RD-4 Dolphin

The Douglas RD‑4 Dolphin was a groundbreaking amphibious transport introduced in 1937 as the company’s response to growing demand for versatile water‑capable aircraft. Built at the Douglas Aircraft Company’s Santa Monica plant, the Dolphin combined a sleek all‑metal hull with a high‑wing layout and twin Pratt & Whitney R‑985 radial engines mounted on struts. Its retractable landing gear allowed seamless transition between runway and water operations, a feature that set a new standard for amphibians. The aircraft could carry twelve passengers or a cargo load of up to 2,500 lb, cruising at 190 mph with a range of 1,800 mi, making it ideal for coastal airlines, military transport, and search‑and‑rescue missions. During World War II the U.S. Navy commissioned over 150 RD‑4s for patrol and liaison duties, appreciating its durability and ease of maintenance. Post‑war, the Dolphin helped establish reliable seaplane routes across the Pacific, linking remote island communities and fostering tourism. Its pioneering design influenced later Douglas models such as the Skyraider and contributed to the broader acceptance of amphibious aircraft in commercial and military aviation, cementing its place in mid‑century aeronautical history.

Douglas

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