In 1943 (with the American involvement in World War 2 in full swing), a design study was completed by engineers of North American Aviation for a heavy-class bomber aircraft for U.S. Material Command. This resulted in the NA-116 proposal which came about at a time when development of the Boeing B-29 "Superfortress" heavy bomber was moving towards flight-testing and eventual service entry (to come in May of 1944). The NA-116 failed to provide any benefit over what the B-29 was already giving to the USAAF so the design fell to aviation history.
The proposed aircraft was a large specimen incorporating a twin-boom configuration, a rarity for an oversized bomber type. To this was added a four-engine arrangement (although a twin-engined form was also entertained), each engine installation driving counter-rotating three-bladed propeller units. A large mainplane was affixed at shoulder height and ran over a centralized fuselage nacelle structure. The twin booms extended beyond the trailing edge of each wing mainplane and terminated at individual rudders, these joined by a high-mounted, shared horizontal plane. To this was added a rather modern, retractable tricycle undercarriage, each leg carrying a dual-wheel configuration.
Inside, there was to be a crew of twelve made up of two pilots, a navigator (also doubling as the bombardier), a radio operator (doubling as a machine gunner) and no fewer than eight dedicated machine gunners spread about the internals of the aircraft.
The proposed defensive armament scheme involved a nose turret, dorsal turret, and rear turret at the end of the fuselage nacelle. Additionally, there were to be dorsal turrets at the midway run of each tail boom as well as at the end of each tail boom. The nose gunner would manage up to 4 x 0.50 caliber heavy machine guns while the dorsal turret had 2 x 0.50 cal HMGs installed side-by-side. Each dorsal boom turret was outfitted with 2 x 0.50 caliber HMGs as well. 2 x 20mm autocannons would be positioned at the end of the fuselage in a trainable mounting. The tail boom gun positions would each sport 2 x 20mm autocannons. All told, this equaled 10 x 0.50 caliber HMGs (though as many as 14 may have been carried before the end) and 6 x 20mm autocannons.
Beyond the standard armament was an internal bomb load of up to 34,000lb of drop stores. The bomb bays were integrated ventrally into the fuselage nacelle as well as each tail boom.
As drawn up, the bomber was to have a running length of 85.8 feet with a wing span of 154 feet. Gross weight would have reached between 80,000lb and 132,000lb. The estimated range of the aircraft was 5,000 miles on a full war load and fully-fueled.
For power, the bomber would have carried four of the experimental Pratt & Whitney PW XR-4360-SSG21-5 engines of 3,450 horsepower, these used to drive the counter-rotating propeller blades at each engine nacelle.