Multi Engine Bombers
NBL-1, NBS-3, NBS-4, & Keystones
Page 4
After a June 1921 crash, the aircraft went back to the factory and reappeared at Mitchel Field in September 1922 with a nacelle equipped for bombing, a new nose radiator, the pilot’s cockpit ahead of the wings, and a rear gunner’s cockpit with twin Lewis guns on the ring and a third firing downward. Fuel for ten hours was contained in the outer booms, and a 2,000-pound bomb might be carried between the wheels.
The flight data given here was evidently an estimate, not actually achieved in tests, for the Owl did not hold Army interest and was scrapped. LWF proposed a twin-engine metal bomber called the XNBS-2, but the company went out of business in April 1923 before it could be built.
The largest aircraft of that generation was designed for the Engineering Division by Walter H. Barling (1890-1965) in response to General Mitchell’s desire for an Army equal of the six-engine German Giant bombers. Designated NBL-l (Night Bombardment Long-distance), the Barling plans were dated May 15, 1920, and a contract for two was made June 23, with Witteman-Lewis in Teterboro, New Jersey, the company that made the lowest bid for the work.
Since the aircraft had to be built in sections and shipped in crates for assembly at Dayton’s Wilbur Wright Field, components had to be framed with the dimensions of railroad tunnels in mind. The parts arrived in Dayton on July 22, 1922, but final assembly had to await construction of a hangar big enough to shelter the giant. The second prototype had been canceled on January 31, 1922, but cost increased to $525,000 for one airplane, instead of the $375,000 estimated for two!
Lt. Harold R. Harris made the NBL-l’s first flight on August 22, 1923. Three wings, four rudders, six engines, and ten landing wheels gave this behemoth a configuration more likely to antagonize the air than to pass through it. Four 420-hp Liberty 12A engines were arranged as tractors, two as pushers. Seven .30-caliber Lewis guns guarded a crew of ten in the spruce barrel fuselage, including two pilots, engineer, bombardier, navigator, radio operator, and four gunners. Up to 2,000 gallons of gasoline made a six-ton load, or half of that fuel could be replaced by 5,000 pounds of bombs. A record flight was made to 6,722 feet with a 4,400-pound load, but this modest altitude capability prevented flight over the mountains to either coast.
Although Mitchell said the Barling “was entirely successful from an experimental standpoint,” it was elsewhere described as “Mitchell’s Folly”, and an Air Force history admits it had “disappointing speed, load, and endurance,” with a range of 170 miles with load divided between fuel and bombs, and 335 miles with fuel only.
Mitchell also wanted to go ahead with the Martin NBL-2, a less-complicated biplane with two 700-hp, 18-cylinder, W-1A Engineering Division engines on the 98-foot lower wing’s leading edge, and a contract for two prototypes was signed on June 17, 1922. Glenn L. Martin had planned the NBL-2, after the Ostfriesland test, as a battleship buster. Essentially an enlarged NBS-1 with four main wheels and four rudders instead of two each, it had four times the bomb load, but only the same four crewmen were needed.
Armament included five Lewis guns and a bomb bay for six 600 or four 1,100-pound bombs, or four 2,000 or even two 4,000-pound bombs could be carried underneath the fuselage. This project was canceled, probably because funds had been used up on the Barling triplane which itself was scrapped in June 1928. Nothing like its size was to be seen in the U.S. bombers until 1937.
After an April 1922 design competition, traditional bomber patterns reappeared in the Elias NBS-3 and Curtiss NBS-4 ordered June 17, 1922; four-place biplanes with box-like biplane tails, and five .30-caliber guns in the usual nose, rear, and tunnel positions. Powered by two Libertys, they had a welded steel tube, instead of wood, fuselage framework. Tested in August 1924, the XNBS-3 was built in Buffalo, did 101 mph with a 1,692-pound bomb load, and the wings could fold back for storage.
The Curtiss NBS-4, first flown on May 13, 1924, by Harold R. Harris, had 90-foot wings with a new Curtiss airfoil and offset windows on each side for the pilots behind the bow cockpit. The first of two examples tested could carry a 1,907-pound bomb load 608 miles.
Neither of these ships was ordered, for they incorporated no real advance over service types. With little performance progress made since the war, Air Service bomber squadrons hardly seemed likely to replace the battleship as the first line of defense. In July 1925, the bomber force was limited to 90 NBS-ls, the same type used five years earlier.
The Debate over National Air Power
Despite the modest size of his striking force Mitchell continued attacking “battleship admirals” and ground generals and predicted enormous capabilities for future aircraft. President Calvin Coolidge demoted him to the rank of colonel, and he was sent to “exile” in Texas, but the disaster of the dirigible Shenandoah in September 1925 gave Mitchell an excuse to issue his most violent denunciation of “incompetency, criminal negligence, and almost treasonable administration.”
This statement resulted in Mitchell’s famous court martial in the fall of 1925, and the accompanying publicity led to Presidential appointment that same year of a board to investigate aviation, under chairmanship of banker-diplomat Dwight W. Morrow. Scores of witnesses presented data and opinions of air power to the board, most of them hostile to Mitchell.
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