The bomber was drawn up with a war load up to 4,000lb, this to be carried mostly internally in a bomb bay section at the belly of the aircraft (also, in keeping with other similar designs of the period, externally-held munitions could / should not be ruled out). Standard armament was to include 3 x 0.30 caliber Browning M1919 air-cooled (medium) machine guns and 1 x 0.50 caliber Browning M2 air-cooled (heavy) machine gun for point self-defense. One 0.30 caliber weapon was to be focused at the nose with another in a rear-facing dorsal position and the final gun found at a rear-facing ventral position. The remaining 0.50 caliber was to be installed at the extreme end of the fuselage to help cover the most vulnerable area of the bomber.
Power for the twin-engined bomber centered on 2 x Pratt & Whitney R-2800-9 "Double Wasp" air-cooled, turbo-supercharged radial piston engines, each delivering 2,000 horsepower and driving four-bladed propeller units. These engines, first run in 1937, became the centerpiece of many-a-classic design of the World War 2 period: the Grumman F6F "Hellcat" naval fighter, the Republic P-47 "Thunderbolt" USAAF fighter, and the Vought F4U "Corsair" naval fighter to name a few.
Estimated performance specs included a maximum speed between 280 and 375 miles-per-hour (sources vary), an operational range out to 2,900 miles, and a service ceiling up to 33,500 feet.
The bomber was being developed around a USAAC specification (Specification XC-214) originating in August of 1939 - just weeks before World War 2 arrived in Europe (September 1st with the German invasion of Poland). Martin was in direct competition with North American (makers of the famous B-25 "Mitchell" medium twin-engined medium bomber) for the requirement but, in any event, neither design proved an outright success. The North American NA-63 was actually ordered and flown as a prototype through the "XB-28" (detailed elsewhere on this site) but the Martin Model 182 was only advanced on paper as the "XB-27" - becoming nothing more than a relatively advanced design study.
The requirement was eventually fulfilled by a collection of other in-service aircraft that could more than meet the demand of different mission types. The changing requirements of war, namely air superiority for the Allies in the march to Rome, Berlin and Tokyo, also played a role in the demise of such aircraft projects.
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