The remaining bombers were redeployed to Australia. They subsequently participated in the defense of Java, flying thence from their Australian bases with a refueling stop at New Guinea. This operation also proved to be a failure.
In the face of a dire shortage of materials, Boeing delivered its new B-17E model half a year behind schedule. In contrast to its predecessors, the B-17E had a front stabilizer and more powerful self-defense weapons, including a tail turret. It was fielded only in the spring of 1942, in time to take part in the Battle of the Coral Sea. The aircraft spotted by Japanese ships sailing to Port Moresby were a squadron of B-17Es.
In the summer of 1942, the British took delivery of 45 B-17E bombers under the name “Fortress IIA,” and in June of the same year, the U.S. Army started to accept deliveries of a new Fortress version - the B-17F - which became the first mass-produced model of the bomber. Externally, the B-17F resembled its immediate its predecessor - the B-17E. However, the new aircraft featured more than 400 design changes, most of them intended to improve and upgrade armor plating, powerplants, fuel tanks and other equipment. The aircraft could carry larger bomb loads and to greater distances; in addition, it was much more durable. Nonetheless, from January 1943, Fortresses almost completely disappeared from the Pacific, where only a few B-17Fs remained in the 5th Bomber Group. On January 27, 1943, American Consolidated B-24 Liberator and B-17 bombers carried out their first massive attack against Germany. Losses of unescorted bombers were catastrophic, reaching as high as 20 % in a single mission. The myth of Flying Fortress invincibility was thus put to rest. Even though the Fortress was superior to its competitors, the average life of a B-17 bomber at that time was only 21 combat missions. In the Pacific, on the other hand, where air battles were fought primarily at middle altitudes, there was less demand for the high-altitude capacities of the Fortress, so the bomber could be safely replaced by a less capable B-24.
It was for the European war theater, with its heavy air defenses and high-performance German fighters like the FW.190 and jet-powered the Me.262 fighters, that Boeing created the most abundant and most battle-worthy version of its bomber - the B-17G. The aircraft was armed with three nose turrets – called the "beard" and "cheeks" – and had a production run of 8680 units, more than any other model. Production started in the autumn of 1943. The aircraft was made on the basis of the XB-40 air cruiser, which had been designed specifically for bomber protection. The air cruiser was, in fact, a four-engine heavy escort fighter that had evolved from the B-17! Manufactured by Lockheed-Vega, the XB-40 fighter made its first flight on November 10, 1942. Its combat effectiveness, however, was quite low owing to lack of engine power, but the designers’ experience of work on self-defense weaponry in the course of the G series project proved helpful.
«Lockheed-Vega» XB-38 «Flying Fortress» - long-range heavy bomber made on the basis of B-17E and powered by in-line «Allison» V-1710-89 engines.
Air cruiser «Lockheed-Vega» XB-40 «Flying Fortress» - an escort fighter also made on the basis of B-17E.
Hybrid «Consolidated» XB-41 – another failed attempt to make an escort fighter on the basis of a strategic bomber.
Lockheed-Vega also developed the prototype of a heavy long-range XB-38 bomber based on the B-17E. It flew for the first time on May 19, 1943. The aircraft was powered by liquid-cooled 1425 hp Allison V-1710-89 engines as a means of contending with shortages of the Cyclones. Performance improvement had been only marginal, and because the engine was required in large numbers for the production of fighter planes, it was decided not to start production of the B-38. There also was an attempt to build a fighter plane on the basis of the B-24 Consolidated. The XB-41 prototype was completed at the end of 1942. It was the longest-range American fighter and was armed with as many as 14 (!) 12.7 mm machine guns. However, in the wake of poor test results, the program never went passed beyond construction of the first prototype.
«Boeing» B-17F on a bombing mission over Europe.
The last G model of Boeing B-17. This version was manufactured in largest numbers. For the most part is was used in Europe.
B-17G bombers were not used in the Pacific. They were replaced in that region by another type of heavy bomber. In 1938, representatives of U.S. Air Corps visited the headquarters of Consolidated in San-Diego and proposed to start production of the B-17 at that company's plants. However, after studying the design documentation for the «Fortress», the management presented an alternative design, one that promised better flight performance, longer range, a higher bomb load and, most important, lower cost. The optimistic proposal was based on a new wing design, recently developed by a team of company engineers led by David Davis. Until then, Consolidated had been for the most part a manufacturer of flying boats. Looking to the huge success of one of its PBY Catalina flying boats, the company management was fairly confident that the military would agree. Another flying boat, the Model 31 featuring a Davis wing, served as the baseline model for the proposed bomber. On February 21, 1939, a contract was concluded for the construction of an experimental Model 32 aircraft, later designated “XB-24,” and nine months later on December 29, 1939, the prototype made its first flight. Such a tight schedule was unheard of for the United States, especially since Ruben Fleet and Isaac Luddon, the company’s designers, were simultaneously working on 7 pre-production YB-24s, making export versions of LB-30A, preparing for the production of the B-24A, and developing a C-87 transport based on the prototype bomber.
«Consolidated» model 31- the first flying boat featuring the extended Davis wing. It became a baseline model for the XB-24.
The prototype of «Consolidated» XB-24.
Flight tests at the Wright Field air base were fairly successful - the XB-24's range eclipsed by 320 km that of the production B-17C, and with external tanks its distance advantage increased to 960-km, despite a heavier bombload. High-altitude speed, however, was somewhat slower than that of the Fortress, although it flew faster at low and middle altitudes. Operational ceiling was also much lower. The military was very pleased with the tricycle landing gear - it had a number of advantages at takeoff and landing, and it significantly reduced the likelihood of runway accidents.
Production of the Liberator started up in August 1939, with 120 bombers ordered by France. These aircraft were, in fact, a modernized version of the pre-production YB-24. XB-24 bombers were also supplied to Britain as an LB-30A bomber, and it was the British who christened the aircraft “Liberator I.” The company had made only 20 B-24A bombers when France was defeated, and the aircraft were offered to the British instead as LB-30Bs, which the British named “Liberator II.” These bombers became the first “Liberators” to see combat. For the most part, the British used them as maritime patrol/antisubmarine aircraft. The United States Air Force acquired only nine B-24A's in the summer of 1941, and these were used primarily in support roles. Britain, on the other hand, received 140 more Liberator II bombers out of a total 167 ordered.
The poor altitude and speed performance recorded by the XB-24 in the Wright Field test flights prompted Consolidated to improve its engines. The prototype was reengined with a new 1200 hp Pratt & Whitney R-1830-41 powerplant equipped with General Electric's B-2 turbocharges in place of the old two-stage supercharges. As a result, in its first test flight on February 1,1941, the new XB-24B reached a maximum speed of 496 km/hr at 6100 meters. In the wake of that performance, an intermediate B-24C bomber version based on XB-24B was launched into production. In all, 40 aircraft of this model were made. The sole purpose of that production run was to prepare production facilities for the next B-24D series. B-24C bombers were supplied to Flight Squadrons as trainer aircraft with notional combat capabilities.
It was only at the beginning of 1942, that the United States started up large-scale production of the Liberator. At the beginning of 1941, the United States government provided funds for Consolidated to build a new aircraft production plant in Texas. Later, Douglas, Ford and North American were also asked to participate in the production of the B-24. Depending on where they were made, the aircraft were variously designated as “B-24D,” “B-24E,” or “B-24G.” However, there was absolutely no difference between the three models. Production rose sharply when mass production guru Henry Ford put his hand to the task. By the beginning of 1944, a new B-24 rolled off a conveyor belt at the Ford Motors assembly plant at Willow Run every 63 minutes. However, such dispersed production gave rise to problems. As the different producers were not overly concerned with standardization, components made at different plants were not interchangeable. The five manufacturers were finally able to resolve these problems by the time the new B-24J model was introduced.
«Consolidated» B-24D – the first mass-produced high-performance model of «Liberator».
«Consolidated» B-24J - it was made in largest numbers.
Instrument panel of «Consolidated» B-24J bomber.(enlarge)
Operational flight squadrons started to receive B-24Ds in July 1942, and on the very first combat missions it became clear that the bomber lacked adequate self-defense weapons. Enemy fighters quickly discovered all the aircraft’s weaknesses: vulnerability to frontal attack, slow rate of turn, and large "blind" areas of self-protection machine guns, especially those in the front. Various field improvements were not producing the desired effect until engineers got a bright idea and installed the tail turret of the Consolidated A-6 at the front of the B-24. In all, 3100 machines of this improved version of the Liberator, designated B-24H, were made. Standardization issues, however, were growing worse. Some of the H series bombers were strikingly unlike each other. To contend with these problems, from the spring of 1944 all production plants switched to the B-24J model - the aircraft produced in largest numbers, 6678 machines in all. The nose of this bomber sported an electrically powered Emerson Electric A-15 gun turret. The J series remained in production until December 1944. In all, 18,188 B-24s were made – a world record for a four-engine aircraft! Even the more pilot-favored B-17 could not boast such massive numbers. The key to Consolidated’s success was its ability to organize large-scale production while keeping process costs and unit costs at a minimum and thus allowing for a low selling price.
The B-24 and the B-17 are often compared with each other. There is nothing unusual in that - aircraft of the same class and function, designed by competing firms will always be compared. However, such an approach is only correct to a degree. First of all, the B-17 and B-24 were used for the most part in completely different war theaters. That is why the percentage of lost aircraft from their total number (for B-17 the figure is 15% and for B-24 – 13%) cannot be used as a measure of their success. The B-17s were mainly used in Europe with its relatively small territory and powerful air defenses. The most important aircraft qualities in these conditions were not bomb load and range but survivability, self defense and flight performance. The B-24 was better adapted to the conditions in the Pacific where air defenses were spread thinly over a huge territory and therefore much less deadly than in Europe. In addition, Asian air defenses were far less advanced than their European counterparts. On the other hand, the bombers had to traverse huge distances. All these differences help to explain why from the beginning of 1943 nearly all Fortresses were reassigned to Europe, while conversely, B-24s, starting from the middle of 1944, were, pulled out from there.
