b. At the 0.5 and 0.7 radii, variation of C with R occurred at numerous 



P n 

 gage locations with the largest variation occurring at the 0.5 radius on the suction 



side for Propeller 4718. 



c. At the 0.9 radius, suction side, the C variation on Propeller 4679 



P 

 occurred toward the leading edge while the C variation on Propeller 4718 occurred 



toward the trailing edge. 



d. Roughening the leading edge with sand produced no noticeable change in 



the C distribution. 



P _ 



4. The variation of C with J led to the following observations: 



a. At most blade locations, C varied linearly with J. Slight second-order 

 nonlinearity occurred on Propeller 4718 at the leading edges and 0.9 radius. On 

 Propeller 4679, nonlinearity occurred at various, more numerous locations on the 

 blade. 



b. Generally, over the chord, C values on the pressure side of the blade 

 were more sensitive to J than on the suction side at the 0.5 and 0.7 radius, while 

 the reverse was true at the 0.9 radius. 



c. On the suction side of the blades at the 0.5 and 0.7 radii the chord 

 position of insensitivity to J occurred not at the trailing edge as expected, but 

 around the 80 percent chord position. 



d. The sensitivity of C to J, increased toward the leading edge, as 

 expected. 



5. Unsteady pressure measurements were performed with the propellers operating 

 in 7.5 degree inclined flow at design J. Quasi-steady and unsteady theoretical 

 comparisons were made, resulting in the following: 



a. Measured first harmonic pressure coefficient amplitude C 1 and phase 

 angle <p. were independent of Reynolds number. 



b. The quasi-steady predictions of C - underestimated the measured values 

 by 30 percent to 50 percent, but generally followed the measured C 1 distribution 

 along the chord. 



c. The quasi-steady first harmonic phase angle prediction of <j), = 90 deg 

 on the suction side and <$>. = 270 deg on the pressure side of the blade was only 

 approximately matched by the measured results. Variations in these predictions 

 occurred at the various radial and chord positions with no obvious trends observed. 

 In some cases, sharp phase changes occurred near the trailing edge. 



41 



