Use of the Charts

The charts* can be used to determine performance and approximate trim conditions for several forward flight conditions by one or more of the procedures provided in Table 3.5. For a more exact computation of trim conditions, the refinements of Chapter 8 should be used.

♦The chart format was originally developed by M. C. Cheney at Lockheed.

The cases illustrated include:

• Main rotor in level flight.

. • Main rotor in level flight with compressibility losses.

• Tail rotor.

• Entire helicopter in level flight.

• Helicopter in autorotation.

• Helicopter in climb.

• Helicopter in dive at constant collective pitch.

• Helicopter with auxiliary propulsion.

• Rotor in a wind tunnel.

(Hint: whenever possible, use even values of tip speed rati, os rather than even values of forward speed, so that the charts can be used without interpolation.)