| Y1B-7 | |
|---|---|
 Y1B-7 of the 31st Bombardment Squadron | |
| General information | |
| Type | Bomber/Observation aircraft |
| Manufacturer | Douglas Aircraft Company |
| Primary user | United States Army Air Corps |
| Number built | 14 |
| History | |
| Manufactured | 1932 |
| First flight | 1931 |
| Retired | January 1939 |
TheDouglas Y1B-7 was a 1930s Americanbomber aircraft. It was the first USmonoplane given theB- 'bomber' designation. The monoplane was more practical and less expensive than thebiplane, and theUnited States Army Air Corps chose to experiment with monoplanes for this reason. At the time the XB-7 was ordered, it was being tested byDouglas Aircraft as an observational plane.
In 1929–1930, theDouglas Aircraft Company designed a new twin-enginedmonoplane observation aircraft to compete with theFokker XO-27, two prototypes of which had been ordered by theUnited States Army Air Corps in July 1929, as Douglas feared that the advanced Fokker would challenge Douglas's role as the major supplier of observation aircraft to the Air Corps. The Douglas proposals resulted in the Air Corps placing an order for two prototypes, theXO-35 andXO-36, on 26 March 1930. The two aircraft were to differ only in the engines fitted, with the XO-35 having gearedCurtiss V-1570-29 Conqueror engines, while the XO-36 used direct-drive V-1570-23, which both produced 600 hp (450 kW) each.[1][2]
The Douglas design hadgull wings mounted high on the aircraft's fuselage, the engines being suspended in streamlinednacelles under the wings by bracing struts. A retractabletailwheel undercarriage was fitted, the mainwheels retracting into the engine nacelles. The fuselage was a semi-monocoque structure with corrugatedduralumin covering, which housed the aircraft's crew of four: a nose gunner/observer, a pilot whose cockpit was situated ahead of the leading edge of the wing, an upper gunner who sat in a cockpit aft of the wing, and a radio operator housed within the fuselage. Armament was two .30 in machine guns.[1][2]
The projected performance of the new twin-engined Douglas and Fokker observation aircraft was much greater than theKeystonebiplanes (theKeystone B-3,B-4,B-5 andB-6) that equipped the Air Corps light bomber squadrons, and both Fokker and Douglas were instructed to complete one of their prototypes as a bomber, with the XO-36 being redesignated theXB-7, with provision to carry up to 1,200 lb (540 kg) of bombs on racks under the fuselage added.[3]
The XO-36 made its first flight at theSanta Monica, California factory of Douglas in spring 1931.[4] On 22 August 1931, the Air Corps placed an order for a small batch of service test aircraft, consisting of seven Y1B-7 bombers and five Y1O-35 observation aircraft. These differed from the prototypes by having smooth fuselage skins rather than the corrugated skins used on the prototype, while the fuselage was 11 in (280 mm) longer to adjust the aircraft'scenter of gravity. A revised fuel system was fitted, with more fuel carried in order to give the two-hour endurance specified by the Air Corps. More powerful Conqueror engines were fitted, with all aircraft using geared engines as used on the XO-35.[3]
The XO-35 was delivered to the Air Corps at its test center atWright Field,Ohio on 24 October 1931, with the XB-7 following in July 1932.[4] The twelve service test aircraft were completed between November 1932 and March 1933.[5] The Y1B-7s equipped the11th and31st Bombardment Squadrons atMarch Field,California,[3] while the Y1O-35s were issued to a number of Squadrons, including the88th Observation Squadron atBrooks Field,Texas.[6] One notable early use of the Y1B-7 was during a May 1933 exercise atFort Knox, where it was able to outrun biplane fighters like theBoeing P-12, showing that the Air Corps needed more modern fighters.[7]
Despite the aircraft's superior performance to the elderly Keystone biplanes, the Douglas monoplane never entered mass production either in the observation or bomber roles because newer, more capable aircraft, such as theMartin B-10, were under development while a change in Air Corps policy meant that it was no longer interested in buying more twin-engined observation aircraft.[8]
In February 1934, US PresidentFranklin D. Roosevelt cancelled allair mail contracts owing to a scandal relating to the award of contracts, thus initiating theAirmail Emergency, where the Air Corps was tasked with carrying the mail until new contracts could be awarded. The O-35s and B-7s were considered some of the most suitable aircraft in the Air Corps inventory for the air mail role, so the six remaining Y1B-7s and the five Y1O-35s, together with the XO-35, were assigned to air mail routes in the western United States, which included hazardous operations over theRocky Mountains, theCascade Range and theSierra Nevada.[9] By the time the Air Corps involvement in air mail flights ended in June 1934, the twelve O-35s and B-7s had flown 1,412 hours on mail flights, while four of the B-7s had been lost as a result of accidents.[10] The last O-35s and B-7s were withdrawn from use in December 1938.[11]
Data from McDonnell Douglas aircraft since 1920 : Volume I[12]
General characteristics
Performance
Armament
Aircraft of comparable role, configuration, and era
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