"William Anderson" wrote in message ...
How exactly did they work? Could the turrets be fired independently at
multiple targets? What crew members controlled them? etc? etc?

From 'Flying Guns: World War 2 - Development of Aircraft Guns,
Ammunition and Installations 1933-45' by Emmanuel Gustin and myself:

"The B 29 finally appeared with five turrets: Front upper, front
lower, aft upper, aft lower, and tail turret; as initially foreseen
the tail also had a 20 mm cannon in addition to the twin .50"s. The
tail guns were exclusively controlled by the tail gunners in his own
compartment, but the other guns were operated from four sighting
stations, one in the nose and three in a compartment aft of the wing.
Each gunner could simultaneously operate two turrets, as the situation
of the moment demanded. The "master gunner" was the upper gunner in
the aft compartment, and he assigned turrets to gunners with his
control panel.

The gunners had to track the attacking aircraft from their sighting
stations, which had a reflector gunsight that generated signal outputs
by a "Selsyn" system. An analog computer used the elevation, azimuth
and range inputs from the gunner to calculate the lead and the
parallax compensation, and aimed the gun turret with an Amplidyne
drive unit. The computer took into account the effects the air
density, the airspeed and the angle of the guns relative to this
airspeed had on the bullet trajectory. A factor that could not be
taken into account was the flexibility of the bomber's fuselage
itself, and its tendency to expand or shrink locally as temperature
varied. These caused a variable misalignment between the sighting
station and the gun turret. The heating effect was large enough to
make alignment of the guns on a butt outdoors, exposed to the sun,
impracticable. The guns had to be harmonised indoors to meet
specifications."

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/