No. 10905. Consolidated 32 XB-24 Liberator (39-680 c/n 1) US Army Air Corps
Photograph from USAF, taken at Lindbergh Field, San Diego, California, USA, December 26, 1939
Aeroplane Photo Supply (APS) Photo No. 165

Consolidated 32 XB-24 Liberator

05/27/2017. Remarks by Johan Visschedijk: "In January 1939, Reuben H. Fleet (Consolidated, company president, and Isaac M. Laddon (chief engineer) approached the USAAC with the proposal that Consolidated produce a long-range bomber superior to the Boeing B-17. Earlier, the USAAC had suggested that Consolidated build the B-17 under license to provide an additional production line, but Consolidated personnel returned from an inspection trip to Seattle convinced that a better aircraft could be designed. By the end of January, a mock-up had been built and inspected at San Diego and on February 1, the USAAC issued Type Specification C-212, a formality as the two companies solicited for proposals, Martin and Sikorsky, only had three weeks to respond. Therefore, on February 21 the Model 32 was recommended for approval and a contract was signed on March 30 for a single prototype, designated XB-24 (s/n 39-556) and to be completed by December 30, 1939. This was followed by orders for seven YB-24s (s/n 40-696 to 40-702) in April and 38 B-24As (s/n 40-2349 to 40-2386) in August.

A speedy development was made possible by the Model 31. The flying-boat's Davis wing with hydraulic flaps and the twin tail was adopted for the bomber and the nose-wheel undercarriage, a first for a heavy bomber was in part adopted from the beaching gear of the Model 31. Two deep bomb bays could carry eight 1,100 lb (499 kg) bombs, twice the capacity of the B-17, and six hand-held 0.30 in (7.62 mm) guns were carried in the nose, waist, dorsal, ventral, and tail positions. Power was provided by four 1,200 hp Pratt & Whitney R-1830-33 Twin Wasps fourteen-cylinder radial engines, fitted with a mechanical supercharger in PBY-type nacelles. Laddon shared the credit for the rapid pace of design and construction with the USAAC, which had allowed Consolidated to proceed unhindered.

The remarkably swift progress lead to wing and fuselage mating on October 26, and on December 29, 1939, the prototype made its first flight from San Diego in the hands of chief pilot Bill Wheatley and test pilot George Newman, together with flight engineers Jack Kline and Bob Keith. The seventeen minute flight was to lead to 18,431 more aircraft, the largest production of any American combat type and the highest number of a bomber aircraft ever. Such a unique production record is all the more remarkable for such a large, four-engined aircraft, and the type operated over more operational fronts for a considerably longer period, and was produce in a greater variety of versions than any other Allied or enemy bomber.

The prototype B-24 design top speed was 311 mph (501 kmh), but was only able to achieve 273 mph (439 kmh), hence on July 26, 1940, the USAAC recommended changes to improve performance, especially at higher altitudes. Subsequently the XB-24 was re-engined with R-1830-41 engines fitted with General Electric B-2 turbo-superchargers on the lower surface of each engine nacelle. The air intakes for the turbo-superchargers were placed on the sides of the engines, and the oil coolers were relocated to the flanks of the front cowlings, which gave the engine nacelles the characteristic elliptical cross-section that became familiar on later production aircraft. Furthermore the prototype was fitted with electrical engine primers, modified engine controls, self-sealing tanks, protective armor in the crew positions, and a larger tailplane, while it had its leading edge slots removed.

Redesignated XB-24B and reserialled 39-680, the modified aircraft was flown again on February 1, 1941, and it was able to attain a maximum speed of 310 mph (499 kmh). On August 13, 1941, the XB-24B was accepted by the USAAF, renamed from USAAC on June 20, 1941. The XB-24B was bailed to the manufacturer and had been converted to a VIP transport by the end of 1944; the aircraft was scrapped at Brookley Field, Alabama on June 20, 1946.

Meanwhile, in April 1940, the French Purchasing Commission had ordered 175 of an export version, the LB-30MF. The term LB-30 was not a US military designation (the USAAC's B-30 was a never built version of the Lockheed Constellation), nor was it a manufacturer's model number (Consolidated's Model 30 was the USN XPB3Y-1 patrol bomber, also never built). To arrive at the LB-30 nomenclature, Consolidated chose the next open number after the last of many company 'LB' (Land Bomber) design concepts of 1938-1940, of which there were twenty, with intermittent gaps, beginning with LB-4 and ending with LB-29, even though it was now using such a number for a totally different purpose. The 'MF' stood for 'Mission Franšaise', the French purchasing mission which ordered the planes.

After the collapse of France, Britain took over 165 aircraft of the French order on June 17, 1940, designated LB-30, British serials AL503 to AL667. Self-sealing fuel tanks, crew protection armor, and tail and dorsal power-operated turrets were specified by the RAF. In December 1940, the RAF allotted the LB-30 the name Liberator, which was later adopted by the USAAC. Reluctant to wait for delivery of their order, the British Purchasing Commission arranged that 26 of the first B-24s still under construction for the USAAC would be delivered to the RAF, in exchange for a similar number of LB-30s.

Thus the first six bombers to come of the production line were modified YB-24s for the RAF, these had de-icers added on wings and tail but no wing slots and no self-sealing tanks. Designated LB-30A Liberator B.Mk.I, these aircraft (s/n AM258 to AM263) were considered non-combat ready by the RAF. After a very basic passenger conversion at Montreal, Canada, the six were used in the unarmed transport role. Owing to their range and endurance at 10,000 ft (3,048 m) of 19.25 hours at 193 mph (311 kmh), these were the only aircraft capable of flying the 2,994 mls (4,818 km) route between Prestwick, Scotland and Montreal. From March 1941 onwards they were used on the Trans-Atlantic Return Ferry Service, which flew ferry pilots back to North America after they had made delivery flights to the UK. The Service was operated by BOAC (British Overseas Airways Corporation) crews and three of the six aircraft were temporarily registered to BOAC (British Overseas Airways Corporation): AM259 as G-AGCD, AM262 as G-AGHG and AM263 as G-AGDS.

Twenty B-24A conversions (s/n AM910 to AM929) followed from March 1941 for RAF Coastal Command's No. 120 and 512 Squadrons as LB-30B Liberator Mk.Is. These were fitted with radar, six 0.303 in (7.7 mm) guns, and a tray of four or six 0.787 in (20 mm) guns under the fuselage.

The remaining YB-24 (s/n 40-702) was fitted with self-sealing tanks and armor and was accepted by the USAAC in May 1941, nine B-24As (s/n 40-2369 to 40-2377) followed in mid-1941. The latter were used by the new USAAC Ferrying Command and operations began on July 1, 1941, over the North Atlantic, and on August 31 over the South Atlantic. Two B-24s (including 40-2373) flew the Harriman Mission to Moscow in September, one returning via the Middle East, India, Australia, and the Pacific; the other via Africa and Brazil. The balance of the original 38 B-24A order, were completed as B-24Cs (s/n 40-2378 to 40-2386)."

Created October 31, 2011