Simplicity
While on the subject of simplicity I would like to butt in if I may.
I can understand how the pilot on AF447 reacted in the way he did. I can’t say that I can explain it but I can understand it. Years ago I pushed the wrong button when my colleague got his fingers caught in a machine. I switched the Run Switch to the “off” position rather than hitting the Emergency Stop button. The Run Switch stopped the machine after its present cycle. The Emergency Stop instantly cut all power. At the point where my colleague got his fingers stuck I had 5 seconds to hit the Emergency Stop to prevent a blade from slicing his fingers off. In the rush I switched the wrong control (I pulled the stick back rather than push it forward). I realised my mistake and I quickly hit the Emergency Stop. Fortunately I reacted fast enough and my colleague still has his fingers.
In the above example I had complete understanding of these controls because I designed them, but I had no practical training on what to do in this circumstance so I did the wrong thing when I needed an instant reaction. However because of my understanding of the controls, and because I had sufficient time, I was able to save the day. Practical training gives you a natural reflex to do something quickly in an emergency situation but understanding gives you the ability to think about the situation and work out what is the right thing to do even if you have not been trained on the procedure. Understanding is gained by theoretical learning and quick response is gained by practical training, actually doing what you should do in real life when a emergency situation occurs.
However these 2 things are related. Training helps understanding and understanding helps training. Sully was not trained on water landings but due to his in depth knowledge he was still able to perform the feat. When learning a complex process you need both. Simplicity is also a factor. After this incident I changed the layout of the front panel including making the Emergency Stop more prominent and simplifying the layout. I simplified the interface. A machine operator or pilot has better things to think about than excessively complex controls. A pilot definitely has many other things to think about. If something is simple it is easier to understand and it is easier to train people on. It is like these 3 things form a triangle. Understanding – Training - Simplicity. You need all 3 sides. If you increase one you naturally increase the other 2. If you reduce one you reduce the other 2. If you make something simpler the person’s understanding will be better and it will be easier to train him. If you make something more complex the person is likely to have a lower understanding and it will be more difficult to train.
A group of semi knowledgeable people generally make things overly complex. One single knowledgeable person can generally make the same thing more simple.
It is easier to make something complex than to make it simple. Unfortunately it is easier to make a complex interface than a simple one.
Obviously an aircraft control system will be a complex system but it should not be made more complex than what it needs to be, and even if someone has done all that is required to get everything totally sussed, surely he would be better off working out how to get laid by his wife than to work out some overly complex interface.