A helicopter of mass 12,000 kg hovers at sea level with a load of 15,149kg. The horizontal blades above the helicopter cause a 18 m diameter air mass to move downward at an average velocity proportional to the over head blade rotational velocity (rpm). Determine the power input in kw required to hover with the load. Take the density of atmospheric air to be 1.18 kg/m^3. Assume air approaches the blades from the top through a large area with negligible velocity and air is forced by the blades to move down with a uniform velocity through an imaginary cylinder whose base is the blade span area. The elevation effects are negligible, and the frictional effects can be disregarded.