The Huff-Daland XLB-5 was the second attempt to produce a twin-engined version of the company’s LB-1 light bomber, coming between the Huff-Daland XLB-3 and the Keystone XLB-3A. The XLB-5 was very similar to these aircraft, differing only in the choice of engines – it was powered by a pair of Liberty V-1650-3 inline engines, while the XLB-3 used Liberty V-1410 engines and the XLB-3A Pratt & Whitney R-1340 radials. The XLB-5 out-performed the Huff-Daland XLB-3 slightly, and was put into production as the Keystone LB-5.
The XLB-5 (and XLB-3) adopted the layout that would be standard on all future Keystone bombers. The engines were mounted on the lower wing, close to the fuselage. The bombardier’s position was in the bottom of the nose, with a gun position above it. The pilot’s cockpit was just behind, under the lower wing. The rear fuselage contained a rear gun position, while the fifth gun was fired through a fuselage tunnel. The XLB-5 retained the single vertical stabilizer of the LB-1, while the XLB-3 and the service test LB-5s used as triple vertical tail.
A single XLB-5 was produced, and was given a 1926 serial number. It was followed by ten service test Keystone LB-5s in 1927, and twenty-five production LB-5As in 1928. The basic design then became the basis of the series of Keystone bombers that ended with the B-6A Panther.
Engine: Liberty V-1650-3
Span: 66ft 6in
Gross Weight: 11,992lb
Maximum Speed: 108mph at sea level
Cruising Speed: 87mph