Readers with memories of World War II aircraft cannot help but recall the big, ugly and seemingly slow Liberator, characteristics which brought the nickname 'Lumbering Lib'. In the European theatre, of course, it was much overshadowed by the Boeing B-17 Flying Fortress, and to those with no detailed knowledge of military aircraft it often comes as something of a shock to learn that not only was Consolidated's Liberator built in considerably greater numbers than the B-17, but was the most extensively produced of the USA's wartime aircraft.

The Liberator's origin, like that of many US wartime aircraft, stems back to the early/mid-1930s, an era in which projects such as the Boeing XB-15 and Douglas XB-19, and development of the B-17, brought a far wider knowledge and appreciation of the 'big bomber'. The Liberator, however, represents the next generation, development of which was spurred by the tense political situation in Europe, and the growing threat of Japanese militancy as that nation overran increasingly larger areas of Manchuria. This then was the background which caused the US Army Air Corps, in January 1939, to invite Consolidated to prepare a design study for a heavy bomber with superior performance to that of the B-17: increased range, greater speed, and a higher operational ceiling were all considered to be essential.

Consolidated wasted little time in submitting a design proposal, identifying it as their Model 32 and, as long range was paramount, it was designed round the Davis wing, first introduced on the company's Model 31 commercial flying boat design, of which a prototype was then nearing completion. Subsequently, the Model 31 was reconfigured to serve as the prototype of a military flying boat for the US Navy under the designation XP4Y-1. In reaching a decision to go ahead with prototype construction of the Model 32, the US Army almost matched the speed set by Consolidated, and seemingly they were determined to maintain this tempo for, in awarding the contract on 30 March 1939, the USAAC stipulated that the construction of this prototype, designated XB-24, must be completed by the end of the year. This was achieved by Consolidated, with the first flight being made on 29 December 1939.

In terms of size the XB-24 was marginally smaller than the Fortress except in span, for the wing was just over 6 ft (1.83 m) greater in length; in terms of wing area, that of the XB-24 was approximately 26 per cent less, emphasising the high aspect ratio of the Davis wing. To ensure maximum capacity within the fuselage structure, the wing was high-mounted in shoulder- wing configuration, and to provide good low-speed handling characteristics and an acceptable landing speed, wide-span Fowler-type trailing-edge flaps were fitted. Construction of the fuselage was conventional, but deep in section to allow for installation of a bomb bay which could accommodate up to 8,000 lbs (3629 kg) of bombs stowed vertically. The bay was divided into two sections by the fuselage keel beam, this being utilised to provide a catwalk for crew transition between the fore and aft sections of the fuselage. The most unusual feature of the bomb-bay was the provision of unique 'roller shutter' doors which retracted within the fuselage when opened for attack, causing less drag than conventional bomb-bay doors that were lowered into the slipstream. The tail unit, with its easily recognisable oval-shape endplate fins and rudders, was generally similar to that which had been developed for the Model 31 flying boat. Landing gear was of the retractable tricycle type, the free-swivelling nosewheel retracting forward into the fuselage, the main units retracting outward and upward so that the wheels were partially housed in underwing wells and faired aft by small blisters. Powerplant of the prototype comprised four wing-mounted 1,200 hp (895 kW) Pratt & Whitney R-1830-33 Twin Wasp engines.

Even before the prototype had flown, Consolidated had begun to receive orders for its new bomber. These included seven service test YB-24s and 36 B-24As for the USAAC, and 120 aircraft 'off the drawing board' for a French purchasing mission. Consolidated must have been highly relieved, therefore, when early flight tests proved successful. To meet the USAAC specification some 'development was necessary to achieve higher speed, but there was no doubt that the XB-24 was able to demonstrate excellent long-range capability. Furthermore, the large-volume fuselage lent itself to adaptation to fulfil other roles and, in fact, it was this versatility combined with long range which was the key to the success of the B-24.

The XB-24 was followed during 1940 by the seven YB-24s for service trials, and these differed from the prototype by the provision of pneumatic de-icing boots for the leading edges of wings, tailplane and fins. But by the time that the first production aircraft began to come off the line at San Diego, France had already capitulated, and the aircraft of the French order were completed to British requirements, as specified in an order for 164 which had been placed soon after that of 120 for France; the French order was later transferred to Britain.

The RAF had allocated the name Liberator to its new bomber, this being adopted later by the USAAF, and the first of these (AM258) flew for the first time on 17 January 1941. They were, however, designated LB-30A by Consolidated, indicating Liberator to British specification, and the first six of these reached the UK during March 1941, flown directly across the North Atlantic. These initial aircraft were used as unarmed transports by BOAC, and later by RAF Ferry Command, to carry pilots and crews to fly back to Great Britain the ever increasing number of aircraft being supplied from the USA. The next batch, received in mid-1941, were to join the RAF as Liberator Is for service with Coastal Command, and these were modified in Britain to equip them with an early form of ASV (Air-to-Surface Vessel) radar, and to increase the standard armament of five 7.62 mm (0.30 in) machine guns to include an underfuselage gun pack, forward of the bomb bay, housing four 20 mm cannon. The Liberator 1 began to equip No. 120 Squadron of Coastal Command in June 1941, and was the first RAF aircraft with the range and endurance to close the 'Atlantic Gap', that area of the ocean in which, until that time, sea convoys were beyond the range of air support from either North America or Great Britain.

In that same month, the USAAF began to receive its first B-24As and these, duplicating the role of the LB-30As in Britain, were allocated first to equip the Air Corps Ferrying Command, operating similar services across the North Atlantic as those of RAF Ferry Command. The first true operational bomber version, however, was the Liberator 11 (Consolidated LB-30), for which there was no USAAF equivalent. It differed from the Liberator 1 in having the fuselage nose extended 2 ft 7 in (0.79 m) by the insertion of a 'plug', to accommodate a maximum crew of 10; by the installation of Boulton Paul power-operated turrets, each housing four 7.7 mm (0.303 in) machine guns, in mid-upper and rear fuselage positions; plus small increases in gross weight, bomb load and service ceiling. The RAF received 139 of this version, these equipping Nos. 59, 86 and 120 Squadrons of Coastal Command, and Nos. 159 and 160 Squadrons. When these two latter squadrons began operations with their Liberators in the Middle East in June 1942, they were the first to deploy these aircraft in a bombing role. One aircraft of this batch (AL504) became the personal transport of Britain's prime minister, Winston Churchill, and operated under the name Commando.

Meanwhile, the XB-24 prototype had been modified to a new XB-24B standard, this introducing self-sealing fuel tanks and armour, but the most significant improvement was the installation of turbocharged R-1830-41 engines. This resulted in the second of the Liberator's easily identifiable features, oval-shaped nacelles, entailed by the relocation of the oil coolers in the sides of the front cowlings. With the introduction of these features, plus dorsal and tail turrets each with two 12.7 mm (0.50 in) machine guns to supplement the original hand-held guns in beam and nose positions, nine aircraft were produced for the USAAF as B-24Cs.

They were followed by the B-24D, the first major production variant, and also the first to be employed operationally by USAAF bomber squadrons. These differed initially by the installation of R-1830-43 engines, but subsequent production batches introduced progressively changes in armament, provision of auxiliary fuel in the outer wings and bomb bay, increases in gross weight and bomb load, and in some late production examples external bomb racks below the inner wing for the carriage of two 4,000 lbs (1814 kg) bombs. In RAF service the B-24D was designated Liberator Ill: Liberator IIIA identified similar aircraft supplied under Lend-Lease with US armament and equipment. Most Liberator 111/111As served with Coastal Command, eventually equipping 12 squadrons. A total of 122 were extensively modified in Britain, receiving ASV radar equipment including chin and retractable ventral radomes, a Leigh Light for the illumination of targets at night (especially surfaced U-boats), increased fuel capacity, but reduced armament, armour and weapon load. These were designated Liberator GR.VS. Some were provided with small stub wings on the forward fuselage to carry eight rocket projectiles. The USAAF also operated B-24Ds in an anti-submarine role, and in 1942 the US Navy began to receive small numbers of this version as PB4Y-1s. However, at the end of August 1943 the USAAF disbanded its Anti-Submarine Command, handing over its aircraft to the US Navy in exchange for an equivalent number of aircraft of bomber configuration to be produced against outstanding US Navy orders. These ex-USAAF B-24s were also designated PB4Y-ls by the US Navy, which service was subsequently to acquire the specially-developed PB4Y-2 Privateer, which featured single tail vertical tail surfaces.

The deployment of USAAF B-24Ds'in the Middle East began in June 1942, one of the first operations being launched by 13 aircraft of Colonel H. A. Halverson's detachment which attacked the Romanian oilfields at Ploesti on 11/12 June 1942 from the RAF base at Fayid in the Suez Canal zone. All 13 aircraft completed what the USAAF described as 'an unsuccessful attack', its only success being to alert the defences of their vulnerability. Consequently, it was a very different story on 1 August 1943, when units sent 177 B-24s against the same target. Although rather more successful in terms of damage caused, of the force which set out from Benghazi 55 Liberators were lost, 53 damaged, and 440 crew killed or posted missing.

By that time, of course, B-24s were being built at an enormous rate, by Consolidated at San Diego and Fort Worth, Douglas at Tulsa, and Ford with a specially built new plant at Willow Run. In mid-1942 the first transport variants began to appear, with nose and tail gun positions deleted, a large cargo door installed in the port side of the fuselage, and accommodation provided for passengers or cargo. The USAAF acquired 276 as C-87s with accommodation for a crew of five and 20 passengers; 24 similar aircraft, but provided with side windows, served with RAF Transport Command as Liberator C.Vlls; and examples flown by the US Navy were designated RY-2. Similar aircraft, but with R-1830-45 engines and equipped as VIP transports, were identified as RY-1 and C-87A by the US Navy and USAAF respectively. One special logistics version was the C-109 fuel tanker, used to ferry 2,900 US gallons (10 977 litres) of aviation fuel per load over the Himalayan 'hump', to supply Boeing B-29 Superfortresses operating from forward bases in China. An XF-7 prototype special reconnaissance version was also produced in 1943, with bomb racks removed and extra fuel tanks provided in the forward section of the bomb bay. This retained the normal defensive armament, and could also accommodate up to 11 cameras. F-7s were used extensively in the Pacific theatre, and later versions included F-7As and F-7Bs with differing camera installations.

The first production aircraft to come from the Ford plant at Willow Run were B-24Es, generally similar to the B-24D except for different propellers and minor detail changes, and this version was built also by Consolidated and Douglas, some having R-1830-65 engines. There followed the B-24G, all but the first 25 of which introduced an upper nose gun turret and had the fuselage nose lengthened by 10 in (0.25 m). These came from a new production line operated by North American Aviation at Dallas, Texas. Similar aircraft produced by Consolidated at Fort Worth, by Douglas and by Ford were designated B-24H.

The major production variant was the B-24J (6,678 built), which came from all five production lines, and which differed from the B-24H in only minor details. B-24Hs and -24Js supplied to the RAF under Lend- Lease were designated Liberator GR.VI when equipped for ASW/maritime reconnaissance by Coastal Command, or Liberator B.VI when used as a heavy bomber in the Middle East and Far East. Those used by the US Navy were identified as PB4Y-Is.

The final production versions were the B-24L, similar to the B-24D with the tail turret replaced by two manually controlled 12.7 mm (0.50 in) machine guns, of which Consolidated San Diego built 417 and Ford 1,250; and the B-24M which differed from the B-24J in having a different tail turret. Convair built 916 of this latter version at San Diego and Ford another 1,677. Odd variants included a single B-24D provided with an experimental thermal de-icing system as the XB-24F; the XB-24K prototype of the single vertical tail version (to have been produced in large numbers as the B-24N, although only the XB-24N prototype and seven YB-24N service test aircraft were built before production ended on 31 May 1945); the single experimental XB-41 bomber escort, armed with fourteen 12.7 mm (0.50 in) machine guns and converted from a B-24D; and five C-87s converted for flight engineer training under the designation AT-22 (later TB-24). Most of the USAAF's Liberators were declared surplus at the war's end, only a few remaining in service. The very last was disposed of in 1953.

From first to last, more than 18,475 Liberators had been built. In addition to those supplied to the RAF, USAAF and US Navy, others had been operated by units of the Royal Australian Air Force, Royal Canadian Air Force and South African Air Force. Nowhere had they been of greater value than in the Pacific theatre, where their long range and versatility created them 'maids of all work'. Operated extensively by the USAAF's 5th and 13th Air Forces, they fought with the US Navy and US Marines over every island step towards the Japanese home islands. In the closing stages their HE bombs or incendiaries added to the quota of destruction on Luzon, Formosa, Okinawa and, in the end, Honshu. The 'Lumbering Lib' had travelled a long and bitter route to final victory.  

Nicknames: Lib; Ford's Folly; Flying Boxcar; Liberator Express (C-87 variant); C-One-Oh-Boom (C-109 fuel-carrying variant); Lamp Lighter (PB4Y-2s dropping parachute flares in Korea).

Specifications (B-24H/J):

Engines: Four 1,200-hp Pratt & Whitney R-1830-65 Twin Wasp turbocharged radial piston engines.
Weight: Empty 36,500 lbs, Max Overload Takeoff 71,200 lbs.
Wing Span: 110ft. 0in.
Length: 67ft. 2in.
Height: 18ft. 0in.

Performance:
Maximum Speed at 25,000 ft: 290 mph
Cruising Speed: 215 mph
Ceiling: 28,000 ft.
Range: 2,100 miles

Armament:
10 12.7-mm (0.5-inch) machine guns in nose, upper/ventral ball turrets and tail turret, and lateral fuselage positions.
12,800 lb. maximum bomb load.

Number Built: 18,000+

Number Still Airworthy: Three (Two B-24Js and one LB-30)