Staff Writer (Updated: 4/19/2016):
The United States Army Air Corps (USAAC) issued a new specification in 1935. This specification required the development of a new multi-engined, long-range heavy bomber capable of exceeding a top speed of 300 miles per hour, besting a range of 3,000 miles, maintaining a service ceiling of at least 35,000 feet and taking on an internal bombload minimum of 8,000lbs. Production of the Boeing B-17 Flying Fortress was well underway and, in 1938, Consolidated was requested to help in its production. As part of the production initiative, Consolidated executives were brought to Boeing's plant in Seattle, Washington to visit the factory. It was this meeting that prompted Consolidated to submit their own heavy bomber design with a more modern flair. The USAAC granted Consolidated a design study in January of 1939 under C-212 with the intent that this new aircraft exceed the performance specifications (speed, range and ceiling) of the B-17 and be ready in time for production before the end of the war.
Consolidated wasted no time in developing their design - the Model 32 - and brought about a few revolutionary changes in the approach of American bomber designs. Model 32 sported a tricycle undercarriage - the first American bomber to do so - doing away with the traditional "tail-dragging" design as utilized by the B-17. The monoplane wings were also held in a high shoulder-mounted position, themselves made wide and holding two engines to each wing leading edge in underslung nacelles. The high wings were of less surface area but promoted a higher fuel efficiency standard than the low-mounted assemblies on a B-17. Of note here was Consolidated's Model 31 (XP4Y Corregidor) foray which utilized the same "Davis" high aspect wing (or "Davis Wing"). This aircraft was of a twin-engine sort and designed as a flying boat. Ultimately, the design fell by the wayside when an order for 200 examples was cancelled by the United States Navy due to program delays and a lack of available Wright engines.
The Davis Wing emerged from the mind of David R. Davis, an aeronautical engineer working on a new wing planform, a planform utilizing a short chord and high aspect ratio along with thickness suitable to fit engines and fuel while maintaining efficiency. His meeting in the summer of 1937 with Consolidated President Reuben H. Fleet allowed the wing design to flourish as one of the most utilized wing planforms of World War 2. The new wing was intended for use on the company's new flying boat design - the Model 31. Despite the Model 31's cancellation (only one example emerged from development), the wing was seen as a good step forward in the design of the upcoming B-24 Liberator and became a major Consolidated design mainstay thereafter.
Other features of the Model 32 included the selection of 14-cylinder Pratt & Whitney R-1830 radial piston engines, deep bomb bay fuselage and a twin vertical fin tail assembly. The development process culminated in an offered contract on March 30th, 1939, for a flyable prototype under the designation of XB-24. The XB-24 was made available and achieved first flight on December 29th, 1939, from Lindberg Field in California with 4 x Pratt & Whitney R-1830-33 radial piston engines of 1,000 horsepower each. The aircraft failed to reach the projected top speed of the original design intentions but, overall, the first flight was a success. To help iron out the prototype design, a further six YB-24/LB-30A evaluation/pre-production models were ordered, built and delivered. These were followed by the B-24, seven examples of which only one was used for service testing. The B-24 featured de-icing boots and deleted the leading edge slots of previous forms.
Orders were beginning to pile up for the new Consolidated design, an amazing feat considering these were being received before the XB-24 had yet to fly. Production began at Consolidated's San Diego plant of which the first six systems were earmarked for the French Air Force as LB-30A models. With the fall of France in 1940, these aircraft made it to British Royal Air Force hands via Lend-Lease. The RAF found their early production forms to be unsuitable for the rigors of combat for they were not even fitted with self-sealing fuel tanks - a valuable characteristic of all military aircraft by the end of the war - and relegated them to ferry type duties. The USAAC called for 36 of the aircraft while the British ordered 164 for the RAF. Upon reception of the aircraft, the British bestowed the name of "Liberator" and the legacy of this multi-engined bomber was now born. Like other British-named American goods (the M3 Lee/Grant medium tank for example), the United States military accepted the British name of Liberator as part of the official designation from then on. First production models became the B-24A/LB-30B.
The XB-24B was designed to exceed the projected top speed of the XB-24. This included replacing the original Pratt & Whitney radials with turbo-supercharged versions in the R-1830-41 of 1,200 horsepower each. The XB-24 prototype served as the conversion model, which now gained a top speed increase equal to 37 miles per hour. The new engines and their turbo-superchargers also forced a revision of the engine cowlings. The XB-24B went on to become the first definitive operational Liberator forms in service with Britain and the United States. Early definitive and quantitative models in general became the B-24D, B-24E and the B-24G.
Liberators were crewed (depending on the model) by 7 to 10 personnel. The pilot and co-pilot were situated in the high-mounted stepped flight deck with views forward, to the sides and above. Of the two seats in the cockpit, the pilot occupied the left hand seat while the co-pilot sat to his right. The pilot was essentially the overlord of the Liberator and ultimately held responsible for the actions and relative well-being of the rest of his crew. The pilot maintained the Liberator's position in flight and was called upon to deliver the aircraft to the target area and back or make split-second decisions based on actions to keep his crew alive. The co-pilot was equally trained in the systems afforded the pilot and was, for all intents and purposes, the pilots right-hand man. He participated in the operation and controls of the Liberator to help alleviate the responsibilities of the pilot. Like the pilot, the co-pilot could be called upon to fully operate the aircraft to and from the target area and, like the navigator, was skillfully trained in the fine art of navigation.
The nose gunner, bomber and navigator were housed under a glazed nose well forward in the design. The nose gunner was perhaps afforded the most stunning (and oft-targeted) position in the Liberator, watching every bombing mission unfold like no other crewman. The nose gunner had access to the powered nose turret if the model of Liberator called for one, fitting 2 x 12.7mm machine guns. Since the front of the Liberator was most susceptible to incoming enemy fighters, this position was also one of the more dangerous on the aircraft.
The bombardier held the most important job in the flight crew. For the Liberator's were designed with bombing in mind, a flight crew without a trained bomber crewmember was ultimately useless in the Allied air campaign. Bombardiers and pilots shared a common role for the bombardier would be called on to take flight control of the bomber when engaging in the bombing run via auto-pilot. Calculations were necessary to unleash payloads directly over target areas, thus requiring bombardiers to maintain a certain level of mettle while blocking out enemy fighters, flak, structural damage or personal combat wounds. Lead bombers were also the elements that triggered the rest of the formation to drop their bombs. Later advances in airborne technologies allowed bombardiers to achieve direct hits even through cloud and smoke coverage.
The navigator was given the important responsibility of getting the crew to the target and back home. This was particularly important of the lead bomber in a given flight group but all navigators needed exceptional know-how of their position to lead a bomber through should the aircraft become displaced from his group. The navigator could utilize the forward-mounted Plexiglas dome to get his bearings as well as relying on physical landmarks down below and his training in the fine art of navigation. Essentially, the pilot and navigator needed to maintain a close working partnership to get everyone to the target area and back home. If "cheek" machine guns were fitted on a Liberator model, the navigator could man one.
The dorsal turret gunner also doubled as the flight engineer and probably maintained the best defensive vantage point, offering an exceptional firing arc when compared to all other available gunner positions. The turret mounted 2 x 12.7mm machine guns. As the aircraft's in-flight mechanic, these individuals maintained a certain level of expert knowledge on the inner workings of the aircraft. His primary duty - along with defense of the upper hemisphere of the bomber - also lay in assisting the pilots on the engine condition and fuel usage.
The radioman was situated within the upper portion of the Liberator's deep fuselage, positioned just behind the cockpit and not aft of the wings as in a B-17. His positioned required him to stay hours on his headset listing for friendly communications, reporting updates to the navigator, reporting situational updates at intervals and communicating with headquarters on mission results. Radiomen were required to keep logs of all pertinent actions and could be called upon to man one of the waist guns if needed.
The forward flight crew was removed from the rear flight crew, with access between the two sections of the bomber made via a thin scaffold running the length of the two bomb compartments. Entry and exit to the aircraft was through a door positioned towards the rear which made for harrowing emergency exits. Forward crewmen were expected to exit the aircraft by walking across the bomb bay scaffold and make their way to the rear all the while fitted with their parachutes and bulky warming flight suits.
The smallest bomber personnel were generally enlisted for operation of the ball turret fitting 2 x 12.7mm heavy machine guns. These fellows wore no parachutes (the small size of the ball turret necessitated this) and made their way inside their turrets after the aircraft was in flight. The ball turret - unlike that on the B-17 - could be retracted into the Liberator's fuselage during take-off and landing. The ball turret was perhaps the coldest position on a given B-24 with many a crewmember reporting frostbite through those frigid high-altitude sorties. At any rate, the ball turret gunner held a distinct view of the action like no other crew member.
Waist gunners were charged with the defense of the Liberator's vulnerable sides through use of single 12.7mm machine guns. As such, these positions aboard Liberators suffered the most casualties by incoming fighters ready to strafe the large profile sides of the bomber. These two positions - left and right - were later staggered to compensate for each gunners firing arc. Unlike other turreted positions in the B-24, spent shell casings at these waist positions were not jettisoned from the aircraft automatically, forcing crewmembers to clear their areas themselves. Since firing from these side-perspective positions required a great deal of hand-to-eye coordination via tracer rounds while taking into account target speed and the Liberator's airspeed itself, waist gunners relied on simple targeting sights in the early years. Only later did they receive assistance in the form of compensating sights to help improve accuracy.
The tail gunner was given perhaps the most important defensive position aboard the Liberator, manning a powered 2 x 12.7mm machine gun turret. Afforded a spectacular view, the tail gunner was charged with defense of the aircraft's "six", a position most often to encounter trailing enemy fighters eager for the easy kill. One point of note here is that if the Liberator were traveling through a rain of flak bursts, the tail gunner would most often times be the safest position aboard the aircraft, with the aircraft already having flown through the exploding shell burst. It was not unheard of for aircrews to bring aboard their own personal forms of protection (plates of steel for instance) against such flak dangers.
The combat box utilized the strengths of individual Liberator firepower and crews. Gunnery crews could work together and bring to bear the power of multiple machine guns against crossing enemy fighters. Though sound in theory, the heat of battle made for something more. Coordinated gunnery was not always possible - especially between bomber crews - but communications within individual bombers were ultimately important.
The final production appearance of the Liberator fell well in line with the original Consolidated design. The wings were held high on the fuselage sides and mounted forward of the fuselage enter. The forward fuselage was stepped with a good amount of glazing while the profile of the fuselage sported broad area sides. The wings were of a long span with engines an equal distance apart. The empennage formed into the characteristic double vertical wing arrangement with rounded vertical fins. As this was America's first tricycle-equipped undercarriage bomber, the aircraft sported a nose wheel just aft of the nose cabin area and forward and under the flight deck floor. Main landing gears were situated outboard of the inner engines and sported large donut-type wheels each. Interestingly, the undercarriage system as a whole was positioned forward of the fuselage center, showcasing all its weight in the forward portions of the aircraft. While on the ground, the Liberator sported a distinctly low sitting profile which played well into the belly turret having the ability to be retracted during such actions. The bomb bay was positioned in the center of the design and divided into two compartments. The first compartment began aft of the cockpit flight deck with the second compartment ending just forward of the belly turret position.
While the B-17 Flying Fortress made heavy use of electrics, the B-24 utilized a great deal of hydraulics with such systems spanning nearly every internal inch of the aircraft. Fuel on the B-24 was situated in the wings, just inboard of the inboard set of engines as well as in the upper portion of the bomb bay. As such, any direct hit could easily set the entire aircraft on fire in seconds. This tendency was oft-remembered by many-a-Liberator-aircrew as a major drawback of the series. In contrast to the B-17 and her inherent dogged ruggedness to absorb similar punishment, the Liberator fell short in this area.