In the year 1933, the development of a two-stroke engine for aircraft was made. It is recorded in the registry of the USNA with number 3232/452.8. The X-250D.

-The Laboratory Division of General Motors Corp. made a two-stroke, 4-double-cylinder X-engine that was liquid cooled. It had direct transmission and a supercharger. Model X-250.

“General Motors Research X-250-F”

-The power was 225 hp at 2,500 rpm.

From Appendix 10: Engine with cylinders in X, composed of four blocks of two cylinders each.

-Each two cylinders of a block were joined by a U-shape combustion chamber. The pistons rose with a slight lag so that when using ports, it ran with the 2-stroke cycle.

-There are some examples such as the Szidlowsky radial engine, "Iso" motorcycle engines, etc.

"The X-259 engine" was from the 1930's"