spread between a high speed (acceleration) stall and a low speed stall becomes very small. Remember when you were studying aerodynamics there was a reference to the coffin corner – this is it. You can’t speed up and you can’t slow down without stalling out the plane. This typically isn’t an issue unless you are experiencing some kind of upset.
2. Apparently the crew was experiencing a turbulent ride. Was it clear air turbulence or were they in the weather? Then they slowed down to .80 mach. That would widen the spread on the airspeed especially since the airspeed was probably bouncing around up and down due to the turbulence. But then they notify the cabin crew of an impending really rough ride. That really raised my eyebrow!
3. They could see that up ahead they were going to encounter a pretty rough ride. Let’s cut to the chase – they had a line of thunderstorms they were about to navigate through. Remember, we don’t fly through thunderstorms, we fly around them. We use the radar to enable us to find the gaps between cells. And you can’t necessarily climb above these cells either. I’ve personally seen cells as high as 50,000 feet. Recall that the tropopause is much higher around the equator allowing these storms to really grow. So they are preparing for the circumnavigation.
4. They began diverting to the left about 12 degrees. This is pretty typical if you start this manoeuvre say about 40 miles prior. But then the other pilot suggested that they should come further left. And then things begin to go wrong. It’s at this point where I wonder whether they flew into a thunderstorm.
5. As we have discussed before, thunderstorms are fraught with peril. Severe up and down drafts, severe turbulence, hail, lightning, heavy rain. Need I say more. They could have easily unintentionally climb because of an updraft. At this point, and with the autopilot off, they would be doing everything they could to recover the plane. They knew the airspeed was slow – that is why they had the throttles at max. Unfortunately, the plane was probably already stalled or close to it at this point. And with severe turbulence it wouldn’t take much to stall the plane out.
6. Should they have been able to recover the plane (in those conditions) I don’t know. With the nose up 40 degrees it’s difficult to say. How effective were the elevators if at all. I’m sure a computer program could determine this but in the heat of the moment who knows. I didn’t read where the other pilot attempted to take control of the aircraft until the very end – probably because the flying pilot capitulated suggesting to me that the non-flying pilot would have been doing the same thing. Interestingly, with the aircraft nose up 40 degrees I’m curious how the Captain even got back into the cockpit. Couldn’t have been easy.
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