B-24 Liberator

The Consolidated B-24 Liberator was produced in greater numbers than any other American combat aircraft, and was used by most of the Allied air forces in World War II. Designed as a heavy bomber, it served with distinction not only in that role, but also as a maritime patrol bomber (known as the PB4Y in U.S. Navy service) and as a heavy transport (where it was designated C-87 or C-109).

Variants/design stages

• XB-24—(Consolidated Model 32). Designed in 1938 as an improvement on the B-17 Flying Fortress, at the request of the Army Air Corps. It featured a wing specially designed for a high aspect ratio, tricycle landing gear, and twin vertical stabilisers. It was ordered in 1939 March, and first flew on 1939 December 29. (×1)
• B-24 - Service test version of the XB-24, ordered on 1939 April 27, less than thirty days after the XB-24 was ordered, before the XB-24 design was even complete. A number of minor modifications were made: elimination of leading edge slots, addition of de-icing boots. (×7; only one used for actual testing)
• B-24A - Ordered in 1939, the B-24A was the first production model. Due to the stringent need for heavy bombers, the B-24A was ordered before any version of the B-24 actually flew. The main improvement over the XB-24 was improved aerodynamics, which led to better performance. (×38: ×20 LB-30A, ×9 B-24C)
• XB-24B - When the XB-24 failed to reach its projected top speed, the Pratt & Whitney R-1830-33 radials rated at 1,000 hp (746 kW) it carried were replaced with R-1830-41 turbo-supercharged radials rated at 1,200 hp (895 kW), increasing its top speed by 37 mph (59 km/h). The addition of the turbo-superchargers made the engine cowlings elliptical. The XB-24B version also lacked the engine slots of the original. (×1 converted XB-24)
• B-24C - Conversion of the B-24A using turbo-supercharged R-1830-41 engines. To hold the supercharger and the intercooler intake, the cowlings were made elliptical and the new items added on the sides. The tail gunner position was improved by adding an Emerson A-6 power turret with twin .50-caliber (12.7 mm) machine guns; a Martin power turret was added to the forward fuselage. (×9 converted B-24A)
• B-24D - First model produced on a large scale; ordered from 1940 to 1942, as a B-24C with better engines (R-1830-43 supercharged engines). During the production run, the tunnel gun in the belly was replaced by a remote-sited Bendix belly turret; this was later replaced by a Sperry ball turret. In late B-24Ds, 'cheek' guns were added. (×2696: 2381 Consolidated, San Diego; 305 Consolidated, Fort Worth, 10 Douglas, Tulsa, Oklahoma)
• B-24E - A slight alteration of the B-24D built by Ford, using R-1830-65 engines. Unlike the B-24D, the B-24E retained the tunnel gun in the belly. Sometimes the Martin top turret was removed and a Bendix chin turret added. Ford also built sub-assemblies for Douglas; these subassemblies were identical to Ford-built B-24Es, except that they used the same engines as the B-24D (R-1830-43 radials). (×801)
• XB-24F - A prototype made to test thermal de-icers, instead of the standard inflatable rubber 'boots'. (×1 converted B-24D)
• B-24G - Sperry ball turret, three .50-calibre (12.7 mm) machine guns in nose. All B-24Gs were built by North American Aviation, which was contracted in 1942. (×25)
• B-24G-1 - Modified Emerson A-6 tail turret in nose instead of 2-3 .50 caliber (12.7 mm) machine guns in earlier models. The B-24G-1 was based on the design of the B-24H (×405)
• B-24H - Because of obvious vulnerability of the B-24 to head-on attack, the B-24H design made by Ford used a nose turret, generally a modified Emerson A-6 tail turret. The entire aircraft was redesigned to better fit the turret; 50 airframe changes were made, including a redesigned bombardier compartment. The tail turret was given larger windows for better visibility, the top turret a higher bubble, and the waist gunner positions were offset, to reduce their interference during battle. (×3100)
• B-24J - The B-24J was very similar to the B-24H, although the defensive improvements made in the B-24H were not incorporated in the B-24J. The B-24J featured an improved autopilot (type C-1) and a bombsight of the M-1 series. B-24H subassemblies made by Ford and constructed by other companies, and any model with a C-1 or M-1 retrofit, were all designated B-24Js. (×6678)
• XB-24K - An experimental aircraft, made by Ford by splicing a B-23 Dragon tail empennage onto a B-24D airframe. The plane was more stable and had better handling than other models, but changing the B-24 design was too expensive to do at the time. However, the XB-24K was the ancestor of the Navy's PB4Y-1. (×1 converted B-24D)
• B-24L - Because of the immense weight of the B-24J, the Army pushed for a lighter version. In the B-24L, the ball turret was replaced by a floor ring mount with two .50 calibre (12.7 mm) machine guns, and the A-6B tail turret by an M-6A. In later planes, no tail armament was installed, and when it arrived to its airfield either an A-6B, an M-6A, or a dual-mount manual .50-caliber (12.7 mm) gun was installed. (×1667)
• B-24M - An enhancement of the B-24L with further weight-saving devices. The B-24M used a more lightweight version of the A-6B tail turret; the waist gunner positions were left open. For better visibility, the windshield was replaced by a ‘knife-edge’ dual pane versions. The B-24M became the last production model of the B-24; a number of the planes built flew only the course between the factory and the scrap heap. (×2593)
• XB-24N - A redesign of the B-24J, made to accommodate a single tail. It also featured improved nose and tail turrets. While 5168 B-24Ns were ordered, World War II ended and there was no longer any need for them. (×1)
• YB-24N - Pre-production service test version of the XB-24N. (×7)
• XB-24P - A modified B-24D, made by Sperry Gyroscope Company to test airborne fire control systems. (×1 converted B-24D)
• XB-24Q - A General Electric conversion of the B-24L, using radar-controlled tail turrets. (×1 converted B-24L).
• XB-41 - Because there were no fighters capable of escorting bomber formations on deep strike missions early in W.W.II, the Army authorised tests for heavily armed bombers to act as escorts for bombing missions. It was completed in 1942. The results of 1943 testing were very negative and the project was quickly cancelled. Performance changed drastically with the addition of more turrets. Also, the escorts were unable to keep up with bomber formations once the bombs had been dropped.
  The XB-41 had fourteen .50-calibre (12.7 mm) machine guns, through the addition of a Bendix chin turret and a dorsal Martin power turret on the mid-fuselage. (×1 converted B-24D)
• LB-30 - Version of the B-24 sent to Britain. (LB- = 'Liberator British'):
• LB-30A - YB-24 (×6)
• LB-30B (Liberator Mark I) - B-24A (×20), used in British Coastal Patrol and Defense Squadron
• Liberator Mark II - Improved LB-30 (×165)
• Liberator Mark III - B-24D (×156)
• Liberator Mark IV-IX - Improved versions, number built varies depending on source of information