The TMN 4-cycle, sleeve-valve cutaway airplane engine was built by Petr Chvatal, of the Czech Republic, circa 2000. After completing only 10 engines, Petr produced a couple of the cutaways to demonstrate its operation. The cylinder liner has intake and exhaust ports cut into it. As the engine runs the liner rotates back and forth within the cylinder, which opens the intake and exhaust ports at the appropriate time in the combustion cycle.