PRATT & WHITNEY TWIN WASP JUNIOR R-1535 SB-4G
The SB-4G is an American 14-cylinder, air-cooled supercharged two-row radial engine which is based on the single-row Wasp Junior and the manufacture of which was launched in 1932. On 13th September 1935, Howard Hughes, flying his Twin Wasp Junior powered Hughes H-1 aircraft, claimed a world speed record for landplanes, 567 km/h. The Twin Wasp Junior also powered many aircraft types in US Air Force and Navy service. The manufacture of the engine was discontinued in 1940, when the Pratt & Whitney company modified its production to better meet the demands of the war-time.
In Finland. Twin Wasp Juniors were installed in the last 55 examples of the 90 Fokker D.XXI fighters that the State Aircraft Factory built under licence. Twin Wasp Juniors were purchased after Bristol Mercury engines, that had initially been used in Fokkers, were reserved for installation in Bristol Blenheim bombers, the production of which was running concurrently.
Max. power output 825 hp. Max engine speed 26250 r/min. Weight 526 kg. Serial number 1600.
Photo from Eugenius.