Martin NBS-1 - Design and Development

Design and Development

The NBS-1 was a wood-and-canvas biplane without staggered wings, employing twin rudders on a twin vertical tail. Its two Liberty 12-A engines sat in nacelles on the lower wing, flanking the fuselage. Ordered under the company designation MB-2 in June 1920, the NBS-1 was an improved larger version of the Martin MB-1 bomber built by the Glenn L. Martin Company in 1918, also known as the GMB or Glenn Martin Bomber. The first flight of the MB-2 took place 3 September 1920.

In addition to more powerful engines, larger wings and fuselage, and simplified landing gear, the NBS-1 also had a unique folding-wings system, hinged outside the engine nacelles to fold backwards for storage in small hangars. Unlike the MB-1, whose engines were mounted between the wings in a fashion similar to the German Staaken R.VI R-bomber, the engines of the NBS-1 were fixed to the lower wing over the landing gear.

The MB-2 was designed as a night bomber and except for a greater load capacity, had reduced performance characteristics compared to its MB-1 predecessor. The first 20 (five MB-2 and 15 NBS-1) were ordered from the Martin Company, which recommended a further 50 be produced to help its struggling financial condition. However the design was owned by the U.S. Army and subsequent contracts for 110 bombers were awarded by low bid to three other companies: Lowe Willard and Fowler Engineering Company of College Point, New York (35 ordered), Curtiss Aircraft (50), and Aeromarine Plane and Motor Company of Keyport, New Jersey (25).

The engines of the last 20 bombers of the Curtiss order came equipped with turbosuperchargers manufactured by General Electric, the first such modification made in production quantity. Although enabling the NBS-1 to reach an altitude of over 25,000 ft (7,650 m), the turbosuperchargers were mechanically unreliable and not used operationally.

The bomber was equipped defensively with five .30 in (7.62 mm) Lewis Guns, mounted in pairs in positions in the nose and upper rear fuselage, and singly in a bottom mount firing behind and beneath the rear fuselage.

The first two Martin MB-2s, Air Service s/n AS64195 and AS64196, were retained at McCook Field in Dayton, Ohio, for R&D flight testing, marked with project numbers P162 and P227 respectively, as was the second NBS-1 (AS64201), marked as P222. Four Curtiss NBS-1s were also assigned to McCook.