The Apache helicopter is a revolutionary development in the history of war. It is essentially a flying tank -- a helicopter designed to survive heavy attack and inflict massive damage. It can zero in on specific targets, day or night, even in terrible weather. As you might expect, it is a terrifying machine to ground forces. In this edition of HowStuffWorks, we'll look at the Apache's amazing flight systems, weapons systems, sensor systems and armor systems. Individually, these components are remarkable pieces of technology. Combined together, they make up an unbelievable fight ing machine -- the most lethal helicopter ever...