Experimental aviation engines face numerous challenges, including the need for energy efficiency, alternative fuel sources, reduced weight and size, greater durability with reliability, emissions reduction, and integration with advanced control and monitoring systems. This study presents the performance of a two-stroke engine with a Uniflow scavenging system with a flathead valve concept, with lower specific fuel consumption than conventional two-stroke aircraft engines. The engine’s maximum speed is limited to 3000 rpm for better cylinder scavenging efficiency, which also eliminates the need for a reduction gearbox, simplifies the design, and reduces the engine’s total mass. 1D simulations were conducted to evaluate combustion and performance parameters using aviation. At the maximum speed of 3000 rpm, the engine achieved a power of approximately 23 kW with boost around 3bar, while at cruise speeds between 2400 and 2700 rpm, the maximum torque is approximately 80 Nm, with specific fuel consumption ranging from 368 to 378 g/kWh. Brake fuel efficiency is around 23%, which is significantly higher than that of conventional two-stroke engines with cross-flow scavenging, with an average efficiency of only 19%. 3D simulations (CFD) showed promising results with swirl and tumble presenting high velocities promoting high turbulence in the combustion chamber. The engine’s high-power density of approximately 90 kW/l makes it a suitable option for equipping experimental aircraft, as it is compact, efficient, and lightweight compared to commercially available options.