ABSTRACT
During forward flight, as the rotor blades go around the azimuth, they experience a time-varying periodic oncoming airspeed. It is assumed that the rotor blade is rotating in a counterclockwise direction when viewed from above the rotor. This condition has been followed throughout the book. The rotor disk can be divided into two half regions: one denoted as the “advancing side” (Figure 3.1), where the relative air velocity of the blade is higher than the rotational speed, and the other denoted as the “retreating side,” where the relative air velocity is lower than the rotational speed of the blade. This asymmetry in the aerodynamic environment leads to time-varying periodic loads. Unlike the hovering condition, the time-varying nature of the blade loading creates a dynamic response of the blade, which must be included in the formulation in forward flight.
