Keystone Aircraft Corp LB-10 / B-3 / B-5
A number of the Keystone aircraft became one-off flying testbeds for various newly developed geared or direct-drive versions of the Hornet and Cyclone engines. This programme gave rise to the new designations LB-8, LB-9, LB-10, LB-11, LB-11A and LB-12. Most of these were conversions from existing LB-6 or LB-7 bombers.
The major production model which followed was the single-tailed LB-10A, powered originally by 525-hp R-1690-3 Hornets, of which 63 were built. These were delivered under the new designation B-3A, the USAAC having adopted a single 'B' category for all types of bomber in 1930. Later, 27 of them were refitted with R-1750-3 Cyclones in place of the Hornets and were redesignated B-5A.
Engine: 525-hp R-1690-3 Hornet
Span: 22.78 m (74 ft 9 in)
Length: 14.88 m (48 ft 10 in)
Gross weight: 5875 kg (12 952 1 b)
Maximum speed: 183 km/h (114 mph).