on the suction side, but to a lesser degree. The pressure side showed irregularities 

 at the lowest speed, similar to those at the 0.5 radius, but produced a large in- 

 crease in C with speed at the trailing edge. 



At the 0.9 radial position on the suction side of Propeller 4718, C increases 



P 

 with speed, with increasing magnitudes toward the trailing edge. On the pressure 



side, only a slight speed effect occurred at the leading and trailing edges. The 

 suction side of Propeller 4679 had pressures increasing with speed in the fore-chord 

 region. The pressure side had little speed dependency except for, again, irregular- 

 ities at the lowest and highest speed condition. 



Generalizing the pressure-coefficient speed-dependence trends are as follows: 



1. Consistent direction of speed dependence - The pressure coefficients 

 increased with increasing speed on both sides of the blade with the exception of 

 the pressure side of Propeller 4679, at the lowest speed run. 



2. C versus V D was a smooth function - In most cases, pressure coefficients 



p R 



plotted against V produced smooth monotonically varying curves, as shown in 

 Figure 14. 



3. Propeller 4718 exhibited slightly greater speed effects for C than did 

 Propeller 4679. 



4. Speed dependence of C occurred in both uniform and inclined flows. 



5. Speed dependence appeared to be independent of J (from results to be 

 discussed subsequently) . 



6. No speed dependence was observed in unsteady pressure measurements (from 

 results to be discussed subsequently) . 



POSSIBLE MEASUREMENT ERRORS CAUSING C VARIATION 

 WITH REYNOLDS NUMBER P 



The above trends do not obviously point to any real flow effects, so the feasi- 

 bility of an instrumentation error as the cause of the speed effects should be con- 

 sidered. The form of the pressure coefficient is: 



p - p 

 C = 



P 1/2 PV„ 2 



20 



