The Martin B-10 medium bomber was a breakthrough design for American military aviation when it appeared in the early 1930s. However, despite its advanced form at the time of introduction, the series was quickly made obsolete at the outbreak of hostilities concerning World War 2. The series managed to persevere during the period through its healthy stable of export customers around the globe. Before the end, over 300 examples of the type were delivered.
The B-10 originated as a private venture initiative by the Glenn Martin Company through the "Model 123" design. This work then begat the XB-907 evaluation models for the U.S. Army and featured Wright SR-120-E radials as well as open-air crew positions. These were seen in April of 1932.
The XB-907A was a revised form incorporating several requested changes. Modifications were made to the wing mainplanes to widen their reach. Engines consisted of 2 x Wright R-1820-19 series radials.
The XB-10 marked official prototype forms for the U.S. Army and brought about the use of enclosed crew positions and revised undercarriage legs. Evaluation models then became YB-10 and YB-10A, the latter shifting from R-1820-25 radials to R-1820-31 turbo-supercharged radials. Fourteen YB-10s were produced to the single YB-10A that was completed.
At its core, the Martin B-10 was a twin-engine, medium-class bomber powered by a pair of Wright R-1820 G-102 "Cyclone" 9-cylinder radial piston engines. The engines were fitted on what would become the USAAC's first attempt at a cantilever low-wing monoplane. The fuselage housed a crew of four that included the pilot and machine gunners. The nose and tail were both glazed over and held defensive armament in the form of machine guns. The aircraft three machine guns in all. A aft section of the fuselage was also glazed over (greenhouse-style) for another crew position and a ventral machine gun was carried near here. All machine guns were of 7.62mm caliber. Internally, the aircraft was cleared to carry upwards of 2,260 pounds of conventional drop ordnance.
After the early B-10 production forms came about, the B-10B (Model 139) followed as primary production versions. These carried R-1820-33 series engines of 775 horsepower (each) and 105 were built to this standard. The B-10M served as a target tug or mail carrier and RB-10MA was a special, modified version of July 1942 flown from Australia to the United States.
YB-12 (Model 139B) arrived as a marginally improved B-10 evaluation model. Over-water safety was improved through installed flotation chambers and Wright engines were given up in favor of 2 x Pratt & Whitney R-1690-11
"Hornet" radials of 775 horsepower (each) instead. Seven of these were produced for April 1940.
B-12A became the first production forms of the YB-12 test models but only 25 units followed to this standard. YB-13 saw PW R-1860-17 "Hornet B" radials of 700 horsepower (each) installed but, despite ten being ordered, none were completed. XB-14 tested PW YR-1830-9 "Twin Wasp" engines of 900 horsepower (each) but only a single YB-12 was converted (and then reverted) for testing. A-15 became a proposed USAAC attack variant but official selection went to the A-14 "Shrike" design offered by competitor Curtiss.
Even while the USAAC began its shift to more modern bomber platforms, export orders (as the "Model 139W") allowed the B-10 lines to remain active for the time being. Customers included the Netherlands with an order of 120, Argentina with 35, and Thailand and Turkey having ordered 26 and 20 respectively.
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Specifications
Glenn L. Martin Company - USA Manufacturer(s)
Argentina; China (Taiwan); Indonesia; Netherlands; Philippines; Soviet Union; Siam (Thailand); Turkey; United States Operators
STANDARD:
1 x 7.62mm machine gun in nose position
1 x 7.62mm machine gun in dorsal position
1 x 7.62mm machine gun in ventral position
OPTIONAL:
Maximum bomb load of up to 2,260 lb of internally-held ordnance.
0 Hardpoints
Model 123 - Base Model Project Designation as pursued by Martin.
XB-907 - US Army Evaluation Designation of Model 123.
XB-907A - Modified US Army Evaluation Designation of Model 123.
XB-10 - USAAC Modified Model based on the XB-907A model.
YB-10 - Modified XB-10 models
B-10 - Base Production Model Designation
YB-10A - based on YB-10 model but fitted instead with Wright R-1820-31 radial piston engines.
B-10B - Initial and Main Production Model Designation.
B-10M - Target Tug Conversion Models of B-10B.
RB-10
YB-12 - Improved B-10 Model fitted with Pratt & Whitney R-1690-11 Hornet radial piston engines.
B-12A - "Improved B-10" Production Model
YB-13 - Proposed Re-engined Variant Model
XB-14
A-15 - Proposed Attack Model Variant
YO-45 - Experimental Testing Platform
Model 139 - Export Designation for B-10 Model
Model 139WA - Argentina Export Model Designation for demonstration model.
Model 139WAA - Argentina Export Model Designation; fielded with Argentine Army units.
Model 139WAN - Argentine Export Model Designation; fielded with Argentine Naval units.
Model 139WC - Chinese Export Model Designation.
Model 139WH - Netherlands Export Model Designation.
Model 139WS - Soviet Demonstrator Model
Model 139WSM - Siam Export Model Designation
Model 139WSP - Proposed Spanish Export Model
Model 139WT - Turkish Export Model Designation
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