Initial specifications

The Liberator originated from a United States Army Air Corps (USAAC) request in 1938 for Consolidated to produce the B-17 under license. After company executives including President Reuben Fleet visited the Boeing factory in Seattle, Washington, Consolidated decided instead to submit a more modern design of its own.^[5]

The new Model 32 combined designer David R. Davis's wing, a high-efficiency airfoil design created by unorthodox means,^[6] with the twin tail design from the Consolidated Model 31 flying boat, together on a new fuselage. This new fuselage was intentionally designed around twin bomb bays, each one being the same size and capacity of the B-17 bomb bays.

In January 1939, the USAAC, under Specification C-212, formally invited Consolidated^[7] to submit a design study for a bomber with longer range, higher speed and greater ceiling than the B-17. The specification was written such that the Model 32 would automatically be the winning design. The program was run under the umbrella group, "Project A", an Air Corps requirement for an intercontinental bomber that had been conceived in the mid-1930s. Although the B-24 did not meet Project A goals, it was a step in that direction. Project A led to the development of the Boeing B-29 and Consolidated's own B-32 and B-36.^[8]

Design

The B-24 had a shoulder-mounted high aspect ratio Davis wing. This wing was highly efficient allowing a relatively high airspeed and long range. Compared to the B-17, it had a 6 feet (1.8 m) larger wingspan but a lower wing area. This gave the B-24 a 35-percent higher wing loading. The relatively thick wing held the promise of increased tankage while delivering increased lift and speed, but it became unpleasant to fly when committed to heavier loadings as experienced at high altitude and in bad weather. The Davis wing was also more susceptible to ice formation than contemporary designs, causing distortions of the aerofoil section and resulting in the loss of lift, with unpleasant experiences drawing such comments as, "The Davis wing won't hold enough ice to chill your drink".^[9] The wing was also more susceptible to damage than the B-17's wing, making the aircraft less able to absorb battle damage.

The wing carried four supercharged Pratt & Whitney R-1830-35 Twin Wasp engines mounted in cowlings borrowed from the PBY Catalina (similar except for being oval in cross-section allowing for oil coolers mounted on each side of the engine) that turned 3-bladed variable-pitch propellers.

The tailplane featured two large oval vertical stabilizers mounted at the ends of a rectangular horizontal stabilizer. As early as 1942, it was recognized that the Liberator's handling and stability could be improved by the use of a single vertical fin. The single fin was tested by Ford on a single B-24ST variant and an experimental XB-24K: it was found to improve handling. However, all Liberators were produced with twin oval fins, with the exception of eight preproduction B-24N aircraft. The B-24N was intended as a major production variant featuring a single tail. Over 5000 orders for this version were placed in 1945, but they were cancelled due to the end of the war. The single fin did appear in production on the PB4Y Privateer derivative.^[10][11][12]

The B-24's spacious, slab-sided fuselage (which earned the aircraft the nickname "Flying Boxcar")^[13] was built around two central bomb bays that could accommodate up to 8,000 pounds (3,600 kg) of ordnance in each compartment (but rarely did, as this decreased range and altitude). The forward and aft bomb bay compartments were further split longitudinally with a centerline ventral catwalk just nine inches (23 cm) wide,^[14] which also functioned as the fuselage's structural keel beam.

An unusual four-panel set of all-metal, tambour-panel "roller-type" bomb bay doors, which operated very much like the movable enclosure of a rolltop desk, retracted into the fuselage. These types of doors created a minimum of aerodynamic drag to keep speed high over the target area; they also allowed the bomb bays to be opened while on the ground since the low ground clearance prevented the use of normal bomb bay doors.^[15] The occasional need during a mission for crewmen to move from fore to aft within the B-24's fuselage over the narrow catwalk was a drawback shared with other bomber designs.

The Liberator carried a crew of up to ten. The pilot and co-pilot sat alongside each other in a well-glazed cockpit. The navigator and bombardier — who could also double as a nose or wiggly ear gunners (guns mounted in the sides of the aircraft nose) — sat in the nose, fronted on the pre-B-24H models with a well-framed "greenhouse" nose with some two dozen glazed panels and with two flexible ball-mounts built into it for forward defensive firepower using .30 caliber (7.62 mm) Browning M1919 machine guns (later versions were fitted with a powered twin-.50 caliber (12.7 mm) M2 Browning machine gun nose turret). The radio/radar operator sat behind the pilots, facing sideways and sometimes doubled as a waist gunner. The flight engineer sat adjacent to the radio operator behind the pilots; he operated the upper gun turret (when fitted), located just behind the cockpit and in front of the wing.

Up to four crew members could be located in the waist, operating waist guns, a retractable lower ball turret gun, and a tail gun turret matching the nose turret. The waist gun hatches were provided with doors. The ball turret was required to be retractable for ground clearance when preparing to land as well as for greater aerodynamic efficiency. The tail gunner's powered twin-gun turret was located at the end of the tail, behind the tailplane.

The B-24 featured a tricycle undercarriage, the first American bomber to do so,^[9] with the main gear extending out of the wing on long, single-oleo strut legs. It used differential braking and differential thrust for ground steering, which made taxiing difficult.^[16]

Armament

The defensive armament of the B-24 varied from transport variants, which were usually unarmed, to bombers armed with up to ten .50 caliber (12.7 mm) M2 Browning machine guns located in turrets and waist gun positions.

Early model Liberators were fitted with a top-mounted turret, a tail turret and single machine guns located in the waist and in the glazed nose. The B-24D initially featured upper, belly and tail turrets, plus swiveling single guns in the waist and on either side of the nose. The belly turret was a periscopically sighted Bendix model. The turret proved unsatisfactory and was soon replaced by a tunnel gun, which was itself omitted. Later D models were fitted with the retractable Sperry ball turret.

The B-24H saw the replacement of the glazed 'green house' nose with a nose turret, which reduced the B-24s vulnerability to head-on attacks. The bombsight was located below the turret.

Long-range naval patrol versions often carried a light defensive armament. Being on long-distance patrols, they generally flew outside the range of enemy fighters. Also, the necessity of range increased the importance of weight and aerodynamic efficiency. Thus naval patrol often omitted top, belly and nose turrets. Some were fitted with a belly pack containing fixed, forward-facing cannon.

Prototypes and service evaluation

The U.S. Army Air Corps awarded a contract for the prototype XB-24 in March 1939, with the requirement that one example should be ready before the end of the year. Consolidated finished the prototype and had it ready for its first flight two days before the end of 1939. The design was simple in concept but, nevertheless, advanced for its time. Consolidated incorporated innovative features such as a tricycle landing gear and Davis wing.

Compared to the B-17, the proposed Model 32 had a shorter fuselage and 25% less wing area, but had a 6 ft (1.8 m) greater wingspan and a substantially larger carrying capacity, as well as a distinctive twin tail. Whereas the B-17 used 9-cylinder Wright R-1820 Cyclone engines, the Consolidated design used twin-row, 14-cylinder Pratt & Whitney R-1830 "Twin Wasp" radials of 1,000 hp (750 kW). The maximum takeoff weight was one of the highest of the period.

The new design would be the first American heavy bomber in production to use tricycle landing gear – the North American B-25 Mitchell medium bomber's predecessor, the NA-40 introduced this feature in January 1939 – with the Consolidated Model 32 having long, thin wings with the efficient "Davis" high aspect ratio design (also used on the projected Model 31 twin-engined commercial flying boat)^[17] promising to provide maximum fuel efficiency. Wind tunnel testing and experimental programs using an existing Consolidated Model 31 provided extensive data on the flight characteristics of the Davis airfoil.^[18]

Early orders, placed before the XB-24 had flown, included 36 for the USAAC, 120 for the French Air Force and 164 for the Royal Air Force (RAF). The name "Liberator" was originally given to it by the RAF, and subsequently adopted by the USAAF as the official name for the Model 24.^[19] When France fell in 1940, their aircraft were re-directed to the RAF. One outcome of the British and French purchasing commissions was a backlog of orders amounting to $680m, of which $400m was foreign orders, US official statistics indicating tooling, plant and expansion advanced the previously anticipated volume of US aircraft production by up to a year. A consequence of the British orders went beyond requests for specific modifications: as the RAF accepted some designs while rejecting others, American production was – to some extent – re-directed along specific lines that accorded with British doctrine, the B-24's capacious bomb bay and ability to carry 8,000 lb ordnance a case in point.^[9]

After initial testing, the XB-24 was found to be deficient in several areas. One major failure of the prototype was that it failed to meet the top speed requirements specified in the contract. As built, the XB-24 top speed was only 273 mph instead of the specified 311 mph. As a result, the mechanically supercharged Pratt & Whitney R-1830-33s were replaced with the turbo-supercharged R-1830s. Additionally, the tail span was widened by 2 ft (0.61 m) and the pitot-static probes were relocated from the wings to the fuselage. The XB-24 was then re-designated XB-24B—these changes became standard on all B-24s built starting with the B-24C model.

An early B-24D

In April 1939, the USAAC initially ordered seven YB-24 under CAC contract # 12464. The US policy at the time, despite neutrality, was that American requirements could be deferred while its Allies could immediately put US production into the war effort. The added advantage was the American types could be assessed in the European war zone earlier. Thus the first six YB-24 were released for direct purchase under CAC contract # F-677 on 9 November 1940. These aircraft were redesignated LB-30A. The seventh aircraft was used by Consolidated and the USAAC to test armor installations as well as self-sealing fuel tanks. Initially, these aircraft were to be given USAAC serials 39–681 to 39-687. Due to deferments of the US requirements, the US purchase was twice postponed, and the serial numbers were changed to 40–696 to 40-702. When the RAF purchased the first six YB-24 aircraft, the serial numbers were reassigned to an early batch of B-24D funded by the deferment.

Flying the B-24

Lindell Hendrix, later a test pilot for Republic Aviation, flew B-24s for the Eighth Air Force.^[20] Hendrix preferred the B-24 to the B-17. In Eighth Air Force combat configuration, the aircraft carried 8,000 pounds (3,600 kg) of bombs. It could manage an altitude of no more than 25,000 ft (7,600 m), three or four thousand feet less than a B-17, but it flew 10–15 mph (16–24 km/h) faster. Its lower altitude made it more vulnerable to flak. Hendrix figured that Germans understood it was easier to hit, and that it carried more bombs.

It was necessary when flying the B-24, to get "on step". This meant climbing to about 500 ft (150 m) above cruise altitude, levelling off, achieving a cruise speed of 165–170 mph (266–274 km/h), then descending to assigned altitude. Failing to do this meant that the B-24 flew slightly nose high, and it used more fuel. The Davis wing made the B-24 sensitive to weight distribution. Hendrix claimed that a lightly loaded B-24 could out-turn a P-38 Lightning. A heavily loaded B-24 was difficult to fly at speeds of less than 160 mph (260 km/h). The B-24's controls were heavy, especially if the control rigging was not properly tensioned.

B-24s leaked fuel. Crews flew with the bomb bay doors slightly open to dissipate potentially explosive fumes. Hendrix did not permit smoking on his B-24, even though he was a smoker. Chain smoker "Tex" Thornton, then in command of the US Army Air Corps' Statistical Control, flew across the Atlantic in a B-24, and was not permitted to smoke. Thornton's Statistical Control group demonstrated that Eighth Air Force B-24s were taking lower casualties than B-17s because they were being given shorter, safer missions. The B-17s actually delivered more bombs to the target than B-24s.^[21]

RAF

Consolidated LB-30A, s/n AM260, used by Atlantic Ferry Command

The first British Liberators had been ordered by the Anglo-French Purchasing Board in 1940. After the Fall of France the French orders were in most cases transferred to the United Kingdom. The RAF found, as did the US, that global war increased the need for air transports and early-type bombers and seaplanes were converted or completed as cargo carriers and transports. LB-30As were assigned to transatlantic flights by RAF Ferry Command, between Canada and Prestwick, Scotland. The first Liberators in British service were ex-USAAF YB-24s converted to Liberator GR Is (USAAF designation: LB-30A). The aircraft were all modified for logistic use in Montreal. Changes included the removal of all armament, provision for passenger seating, a revised cabin oxygen and heating system. Ferry Command's Atlantic Return Ferry Service flew civilian ferry pilots, who had delivered aircraft to the UK, back to North America. The most important role, however, for the first batch of the Liberator GR Is was in service with RAF Coastal Command on anti-submarine patrols in the Battle of the Atlantic.^[22]

LB-30A (YB-24) in RAF service

Later in 1941, the first Liberators entered RAF service. This model introduced self-sealing fuel tanks, a 2 ft 7 in (79 cm) plug in the forward fuselage to create more space for crew members and, more vitally, ever more equipment such as ASV Mark II radar (anticipated early in the Liberator's development when Reuben Fleet told the engineering team he had a gut feeling the nose was too short). The Mark II was the first Liberator to be equipped with powered turrets, one plane having them installed before leaving San Diego, the remainder having them installed in the field: four Browning Boulton Paul A-type Mk IV with 600 rounds of .303 in the dorsal position; and a Boulton Paul E-type Mk II with 2200 rounds in the tail (later increased to 2500 rounds), supplemented by pairs of guns at the waist position, a single gun in the nose and another in the belly, for a total of fourteen guns. The maximum take-off weight was slightly raised to 64,250 pounds, the maximum altitude lifted from 21,200 to 24,000 feet but the maximum speed was reduced to 263 mph, largely as a result of increased drag.^[9]

The Liberator II (referred to as the LB-30A by the USAAF^[19]) were divided between Coastal Command, Bomber Command, and British Overseas Airways Corporation (BOAC). Both BOAC and the RAF used converted Liberator IIs as unarmed long-range cargo carriers. These aircraft flew between the United Kingdom and Egypt (with an extensive detour around Spain over the Atlantic), and they were used in the evacuation of Java in the East Indies. BOAC also flew trans-Atlantic services and other various long-range air transportation routes.

Consolidated Liberator Mk.I of 120 Squadron Coastal Command RAF, used from December 1941

Two RAF bomber squadrons with Liberators were deployed to the Middle East in early 1942. While RAF Bomber Command did not use B-24s as strategic bombers over mainland North West Europe, No. 223 Squadron RAF, one of Bomber Command's 100 (Bomber Support) Group squadrons, used 20 Liberator VIs to carry electronic jamming equipment to counter German radar.

In October 1944, two RAF Liberator squadrons (357 and 358) were deployed to Jessore India in support of British SAS, American OSS and French SIS underground operations throughout SE Asia. The aircraft were stripped of most armaments to allow for fuel for up to 26-hour return flights such as Jessore to Singapore.^[23]

Liberators were also used as anti-submarine patrol aircraft by RAF Coastal Command. RAF Liberators were also operated as bombers from India by SEAC and would have been a part of Tiger Force if the war had continued. Many of the surviving Liberators originated in this Command.

Antisubmarine and maritime patrols

AAF Antisubmarine Command (AAFAC) modifications at the Consolidated-Vultee Plant, Fort Worth, Texas in the foreground in the olive drab and white paint scheme. To the rear of this front line are partly assembled C-87 "Liberator Express Transports".

Anti-Submarine Weapons: Leigh light used for spotting U-boats on the surface at night, fitted to a Liberator aircraft of Royal Air Force Coastal Command. 26 February 1944.

The Liberators made a significant contribution to Allied victory in the Battle of the Atlantic against German U-boats. Aircraft had the ability to undertake surprise air attacks against surfaced submarines. Liberators assigned to the RAF's Coastal Command in 1941, offensively to patrol against submarines in the eastern Atlantic Ocean, produced immediate results. The introduction of Very Long Range (VLR) Liberators vastly increased the reach of the UK's maritime reconnaissance force, closing the Mid Atlantic Gap where a lack of air cover had allowed U-boats to operate without risk of aerial attack.^[24][25]

For 12 months, No. 120 Squadron RAF of Coastal Command with its handful of worn and modified early model Liberators supplied the only air cover for convoys in the Atlantic Gap, the Liberator being the only airplane with sufficient range. The VLR Liberators sacrificed some armor and often gun turrets to save weight, while carrying extra aviation gasoline in their bomb-bay tanks. Liberators were equipped with ASV Mk. II radar, which together with the Leigh light, gave them the ability to hunt U-boats by day and by night. Before the Leigh Light, not a single enemy submarine had been sunk in over five months, but in combination with radar, it was so overwhelmingly effective that many German submarine crews chose to surface during the day so that they could at least see the aircraft attacking them and have a chance to fire their anti-aircraft weaponry in defense.^[26][27]

These Liberators operated from both sides of the Atlantic with the Royal Canadian Air Force and the Army Air Forces Antisubmarine Command and later, the US Navy conducting patrols along all three American coasts and the Canal Zone. The RAF and later American patrols ranged from the east, based in Northern Ireland, Scotland, Iceland and beginning in mid-1943 from the Azores. This role was dangerous, especially after many U-boats were armed with extra anti-aircraft guns, some adopting the policy of staying on the surface to fight, rather than submerging and risking being sunk by aerial weapons such as rockets, gunfire, torpedoes and depth charges from the bombers. American Liberators flew from Nova Scotia, Greenland, the Azores, Bermuda, the Bahamas, Puerto Rico, Cuba, Panama, Trinidad, Ascension Island and from wherever else they could fly far out over the Atlantic.

The sudden and decisive turning of the Battle of the Atlantic in favor of the Allies in May 1943 was the result of many factors. The gradual arrival of many more VLR and in October, PB4Y navalized Liberators for anti-submarine missions over the Mid-Atlantic gap ("black pit") and the Bay of Biscay was an important contribution to the Allies' greater success. Liberators were credited in full or in part with sinking 93 U-boats.^[28] The B-24 was vital for missions of a radius less than 1,000 mi (1,600 km), in both the Atlantic and Pacific theaters where U.S. Navy PB4Y-1s and USAAF SB-24s took a heavy toll of enemy submarines and surface combatants and shipping.

USAAF

B-24s bomb the Ploiești oil fields in August 1943.

Strategic bombing, 1942–1945

The bomb bay of a surviving B-24J Liberator in 2016

On 12 June 1942, 13 B-24s of the Halverson Project (HALPRO) flying from Egypt attacked the Axis-controlled oil fields and refineries around Ploiești, Romania. Within weeks, the First Provisional Bombardment Group formed from the remnants of the Halverson and China detachments. This unit then was formalized as the 376th Bombardment Group, Heavy, and along with the 98th BG formed the nucleus of the IX Bomber Command of the Ninth Air Force, operating from Africa until absorbed into the Twelfth Air Force briefly, and then the Fifteenth Air Force, operating from Italy. The Ninth Air Force moved to England in late 1943. This was a major component of the USSTAF and took a major role in strategic bombing. Fifteen of the 15th AF's 21 bombardment groups flew B-24s.

For much of 1944, the B-24 was the predominant bomber of U.S. Strategic Air Forces (USSTAF) formerly the Eighth Air Force in the Combined Bomber Offensive against Germany, forming nearly half of its heavy bomber strength in the ETO prior to August and most of the Italian-based force. Thousands of B-24s flying from bases in Europe dropped hundreds of thousands of tons of high explosive and incendiary bombs on German military and industrial targets.

The 44th Bombardment Group was one of the first two heavy bombardment groups flying the B-24 with the 8th Air Force in the fall/winter air campaigns in the European Theater of Operations.^[13] The 44th Bomb Group flew the first of its 344 combat missions against the Axis powers in World War II on 7 November 1942.^[13]

15th Air Force B-24s fly through flak and over the destruction created by preceding waves of bombers.

The first B-24 loss over German territory occurred on 26 February 1943. Earlier in the war, both the Luftwaffe and the Royal Air Force had abandoned daylight bombing raids because neither could sustain the losses suffered. The Americans persisted, however, at great cost in men and aircraft. In the period between 7 November 1942 and 8 March 1943, the 44th Bomb Group lost 13 of its original 27 B-24s.^[13] For some time, newspapers had been requesting permission for a reporter to go on one of the missions. Robert B. Post and five other reporters of The New York Times were granted permission. Post was the only reporter assigned to a B-24-equipped group, the 44th Bomb Group. He flew in B-24 41-23777 ("Maisey") on Mission No. 37 to Bremen, Germany. Intercepted just short of the target, the B-24 came under attack from JG 1's Messerschmitt Bf 109s. Leutnant Heinz Knoke (who finished the war with 31 kills) shot down the Liberator. Post and all but two of the 11 men aboard were killed. Knoke reported: "The fire spread out along the right wing. The inboard propeller windmilled to a stop. And then, suddenly, the whole wing broke off. At an altitude of 900 metres there was a tremendous explosion. The bomber had disintegrated. The blazing wreckage landed just outside Bad Zwischenahn airfield."^[31]

A B-24M of the 448th Bombardment Group, serial number 44-50838, downed by a Messerschmitt Me 262 jet fighter

A total of 177 B-24s carried out the famous second attack on Ploiești (Operation Tidal Wave) on 1 August 1943. This was the B-24's most costly mission. In late June 1943, the three B-24 Liberator groups of the 8th Air Force were sent to North Africa on temporary duty with the 9th Air Force:^[13] the 44th Bomb Group joined the 93rd and the 389th Bomb Groups. These three units then joined the two 9th Air Force B-24 Liberator groups for low-level attack on the German-held Romanian oil complex at Ploiești. This daring assault by high-altitude bombers at treetop level was a costly success. The attack became disorganized after a navigational error which alerted the defenders and protracted the bomb run from the initial point. The 44th destroyed both of its assigned targets, but lost 11 of its 37 bombers and their crews. Colonel Leon W. Johnson, the 44th's commander, was awarded the Medal of Honor for his leadership, as was Col. John Riley "Killer" Kane, commander of the 98th Bomb Group. Kane and Johnson survived the mission but three other recipients of the Medal of Honor for their actions in the mission—Lt. Lloyd H. Hughes, Maj. John L. Jerstad and Col. Addison E. Baker—were killed in action. For its actions on the Ploiești mission, the 44th was awarded its second Distinguished Unit Citation.^[13] Of the 177 B-24s that were dispatched on this operation, 54 were lost.^[13]

Assembly ships

Main article: Assembly ship

B-24D-30-CO assembly ship First Sergeant, 458th Bomb Group

In February 1944, the 2nd Division authorized the use of "Assembly Ships" (or "Formation Ships") specially fitted to aid the assembly of individual group formations. They were equipped with signal lighting, provision for quantity discharge of pyrotechnics, and were painted with distinctive group-specific high-contrast patterns of stripes, checkers or polka dots to enable easy recognition by their flock of bombers. The aircraft used in the first allocation were B-24Ds retired by the 44th, 93rd and 389th Groups. Arrangements for signal lighting varied from group to group, but generally consisted of white flashing lamps on both sides of the fuselage arranged to form the identification letter of the group. All armament and armor were removed and in some cases the tail turret. In the B-24Hs used for this purpose, the nose turret was removed and replaced by a "carpetbagger" type nose. Following incidents when flare guns were accidentally discharged inside the rear fuselage, some assembly (formation) ships had pyrotechnic guns fixed through the fuselage sides. As these aircraft normally returned to base once a formation had been established, a skeleton crew of two pilots, navigator, radio operator and one or two flare discharge operators were carried. In some groups an observer officer flew in the tail position to monitor the formation. These aircraft became known as Judas goats.^[34]

"Carpetbaggers"

B-24 cockpit

From August 1943 until the end of the war in Europe, specially modified B-24Ds were used in classified missions. In a joint venture between the Army Air Forces and the Office of Strategic Services (OSS) code-named Operation Carpetbagger, pilots and crews flew specially modified B-24Ds painted with a glossy black anti-searchlight paint to supply friendly underground forces throughout German-occupied Europe. They also flew C-47s, Douglas A-26 Invaders, and British de Havilland Mosquitos.

Carpetbagger aircraft flew spies called "Joes" and commando groups prior to the Allied invasion of Europe on D-Day and afterward, and retrieved over 5,000 officers and enlisted men who had escaped capture after being shot down. The low-altitude, nighttime operation was extremely dangerous and took its toll on these airmen. The first aircrews chosen for this operation came from the anti-submarine bomb groups because of their special training in low altitude flying and pinpoint navigation skills. Because of their special skills, they were called upon to fly fuel to General George Patton's army during the summer and early autumn of 1944 when it outran its fuel supply. When this mission was completed, it was recorded that 822,791 US gallons (3,114,264 L) of 80 octane gasoline had been delivered to three different airfields in France and Belgium.^[35]

The 859 BS was converted from day bombardment to these operations and then transferred to the 15th Air Force.

Transport variants

C-109 version

C-109 tanker unloading

The C-109 was a dedicated fuel transport version of the B-24 conceived as a support aircraft for Boeing B-29 Superfortress operations in central China.^[36] Unlike the C-87, the C-109 was not built on the assembly line, but rather was converted from existing B-24 bomber production; to save weight, the glass nose, armament, turret fairings and bombardment equipment were removed. Several storage tanks were added, allowing a C-109 to carry 2,900 gal (11,000 L) of fuel weighing over 22,000 pounds (10,000 kg).

Plans originally called for 2,000 C-109s to support 10 groups of B-29s (approximately 400) in China, but the capture of the Mariana Islands provided a far more easily resupplied location for raids on mainland Japan, and the plans were greatly scaled back. Only 218 C-109s were actually converted. After the transfer of the B-29s, the C-109s were reassigned to the Air Transport Command. According to the history of the U.S. Army Air Forces in World War II, at least one squadron was assigned to the IX Troop Carrier Command in Europe to transport gasoline to advancing ground and air forces on the Continent after the Normandy invasion.

However, whereas a combat-loaded B-24 could safely take off with room to spare from a 6,000 ft (1,800 m) runway, a loaded C-109 required every foot of such a runway to break ground, and crashes on takeoff were not uncommon. The aircraft demonstrated unstable flight characteristics with all storage tanks filled, and proved very difficult to land fully loaded at airfields above 6,000 ft (1,800 m) MSL in elevation, such as those around Chengdu. After it was discovered that these problems could be alleviated by flying with the forward storage tank empty, this practice became fairly routine, enhancing aircrew safety at the cost of some fuel-carrying capacity.^[37] Many C-109s were lost in flying the Hump airlift to China.

The Singing Cowboy Gene Autry served in the Air Transport Command (in the same squadron as Barry Goldwater), and described flying the C-109 over "The Hump" as "the thrill that lasts a lifetime".^[38]

B-24 bombers were also extensively used in the Pacific area after the end of World War II to transport cargo and supplies during the rebuilding of Japan, China, and the Philippines.

U.S. Navy and U.S. Marine Corps

PB4Y-1

PB4Y-1 Liberator

B-24s were also used by the U.S. Navy and U.S. Marine Corps for ASW, anti-ship patrol, and photographic reconnaissance in the Pacific Theater, and by the U.S. Coast Guard for patrol and SAR. Naval B-24s were redesignated PB4Y-1, meaning the fourth patrol bomber design built by Consolidated Aircraft. Navy PB4Y-1s assigned to Atlantic ASW and all Coast Guard PB4Y-1s had the ventral turret replaced by a retractable radome. Also, most naval aircraft had an Erco ball turret installed in the nose position, replacing the glass nose and other styles of turret.

The Consolidated Aircraft Company PB4Y-2 Privateer was a U.S. Navy patrol bomber that was derived directly from the B-24 Liberator. The U.S. Navy had been using B-24s with only minor modifications as the PB4Y-1 Liberator, and along with maritime patrol B-24s used by RAF Coastal Command this type of patrol plane had been quite successful. A fully navalized design was seen as advantageous, and Consolidated Aircraft developed a purpose-built long-range patrol bomber in 1943, designated PB4Y-2. The Privateer had non-turbosupercharged engines for weight savings and optimal performance at low to medium patrol altitudes, and was visually distinguishable from the B-24 and PB4Y-1 by its longer fuselage, single tall vertical stabilizer (rather than a twin tail), two dorsal turrets, and teardrop-shaped waist gun blisters (similar in appearance to those on Consolidated's own PBY Catalina).

Australia

The crew of a No. 21 Squadron RAAF Liberator with their aircraft

SAAF

Two squadrons of the South African Air Force (SAAF) also flew B-24s: 31 and 34 Squadrons under No 2 Wing SAAF based at Foggia, Italy. These two squadrons engaged in relief flights to Warsaw and Kraków in Poland to support the Polish Uprising against Nazi Occupation.^[41]

Luftwaffe use

Three B-24s were captured and then operated by the German secret operations unit KG 200, which also tested, evaluated and sometimes clandestinely operated captured enemy aircraft during World War II.^[42]

One of these was captured at Venegono, Italy, on 29 March 1944. It was used on penetration missions in RAF bomber streams at night in Luftwaffe markings. On a ferry flight from Hildesheim to Bavaria on 6 April 1945, it was shot down – by German anti-aircraft fire.

Crashed B-24s were the source of the landing gear units for the strictly experimental Junkers Ju 287 V1 first prototype jet bomber airframe in 1945.

Soviet use

Only one B-24 was officially delivered to the USSR according to the Lend-Lease agreements, stranded in Yakutsk while flying a government mission to the Soviet Union in November 1942. In addition, 73 Liberators of various models that had force-landed on European airfields were recovered and 30 of them were repaired and used by the 45th Bomber Aviation Division.^[43] The regiment concerned appears to have been the 890th Bomber Aviation Regiment at Baranovichi until 1944, and then Kazan.

Chinese use

B-24 Bomber flying over China during WW2

The B-24 bombers of the 308th Bombardment Group (Heavy) joined the battlefield in March 1944 as the heavy bombers of the Fourteenth Air Force to fight against the Japanese during the Second Sino-Japanese War (WW2 in China). About 48 B-24Ms were provided by the U.S. to the Chinese Nationalist Air Force after WW2 and were used during the Chinese Civil War. The PLAAF had two B-24Ms captured from the Chinese Nationalists during the Chinese Civil War and operated until 1952.

U.S. Army Air Forces variants

XB-24

Single prototype ordered by Army Air Corps on 30 March 1939. Powered by four Pratt & Whitney R-1830-33 Twin Wasps rated at 1,200 horsepower (890 kW) for takeoff and 1,000 horsepower (750 kW) at 14,500 feet (4,400 m). Bombload of eight 1,000 lb (450 kg) bombs, with defensive armament of three 0.5 in (12.7 mm) and four 0.30 in (7.62 mm) machine guns. First flew 29 December 1939. Later converted to XB-24B.^[50][51]

YB-24/LB-30A

Pre-production prototypes, six of which were sold to the UK directly as the LB-30A. US funds and serial numbers were deferred to the B-24D production. The seventh (40-702) remained in U.S. service as the sole YB-24 for service test. (Total: 7)

B-24

Ordered on 27 April 1939, less than 30 days after the XB-24 was ordered and before its completion. Minor modifications included eliminating leading-edge slots and adding de-icing boots. (Total: 1, converted YB-24.)

LB-30A Diamond Lil from the Commemorative Air Force. Airframe returned to B-24A configuration and renamed Ol' 927. She was renamed back to Diamond Lil in May 2012.^{[N 1]}

B-24A/LB-30B

Ordered in 1939, the B-24A was the first production model. Due to the need for long-range aircraft, the B-24A was ordered before any version of the B-24 flew. Aerodynamics improvements over the XB-24 led to better performance. Nine built as transports, transferred to Ferrying Command; while twenty were sold to the UK (before Lend-Lease) as LB-30Bs. (Total: 20 LB-30B; 9 B-24A)

Liberator B Mk II/LB-30

The first combat-ready B-24. The modifications included a three-foot nose extension, a deeper rear fuselage, wider tailplane, self-sealing fuel tanks, and armor. Built to British specifications with British equipment so there was no B-24 equivalent but it was similar to the B-24C. Except for the first aircraft which was completed as a pattern aircraft, and subsequently lost in a test flight, the rest of the run was completed without armament, which the British would fit after being flown to the UK. With the US entry into the war in December 1941, some 75 were requisitioned by the USAAF during delivery and retained the LB-30 designation in service. These were delivered unarmed. Browning M2 .50 in (13 mm) guns were fitted throughout; single guns were mounted in the nose, both waist positions, and the ventral tunnel; and a twin manual mount in the tail replaced the British 4 .303 in (7.70 mm) Browning tail turret, and a Martin turret with two guns replaced the Boulton Paul dorsal turret. Fifteen were sent to the south west Pacific, including some to Java to assist the Dutch East Indies, while three went to Alaska, six to Midway Island immediately after the naval battle in June. Six were lost in various accidents. Twenty-three were later returned to the UK in 1943. Seventeen were fitted with ASV radar and used in the Panama Canal Zone. (Total production: 165)

XB-24B

A newly funded conversion of the XB-24 after it failed to reach its projected top speed. The 1,000 hp (750 kW) Pratt & Whitney R-1830-33 radials were replaced with R-1830-41 turbo-supercharged radials rated at 1,200 hp (890 kW), increasing its top speed by 37 mph (60 km/h). The engine cowlings were made elliptical to accommodate the turbo-superchargers. The XB-24B also lacked the original's engine slots. It was re-serialed. (Total: one converted XB-24) XB-24B 39-680 was converted into a luxury airliner for Consairway which included gutting the interior, cutting new windows, and dividing the interior into compartments with individual and bench seating and two-tier Pullman-style sleeping berths. Trim was added for sound-proofing, and a galley with refrigerator and hot plates.^[9]

B-24C

New production funded from deferred funds after LB-30A to the UK. Used the engine package tested in the XB-24B and the new fuselage of the LB-30. The tail air gunner position was improved by adding a hydraulically powered Consolidated A-6 turret with twin .50 in (12.7 mm) machine guns; a Martin powered dorsal turret was added to the forward fuselage. One (#84) converted to prototype the "three in nose" armament for the B-24D. FY funds and serial numbers transferred from B-24A. (Total: nine)

B-24Ds of 93rd Bomb Group in formation. Nearest aircraft is Joisey Bounce, almost hidden is wingman The Duchess, next higher is Boomerang with wingman Thunder Mug.

B-24D

First to see large scale production; ordered from 1940 to 1942, as a B-24C with more powerful R-1830-43 supercharged engines. The D model was initially equipped with a remotely operated and periscopically sighted Bendix belly turret, as the first examples of the B-17E Flying Fortress and some early models of the B-25 Mitchell medium bomber had used, but this was unsatisfactory and was discontinued after the 287th aircraft. Later aircraft reverted to the earlier manually operated "tunnel" mounting with a single .50 in (12.7 mm) machine gun. The tunnel gun was eventually replaced by the Sperry ball turret, which had also been adopted by the later B-17E Fortresses, but made retractable for the Liberator as the fuselage was very close to the ground. Late B-24Ds had "cheek" guns mounted on either side of the nose, just behind the "greenhouse". (Total: 2,696: 2,381 Consolidated, San Diego; 305 Consolidated, Fort Worth; 10 Douglas, Tulsa, Oklahoma).

B-24E

B-24E

A slight alteration of the B-24D built by Ford, using R-1830-65 engines. The B-24E retained the belly tunnel gun. The USAAF used the B-24Es primarily as trainers as were the aircraft produced by Consolidated at San Diego (CO). Ford also built sub-assemblies for Douglas and Convair Fort Worth; these sub-assemblies were identical to Ford-built B-24Es, except that they used the same R-1830-43 radial engines as the B-24D. These sub-assemblies were called KD (knock down) kits and were trucked from Willow Run to the Southwest for the final assembly. (Total: 801)

XB-24F

A prototype made to test thermal de-icers to replace the standard inflatable rubber "boots". (Total: one converted B-24D)

B-24G

Designation for B-24D aircraft built by North American Aviation pursuant to a 1942 contract. Equipped with Sperry ball turret and three flexible .50 in (12.7 mm) machine guns in nose. (Total: 25)

B-24G-1

as B-24G but with A-6 nose turret. Most were operated by the 15th Air Force in Italy. (Total: 405)

B-24H

Because of the vulnerability of the B-24 to head-on attack with the earlier "greenhouse" nose, the B-24H design incorporated an electrically powered Emerson A-15 nose turret above the bombardier's position, similar to where the Frazer-Nash FN5 nose turret on the Avro Lancaster was placed. Approximately 50 other airframe changes were made, including a redesigned bombardier compartment. The tail turret was given larger windows for better visibility and the Martin A-3 dorsal turret received an enlarged "high hat" dome. The waist gunner positions were enclosed with Plexiglass windows, and laterally offset to reduce interference between the waist gunners. Most H model aircraft were built by Ford at Willow Run. (Total: 3,100)

A 3-view line drawing of a B-24J

B-24J

The B-24J was similar to the B-24H, but shortages of the Emerson nose turret required use of a modified, hydraulically powered Consolidated A-6 turret in most J model aircraft built at Consolidated's San Diego and Fort Worth factories. The B-24J featured an improved autopilot (type C-1) and a M-1 series bombsight. B-24H sub-assemblies made by Ford and constructed by other companies and any model with a C-1 or M-1 retrofit, were all designated B-24J. The J model was the only version to be built by all five factories involved in B-24 production. (Total: 6,678)

XB-24K

Developed from the B-24ST, with a single fin and rudder replacing the twin tail on the standard Liberator.^[11] The improved performance and handling of the B-24ST and XB-24K led to the decision to incorporate a single tail in the PB4Y-2 and B-24N. (Total: one converted B-24D)

B-24L

Because of the excessive weight of the B-24J, the Army requested a lightened version. In the B-24L, the Sperry ball turret was replaced by a floor ring mount with two .50 in (12.7 mm) machine guns, and the A-6B tail turret by an M-6A. Later aircraft were delivered from the factory without tail guns. An A-6B or M-6A turret (190 total), a hand-held but hydraulically assisted twin .50 in (12.7 mm) mount (42) or a manually operated twin .50 in (12.7 mm) mounting was installed at a depot before delivery to operational units. The L model was built at Willow Run and Consolidated's San Diego factory. (Total: 1,667)

B-24M-20-CO Bolivar Jr. 431st Bomb Squadron, 11th Bomb Group

B-24M

Improved B-24L with further weight-savings. The B-24M used a lighter version of the A-6B tail turret; the waist gunner positions were left open, and the retractable Sperry ventral ball turret was reintroduced. For better visibility from the flight deck, the windshield in Ford-built aircraft was replaced by a version with less framing from Block 20 onward. The B-24M became the last production model of the B-24 and many flew only from the factory to the scrap yard. (Total: 2,593)

XB-24N

A redesign of the B-24J, made to accommodate a single tail. It also featured an Emerson 128 ball turret in the nose and a stationary tail gunner's position. While 5,168 B-24Ns were ordered, the end of the war resulted in cancellation of all contracts before production could begin. Its single tail was said to be the inspiration for the PB4Y-2 Privateer's similar single fin/rudder tail design. (Total: one)

YB-24N

Pre-production service test version of the XB-24N. (Total: seven)

XB-24P

A modified B-24D, used by Sperry Gyroscope Company to test airborne fire control systems. (Total: one converted B-24D)

XB-24Q

A General Electric conversion of the B-24L. Used to test a radar-controlled tail turret intended for use in the Boeing B-47 Stratojet. (Total: one converted B-24L)

XB-41

With no fighters capable of escorting bombers on deep strike missions early in World War II, the Army authorized heavily armed bombers as "gunship" escorts, which resulted in both the B-17 derived YB-40 Flying Fortress gunship and its Liberator-derived XB-41 counterpart. The XB-41 had fourteen .50 in (12.7 mm) machine guns, including a Bendix chin turret and a second Martin A-3 turret on the upper fuselage. One aircraft was completed in 1942. Performance was degraded drastically with the additional turrets and were unable to keep up with bomber formations, particularly when bombs had been dropped. Following testing in 1943 the project was canceled. (Total: one converted B-24D)

B-24ST

An experimental aircraft, The B-24ST (for Single Tail, an unofficial designation applied by Ford) was made by Ford by fitting a single fin an rudder onto a B-24D airframe. The aircraft was more stable and had better handling than other models and was used as the basis of the XB-24K.^[11]

AT-22 or TB-24

C-87 used for flight engineer training.

• RB-24L: Developed for training B-29 gunners on an identical remote gun system installed on a B-24L.
• TB-24L: As with the RB-24L, but with additional radar equipment.

Experimental B-24J-15-CO with B-17G nose grafted on, with a chin turret, a modification not adopted for production

C-87 Liberator Express

Transports with accommodation for 20 passengers.

• C-87A: VIP transports with R-1830-45 instead of -43 engines and sleeping berths for 16 passengers.
• C-87B: Projected armed transport with nose guns, dorsal turret, and ventral tunnel gun; not produced.
• C-87C: U.S. Army Air Force/Air Force designation for the RY-3.

XC-109/C-109

Tankers used to ferry fuel from India to China to support early B-29 raids against Japan.

XF-7

Photographic reconnaissance variant developed from the B-24D.

F-7

Photographic reconnaissance variant developed from the B-24H; -FO block.

F-7A

Photographic reconnaissance variant developed from the B-24J; three cameras in the nose and three in the bomb bay.

F-7B

Photographic reconnaissance variant developed from the B-24J; six cameras in the bomb bay.

BQ-8

A number of worn-out B-24D and B-24Js were converted as radio-controlled flying bombs to attack German targets. Joseph P. Kennedy Jr. was killed in a BQ-8 during Operation Anvil.^[53]

U.S. Navy nomenclature and sub-variants

PB4Y-1

U.S. Navy designation applied to 976 navalized B-24D, J, L and M models built at Consolidated's San Diego factory, as well as one North American-built B-24G. Later aircraft were equipped with an ERCO nose turret.^[54]

PB4Y-1P

Photographic reconnaissance variant developed from the PB4Y-1.

PB4Y-2 Privateer

A developed PB4Y with a large single fin, a lengthened fuselage and many other improvements and changes.

P5Y

Proposed twin-engined patrol version of PB4Y-1. Unbuilt.^[55]

RY-1

U.S. Navy designation for the C-87A.

RY-2

U.S. Navy designation for the C-87.

RY-3

Transport variant of the PB4Y-2.

R2Y

Liberator Liner built using a new fuselage for the US Navy as an airliner with 48 seats

British Commonwealth nomenclature and sub-variants

Color photograph of an RAF B.Mk.II

Liberator C Mk.I

YB-24/LB-30A RAF direct purchase aircraft. (Total: 9) Unsuitable for combat, rebuilt as transports and used by BOAC between the UK and Canada, including transferring aircrew ferrying Lend-Lease aircraft.

Liberator B Mk.I

B-24A/LB-30B, RAF direct purchase aircraft. (Total: 20) Unsuitable for combat, some rebuilt for other roles.

Liberator GR Mk.I

Mk.I rebuilt as General Reconnaissance for anti-submarine patrol. Fitted with belly pannier with an additional four fixed forward firing 20 mm (0.787 in) Hispano cannon and ASV radar which included two underwing Yagi–Uda antennas and four large antenna "stickleback" masts above the rear fuselage.

Liberator B Mk.II

LB-30. First combat-ready Liberator. Modifications included a three-foot nose extension as well as a deeper aft fuselage and wider tailplane and self-sealing fuel tanks and armor. Built to British specifications with British equipment and Boulton Paul turrets, so there was no B-24 equivalent but similar to the B-24C. The top turret was further back on the fuselage compared to any US variant, and in line with the trailing edge of the wing. Except for the first aircraft (completed as a pattern but lost in a test flight), the rest were completed without armament, which the British fitted in the UK. With the American entry into the war, the USAAF requisitioned about 75, which it operated under Consolidated's LB-30 designation, but 23 were returned in 1943. (Total production: 165)

Liberator C Mk.II

Mk.II transport. Some B Mk.IIs were rebuilt as transports, including one as the personal transport of British Prime Minister Winston Churchill, which was named 'Commando', which was later extensively rebuilt to C Mk.IX standard, with a single fin.

Liberator B Mk.III

B-24D with one nose .303 in (7.70 mm) Browning machine gun, two in each waist position, and four in a Boulton Paul tail turret similar to that used on the Handley Page Halifax. The Martin dorsal turret was retained. (Total: 156)

• Liberator B Mk IIIA: Mk.III with American equipment and weapons.

Liberator GR Mk.III

Mk.III General Reconnaissance for RAF Coastal Command for anti-submarine role with radar (with Yagi–Uda antenna) and Leigh Light.

• Liberator GR Mk IIIA: GR.III with American equipment and weapons.

RAF Coastal Command ASV Mk.II-equipped Liberator GR.III of No. 120 Squadron RAF

Liberator B Mk.IV

Unused designation reserved for B-24E.

Liberator B Mk.V

B-24D bomber with more fuel but less armor, armed as per Mk.III.

Liberator GR Mk.V

General Reconnaissance Mk.V for RAF Coastal Command for anti-submarine role with radar (some mounted under the nose) and Leigh Light. Some fitted with eight zero-length rocket launchers, four on each wing, with others being fitted with stub-wings either side of the lower forward fuselage to hold eight RP-3 rails.

Liberator B Mk.VI

B-24H bomber with nose turret, and Boulton Paul tail turret and retaining the rest of their armament.

Liberator GR Mk.VI

B-24G/H/J RAF Coastal Command anti-submarine patrol. Some had top turret removed in service, and early examples had Yagi–Uda antenna on older greenhouse nose.

Liberator C Mk.VI/C Mk.VIT

Mk.VI converted as a cargo aircraft.

Liberator C Mk.VII

RAF C-87 transport.

Liberator B Mk.VIII

RAF B-24J bomber.

Liberator GR Mk.VIII

Mk.VIII for RAF Coastal Command anti-submarine patrol. Some had top turret removed in service, and belly turret replaced with semi-recessed radar dome.

Liberator C Mk.VIII

Mk.VIII converted as a cargo aircraft.

Liberator C Mk.IX

RAF RY-3/C-87C transport with a single fin replacing the twin fins on most Liberator versions.

Late in the war RAF Liberator aircraft modified in England for use in South East Asia had the suffix "Snake" stenciled below the serial number to give them priority delivery through the Mediterranean and the Middle East.^[56]

Notes

Citations

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