Ask Captain Lim

Hi Lim, 
 
Further to your comments on the FBW systems... These systems are always active as they form the only links between the control input of the pilot flying and the control surface. It is the protection system that is activated on take off. If the FBW the system only came on when the aircraft was airborne then the pilot flying would not be able to rotate the aircraft at the required Vr speed and thus would not take off. The "weight switch" that you mention is located in the nose wheel strut and is there as a safety feature to backup the onboard computer system.  
 
On most FBW airliners there are 4 computers, of which three are always on with one redundant. Of these systems, if one fails then the others can take over the failed computers system. So as you can see, an FBW REPLACES the hydraulic systems employed. One advantage of the FBW control system is that, if a control surface fails, like the ailerons, then the onboard computers can re-route the control input to other surfaces to produce the desired effect with out the pilot having to change the way he/she flies the aircraft. An expansion on the FBW principle is the FADEC system. 
 
On the subject of the APS, the Airbus philosophy of total protection, while it had its teething problems, is the best in the world. You take an A320, 330, 340 up and try and crash it. If all systems are working properly, then it should stay in the air regardless of what you do to it.  
 
Personally, if I was flying long distance, I would much rather be in an A340 than a 777 if an engine failed en-route. As that is one thing you have failed to mention, the safety aspect of having 4 engines over 2. Just so you know, I am cross qualified on, 737 classics, 777 and A320 through to A340. Of the transitions between aircraft, I found the transition from A320 to A330 the easiest as they use the same identical cockpit. 
 
Yours 
Keiron