Experimental Investigation of the Effect of Propeller Blade Pitch on Propeller-Produced Unsteady Bearing Forces and Moments

Experimental results are presented to show the effect of pitch- diameter ratio on propeller-produced unsteady loads. Eight three-bladed propellers with changes of equal increments of pitch resulting in pitch-diameter ratios from 0.58 to 1.75 were tested in three-cycle and four-cycle wake screens. The data indicated that, in general, for the same thrust loading coefficient C sub Th, the unsteady thrust and bending moments tend to decrease with increasing pitch whereas the torque increases and the side forces change negligibly. However, it is impracticable to reduce unsteady thrust by altering pitch.