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3.12.  HOVERING

A helicopter hovers when it maintains a constant position at a selected point in the air, usually a few feet above the ground. To hover, a helicopter main rotor must supply lift to equal the total weight of the helicopter, including crew; fuel; passengers and cargo, if carried; and armament, if armed. The necessary lift is created by rotating the blades at high velocity and increasing the blade angle of attack.

At a hover, the rotor system requires a great volume of air upon which to work. This air must be pulled from the surrounding air mass; this is an expensive maneuver that takes a great deal of horsepower. The air delivered to the rotating blades is pulled from above at a relatively high velocity, forcing the rotor system to work in a descending column of air.

The main rotor vortex and the recirculation of turbulent air add resistance to the helicopter while hovering. Such an undesirable air supply requires higher blade angles of attack and an expenditure of more engine power and fuel. In addition, the main rotor is operating in air filled with abrasive materials that cause heavy wear on helicopter parts while hovering in ground effect.

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