Martin 139 / B-10 / 146 / B-12 / 166 / B-14

The Martin Model 139 was a twin-engined mid-wing monoplane bomber developed from the experimental Model 123 of 1932. Introduced in 1934, Glenn Martin‘s B-10, the first American bomber with 200-plus mph speeds, revolutionized bomber de-velopment with retractable landing gear, cowled engines, all-metal cantilever monoplane configuration, enclosed cockpit, internal bomb-bay and movable gun tur-rets.

During 1934 48 Model 139 were delivered to the USAAC. Fifteen were fitted with 503kW Wright R-1820 Cyclone engines as YB-10 and 33 with 577.5kW Pratt & Whitney R-1690 Hornet engines as YB-12 and B-12A, a number of which were later converted into twin-float seaplanes for coastal patrol duties.

Development of the Model 139 led to numerous improvements being made, including the installation of 551.4kW SGR- 1820-G3 Cyclone engines, a Sperry automatic pilot and the addition of wing flaps, constant-speed propellers, de-icers and numerous structural and maintenance refinements. During 1935 and 1936 103 of the improved aircraft (B-10B) were delivered to the USAAC.

The 1935 Martin 146 was an enlarged B-10 with two Wright R-1820 engines. With a widened fuselage, it was the first large airplane to use Fowler flaps. One was built for Wright Field testing, NX15550, plus exports as the B-10B. Licensed production in 1936 to Fokker Netherlands was never implemented and was replaced by an order for Model 139WH to use in the East Indies.

On 1 July 1936 the bomber was released for export and was subsequently ordered by six foreign governments, the Netherlands East Indies alone receiving 120 Model 139W and Model 166 with 670.7kW Cyclone engines. The Model 166 aircraft introduced improved aerodynamics and performance characteristics and featured a continuous cockpit enclosure instead of the previous separate enclosures.

Model 139 / YB-10
Engines: 2 x 503kW Wright R-1820 Cyclone

Model 139 / YB-12 / B-12A
Engines: 2 x 577.5kW Pratt & Whitney R-1690 Hornet

Model 139 / B-10B
Engines: 2 x 551.4kW Wright SGR-1820-33 Cyclone
Propellers: constant-speed
Top speed: 343 km/h / 212 mph
Take-off weight: 7439 kg / 16400 lb
Empty weight: 4391 kg / 9681 lb
Wingspan: 21.49 m / 70 ft 6 in
Length: 13.64 m / 44 ft 9 in
Height: 4.70 m / 15 ft 5 in
Wing area: 62.99 sq.m / 678.02 sq ft
Ceiling: 7375 m / 24200 ft
Range w/max.fuel: 2000 km / 1243 miles
Armament: 3 x 7.62mm machine-guns, 1000kg of bombs
Crew: 3

Model 139W
Engines: 2 x 670.7kW Cyclone

Model 166
Engines: 2 x 670.7kW Cyclone

Martin B-10 / B-12 / B-14