The Martin XLB-4 was a 1920s proposal for a light bomber by the Glenn L. Martin Company.

Design and development

The XLB-4 would have been a biplane bomber of all metal construction, powered by two Pratt & Whitney R-1690 Hornet radial engines. The United States Army Air Corps (USAAC) ordered a single prototype serialled 27-332, but the aircraft was cancelled because the USAAC leadership was lukewarm about experimenting with all-metal aircraft.^[1][2]

Specifications (XLB-4 estimated)

General characteristics

• Crew: 5
• Length: 44 ft 8 in (13.61 m)
• Wingspan: 76 ft (23 m)
• Height: 16 ft 7 in (5.06 m)
• Wing area: 1,203.0 sq ft (111.76 m²)
• Empty weight: 5,891 lb (2,672 kg)
• Gross weight: 11,982 lb (5,435 kg)
• Powerplant: 2 × Pratt & Whitney R-1690 Hornet 9-cylinder air-cooled radial piston engines, 525 hp (391 kW) each

Performance

• Maximum speed: 69 mph (111 km/h, 60 kn)
• Wing loading: 9.98 lb/sq ft (48.7 kg/m²)