Just wondering if I could pick the brains of a few experts about some nagging questions I have regarding Anti Aircraft Artillery, or Flak. Talking large scale stuff here, not 20mm or 37mm or 40mm...

1) How do you get the shells to go off at the right alititude? Was it a timing mechanism incorporated into the warhead of each shell? If so, how long did it take to set it to the proper altitude?

2) For the US, I know they developed proximaty fuses for their 5 inch guns that worked wonders in the Pacific against the kamikaze aircraft. Can anyone explain how it exactly worked? It would seem to require a high degree of computing ability due to the short time involved regarding 2 objects moving together at high rates of speed.

3) Was Flak an effective use of men, munitions, and armament? I once read (if I recall correctly) that pre-war German thinking felt that it would require 50 88mm or larger shells or so to bring down a bomber. Reality soon showed it required over 10,000. (Again, final figure may be off due to fuzzy memory). How much more effective would it have been to have those shells and guns employed in anti-tank roles? Could the addition of those thousands of guns on the Eastern Front from 1942-1944 have made a real impact?