A new fuselage was designed, with the pressurized cockpit being moved well forward near the nose. The wing was tapered and had rounded wingtips, and was mounted low on the fuselage. Other Me 309 components were to be used, such as the tricycle landing gear, and the vertical tail assembly was similar to the one used for the Me 309 V1. Armament was not decided upon for the 509, but it is thought that two MG 131 13mm machine guns and two MG 151 20mm cannon were to be used. In April 1945, the Japanese completed a very similar project, the Yokosuka R2Y Keiun.
All dimensions approximate.
The Yokosuka R2Y Keiun , which was built for the Japanese Navy use, was an aircraft very similar in design to the Messerschmitt Me 509.