The Rotary Atkinson Cycle Engine has not been widely adopted in production vehicles, with the Wankel engine being the most notable rotary design, yet it has faced challenges in market success. There is a demand for lightweight and powerful rotary engines in aviation, but certification hurdles remain due to the complexity of the designs and the precision required for their geometries and seals. The Wankel engine's sealing issues between the rotors and housing have been managed but not fully resolved, leading to ongoing concerns about fuel and oil consumption. While circular housings are easier to manufacture, straight sliding components present more difficulties. Overall, the rotary engine designs are hindered by technical challenges that have prevented broader implementation in both automotive and aviation sectors.