The Tsu-11 was a primitive, motorjet-style jet engine produced in small numbers in Japan in the closing stages of World War II. It was principally designed to propel the Japanese Ohka flying bomb, a kamikaze weapon.
The Tsu-11 used a four-cylinder inverted inline Hitachi Hatsukaze Ha 11 piston engine to drive a single-stage compressor. A fuel injection system was fitted behind the compressor. In operation, fuel would be mixed with the compressed air and the resulting mixture ignited, creating thrust.
The engine was first tested hung underneath a Yokosuka P1Y bomber sometime in 1944 and was deemed successful enough to order into production. The Ohka was adapted to accommodate the engine in a lengthened fuselage with jet intakes added at the sides. This configuration was designated Ohka Type 22. 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.
A single example of a Tsu-11 engine exists, preserved at the National Air and Space Museum in Washington DC. In 1997 it was installed in the museum's Ohka 22 during its restoration. Engineering analysis of the engine during the restoration process suggested that the fuel injection and combustion probably contributed little to the power of the engine, with most of the thrust actually being produced by the compressor - in effect, an afterburning ducted fan engine.