The Hitachi Hatsukaze also known as the Hitachi model GK4, was Hitachi's fourth design in a series of aircraft engines built in Japan prior to and during World War II. The original Hatsukaze was a license-built Hirth HM 504. Hatsukazi engines were air-cooled, four-cylinder, inverted inline engines developing around 82 kW (110 hp).
The naval version of the engine was designated GK4, the army version as Ha-47.
The Hatsukaze Model 12 was the power section linked to a compressor to create a primitive jet engine called a motorjet, the resulting Tsu-11 was intended to power Yokosuka MXY7 Ohka 22flying bombs. The standard Hatsukaze 11 engine was modified at a Navy arsenal by replacing the propeller drive shaft and engine front crankcase cover with a step-up gearbox. After modification, the engine was designated as the . The gearbox increased engine output shaft RPM at a 1:3 ratio. At engine speed of 3,000 RPM, the compressor section was operating at 9,000 RPM. The compressed air was then ducted into a combustion chamber where a liquid fuel was sprayed. The heated compressed air then exits through the tailpipe providing static thrust of 180 kg (396 lb). It is likely that about 1/3 of the total thrust was contributed by adding the combustion chamber aft of the compressor.
The Tsu-11 was also selected to power the Yokosuka MXY-9 Shuka ("Autumn Fire"), a trainer intended to prepare pilots for the Mitsubishi J8M rocket-powered interceptor. Neither of these aircraft entered service, however, as their development took place too late in the war.