Aviation of World War II

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Multipurpose Flying Boat


Douglas Dolphin. The Dolphin amphibious flying boat was a cantilever monoplane with a high wing, first flown in July 1930.

The boat had an all-metal hull and a wooden wing with plywood sheathing. In flight, or when operating from the water, the main landing gear was retracted above the waterline. The pilots sat side by side in a fully enclosed cockpit in front of the wing. The passenger compartment began behind them. The Dolphin had a distinctive auxiliary aerodynamic surface over the tops of the engine nacelles to eliminate flow problems. Early examples had a pair of auxiliary keels to provide additional longitudinal stability.

The first two boats were purchased by Wilmington-Catalina Airlines to carry passengers between Los Angeles and Santa Catalina Island, becoming the first successful Douglas airliners. Subsequent examples were ordered by the US Navy and the US Coast Guard for use as transport and search and rescue vehicles. The US Army Air Corps ordered several boats under the designations C-21, C-26 and C-29. Many were eventually used for their original purpose as luxury vehicles. The flying boats were owned by William Boeing, founder of Boeing, and Philip K. Wrigley, son of the founder of Wm. Wrigley Jr. Company. William K. Vanderbilt bought two boats with custom interiors for use on the Vanderbilt Alva.

One Dolphin was acquired by the US Navy to transport President Franklin D. Roosevelt. Although it was never used by Roosevelt, it was the first aircraft designed to carry the President of the United States.

In 1933, after landing on the high seas, the USCG RD-4 carried out several rescue operations at sea to rescue civilian sailors from a merchant ship, which resulted in impressive news reports and amazed the American public.

Serial production of Dolphin boats continued until 1935. Most of these vehicles ended up in the Army, Navy, and the US Coast Guard. Several of these boats survived World War II.

A total of 58 Dolphin boats were produced.

Dolphin Specification
Crew 2
Wingspan, m 18.29
Wings area, m² 55.00
Length, m 13.74
Height, m 4.27
2 PE Pratt Whitney R-1340-96 Wasp, power, h.p. 2×450
Weight, kg
Empty 3175
Loaded weight 4323
Maximum speed, km/h 251
Cruising speed, km/h 217
Service ceiling 5,180
Service range, km 1,159
Payload, passengers up to 6

At least 17 versions of the Dolphin were produced, differing from each other in power plants and the layout of the passenger compartment. The main modification was the 14th built boat, which received a reconstructed stabilizer and one large keel. They also increased the wing area and lengthened the hull.

Photo Description
Drawing Douglas Dolphin

Drawing Douglas Dolphin

Douglas Dolphin RD-2 1940

Douglas Dolphin RD-3 1930


  • "Encyclopedia of military engineering" /Aerospace Publising/
  • "American warplanes of World War II" /under cor. David Donald/