<p>The early success of its Hudsons in operational service with the RAF induced Lockheed to initiate the design of a more advanced version. This was based on the company's somewhat larger Model 18 Lodestar civil airliner, but the resulting aircraft was very similar in appearance to the Hudson.
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<p>Designated Ventura I, the new aircraft differed from the Hudson in having a wider and deeper fuselage with a length increase of 16 per cent, more powerful Pratt & Whitney engines each rated at 2,000 hp (1,491 kW), the introduction of a proper ventral gun position with two 0.303-in (7.7-mm) machine guns and, because of the more voluminous fuselage and greater engine power, a bomb bay able to accommodate a maximum bomb load of 2,500 lb (1,134 kg).
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<p>When the Ventura was included in the Lend-Lease program it was procured initially for the RAF under the designation B-34, but with the cancellation of British orders the outstanding aircraft began to enter USAAF service initially as R-37s, based on the manufacturer's model number, and later as B-34A Lexingtons, and these were used mainly for maritime patrol. In addition, a small number were procured as navigational trainers, and these were allocated the designation B-34B. In 1942 the US Army ordered 550 examples of a new version with 1,700-hp (1,268-kW) Wright R-2600-31 Cyclone 14 engines, for use in a patrol/reconnaissance role under the designation O-56, but only 18 of these aircraft had been received, becoming instead B-37, before the balance of 532 on order were cancelled.
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<hi style=hdr1>Specification</hi>
<list style=aflst>
<item><hi format=bold>Type:</hi> four/five-seat medium bomber
<item><hi format=bold>Powerplant (B-34A):</hi> two 2,000-hp (1,491-kW) Pratt & Whitney R-2800-31 Double Wasp radial piston engines
<item><hi format=bold>Performance:</hi> maximum speed 315 mph (507 km/h) at 15,500 ft (4,725 m); cruising speed 230 mph (370 km/h); service ceiling 24,000 ft (7,315 m); range 950 miles (1,529 km)
<item><hi format=bold>Weights:</hi> empty 17,275 lb (7,836 kg); maximum take-off 27,250 lb (12,360 kg)
<item><hi format=bold>Dimensions:</hi> span 65 ft 6 in (19.96 m); length 51 ft 5 in (15.67 m); height 11 ft 11 in (3.63 m); wing area 551 sq ft (51.19 m<su>2</su>)
<item><hi format=bold>Armament:</hi> two forward-firing 0.50-in (12.7-mm) machine guns in fuselage nose and six 0.30-in (7.62-mm) guns on flexible mounts in nose, dorsal and ventral position, plus up to 2,500 lb (1,134 kg) of bombs in bomb bay
