METHODS FOR ESTIMATING HOVER PERFORMANCE

The sophisticated prescribed wake digital computer program described in reference 1.5 is considered to be an investigative tool for studying hover performance, but not a practical way for making quick engineering estimates. For
this purpose, three methods are suggested, one of which should satisfy the needs of the moment:

• Combined momentum and blade element method

• Hover charts

• Adjustment of existing whirl tower data

Each method has its special advantages. The combined momentum and blade element method is flexible but tedious unless a computer is available. The chart method is fast but is restricted by the assumptions that were used in preparing the charts, which may not be strictly applicable to the rotor being analyzed. The adjustment of existing whirl tower data has its greatest usefulness when the rotor being analyzed shares a special feature, such as airfoil section, with a rotor that has already been tested. Each method is described in the following paragraphs.