Consolidated B-24 Liberator – Introduction and Development

The Consolidated B-24 Liberator was produced in larger numbers than any other American military aircraft, and was the first American aircraft to enter mass production, but despite this the Liberator is still less well known than the Boeing B-17 Flying Fortress or the B-29 Superfortress. Each of these aircraft gained their fame by being closely associated with a particular campaign – the B-17 with the Eighth Air Force bombing campaign over Europe and the B-29 with the bombing of Japan. In fact even by the end of the war the B-24 Liberator equipped nearly a third of the Eighth Air Force's heavy bomber units, fifteen groups of the Fifteenth Air Force, operating from Italy, and was serving in just about every part of the war against Japan, from India to Alaska. In total 18,188 Liberators were built, and at its peak in September 1944 6,043 aircraft were on the strength of the USAAF, equipping forty five groups.

The LB-30 designation was inherited from an original French order for a heavy bomber. The French had issued the specification for this aircraft in May 1938, and Consolidated had responded with the Model 30, a land bomber based on their Model 29 flying boat, thus LB-30. By the time the French placed an order for the aircraft, in June 1940, Consolidated had moved on to the Model 32 (or XB-24), and it would be this aircraft that would be delivered to the RAF as the LB-30A (some sources suggest that LB stood for Liberator, British, but if this was the case, then one would expect the aircraft to have been either the LB-32, to match the model number for the B-24, or LB-24 to match the B-24).

Model 31

A key element in the design of the B-24 was the Davis wing. This was a wing based on the shape formed by a falling raindrop, and produced long, thin but very efficient wings. Consolidated first used the Davis wing on their Model 31 flying boat (given the Naval designation XP4Y). This was a twin engined, twin tailed aircraft, which proved to be far superior to the Consolidated PBY-3 Catalina,

Model 32

Both the twin tail and the Davis wing would be carried over to the design of Consolidated’s Model 32. This aircraft was produced to satisfy an Army Air Corps specification for a bomber with a range of 3,000 miles, a top speed of 300 mph and a maximum bomb load of 8,000lbs. The aim was to produce an aircraft with a superior performance to the Boeing B-17 Flying Fortress.

The Davis wing was not the only advanced feature of the Model 32. It also featured a tricycle landing gear – one wheel in each wing and the third wheel in the nose, rather than in the tail as was more common. This arrangement allowed for faster landings and take-offs, and made better use of the Davis wing, but did require the pilots to adapt a new method of landings and taking off, which in some cases caused accidents. Air Force statistics show that the B-24 suffered more accidents for every 100,000 hours in the air than the B-17 – 75 vs. 55 in 1942, falling to 29 vs. 23 in 1945, although both types were much safer than the single engined fighters.  

The aircraft had a large fuselage, capable of carrying eight 1,000lb bombs in two rows of four in the bomb bay, twice the capacity of the B-17. This extra space would make the B-24 a much more versatile aircraft.

XB-24

Liberator I
Liberator I

On 30 March 1939 Consolidated were awarded a contract to produce one XB-24 prototype aircraft, and given nine months to build it. The aircraft was ready eight months and 28 days later. It made its first flight on 29 December 1939, and the flight tests soon proved that the new aircraft did indeed have superior range to the B-17, 200 miles longer when fully loaded. To a certain extent this longer range would prove to be illusory. The XB-24 was un-armoured and lacked self-sealing fuel tanks, both of which had to be added to make the aircraft truly combat ready.

The XB-24 was originally powered by Pratt & Whitney R-1830-33 engines, with mechanical two-speed superchargers. In early tests these failed to achieve the expected speeds, and so were replaced with R-1830-41 engines with GE B-2 turbo-superchargers. The aircraft had been built with leading edge wing slots, but these were also removed during the testing process.

The aircraft was given the Liberator name by the Consolidated workforce. A contest was held at the San Diego factory, which is said to have been won anonymously by Dorothy Fleet, the wife of the company’s founder. In a reversal of the normal pattern at this date, this name was then adopted by the RAF.

The French Order

At the outbreak of the Second World War the French Air Force was desperately short of modern aircraft. In an attempt to fill the gap a number of orders were placed for American aircraft. Amongst them was the first production order for B-24s, for 120 B-24As, under the designation LB-30MF. These were to be armed with two .30in guns in the tail and single .50in guns in the waist and nose positions. None of these aircraft had been delivered before the fall of France. The order was split between the RAF and the USAAC. Britain received six LB-30As, twenty Liberator Is (LB-30Bs) and a number of Liberator IIs, with the remaining aircraft going to the USAAC, nine as B-24As. The rest were completed as B-24Cs and B-24Ds.

YB-24

Although the Army ordered seven YB-24 service test aircraft on 27 April 1939, only one was actually built. The remaining six aircraft were completed as B-24Ds. Another six aircraft were completed to the YB-24 standard and were provided to the British, where they were given the designation LB-30A and used as long range transport aircraft. All thirteen of these aircraft were built using airframes that had originally been intended for the French order.

The single YB-24 was similar to the XB-24B, featuring self sealing fuel tanks and spinners on the propeller hubs. The only significant changes made to the design were the removal of the leading edge slots from the wings and the installation of de-icing boots on the leading edge of the wings and tail surfaces.

Comparison to the B-17

The B-24 is inevitably compared to the B-17. The Liberator could carry a higher bomb load over longer distances than the B-17, although as the B-24 gained armour, self sealing tanks and more guns and the B-17 gained longer range the gap closed. It still had enough of an edge to make it the bomber of choice in the Pacific, where it took part in some of the longest raids of the war, the 2,400 mile round trips to Balikpapan.

Statistically the B-24 had a slightly lower loss rate than the B-17, but it was felt to be less rugged than the B-17, and the Davis wing would prove to be prone to collapse completely if damaged. As the aircraft gained in weight, the stability of the aircraft suffered and it became harder to hold the B-24 in the rigid box formations called for over Europe.

The larger fuselage of the B-24 meant that it was always more flexible than the B-17. It was much suitable for use as a cargo plane or transport plane (C-87) and as a fuel tanker (C-107). Its initially longer range also gave it an advantage as a long range naval patrol aircraft, although here the lack of stability could be a real disadvantage, making it a tiring aircraft to fly.

Consolidated B-24D Liberator lost during Operation Tidalwave
Consolidated B-24D Liberator lost during Operation Tidalwave

In one area the B-24 was clearly inferior to the B-17. That aircraft had been designed in the interwar years, and some attention had been paid to crew comfort. Early versions could carry bench seats in the rear fuselage, access was via doors in the fuselage, and each crewman had a clear station. In contrast access to the B-24 was haphazard, with most crewmen clambering in via the bomb bay or the nose wheel door opening. The navigator lacked a dedicated position and tended to occupy either the nose or share the radio operator’s position. The nose position and turrets were not manned during take off or landing, as the nose wheel was prone to collapse, making those positions rather vulnerable. In one area the B-24 did outscore the B-17 – if the ventral ball turret got stuck in the down position, on the B-17 there was a real danger of it being crushed in a bad landing, but the B-24 was more likely to end up nose-down, with the ball turret safely up in the air! In the end most aircrew grew to love the aircraft they were flying, because it was that aircraft that kept them alive. 

 Consolidated B-24 Liberator (Crowood Aviation), Martin W. Bowman. A well balanced book that begins with a look at the development history of the B-24, before spending nine out of its ten chapters looking at the combat career of the aircraft in the USAAF, the US Navy and the RAF.
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How to cite this article: Rickard, J (7 February 2008), Consolidated B-24 Liberator – Introduction and Development , http://www.historyofwar.org/articles/weapons_B-24_Development.html

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