Developed from the Model 167 Maryland, the Martin Model 187 Baltimore was produced to British specifications, and featured a deeper fuselage for better crew communications and more powerful engines. Direct orders from Britain resulted in 50 Baltimore Mk Is, 100 Mk IIs and 250 Mk IIIs. The passing of the Lend-Lease Act allowed the USAAF to procure the type on behalf of the RAF, resulting in 281 Mk IIIAs with an electrically-actuated dorsal turret, 294 Mk IVs with minor detail changes and 600 Mk Vs which introduced slightly uprated engines. The Lend-Lease aircraft received the designations A-30 (Mk IIIA) and A-30A (Mks IV and V) in USAAF nomenclature. A small number were retained in the United States for trials and training purposes.
Specification
Martin—A-30A Baltimore
Type:four-seat light bomberPowerplant:two Wright R-2600-19 Cyclone 14-cylinder radial piston engines, each rated at 1,660 hpPerformance:maximum speed 305 mph; service ceiling 23,300 ft; range 1,082 miles with 1,000-lb bomb loadDimensions:wing span 61 ft 4 in; length 48 ft 51/2 in; height 17 ft 9 in; wing area 538.5 sq ftArmament:four 0.303-in machine guns in wings and either two or four in dorsal turret; two 0.3-in machine guns in ventral position and provision for four similar guns in fixed rearward-firing position; bomb load of up to 4,000 lb