Anyway, coming back, every design evolves as time passes by. So is the case with aviation. During the early few years, the airplanes that were built were very small and very very simple. It was just a petrol engine with blades at the front and an airframe attached to it. Now aviators wanted a slightly bigger and a bit more features added. Then came the idea of using pulleys and cable links which were added to manage the control surfaces. But trust me, it took Arnold Schwarzenegger's strength to move the pulleys and cables to operate these machines, that too when flying high above the ground and winds hitting you at hundreds of kilometers per hour!! But somehow the pilots handled it.
Then another guy wanted to sit behind and watch the earth below when his friend was flying :) This made the plane larger and it was just not that easy to control by pulleys. So, aviators began using servo motors which were linked to the pilot’s controls by mechanical links and the servo motors movements were in accordance to the pilots inputs. But as you all know these motors were too heavy. And as the size of the airplanes increased, the motors had to be bigger accordingly. This was the driving force to implement the FBW Systems.
Remember very old classical english movies where a bomb is put very far and a very long thread smeared with gun powder extended all the way from the explosive charge towards a safe place and when ignited, it will burn all the way through and then explode?? Coming to today's version of the same scenario, you place the explosive, come very far-press a button- a radio signal is transmitted to it and it explodes.
So, in lay man's words, a Fly by Wire system is very similar. Earlier mechanical and pulley systems go with the old method and the today's version is like an electrical signal goes from the pilot's control to the stand alone mechanical unit near to the control surface.
But that’s just the very higher level of explaining about FBW. I guess i can now move to the architecture of it.
So, as you can see, the pilot’s inputs go to a set of computers. These computers generate the signals to be sent to the mechanical units based on a set of rules. One of them is considering the inputs from sensors which are placed all over the plane which gather information on thousands of parameters every single moment.
Other is getting feedback information from the control surfaces itself because nothing always works as it is intended to!!
The multiple blocks indicate redundancy in the whole system which is a big advantage when compared to older techniques of controlling an aircraft. Remember that if any mechanical link breaks, you have no control over the control surface in the chain. This is not the case with FBW because, there are multiple computers doing the same thing and multiple wires that connect to the control unit taking different paths on the plane so that even if one the wires get broken due to an accident, the other wire which is routed through a different path is still very existent and the whole thing is still operational :)
Fly by Wire is not as simple as it seems to be. Hope this was a good start. Lots of posts related to FBW to come in the coming days.
