This paper aims to improve the performance of rotary wing aerofoils by controlling the boundary layer using a Co flow jet. By supplying additional mass flow close to the foremost edge and removing the equal amount of mass flow from the trailing edge, the co-flow jet method produces circulation over an aerofoil top surface. The NACA 0015 aerofoil equation of state is used to simulate at Mach 0.05 with the k-omega SST equation. The results proved that stalling angle improved by 40% and the coefficient of lift improved by 83% compared to the existing aerofoil for rotary wings. A helicopter blade can be made lighter and more aerodynamic by using this method.