Like the equally successful North American P-51 Mustang fighter, the Liberator was designed in a great hurry. In January 1939 the USAAC invited Consolidated to submit a design study for a bomber with greater range, higher speed, and altitude performance than the B-17. A contract for a prototype was awarded in March, requiring that it be ready before the end of the year. The design was simple in concept but advanced for its time: at about 32 tonnes maximum takeoff weight it was one of the largest aircraft yet, it used tricycle landing gear instead of a tailwheel, and it featured a very long, thin high aspect ratio wing for maximum fuel efficiency. Compared to the B-17, the Liberator was shorter, had 25% less wing area (but with a 6' greater span), and substantially greater carrying capacity. Like the B-17, it was powered by four 30-litre air-cooled radial engines in the 1000hp class, but twin-row 14-cylinder Pratt & Whitney Twin Wasps rather than 9-cylinder Wright Cyclones.
Consolidated finished the prototype, by then known as the XB-24, ready for its first flight with just two days to spare before the end of 1939. Seven more YB-24 development aircraft flew in 1940 and production tooling began. Early orders - placed even before the XB-24 had flown - included 36 for the USAAC, 120 for the French Armée de l' Air, and 164 for the RAF. Most of the first production Liberators went to Britain, including all those originally ordered by the Armée de l' Air after France collapsed in 1940.
As so often with new aircraft types, the first versions were not combat-capable. Initial Liberator deployment in March 1941 was with BOAC on trans-Atlantic transport duties. Soon after, equipped with primitive but functional ASV Mk.II radar, it entered active service with Coastal Command where its long range made it indispensable for anti-submarine patrols. (See Battle of the Atlantic.)
Later in 1941 the Liberator II arrived, which introduced the survivability features which were essential if the Liberator was to take up its design role as a bomber: self-sealing fuel tanks and powered defensive gun turrets. At the same time, Consolidated added a 2'7" plug in the forward fuselage to create more space for crew members and also (it is said) to make the airplane look better! Liberator IIs were split between Coastal Command, Bomber Command and BOAC. Two RAF squadrons deployed to the Middle East in June 1942 and became the first to operate the Liberator in its primary role: as a bomber.
At the same time, the USAAF began to take delivery of its first B-24As, like the British, using them as transports to begin with. Continued development work by Consolidated produced a handful of transitional B-24Cs with turbocharged instead of mechanically supercharged engines (and in consequence the characteristic flattened oval nacelles that would distinguish all subsequent Liberator models).
The first true mass-production model, the B-24D (or Liberator III in Commonwealth service) was introduced in early 1943; it had turbocharged engines and increased fuel capacity. Three extra 0.50in machine guns brought the defensive armament up to ten guns in total, and at around 27 tonnes maximum take-off weight, it was one of the heaviest aircraft in the world: only the British Lancaster and Halifax bombers were in the same class.
USAAF B-24s began their combat career in June 1942 with a raid launched from Egypt by 13 aircraft against the German-occupied Romanian oilfields of Ploesti. The attack was described as "unsuccessful" by the USAAF, but it alerted the defenders, and when 177 B-24s returned on 1st August 1942, 55 failed to return.
Liberator production increased at an astonishing rate through 1942 and 1943: Consolidated had tripled the size of their plant at San Diego and built a big new plant outside Fort Worth, Texas; more production came from Douglas in Tulsa; and North American were building a plant at Dallas. None of these were minor operations, but they were dwarfed by the vast new greenfields factory built by Ford at Willow Run, near Detroit. This was easily the largest factory in the USA, and the largest anywhere outside the USSR.
In April 1942 the C-87 dedicated transport version of the Liberator entered production at Fort Worth: it had a large cargo door, no gun turrets, a floor in the bomb bay for freight, and side windows. In August, the Ford plant at Willow Run came on-stream, making the B-24E, which was almost identical to the B-24D. As the year went by, Liberator squadrons deployed to all theatres: Africa, Europe, the Atlantic, India and the Pacific, where to simplify logistics it was designated the standard heavy bomber, replacing the shorter-range B-17 which had not distinguished itself against Japan.
1943 saw the introduction of the definitive Liberator, which was 10 inches longer, had a powered gun turret in the nose to reduce vulnerability to head-on attack, and was fitted with an improved bomb sight, autopilot and fuel transfer system. North American made the B-24G at Dallas, while those from the Consolidated, Douglas and Ford factories were designated the B-24H. All five plants switched over to the almost identical B-24J in August 1943. The later B-24L and B-24M differed only in defensive armament arrangements.
An astonishing 18,482 Liberators were completed before production ceased in May 1945. In addition to the thousands that saw service with the USAAF, the RAF flew about 2100 examples, the RCAF 1200 B-24Js, the US Navy about 1000 PB4Y-1s (plus almost 800 of the Liberator-derived PB4Y-2 Privateer patrol bomber), the RAAF 275 B-24L, J and M variants, and Liberators equipped two squadrons of the Royal South African Air Force in the Mediterranean theatre. At one stage the USAAF alone had 6043 B-24s on strength: it equipped 46 bomber groups and 41 squadrons of the RAF.
last flying b-24
last flying b-24 http://www.collingsfoundation.org/tour_b-24j.htm