Hi 411A, you wrote:
<font face="Verdana, Arial, Helvetica" size="2">AirBus seem to make changes to the software every time there is an incident/accident. Surely the question must be.....WHY was it not designed properly in the first place? </font>
The Airbus is an highly computerized airplane. Airbus made this approach in the believe and goodwill to increase saftey: reducing pilots workloads, providing crew, passengers and aircraft with all kind of safety systems, some of them even overrides
wrong pilots inputs.
But this philosophy is not free of risks. Like any other computer system, Soft- and Hardware designers are given in the beginning of their work a specification envelope. Based on this specifications, they create, design, build Hardware and write Software. The varification process comes afterwards, to see and check, if all the systems work properly under all circumstances WITHIN the given speficication envelope. The flight test is also part of this varification process.
The ideal case is, that on every given input (within the specifications) the computer produces a correct output. In an aircraft computer system this means, that the Hard- Software senses for example dangerous situations (input) and takes corrective action (output). Ideally these systems works great and increase saftey dramatically. But only
within the given specification envelope!
And here lies the danger of Airbus philosphy and in fact of every automated system: Something occurs
outside the specification envelope which has not been foreseen by the engineers, computer designers, etc. This can be in case of an aircraft weather phenomena, technical defects, runway conditions, or a combination of everything, etc.
The worst case scenario is, that the pilot can't react to this situation, because the computer doesn't allow him/her to do so, because the computer
does not see this specific input, thread, or situation.
Because of this reason, we see after almost every Airbus incident/accident a change in Soft- and Hardware. Guys, don't get me wrong. I don't want to contribute in an emotional Airbus vs. Boeing clash. But I just hope, the engineers have prepared and designed the systems on an Airbus in a way, that in a couple of years, when the A320 is flown somewhere as a cheap old model (maybe to replace an old 737-200
) in a third world operator (maybe in poor technical conditions), it brings the people on board safely from A to B.