The variation of first harmonic amplitudes with J on the pressure side of the 

 blades appeared to be less than on the suction side. A general trend occurred at 

 the 0.5 and 0.7 radius positions where the leading-edge values dropped with decreas- 

 ing J, while the midchord values slightly increased. Dissimilar trends occurred at 

 the 0.9 radius position for both propellers, again possibly caused by tip-vortex 

 effects. 



The first harmonic phase angles on either propeller did not produce any consist- 

 ent trend with variation in J. The phase angles in various cases increased, 

 decreased, or remained constant. Some evidence indicates that the variations in 

 phase angle with J were coupled to trends in amplitudes that deviated from the pre- 

 viously stated general trends. The suction side of Propeller 4718 at the 0.5 and 0.7 

 radius positions showed large variations in phase in the mid- to aft-chord region. 

 These could be coupled to larger-than-expected amplitudes in the same region at 

 low J. 



Quasi-steady predictions of first -harmonic amplitudes were calculated, producing 

 good correlation with the measured trends on the suction and pressure sides of the 

 blade. As with the design J correlations, the quasi-steady analysis underpredicted 

 the measured amplitudes by 30 to 50 percent. On the blade suction side, the quasi- 

 steady result produced decreasing amplitudes with J in the midchord region, similar 

 to the measured result. On the blade pressure side, the quasi-steady calculation 

 produces a similar consistent trend of first harmonic amplitude with J over most of 

 the chord with a similar decrease in amplitude at the leading edge. 



The quasi-steady analysis was performed on Propeller 4718 using both the first 

 and second order C versus J curves. On gages where a noticeable nonlinearity 

 occurred, variations in the quasi-steady predictions occurred, as seen by comparing 

 Figures 30 and 31 in the leading-edge regions. It appears that the second-order 

 curves more closely resemble the measured results implying dependence of the fluc- 

 tuating pressures on the nonlinear variation of C with J observed in uniform flow. 



The quasi-steady procedure generally predicted a constant first-harmonic phase 

 angle with J of <(>- = 90 deg on the blade suction side, and <(>.. = 270 deg on the blade 

 pressure side. This consistency of phase angle weakly supports the concept that 

 phase angle variations with J are related to variations in the trends observed in 



39 



