A chilling story

Stall diagram from FAA manual

About two and a half years ago, a loaded Air France passenger jet plunged into the Atlantic Ocean. It had been through a very turbulent storm at night but other airliners had gone through (or around) the same storm with no problem. What had happened? The airplane had an advanced method of automatically sending information about its situation and its controls back to a receiving station in France so even though they couldn't find the data recorders on the plane itself, the company had some ideas about what went wrong.

But in April this year, amazingly, the flight data recorders and the voice recorder were found and recovered. And they still worked! That enabled a piecing together of what caused the crash. An article in Popular Mechanics magazine titled What Really Happened Aboard Air France 447 by Jeff Wise is a well written summary of what has been found from the recovered recorders. It mixes excerpts from the voice recordings of the pilots with facts from the data recorders to tell what it was like in the cockpit of the doomed jet. The writer is not only a pilot but has also written books on human reactions to fear. Reading the story is like reading an adventure novel but it's scarier because it really happened. The only complaint I have with the article is that there should be an illustration showing how stall works in airplanes and how the plane could have its nose up and yet be losing altitude. I've included the image here to help with that a bit. Imagine that the plane is no longer moving forward fast enough to produce lift at its wings. In a stall, it is falling down while pointing up - almost like a leaf falling from a tree.

Learning about the human reactions and why they may have made them was enlightening. The author gives some possible explanations why the least experienced pilot made the mistakes he did and why all the pilots may have acted so illogically. But, as an engineer, I found that the human interactions with the plan's controls were just as interesting. The pilots made many mistakes but they were made worse by the design of the airplane's control system.

From my perspective, the design of the Airbus 330 is flawed. The plane is controlled through a pair of sticks at each pilot's seat (pilot and copilot). They don't use the familiar yoke or wheel and they are not physically tied together. So, one person can be doing one thing with the controls and the other can be doing something else without realizing what is going on. And even more perplexing, the Airbus averages the values if the two controls are different! This isn't a political process where compromise is important - it is a precise technical activity.

I don't bring this to your attention to scare you or to keep you from flying on commercial airlines. It is still safer to fly in an airplane than to travel in just about any other way. But it scares me a bit that technology can be so advanced and still allow things like this to happen. As I said in my post "This day in engineering history", it is important that we learn from mistakes like this. And we all need to learn how to act in an emergency without panicking. It could save your life.

Picture from Federal Aviation Administration publication Pilot's Handbook of Aeronautical Knowledge - Chapter 4

[Update - The final report, in English, on this tragedy can be found in a PDF file at this link. This is from the French Office of Investigations and Analysis for Civil Aviation Safety called the BEA, Bureau d'Enquêtes et d'Analyses]