An unloaded helicopter of mass 12,000 kg hovers at sea level while it is being loaded. In the unloaded hover mode, the blades rotate at 550 rpm. The horizontal blades above the helicopter cause a 18-m-diameter air mass to move downward at an average velocity proportional to the overhead blade rotational velocity (rpm). A load of 14,000 kg is loaded onto the helicopter, and the helicopter slowly rises. Determine (a) the volumetric airflow rate downdraft that the helicopter generates during unloaded hover and the required power input and (b) the rpm of the helicopter blades to hover with the 14,000-kg load and the required power input. Take the density of atmospheric air to be 1.18 kg/m3. 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.
An unloaded helicopter of mass 12,000 kg hovers
at sea level while it is being loaded. In the unloaded
hover mode, the blades rotate at 550 rpm. The horizontal
blades above the helicopter cause a 18-m-diameter air mass
to move downward at an average velocity proportional to
the overhead blade rotational velocity (rpm). A load of
14,000 kg is loaded onto the helicopter, and the helicopter
slowly rises. Determine (a) the volumetric airflow rate
downdraft that the helicopter generates during unloaded
hover and the required power input and (b) the rpm of the
helicopter blades to hover with the 14,000-kg load and the
required power input. Take the density of atmospheric air
to be 1.18 kg/m3. 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.
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