In 1943, aware of Nazi Germany's advances in the field of jet propulsion, the Army Air Forces (AAF) asked the General Electric Company to devise a more powerful engine than its prospective axial turboprop. This was a tall order, but it eventually brought about the production of the J35 and J47 turbojets. In 1944, 1 year after the jet engine requirements were established, the War Department requested the aircraft industry to submit proposals for various jet bombers, with gross weights ranging from 80,000 to more than 200,000 pounds. This was another challenge, and only 4 contractors answered the call.
Pressed for time, the AAF in 1946 decided to skip the usual contractor competition, review the designs, and choose among the proposed aircraft that could be obtained first. The multi jet engine B-45, larger and more conventional than its immediate competitor, won the round, with the understanding that if a less readily available bomber was to prove superior enough to supplant it (which the Boeing XB-47 did), that aircraft would also be purchased.
Testing of the XB-45 prompted pre-production changes. North American Aviation, Incorporated, redesigned the nose panel, increased the aircraft's stabilizer area, and lengthened the tailplane by nearly 7 feet. In August 1948, 22 of the 90 B-45s, ordered less than 2 years before, reached the newly independent Air Force. However, the B-45's increased weight, excessive takeoff distance, and numerous structural and mechanical defects generated scant enthusiasm.
With a first-flight date of March 17, 1947, the North American B-45 Tornado was the first jet-powered bomber to be put into production in the United States and the first to enter operational service with the USAF. The more capable B-45C model differed from earlier models of the B-45 in several respects; the most obvious difference in the appearance of the C model was the 1200-gallon fuel tank mounted at each wingtip.
Meanwhile, the B-47's future production had become certain, and in mid 1948 the Air Staff actually began to question the B-45's intrinsic value as well as its potential use. Soon afterwards, as President Truman's budgetary axe slashed Air Force expenditures, the programmed production of B-45s was reduced to a grand total of 142, a decrease of 51 aircraft.
Although continuously plagued by engine problems, component malfunctions, lack of spare parts, and numerous minor flaws, the B-45 regained importance. Like all bombers produced after the end of World War 11, the B-45 was designed to carry both conventional and atomic bombs. In mid 1950, when US. military commitments to the Korean War reemphasized the vulnerability of the North Atlantic Treaty Organization forces in Europe to Soviet attack, the Air Force made an important decision. Since the US. planned to produce large quantities of small atomic and thermonuclear weapons in the near future, the use of such weapons, heretofore a prerogative of the strategic forces, would be expanded to the tactical forces, particularly in Europe.
The program that ensued, under the code name of Backbreaker, entailed difficult aircraft modifications because several distinct atomic bomb types were involved and large amounts of new electronics support equipment had to be fitted in place of the standard components. In addition, the 40 B-45s allocated to the Backbreaker program also had to be equipped with a new defensive system and extra fuel tanks. Despite the magnitude of the modification project, plus recurring engine problems, atomic capable B-45s began reaching the United Kingdom in May 1952, and deployment of the 40 aircraft was completed in mid June, barely 30 days behind the Air Staff deadline.
The configuration of the B-45 is reminiscent of a World War II bomber equipped with jet engines instead of propellers driven by reciprocating power plants. The unswept wing had an average airfoil thickness ratio of about 14 percent and was equipped with trailing-edge single-slotted flaps for lift augmentation in landing and takeoff. Lateral control was accomplished with the use of conventional ailerons.
All control surfaces were hydraulically boosted, and an electrically actuated tab on the elevator was used to maintain longitudinal trim. The aerodynamic power of the trim-tab-elevator combination was so great that, in the event of an inadvertent maximum tab deflection, the pilot's strength was insufficient to overcome the resulting large elevator hinge moments if the hydraulic boost system failed or was turned off. Total in-flight destruction of at least one B-45, the aircraft operated by NACA, was probably caused by this combination of circumstances that resulted in a normal load factor far greater than the design value. The technology of power-assisted controls was in its infancy at the time of development of the B-45, and much was yet to be learned about the effective and safe application of such control techniques.
In performing the landing maneuver, pilots found that speed and flight-path angle during the approach as well as touchdown point on the runway were difficult to control with precision because of the absence of speed brakes or some other means of increasing the drag of the aircraft. As a result of the low drag, only a small amount of engine thrust was required in the approach configuration. In this low thrust range, changes in thrust with throttle movement required a relatively long period of time and rendered control of flight path and speed difficult. At higher thrust levels, changes in thrust with time were more rapid. Hence, higher aircraft drag and consequently higher required thrust would have been desirable in the approach and landing configurations. Somewhat similar problems with speed control were experienced with the Messerschmitt Me 262, the first jet fighter to enter operational service. Again, experience taught important lessons applicable to the design of later jet-powered bomber aircraft.
Manned by a crew of four, the B-45 had two pilots seated in tandem under a transparent canopy, a bombardier located in the nose, and a tail gunner. Only the pilots were equipped with ejection seats. In an emergency, the bombardier, located in the nose of the aircraft, was expected to evacuate through a hatch located in the side of the fuselage. To minimize the hazards associated with the high-velocity airstream, a fuselage flap was deployed ahead of the hatch to deflect the airstream away from the exiting bombardier. An escape hatch with deflector flaps was also provided for the tail gunner. Environmental control for the crew included pressurization, heating, and cooling.
With a gross weight of 110, 050 pounds, the B-45 was in the same weight class as the wartime Boeing B-29 but had a maximum speed advantage over the B-29 of more than 200 miles per hour. A 10 000-pound weapon load could be delivered by the B-45 at a mission radius of 1008 miles. Ferry range of the aircraft was 2426 miles. The maximum lift-drag ratio of the B-45 was 16.3, about the same as that of the B-29, and its zero-lift drag coefficient was a much lower 0.0160 as compared with 0.0241 for the earlier aircraft.
The Tornado first entered service with the Strategic Air Command in November 1948, and final retirement of the type from operational service took place in 1958. The Air Force accepted a total of 142 B-45s in various configurations, 51 aircraft fewer than originally ordered. The B-45 program included 3 experimental XB-45s aircraft (one of which was completed as a preproduction example), 96 production B-45As (some of which were designated as B-45A-5s reflecting in-production improvements), 10 B-45Cs , and 33 RB-45Cs. The aircraft were produced by North American Aviation, Incorporated, of Inglewood, California, with most of the aircraft being built in a former Douglas facility at Long Beach, California.
The B-45 served well as a reconnaissance aircraft during the Korean war. The reconnaissance models were designated RB-45Cs and assigned to the Strategic Air Command. The Tornado performed classified, deep penetration photographic intelligence missions over many cold war communist countries. The reconnaissance version of the B-45 became the forerunner of the U-2 and SR-71 surveillance aircraft.
All told, and in spite of its many valuable secondary functions, the B-45 did not achieve great glory. The entire contingent, Backbreaker and reconnaissance models included, was phased out by 1959. Yet, the B-45 retained a place in aviation history as the Air Force's first jet bomber and as the first atomic carrier of the tactical forces.
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