Lockheed XB-30 (Model L-249) Four-Engined Heavy Bomber Aircraft Proposal
The Lockheed XB-30 Heavy Bomber proposal existed only as a design study heading into World War 2 - the aircraft based on the L-049 Constellation airframe.
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Before the Boeing B-29 "Superfortress" made its introduction in 1944 and forever changed the direction of the war in the Pacific, there were competing design submissions put forth by players in Consolidated, Douglas, and Lockheed. All were drawn up to fulfill a new U.S. Army heavy bomber requirement intended to provide the air service arm with a capable high-flying platform of considerable range. Consolidated delivered its B-32 "Dominator", which was introduced in January of 1945 and 118 examples were procured, while the Douglas XB-31 and Lockheed XB-30 managed only design studies before attention wholly settled on Boeing's entry.
Origins of the Lockheed XB-30 lay in the latter half of the 1930s when another World War in Europe (or a direct conflict with Japan in the Pacific) seemed a very likely possibility. This pressed Army authorities to pursue a new generation of bombers capable of excellent range while carrying a useful war load and flying higher than designs before it. Technological developments and political events in Europe influenced a committee arranged by General "Hap" Arnold and their recommendation was to pursue a new heavy-class aircraft. The arrival of World War 2 in September of 1939 added to the urgency and design studies were ordered by the Army.
The heavy bomber categorization dictated some of the inherent design of the aircraft during this period - a multi-person crew would be required to manage the onboard systems and stations, an aircraft of considerable dimension was needed to contain crew spaces, fuel tank, and bombs, and a four-engined configuration was required to ensure the bomber held the needed power and range to travel as far and as high as needed. The Army sought a bomber with a range of at least 5,000 miles.
Lockheed's entry was based on their L-049 "Constellation" ("Connie") transport (detailed elsewhere on this site) which was under development at the time. A first-flight of this aircraft occurred in January of 1943 and 88 were eventually built -fourteen inducted into the U.S. military (as the "C-69") and seventy-four constructed for commercial passenger service. This design origin meant that the Lockheed study - designated "XB-30" with the company model designator of "L-249" - carried the same general shape and configuration as the Model L-049. The bomber form therefore had the same tubular, somewhat deep fuselage, mid-set wing mainplanes, and triple-rudder tail unit. Each wing mainplane carried two engine nacelles. The flight deck was held forward in the design overlooking the nose and various crew positions were set about the fuselage, some arranged with defensive armament to protect the aircraft. It was estimated that the L-249 would require a crew of ten for optimal operation. A tricycle undercarriage gave the L-249 a most modern appearance - another quality carried over from the Constellation.
Dimensionally, engineers drew up an aircraft with a wing span of 123 feet, a length of 104.7 feet and a height of 23.8 feet. Empty weight was 51,616lb against an estimated Maximum Take-Off Weight (MTOW) of around 86,000lb. For propulsion, the Wright R-3350-13 series radial was selected, each unit outputting 2,200 horsepower. The engines were held in nacelles along the wing leading edges, two engines to a wing, and driving three-bladed propellers. The engine also went on to power the Boeing B-29, was standard in the Lockheed Constellation series, and eventually used in the Douglas A-1 "Skyraider" attacker (of Vietnam War fame) seen in the post-war years.
Since the bomber would become a target for enemy interceptors it was to carry its own defensive armament. A 20mm cannon along with four 0.50 caliber heavy machine guns, would be fitted to a remotely-controlled tail turret to protect the aircraft's vulnerable "six" position. Two dorsal turrets were also envisioned, each armed with four 0.50 caliber heavy machine guns - providing all-around security. Another two-to-four-gunned turret was to be set ventrally. There would also be remote-controlled side-mounted turrets along the forward sides of the fuselage. Internally, the bomb load ranged up to 16,000 lb of conventional drop ordnance.
Lockheed engineers were able to conduct some testing on components related to the XB-30 design during 1940. Some performance estimates were detailed for the Lockheed submission - a maximum speed of 382 miles per hour, an operational range out to 5,333 miles, and a service ceiling up to 17,832 feet (requiring pressurization of the crew sections).
The progress already seen by Army authorities in the Boeing B-29 submission worked against the L-249 project which was still attempting to get its feet underneath it. Lockheed managed a scale model of their aircraft but its proposal was not selected for further development and promptly fell to aviation history. Similarly the Douglas XB-31 only managed to reach the design stage and was left out of further Army plans. Thus the path for the Boeing B-29 to shine in the Grand War was laid.