controllable pitch propeller. The components Mo 3 and My 4 are the most 
important for determination of the time-average and unsteady stresses in 
the blades of a propeller. 
CENTRIFUGAL AND GRAVITATIONAL LOADS 
The results of the air-spin experiments, corrected for interactions, 
are presented in Table 6. The time-average values arise from centrifugal 
force whereas the first harmonic arises from gravitational force. There- 
fore, the mean values should vary as ma where n is the propeller rotation- 
al speed, and the first harmonic should be independent of n. 
For the mean values, which arise from centrifugal force, signficant 
nonzero values were obtained only for the Hae Fo ee and M, components. 
Any realistic propeller would have nonzero values of centrifugal loading 
— — 31 
components Go, and (Me: 
Nonzero values of oe and Coe are pro- 
duced by the nonzero values of skew and rake of the propeller evaluated. 
The components CO and mm), should be zero for any geometry, however, 
a small value of (Ey was measured. This small nonzero (Pade probably 
arises from inaccuracies in the air-spin experiment and interaction 
matrix. For all components the experimentally determined mean value 
varies essentially as i The experimental air-spin results were faired 
so that the values of the mean loading components used for separating 
hydrodynamic loads from total loads varied exactly as mee 
For the first harmonic loads, which arise from acceleration due to 
gravity, nonzero values were obtained only for the #09 M and Ee flexures. 
For Mie and Geile the phase angles are +96 degrees and -96 degrees, 
respectively; therefore the maximum and minimum values of these components 
occur when the blade is approximately horizontal. This would be expected 
from the geometry. The phase angle for ile is -159 degrees; therefore 
Ny seesTal R.J., "A Method of Calculating the Spindle Torque of a 
Controllable-Pitch Propeller at Design Conditions," David Taylor Model 
Basin Report 1529 (August 1961). 
26 
