AF447 and the One Legged Stool

I have long been a believer in the one-legged stool theory of aviation safety. Now, I know have very few readers but since some are not in the USA let me set forth with some particularity what a one-legged stool is. Most stools have three legs and are therefore quite stable when someone sits on them. A stool with one leg allows a person to sit on it and rest just as much but does require that he remain alert. Drifting off to sleep on a three legged stool can be easy. Drifting off to sleep while on a one legged stool is just as simple but has obvious consequences: you fall and that wakes you up.

One consequence of the ultra reliability of any electrical system is that monitoring it becomes so very boring. The aircraft systems are reliable. If something fails, there is a primary backup, if that fails there is a secondary backup, etc. It is so very boring. The Fly By Wire takes this even one step further and declares that the computers are so reliable that they should even be able to override pilot input since pilots are less reliable. Only in Alternate Law Mode does the computer surrender control of the airplane to the pilot and even that is done piecemeal with only certain systems surrendered to pilot control during the various Alternate Law modes.

But what about the Pilot's mode? Pilots have various modes too. Alert, drowsy, asleep, "in the loop", "out of the loop", etc. Qantas used to force pilots to work out a position report using pen and paper rather than simply pressing a button. This would keep the pilots mentally in the loop should trouble occur. We all know that on long flights there are a variety of breaks some of which are mandatory and some of which are optional.

Physical presence on the flight deck is one thing. Mental presence is another. A pilot who is sleeping in the cockpit or merely dozing there requires some time to get back into the loop.

Some have alleged that failure to deviate around weather indicates a dozing flight crew. All we can really say is that we have no indication that the pilots were in their seats and alert. We have some indications that fatigue may have overcome a sole occupant of the cockpit. While we can think that a pilot would not nap as the plane was penetrating the convergence zone it is possible and he might have asked to be roused and the pilot who was to have him awakened fell asleep.


Dealing with suddenly being dumped into Alternate Law Mode is difficult when the pilot is awake and fully aware of his situation. If a stall developed we all wonder why but mostly we wonder why was there no reaction to it. After all, by the third lesson student pilots are practicing stalls and having it drummed into them to lower the nose instantly and add power instantly. Nothing about that changes as one progresses from student pilot in a Cessna 172 to the left-seat of a multi-engined airliner. What changes is the excitement. A student pilot on his third lesson is "in the loop". He has full situational awareness. The professional pilot in an airliner has thousands of hours of sitting there punching buttons into a computer that does the flying. Its boring. We need to bring back that one-legged stool. Keep the pilots from getting complacent.

We all wonder how the airframe could become involved in a deep stall but the question that also must be addressed is how did it all begin. If it takes too long to wake up and gain situational awareness, a brief nap can be fatal. Airline pilots really do not practice stalls. They practice approaches to stalls. Once the airspeed deteriorated and a stall started to develop action can be taken. Once a stall is fully developed and the plane is in a deep stall wherein control surfaces are functionally ineffective there is far less that can be done and the pilot is in unknown territory. It is possible the pilot woke up to a nightmare. Often an instructor will have a student practice suddenly being required to select an emergency landing zone and make the approach to a landing in some pasture rather than on an airport runway. The practice usually ends just above the farmer's field but a good instructor will sometimes actually have a student make such a landing. A recently awakened pilot might not have been able to cope with a deep stall because he had only been given simulator time for an approach to a stall. There is no Emergency Checklist for a deep stall. You either know what to do or you don't. It either works or it doesn't. There is no time to do aught but act. If there was a double flame-out (doubtful) differential thrust could not be used.