The Erco 250TH Turrets have the approximate shape of a tear drop. They are installed in the waist positions on either side of the PB4Y-2 airplane—the Erco 250TH-1 on the starboard side and the Erco 250TH-2 on the port side. With their wide cone of fire they protect the plane from beam or belly attacks, besides offering a considerable area of protection from above. In operation they are somewhat similar to a ball type turret inasmuch as the gunner moves with his guns and sight in the direction he moves his control handles.
Facts and Figures
POWER: The Erco Tear Drop operates hydraulically on pressure built up by a hydraulic pump driven by a constant speed electric motor.
SIGHT: Its sight is a standard Navy Mk 9 reflector sight fully described in the introduction to this section.
ELEVATION: Both turrets can raise their guns 55° above horizontal in elevation and depress them 95° below horizontal.
AZIMUTH: In azimuth, the Erco Tear Drop turret allows the guns a movement of 135°, 55° towards the bow from the beam and 80° towards the tail of the airplane from the beam.
ARMOR: The armor plate in the turret protects the gunner from fire in any direction he turns his guns. It consists of three groups: (1) 1 1/2″ thick bullet-proof glass in front of his face, (2) 5/16″ armor plate in front of his body, and (3) 5/16″ armor plate under his feet.
STOWING: The stowing position is 0° elevation with guns pointed in the extreme aft position in azimuth (80° aft of the beam).
Illustrations and performance details of the Erco 250SH Ball Turret mounted in the PB4Y Privateer from Aircrewman’s Gunnery Manual, Aviation Training Division, Office of the Chief of Naval Operations, U.S. Navy, 1944.
Erco Ball Turret
ERCO 250SH-2, 2A or 3
The Erco Ball Turret is the bow installation in the Navy PB4Y-1 and PB4Y-2 airplanes. It serves a double purpose in taking care of any bow attacks on the Liberator besides being used for strafing, in anti-submarine warfare. Inasmuch as this turret is of the ball type, the gunner moves with his guns and sight in elevation and azimuth as he moves his control handles. It is a relative of the Martin 250SH Bow Turret of the PBM-3 airplanes and has many points of similarity in design and action.
There are several models which for the most part are the same—the Erco 250SH-2 or 2A used in the bow position of the PB4Y-1 airplane and the Erco 250SH-3 used in PB4Y-2 airplane.
Facts and Figures
POWER: The Erco 250SH operates hydraulically on pressure built up by a hydraulic pump driven by a constant speed electric motor.
SIGHT: Its sight is the standard Navy Mk 9 reflector sight, fully described in the introduction of this section.
ELEVATION: From the horizontal position the turret ball, and consequently the guns, may be depressed a maximum of 70° and elevated a maximum of 85°.
AZIMUTH: This type of turret is capable of revolving 360° in azimuth, but for the installation in the bow of the PB4Y-1 or PB4Y-2 airplanes, its motion is restricted to 80° either side of the center line of the plane.
ARMOR: The armor plate of the turret consists of three parts to protect the gunner from enemy fire and flak: (1) 1½” laminated bullet proof glass to protect his face. (2) ½” armor plate in front to protect the gunner’s body, no matter where his guns are pointed. (3) ¼” armor plate bolted to the floor to protect his feet.
STOWING: The stowing position is 0° azimuth and 0° elevation, guns pointing straight forward.
The Sperry ball turret was used on both the B-17 Flying Fortress and the B-24 Liberator as well as the Navy’s PB4Y Liberator. The B-17’s Sperry was not retractable. The Liberator’s ground clearance was minimal and so a hoist was required to lift the turret into the airframe. The Sperry ball turret could spin 360 degrees, making it impractical to store much ammunition outside the turret. Small ammo boxes rested on the top of the turret and the remaining ammo belts were stowed in the already cramped turret by means of an elaborate feed chute system.
With its gunner visible in the back cockpit, this Japanese dive bomber, smoke streaming from the cowling, is headed for destruction in the water below after being shot down near Truk, Japanese stronghold in the Carolines, by a Navy PB4Y on July 2, 1944.
Lieutenant Commander William Janeshek, pilot of the American plane, said the gunner acted as though he was about to bail out and then, suddenly, sat down and was still in the plane when it hit the water and exploded.