The Boeing B-17E and the Myth of the Bendix Ventral Turret

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.

An early production B-17E with a Sperry model 645705-D remote turret installed. The sighting periscope is visible in the blister aft of the turret, and the gunner’s scanning windows are visible on the fuselage sides.
Another nice shot showing the Sperry remote turret installation. The remote belly turret was produced using the same structural elements of the manned engineer’s Sperry dorsal turret, in this picture it is possible to compare the shapes of the two directly.
Close up of the Sperry remote turret. Spent shell casings were ejected through the rectangular opening visible between the guns. No windows are present on this turret.
A Boeing factory photograph showing the aft fuselage compartment looking forward.  The remote turret housing is the round object mounted to the floor, the gunner’s sighting arrangement is visible in the foreground of the picture.  The gunner’s scanning windows are located just above the walkways on either side.  To use the remote turret the gunner was required to lay facing aft between the feet of the waist gunners, a problematic arrangement for all concerned!
Here is the Bendix retractable remote turret from the B-25C/D Factory manual. Note the different shape of the turret, and the windows for the sight and the elevation compensator located on the turret itself.
Kora from the Czech Republic produce several conversion sets containing Sperry remote turrets in 1/72 scale, although they too call them Bendix. Many of the resin bits are interior details. This particular set also contains PE aerials for the SCR-521/ASV search radar.
A close up of the turret and sighting blister parts from the Kora set. Modelers could fashion the turret using a spare ventral turret by sanding off the panels and adding an ejector chute. The blister would have to be vacuformed. Scanning windows must be cut into the fuselage sides by the modeler.
Here is a screen capture from John Ford’s film “The Battle of Midway” showing 41-2397 in the Hawaiian Air Depot scheme with the Sperry remote belly turret in June of 1942. This aircraft was named “JOE BFTSPLK” after a popular comic strip character, but it is unclear exactly when the name was applied.
Here is 41-2397 again, this time being serviced on Espiritu Santo in December 1942 just six months later. Note that she has now been refitted with a manned Sperry ball turret. B-17Es were designed so that the remote turret could be replaced with a ball turret, but not the other way around. (Ralph Morse photograph)
Another still from Ford’s film and another HAD ship, 41-2437 with a Sperry remote turret on Midway. On 06MAY42 ALNAV 97 directed that the red and white tail stripes and red centers of US national markings be painted out to avoid any confusion with the red Japanese Hinomaru markings. On 41-2437 the rudder appears to have been painted over using black paint.
Here is 41-2437 six months later refitted with a Sperry ball turret and still wearing her Hawaiian Air Depot scheme. She also carries twin .50s in the radio operator’s position. B-17s with the manned ball turret are often seen airborne with the guns pointed directly down. In this position the gunner’s access door would open into the fuselage, allowing the gunner to leave the cramped turret and move about the aircraft. (Ralph Morse photograph)
A nice shot of 41-2444 on Espiritu Santo in DEC42. She has been refitted with a manned Sperry ball turret and the remote sighting blister has been removed, but the side scanning windows remain. (Ralph Morse photograph)
Some crews removed the ineffective remote turret and made do with what they could improvise. The crew of 41-2432 has mounted twin .50s on a flexible mount in the fuselage opening. This provides another option for modelers who don’t want to be troubled with the turret issue. Note the replacement vertical stabilizer which dates the photograph as being taken after SEP42. 41-2432 carried pin-up nose art and was named “The Last Straw”.  (Australian War Memorial photograph)

19 thoughts on “The Boeing B-17E and the Myth of the Bendix Ventral Turret

  1. The structure is the same so yes, the same basic shape. You’d have to account for the ejector chute and there appears to be a slight bulge added on the bottom near the back, but a spare top turret could be modified to model one.

    Liked by 1 person

    1. THANK YOU! I have been saying this for years and yet book after book comes out referring to the “Bendix” turret. I have a copy of the E Pilots Manual which states this and the engineering drawing of the installation also shows it is a Sperry. I shared this on our B-17 Modelers page on Facebook, I hope you don’t mind.

      Liked by 1 person

  2. Thanks Karl! I am happy you posted a link, it does no good to research this stuff if nobody can find it. Once you see the differences between the Sperry and Bendix turrets it’s pretty obvious, but we have seen them called the wrong thing for so long it has just become accepted. I was surprised at how quickly the remote turrets were replaced with the manned ball turrets in service.


  3. Please make the change to the WIKI B-17 article and add your references and Karl’s to the reference notes area. The Sperry turret number is an example.

    Liked by 1 person

  4. Well, as expected, ran into one guy that insists that is a Bendix as there are numerous books that state that as a fact. Even though we have primary source material… Ah well, all you can do is try!

    Liked by 1 person

    1. It’s been repeated for so long it’s hard to shake the convention. For any who still doubt that the belly turret was actually a Sperry number 645705-D, please refer back to an original B-17E manual and provide the Bendix part number. Should be easy enough, and an original manual part number would be irrefutable.


  5. Heck, I have the Boeing installation drawing but that doesn’t convince ’em either. Posted both that and the Pilot’s Manual reference. No luck…

    Liked by 1 person

  6. Some shameless self-promotion here: Those of you interested in the combat story of early B-17Es with the remote belly turret are invited to read my new book, KANGAROO SQUADRON: AMERICAN COURAGE IN THE DARKEST DAYS OF WORLD WAR II. It was published just a couple of months ago. Some of you may cringe, but I decided to dodge the Sperry versus Bendix argument by not mentioning the manufacturer at all–that’s the sort of ephemera that bores most casual readers–though I included plenty of references to the turret’s use and unpopularity. The photo gallery also includes a Boeing photo of the interior showing the pad the gunner had to lie on, and the complex mirrored sighting system.

    Liked by 1 person

  7. Seems like you have missed a chance to correct years of erroneous information. And it IS important to put forward correct information on the type of turret used in the early B-17E’s.

    Liked by 1 person

      1. I did correct other facts also there namely about Jerry Smith who landed his Spitfire on the Wasp on May 9th, 1942.

        Liked by 1 person

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