B-29 remote controlled bottom rear turret

Armament

The B-29 was equipped with heavy armament, featuring four remotely controlled, power-operated gun turrets (two dorsal and two ventral), each with two Model M-2 .50-caliber machine guns.
A fifth gun turret in the tail housed a Model M-3 20mm cannon with a .50-caliber machine gun on either side.
Normally, 500 rounds of ammunition were carried for each machine gun, but sometimes up to 1,000 rounds per gun were carried. There were 110 rounds for the cannon.
In many cases during World War II, the cannon was removed, leaving just the two machine guns in the tail position. Occasionally, a third machine gun was mounted in its place.
Late-production B-29As had four machine guns in the forward dorsal turret.
The upper rear turret’s lower limit of fire was horizontal, and the upper forward turret’s lower limit was 2.5 degrees below horizontal.
The forward and rear lower turrets’ upper limit of fire was 5 degrees above horizontal.
The tail turret’s rear limits of fire were 30 degrees above and below the horizontal centerline and 30 degrees right and left of the vertical centerline, forming a pyramid-shaped area of fire within these limits.
The four upper and lower gun turrets were each supplied with 1,000 rounds of ammunition (500 rounds per gun).
When the four-gun upper forward turret appeared, another 1,000 rounds were supplied (2,000 total, 500 per gun).

Sighting Stations

Three sighting stations in the rear compartment: one on either side of the fuselage and one atop the fuselage on the centerline just aft of the rear dorsal turret.
A fourth sighting station at the bombardier’s position.
The rear compartment housed the General Electric Central Fire Control (CFC) system.
The bombardier was responsible for the forward lower turret.
The center gunner was responsible for the two dorsal turrets.
The left and right waist gunners were responsible for the aft ventral turret, having both primary and secondary control of that turret.

Fire Control Systems

Most B-29s and B-29As were fitted with the General Electric Central Fire Control (CFC) system.
311 Bell-built B-29B airplanes were modified to employ an advanced AN/APG-15B airborne radar-directed fire control system, which automatically fired at approaching fighters.
Most B-29s were fitted with the AN/APQ-13 radar bombardment system for ‘through the clouds’ bombing.
Some B-29s were equipped with the AN/APQ-7 Eagle radar bombardment system, featuring a large wing carried underneath the aircraft.

Blister Windows

Two of the CFC sighting stations (port and starboard in the rear compartment) had ‘blister’ type Plexiglas windows.
These windows had a tendency to blow out at altitude, causing sudden decompression. Crew members could be blown out if not securely strapped in with high-quality safety belts, leading to tragic results.
There has been no documented report of the top sighting station’s blister window blowing out.

Crew Protection

Korean War Modifications

During the Korean War, each machine gun had only 100 rounds of ammunition.
The 20mm cannons were not employed in Korea, having been removed after World War II.