| 词条 | Keystone B-4 | |||||||||||||||||
| 释义 |
The Keystone B-4 was a biplane bomber, built by the Keystone Aircraft company for the United States Army Air Corps. Design and developmentOriginally ordered by the United States Army Air Corps as the LB-13 light bomber. When the LB- designation was dropped in 1930, the first five planes were redesignated Y1B-4. (The Y1B- designation indicates that funds for the design did not come from the normal annual funds.) The first B-3A (S/N 30-281) was converted to Y1B-4 configuration with the addition of R-1860-7 radial engines and low pressure tires. Because of more powerful engines, the performance of the Y1B-4 was a slight improvement on the B-3, but the only difference between the two planes was their engines. On April 28, 1931, the army ordered 25 improved Y1B-4s as the Keystone B-4A. This production version was part of the last biplane bomber order made by the Army Air Corps (along with 39 B-6As, identical in all respects except their make of engine), and the B-4As, delivered between January and April 1932, were the last biplane bombers delivered to the Air Corps. Operational historyB-4 was the last of the Keystone biplane bombers ordered by the U.S. Army in late 1931. These aircraft were used primarily as observation and reconnaissance aircraft as early as 1934 when the Martin B-10B went into operational service. Some remained in service into the early 1940s. Variants
Seven aircraft ordered but delivered as the Y1B-4 and Y1B-6 with different engine installations.
Five pre-production aircraft, as the LB-10 but with two 575 hp (429 kW) Pratt & Whitney R-1860-7 engines.
Production version of the Y1B-4, 25 built. Operators
Specifications (B-4A){{Aircraft specifications|plane or copter?=plane |jet or prop?=prop |crew=5 |length main=48 ft 10 in |length alt=14.9 m |span main=74 ft 8 in |span alt=22.8 m |height main=15 ft 9 in |height alt=4.8 m |area main=1,145 ft² |area alt=106.4 m² |empty weight main=7,951 lb |empty weight alt=3,607 kg |loaded weight main=12,952 lb |loaded weight alt=5,875 kg |max takeoff weight main= |max takeoff weight alt= |number of props=2 |engine (prop)=Pratt & Whitney R-1860-7 |type of prop=radial engines |power main=575 hp |power alt=429 kW |max speed main=130 mph |max speed alt=110 kn, 210 km/h |cruise speed main=103 mph |cruise speed alt=90 kn, 167 km/h |range main=850 mi |range alt=760 nmi, 1,400 km |ceiling main=14,000 ft |ceiling alt=4,300 m |climb rate main=580 ft/min |climb rate alt=30 m/s |loading main=11.31 lb/ft² |loading alt=55.22 kg/m² |power/mass main=0.0888 hp/lb |power/mass alt=146 W/kg |guns=3 × .30 in (7.62 mm) Browning machine guns |bombs=2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs }} See also{{Aircontent|related=
|similar aircraft= |lists=
}} External links{{commons category|Keystone B-4}}
5 : Keystone aircraft|Light bombers|United States bomber aircraft 1930–1939|Biplanes|Twin piston-engined tractor aircraft |
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