The Huff-Daland LB-5 was the first of the Huff-Daland twin-engined biplane bombers to enter service with the US Army Air Corps. The Huff-Daland/Keystone series of bombers were to be the dominant USAAC bombers until the advent of the monoplane era in the early 1930s.
The Huff-Daland XLB-5 (serial number 26-208) was similar to the XLB-3A (which was in turn a twin-engined designed based on the single-engined LB-1) except for the use of a pair of conventional water-cooled 420 hp Liberty engines instead of the air-cooled Wasp radials of the XLB-3A Unlike the XLB-3, the single vertical rudder of the XLB-5 was not supplemented by a pair of smaller vertical rudders mounted outboard on the horizontal tailplane. The Liberty engines were mounted on top of the lower wing. A crew of five was carried: a pilot, a copilot, a bombardier, plus two gunners.
The XLB-5 was a safe and reliable aircraft, and had the ability (unusual for the time) to fly for half an hour on one engine only. Impressed by this capability, the Army ordered ten production LB-5s. The serials were 27-335/344. The LB-5 differed from the XLB-5 in reverting to the single vertical rudder being supplemented by a pair of smaller rudders mounted outboard on the horizontal tailplane.
Following the delivery of the last LB-5, the Huff-Daland company changed its name to Keystone. Under the new Keystone name, the company delivered twenty-five LB-5As to the Army (serials 28-001/025). They differed from the LB-5 in having twin vertical tails rather than the single large rudder with two smaller rudders on each side.
The LB-5 became known as *Pirate* by the company, although this name was never officially adopted by the USAAC. The LB-5/LB-5A aircraft all used surplus Liberty engines left over from World War 1 and had performance only marginally better than WW 1 aircraft.
The LB-5 and LB-5A formed the basis of the remainder of the LB-series aircraft, all built by Keystone. The LB-6 to LB-14 all had radial engines and various modifications to the wings, fuselage, and tail, but such changes usually resulted in a completely new designation for the aircraft.
Specification of the Huff-Daland LB-5:
Two 420 hp Liberty V-1650 liquid-cooled V-12 engines. Maximum speed 107 mph at sea level. Service ceiling 8000 feet, Absolute ceiling 8800 feet. An altitude of 5000 feet could be attained in 20 minutes. Range 435 miles with 2312 pounds of bombs. Weights: 7024 pounds empty, 12,155 pounds gross. Wingspan 67 feet, length 44 feet 8 inches, height 16 feet 10 inches, wing area 1138.7 square feet. Two Lewis machine guns in an open gunner's position in the nose, two Lewis machine guns in an open dorsal gunner's position, one Lewis gun firing downward through an opening in the lower fuselage.