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2 Answers

HIGE/HOGE Angle of Attack

Asked by: 3437 views Aerodynamics, Helicopter

Does Angle of Attack change when hovering in and out of ground effect?

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2 Answers

  1. Nathan Parker on Aug 02, 2012

    Yes. When hovering out of ground effect, there is a downflow of air that reduces the AoA of the rotor blades; as the helicopter nears the ground, there is an increase of pressure as the airflow attempts to go through the ground, but is deflected to the sides. This increase in pressure reduces the airflow, increasing the AoA on the rotor blades.

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  2. Christopher Arndt on Mar 12, 2013

    Mr. Parker is on the right track but he is not correct. The same angle of attack is required to hover OGE and IGE. A different angle of incidence is required.

    This is due, like Mr. Parker stated, that OGE hover increases the velocity of airflow through the rotor system because the Earth is not close by to slow it down. This increase in velocity (called induced flow) increases the angle of incidence required to maintain the same angle of attack.

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