Keystone B-4

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The Keystone B-4 was a biplane bomber originally ordered by the United States Army Air Corps as the LB-13. 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.)

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 were their engines. In 1932, 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.

[edit] Specifications (B-4A)

General characteristics

• Crew: 5
• Length: 48 ft 10 in (14.9 m)
• Wingspan: 74 ft 8 in (22.8 m)
• Height: 15 ft 9 in (4.8 m)
• Wing area: 1,145 ft² (106.4 m²)
• Empty weight: 7,951 lb (3,607 kg)
• Loaded weight: 12,952 lb (5,875 kg)
• Max takeoff weight: lb (kg)
• Powerplant: 2× Pratt & Whitney R-1860-7 radial engines, 575 hp (429 kW) each

Performance

• Maximum speed: 130 mph (110 kt, 210 km/h)
• Cruise speed: 103 mph (90 kt, 167 km/h)
• Range: 850 mi (760 nm, 1,400 km)
• Service ceiling: 14,000 ft (4,300 m)
• Rate of climb: 580 ft/min (30 m/s)
• Wing loading: 11.31 lb/ft² (55.22 kg/m²)
• Power/mass: 0.0888 hp/lb (146 W/kg)

Armament

• Guns: 3× .30-calibre (7.62 mm) Browning machine guns
• Bombs: 2,500 lb (1,100 kg); 4,000 lb (1,800 kg) on short runs

[edit] References and external links

• Encyclopedia of American Aircraft
• Photograph
• USAF Museum article on B-4
• USAF Museum article on LB-13

[edit] Related content

Related development

• Keystone B-3
• Keystone B-5
• Keystone B-6

 

Designation sequence

• LB-series: LB-10 - LB-11 - XLB-12 - LB-13 - LB-14
• B-series: XB-1 - B-2 - B-3 - B-4 - B-5 - B-6 - Y1B-7

Related lists

• List of bomber aircraft
• List of military aircraft of the United States