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Pratt & Whitney R-1535
Twin Wasp Junior

The Engine Specifications
In 1932, Pratt & Whitney introduced the R-1535 Twin Wasp Junior.  The R-1535 used fourteen Wasp Junior cylinders arranged in two rows.  Starting out at 600 hp, this engine was producing 825 hp by World War II.

Compared to the Hornet it gave similar power, was heavier and more expensive but with a smaller diameter resulted in less drag and improved pilot view in a single engine aircraft.  Not sold in large numbers, Howard Hughes used the R-1535 to power his H-1 Racer to set the world absolute speed record in 1935.

14-cylinder, twin-row, air-cooled radial
displacement: 1,535 cubic inches (25.2 liters)
Bore x stroke: 5 3/16 x 5 3/16 in
Models Used by
R-1535: 700 hp (521 kW)
R-1535-13: 825 hp (614 kW)
Hughes H-1 Racer
Northrop A-17
Related Pages
More about Pratt & Whitney

page updated 11 February 2004



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Kenneth W Shanaberger 2000 - 2010