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 pro¬gramme 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 follow¬ed 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.
LB 10A
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).
All Aero 