Witteman-Lewis XNBL-1 - Design and Development

Design and Development

Development of the XNBL-1 (Experimental Night Bomber, Long Range) Barling Bomber is generally attributed to Gen. William "Billy" Mitchell, who in 1919 discovered Walter H. Barling, who had previously worked for the Royal Aircraft Factory. Mitchell asked Barling to design a bomber capable of carrying enough bombs to sink a battleship. Mitchell's goal was to demonstrate the effectiveness of airpower by sinking a battleship from the air, and needed a large, strategic bomber in order to accomplish this feat. Mitchell projected the cost of two prototype bombers at $375,000. On 15 May 1920, the Army Engineering Division sought bids for the construction of a bomber based on Barling's sketches, with the requirement that it be capable of carrying a 5,000 lb (2,300 kg) bomb load, to an altitude of 10,000 ft (3,000 m) at a speed of no less than 100 mph (160 km/h).

Barling had previously designed the Tarrant Tabor, which was similar in concept but was destroyed in a fatal nose-over crash on its first flight in 1919. The nose-over had probably been caused by the high placement of two of the engines. Like the Tabor, the Barling Bomber was a large six-engined triplane with a cigar-shaped fuselage. Unlike its predecessor, the Barling had all of its engines mounted level with the fuselage. The aircraft used three wings, but was not actually a triplane. More correctly, it was a two-and-a-half wing aircraft. The middle wing had no control surfaces, and was shorter and narrower than the two primary wings. The top and bottom wings had a chord of 13 ft 6 in (4.11 m), and each had a surface area of about 2,000 sq ft (190 m2). The stabilizer and elevator surfaces were 575 sq ft (53.4 m2) with an 8 ft (2.4 m) chord. The fins and rudders looked like a box kite, and had a surface area of 250 sq ft (23 m2). The undercarriage consisted of 10 wheels, including two wheels mounted towards the front of the aircraft (to prevent a nose-over on takeoff) and a tail skid.

The Engineering Division was forced to use Liberty engines because of an abundant supply of the engines. To power the Barling, four 420 hp Liberty engines were mounted between the lower and middle wings in a tractor arrangement, and an additional two in a pusher position. The gross weight of the bomber was 42,569 lbs. It had a fuel capacity of 2,000 gallons, and carried 181 gallons of oil.

Two pilots set in separate cockpits either side of the fuselage, while a bombardier sat in the nose. One or two flight engineers sat behind the cockpits to help tend the engines, a first for any aircraft. A radio operator and a navigator were seated next to them.

The Barling was armed with seven .30-caliber Lewis machine guns, which were operated from five stations. The gun stations gave the gunners a field of fire that covered practically the whole area around the bomber. Bomb racks were mounted in an enclosed bomb bay beneath the gasoline tanks. The bomb bay could accommodate any bomb in the air service inventory, including the 2,000- and 4,000-lb bombs that had been designed specifically to sink a battleship. The Barling incorporated bomb bay doors on the bottom of the fuselage, one of the first aircraft to feature such an innovation.