McDonnell’s answer to R-40C was the Model 1 (its first design) officially proposed on April 11, 1940. Four Model 1 variations were submitted that differed only by engine type. While the Model 1 design appeared fairly conventional, it was possibly the most radical of the designs submitted. The Model 1’s shape was a direct evolution of concepts James McDonnell was working on during his last days with the Martin Company.
The Model 1 featured unprecedented streamlining and incorporated airfoil-shaped fillets where the wing and fuselage joined. The proposed engines were the 24-cylinder Allison V-3420-B2, 24-cylinder Pratt & Whitney H-3130, 24-cylinder Pratt & Whitney X-1800-A2G, and 42-cylinder Wright R-2160 Tornado; all were liquid-cooled. Regardless of the type selected, the engine was buried in the fuselage aft of the pilot. Engine power was transmitted via extension shafts and right angle gear drives to a pair of two-speed, four-blade, pusher propellers mounted on the wings. The aircraft featured gear-driven radiator cooling fans. Originally the aircraft was to be armed with two .30-cal. machine guns and two 20 mm cannons, but armament varied throughout the design process. However, armament always consisted of a combination of two to four machine guns and one to four cannons.
Allison V-3420-powered McDonnell Model 1 cutaway dated April 3, 1940. Armament now includes six guns: two machine guns in the fuselage sides, two more (or 20 mm cannons) toward the nose, and two 20 mm cannons in the nose.
The X-1800 and R-2160-powered designs did not meet the specifications of XC-622 and were dropped from the R-40C competition. With a two-stage supercharger for the V-3420 engine and a two-stage, two-speed supercharger for the H-3130, both engines provided sufficient power for their respective Model 1 designs to achieve the XC-622 specifications.
It would take an estimated 42 months to develop the engine and power drives for the Model 1. In addition, the Model 1 was the heaviest aircraft in the competition. These and other factors resulted in the two remaining Model 1 proposals to be ranked 21st and 22nd out of 26 submissions. Even so, the Model 1 did interest the Air Corps enough for them to purchase engineering data and a wind tunnel model on June 6, 1940 for $3,000. This was the McDonnell Aircraft Corporation’s first sale to the Army Air Corps.
The new engines involved with the R-40C competition became known as the “hyper” engines, an abbreviation of high-performance. The aircraft that won the competition were the Vultee XP-54 Swoose Goose, Curtiss XP-55 Ascender, and Northrop XP-56 Black Bullet. All were built and were pusher designs that failed to meet expectations and were fraught with technical difficulties. None of the hyper engines or R-40C aircraft entered production. The Model 1 evolved into the McDonnell XP-67 Moonbat that, although not successful, was built and did fly.
