B-24 Liberator Variants 1940-1945


The basic design was developed in 1938 with a production Contract coming in 1939. It called for a single airplane, a structural test model and a set of engineering reports. The airplane was designed around the "high aspect ratio" Davis wing equipped with Fowler flaps. A series of wing slots were built into the wing panels near the tips. Positions for six .30 caliber machine guns were located in the nose, waist and tail. The airplane was engineered, built and tested and flew within nine months.


The small block build of YB-24s was for evaluation. On these, the leading edge slots were deleted, and deicer boots were added to the wings and tail surfaces. One plane was delivered to the USAAC as an YB-24, and the remaining six were delivered as B-24Ds directly to the British and went into service.


The B-24A was basically the twin of the prototype XB-24 and YB-24 but the wing slots were removed. The B-24A had had a pair of .30 caliber machine guns in the tail and .50 caliber machine guns in the nose in six fixed positions as well as .30s in the waist and one rear pointing .30 on the underside tunnel. There was no top turret and the pitot tubes were located horizontally under the small navigation windows. The power plants were four cylindrical Pratt & Whitney (P & W) R-1830-33 engines. Probably one of the most unique features of the B-24 was the Davis "high aspect ratio" wing that gave the plane its aesthetic look at 110' throughout production.


With the fall of France, the order for the first 26 B-24As were revised for delivery to the Royal Air Force under the designation of LB-30 but were used for Ferry Service. The British experience with the LB-30 then gave rise to the redesign of the LB-30 with improved armament, self-sealing fuel tanks and armor plating. Also a belly blister was added housing four 20 MM cannons, depth charge racks in the bomb bay and an array of antennae. They were dedicated to Costal Command, and modified by the British and referred to in sequence of variants as: Liberator I, Liberator II and Liberator III. The last of these were actually straight up B-24s for all practical purposes. 


When the one XB-24 was converted in 1940 to incorporate the turbo-supercharged P & W R-1830-41 engines in elliptical cowls, it was re-designated as the XB-24B. It continued to be used as a platform for further changes and modifications.


With the RB-24C, the overall fuselage length was increased from 63' 9" to 66' 4" and included power-operated turrets and self-sealing fuel tanks. The powered turrets with .50 caliber machine guns were located in the tail and on the dorsal (top turret) aft of the wing. Manually operated .50 caliber guns were still maintained in the nose, ventral and waist positions.


Although only nine were manufactured at CO, the B-24C was the "production breakdown" variant based on the previous work being done at CO on the XB-24B and followed right on the heels of the last Liberator IIs which laid the formation for the full production of the B-24D. (At the outset of the "D" block at CO, the "C" block was still being built.)


The first "real" production bomber in the Liberator Family was the B-24D. P & W R1830-43 engines were the basic power plant. The dorsal turret was moved forward and placed just aft of the cockpit. Armament changes included removal of the ventral tunnel gun and upgrading the remaining positions all with .50 caliber machine guns. A later addition which was added in the Block "15" builds at San Diego (CO). The scanning windows for the ventral guns remained in production into the Block "160" build at CO. Design changes during "D" production also provided for auxiliary fuel tanks in the outer wing panels and provisions for additional bomb bay fuel tanks. A small navigator's observation dome was also located on the top of the forward fuselage section. The basic exterior paint color of all B-24Ds was olive drab (OD) over neutral gray undersurfaces.


Similar to the B-24 D, the B-24E had different propeller blades (both the D and E had the narrow "needle" prop blades at first and then switched to the wider "paddle" blades as production went on). R-1830-65 engines powered the "E". Because of the now heavy demand for the B-24, a fifth production plant, Ford Willow Run (FO) was added to the existing four with its first production run being designated the "E." FO also produced "knock-down kits" (KDs) which were shipped to Fort Worth (CF) and Tulsa (DT) for the production of B-24Es.


The B-24G was very similar to the B-24D. Initially powered by R-1830-43 engines, by mid production R-1830-65s were being installed. Also after the first 25 were built a power operated nose turret was installed. Subsequent to this the Sperry ball turret was also introduced. The weight of the "G" on average was also heavier than the "H" or "J". It should be noted that the B-24G was, for all practical purposes, a wholly North American (NT) operation. 


Very similar to the B-24G, the B-24H coincided with some of the activities going on with the "G." Improvements were made to waist gun location that staggered the gunners on each side. The Emerson turrets for the nose and the MPC for the tail were now standard. The overall length of the Liberator now grew to 67' 3 & 3/16" or almost a foot longer than the "D" or "E." Increased protective armor plating was installed around the pilot's deck. Yet, one of the most effective changes was the addition of the left (port) aileron that greatly enhanced the trimming of either wing. Also the OD paint was discontinued with the "H" at all facilities in March of 1944 so that all ships would now be shipped with their natural metal finish (NMF).


In many respects the B-24J resembled the B-24H but in NMF. The Emerson nose turret (cylindrical) became standard production although the Consolidated Turret (sloped front) was used on several blocks at CO. Enclosed waist guns with jetisonable K-6 mounts were added. The pitot tubes were now located at a slightly raised angle and above the navigator's observation window. A new redesigned autopilot and bombsight were added. There were also minor differences in the Libs produced at the different plants within the production pool. Such things as boot-type de-icers, different bombardiers scan windows, flush type pitots, different paint schematic for the anti-glare panel, inward/outward nose gear door panels and wingtip lights ALL of which could give mechanics working in the various Theatres of Operation nightmares. Several different sets of prints were required to understand which parts were "interchangeable" or "custom" depending upon the originating plant." It should be noted also that the "J" was built in larger numbers than all the other variants and was built at all five plants within the Liberator Production Pool.


The B-24L was extremely similar to the B-24J. It did, however, incorporate two hand-held .50 caliber machine guns (stingers) in the tail. Also the size of the navigator's observation window was elongated with a convex window on the FO Liberators. It should also be noted that "production models" of the B-24Ms from FO were shipped without any tail armament that was then added at Modification Centers (MODs).


Almost identical to the B-24L, the "M's" incorporated a lightweight tail turret housing a pair of hand-held .50 caliber machine guns. Also the cockpit windshield and side windows were simplified with less obstruction. The FO "M's" all had the larger, rectangular, convex navigator's observation window as opposed to the CO smaller square window.

XB-24N & YB-24N 

Ford Willow Run had converted a B-24J into a single-tail airplane, added a Sperry ball turret to a modified nose and then further modified the tail. Seven of these had been completed when the Orders for the B-24N were cancelled effectively bringing to an end the Liberator Production Pool.


Nicknamed the Liberator Express, the C-87 was a transport version of the B-24D, which seated 25 passengers. A large door was incorporated into the left side of the fuselage. Four P & W R-1830-43 engines powered these airplanes. An alternate version, the C-87A carrying 16 passengers was modified as a VIP carrier. These planes were basically all built at the CF plant.


The C-109 was an unarmed tanker that originally had a glass nose when built-up as a prototype. When B-24Js and B-24Ls were converted into C-109s, they then had solid noses.

F-7A and F-7B 

These were modified B-24Ds and J's in which were installed up to 11 cameras located in the nose, bomb bay and tail. Basic defensive armament remained intact.


The PB4Y-1 was the US Navy's equivalent to the twin-tailed B-24D. Early on, many of these received from the AAF had their glass noses retrofitted with Erco bow turrets. Production PB4Y-1s were delivered with Consair nose turrets. The belly ball turret was often re-placed with search radar.


Known as the Privateer, the PB4Y-2 was noticeably different from its predecessors. The overall length was extended and a larger single-fin tail and rudder were installed. The wingspan was increased. Waist windows were given ERCO turrets blister enclosures, and an additional dorsal turret was added aft of the wing. The R-1830-94 engines were used in oval nacelles but with larger dimensions and in vertical orientation instead of horizontal. Superchargers were removed due to the low-level use of the Privateer, and this also prompted the return to "needle" props. 

Courtesy: Steven Puhl, Ford Willow Run B-24 Plant Historian (Retired)