If you are planning to model one of the Hawaiian Air Depot scheme Boeing B-17E Flying Fortresses, or any one of the first 112 B-17Es produced for that matter, something which will have to be dealt with is the belly turret. Model kits contain the manned Sperry ball turret, but the remote Bendix turret is needed. At least that is the conventional wisdom. In this case it turns out the conventional wisdom has gotten it all wrong. Not only is the Sperry ball turret appropriate in some cases, the B-17E never carried the Bendix remote turret in the first place.
Unfortunately, almost every reference will state that the early B-17E Flying Fortress carried a Bendix belly turret, and almost every reference gets it wrong. The first B-17Es were not built with a Bendix remote turret, but a Sperry model 645705-D remote turret instead. From the B-17E Erection and Maintenance Manual 01-20EE-2:
“(4) BOTTOM TURRET – The bottom turret is installed in the rear fuselage section just aft of the radio compartment. Two installations are provided as follows:
“(a) On airplanes AC serial numbers 41-2393 to 41-2504 inclusive, the Sperry number 645705-D remote sighted twin .50-caliber bottom turret is installed. The sighting station for this turret is installed directly to the rear, and is operated from the prone position with the gunner heading aft. Ammunition boxes for 500 rounds per gun are attached to the turret. Provision has been made on these airplanes for interchangeability with the spherical turret.
“(b) On airplanes, serial numbers AC 41-2505 to 41-2669, inclusive, and AC 41-9011 to 41-9245 inclusive the Sperry number 645849-J spherical bottom turret is installed. On these airplanes no provision is made for interchangeablitity with the remote-sighted gun. Ammunition boxes for 500 rounds per gun are installed within the turret.”
The difference is not merely semantics or nomenclature, the two turrets are unrelated. The Bendix remote turret was retractable, and its sighting aperture was located on the mount itself between the guns. Bendix turrets were carried by the B-25B through the first part of the B-25G production runs, but were discontinued midway through the G model. They were also carried by the B-24D. Later, the Bendix design was modified and appeared as the chin armament on the experimental YB-40 gunship. It was standardized as B-17F nose armament late in B-17F production and carried on all B-17Gs.
The Sperry number 645705-D was also remotely sighted, but the sighting periscope was located aft of the turret in a clear blister. The gunner was also provided with six small scanning windows, two square windows on the underside of the fuselage, and two rectangular windows on each fuselage side. The Sperry remote ventral turret was constructed using the same structural elements as the manned Sperry dorsal turret but without the clear perspex panels.
Neither remote turret was successful. Crews reported difficulty in acquiring and sighting their targets. Mechanical reliability was also an issue. Gunners using the Sperry remote turret often became nauseous due to having to lay prone facing aft to use the sight. Many crews decided the turret was not worth the weight and deleted it entirely or replaced it with the manned Sperry ball turret at the first opportunity. No kills were recorded by gunners using the Sperry remote turret.