The Douglas Y1B-7 was a 1930s American

bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped ...

aircraft. It was the first US

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes. A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...

given the ''B-'' 'bomber' designation. The monoplane was more practical and less expensive than the

biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...

, and the

United States Army Air Corps The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical r ...

chose to experiment with monoplanes for this reason. At the time the XB-7 was ordered, it was being tested by

Douglas Aircraft The Douglas Aircraft Company was an American aerospace manufacturer based in Southern California. It was founded in 1921 by Donald Wills Douglas Sr. and later merged with McDonnell Aircraft in 1967 to form McDonnell Douglas; it then operated as ...

as an observational plane.

Design and development

In 1929–1930, the

Douglas Aircraft Company The Douglas Aircraft Company was an American aerospace manufacturer based in Southern California. It was founded in 1921 by Donald Wills Douglas Sr. and later merged with McDonnell Aircraft in 1967 to form McDonnell Douglas; it then operated as ...

designed a new twin-engined

observation aircraft to compete with the Fokker XO-27, two prototypes of which had been ordered by the

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, the XO-35 and XO-36, on 26 March 1930. The two aircraft were to differ only in the engines fitted, with the XO-35 having geared

Curtiss V-1570 The Curtiss V-1570 Conqueror was a 12-cylinder vee liquid-cooled aircraft engine. Representing a more powerful version of the Curtiss D-12, the engine entered production in 1926 and flew in numerous aircraft.Gunston 1989, p. 46. Design and dev ...

-29 Conqueror engines, while the XO-36 used direct-drive V-1570-23, which both produced each.Pelletier ''Air Enthusiast'' March/April 2002, pp. 30, 32.Francillon 1979, pp. 135–136. The Douglas design had

gull wing The gull wing is an aircraft wing configuration, known also as ''Pulaski wings'', with a prominent bend in the wing inner section towards the wing root. Its name is derived from the seabirds which it resembles. Numerous aircraft have incorporat ...

s mounted high on the aircraft's fuselage, the engines being suspended in streamlined

nacelle A nacelle ( ) is a "streamlined body, sized according to what it contains", such as an engine, fuel, or equipment on an aircraft. When attached by a pylon entirely outside the airframe, it is sometimes called a pod, in which case it is attached ...

s under the wings by bracing struts. A retractable

tailwheel undercarriage Conventional landing gear, or tailwheel-type landing gear, is an aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynami ...

was fitted, the mainwheels retracting into the engine nacelles. The fuselage was a semi-

monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...

structure with corrugated

duralumin Duralumin (also called duraluminum, duraluminium, duralum, dural(l)ium, or dural) is a trade name for one of the earliest types of age-hardenable aluminium alloys. The term is a combination of '' Dürener'' and ''aluminium''. Its use as a tra ...

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. The projected performance of the new twin-engined Douglas and Fokker observation aircraft was much greater than the Keystone

s (the

Keystone B-3 The Keystone B-3A was a bomber aircraft developed for the United States Army Air Corps by Keystone Aircraft in the late 1920s. Design and development The B-3 was originally ordered as the LB-10A (a single-tail modification of the Keystone LB-6) ...

, B-4,

B-5 B5, B05, B-5 may refer to: Biology * ATC code B05 (''Blood substitutes and perfusion solutions''), a therapeutic subgroup of the Anatomical Therapeutic Chemical Classification System * Cytochrome ''b''5, ubiquitous electron transport hemoprotein ...

and B-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 the XB-7, with provision to carry up to of bombs on racks under the fuselage added.Pelletier ''Air Enthusiast'' March/April 2002, p. 32. The XO-36 made its first flight at the

Santa Monica, California Santa Monica (; Spanish language, Spanish: ''Santa Mónica'') is a city in Los Angeles County, California, Los Angeles County, situated along Santa Monica Bay on California's South Coast (California), South Coast. Santa Monica's 2020 United Sta ...

factory of Douglas in spring 1931.Francillon 1979, p. 137. 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 longer to adjust the aircraft's

center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...

. 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.

Operational history

The XO-35 was delivered to the Air Corps at its test center at

Wright Field Wilbur Wright Field was a military installation and an airfield used as a World War I pilot, mechanic, and armorer training facility and, under different designations, conducted United States Army Air Corps and Air Forces flight testing. Loca ...

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

on 24 October 1931, with the XB-7 following in July 1932. The twelve service test aircraft were completed between November 1932 and March 1933.Pelletier ''Air Enthusiast'' March/April 2006, pp. 33–34. The Y1B-7s equipped the 11th and 31st Bombardment Squadrons at

March Field March is the third month of the year in both the Julian and Gregorian calendars. It is the second of seven months to have a length of 31 days. In the Northern Hemisphere, the meteorological beginning of spring occurs on the first day of Ma ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, while the Y1O-35s were issued to a number of Squadrons, including the

88th Observation Squadron The 436th Training Squadron is a non-flying training squadron of the United States Air Force. The 436th Training Squadron, located at Dyess Air Force Base, Texas, is a geographically separated unit (GSU) within Air Combat Command’s 552nd Air ...

at Brooks Field,

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

.Pelletier ''Air Enthusiast'' March/April 2006, p. 34. One notable early use of the Y1B-7 was during a May 1933 exercise at

Fort Knox Fort Knox is a United States Army installation in Kentucky, south of Louisville and north of Elizabethtown. It is adjacent to the United States Bullion Depository, which is used to house a large portion of the United States' official gold res ...

, where it was able to outrun biplane fighters like the

Boeing P-12 The Boeing P-12/F4B was an American pursuit aircraft that was operated by the United States Army Air Corps , United States Marine Corps, and United States Navy. Design and development Developed as a private venture to replace the Boeing F2B an ...

, showing that the Air Corps needed more modern fighters.Pelletier ''Air Enthusiast'' March/April 2006, pp. 32–33. 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 the

Martin B-10 The Martin B-10 was the first all-metal monoplane bomber to be regularly used by the United States Army Air Corps, entering service in June 1934.Jackson 2003, p. 246. It was also the first mass-produced bomber whose performance was superior to ...

, were under development while a change in Air Corps policy meant that it was no longer interested in buying more twin-engined observation aircraft.Francillon 1979, p. 138. In February 1934, US President

Franklin D. Roosevelt Franklin Delano Roosevelt (; ; January 30, 1882April 12, 1945), often referred to by his initials FDR, was an American politician and attorney who served as the 32nd president of the United States from 1933 until his death in 1945. As the ...

cancelled all

air mail Airmail (or air mail) is a mail transport service branded and sold on the basis of at least one leg of its journey being by air. Airmail items typically arrive more quickly than surface mail, and usually cost more to send. Airmail may be the ...

contracts owing to a scandal relating to the award of contracts, thus initiating the Airmail 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 least unsuitable 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 the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

, the

Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...

and the

Sierra Nevada The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...

.Pelletier ''Air Enthusiast'' March/April 2006, p. 35. 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.Francillon 1979, p. 139. The last O-35s and B-7s were withdrawn from use in December 1938.Pelletier ''Air Enthusiast'' March/April 2006, p.40.

Variants

;XO-35 :Prototype twin-engined observation aircraft. Two geared Curtiss V-1570-29 engines driving three-bladed propellers. One built. ;XO-36 :Prototype twin-engined observation aircraft. Two direct-drive Curtiss V-1570-23 engines driving two-bladed propellers. Redesignated XB-7. One built. ;XB-7 :Prototype light bomber, with two direct-drive 600 hp V-1570-23 engines driving two bladed propellers. One built. ;Y1O-35 :Service test batch of observation aircraft, powered by V-1570-39 or V-1570-53 engines. Five built. ;Y1B-7 :Service test batch of bombers, powered by V-1570-33 or 675 hp V-1570-53 engines. Seven built.

Operators

; *

Specifications (Y1B-7)

References

Notes

Bibliography

* Francillon, René J. ''McDonnell Douglas Aircraft since 1920.'' London: Putnam, 1979. . * Pelletier, Alain J. "Bombers as Postmen: Boeing Y1O-35 and Y1B-7". ''Air Enthusiast,'' No. 122, March / April 2006, pp. 30–40. ISSN 0143-5450. * Wagner, Ray. ''American Combat Planes''. New York: Doubleday, 1982. .

External links

Douglas B-7

Fact Sheet: Douglas Y1B-7
{{DEFAULTSORT:Douglas Y1b-7 B-07 Gull-wing aircraft Douglas B-07 Aircraft first flown in 1931 Twin piston-engined tractor aircraft