Keystone XLB-3

The Keystone XLB-3 (originally built under the Huff-Daland name) was a prototype bomber biplane developed in the United States in the late 1920s. It was a twin-engine development of the single-engine LB-1, brought about by a change in policy by the USAAC.

Design and development

The shift from a nose-mounted engine to engines mounted in nacelles on the lower wing created an opportunity to provide stations for two extra crewmembers: a bombardier and a nose-gunner, bringing the total to five. The LB-1's single tailfin and rudder was augmented by an extra rudder either side of it.

Operational history

A single prototype was constructed, and delivered to the USAAC for evaluation at the end of 1927. Evaluation, however, showed that performance was actually inferior to that of the single-engine LB-1. The decision was taken to change the XLB-3's water-cooled Liberty engines for air-cooled radials, at which point it was redesignated XLB-3A. With performance still unsatisfactory, development was abandoned in favor of a parallel design, the LB-5.

Variants

• XLB-3 - original version with Liberty V-1410 engines (1 built)
  • XLB-3A - version with Pratt & Whitney R-1340 engines (1 converted from XLB-3)

Specifications (XLB-3A)

Data from Jane's Encyclopedia of Aviation^[1]

General characteristics

• Crew: Five - pilot, copilot, bombardier, two gunners
• Length: 45 ft 0 in (13.72 m)
• Wingspan: 67 ft 0 in (20.42 m)
• Height: 16 ft 10 in (5.13 m)
• Wing area: 105.8 ft² (1,038 m²)
• Empty weight: 6,065 lb (2,756 kg)
• Gross weight: 11,682 lb (5,310 kg)
• Powerplant: 2 × Pratt & Whitney R-1340, 410 hp (305 kW) each

Performance

• Maximum speed: 116 mph (186 km/h)
• Range: 544 miles (870 km)
• Service ceiling: 11,210 ft (3,400 m)
• Rate of climb: 550 ft/min (2.8 m/s)

Armament

• 2 × trainable .303 in (7.7 mm) Lewis guns in open position in nose
• 2 × trainable .303 in (7.7 mm) Lewis guns in open dorsal position
• 1 × trainable .303 in (7.7 mm) Lewis gun in ventral hatch
• 2,205 lb (1,000 kg) of bombs

References

Notes

Bibliography

• National Museum of the USAF XLB-3 fact sheet
• National Museum of the USAF XLB-3A fact sheet
• American Bombing Aircraft