measured. These measurements are very difficult to perform and are subject to error. 

 In this case, the nose-tail line was specified by calculating it from design values 

 of chordlength, pitch, skew, and rake. Actual values of pitch, skew, and rake 

 occurring during the pressure measurement test could not be measured. Therefore, 

 design values were used and varied slightly to place the measured offsets close to 

 the design values. The relative position of each measured offset remained constant, 

 while the section was displaced to match the design section. This was performed by 

 calculating two common points near the ends of each section, and adjusting the 

 measured section to minimize the difference in the location of the points between 

 the two sections. 



MEASURED RESULTS 



Figure 34 shows the comparison between the measured and design blade sections 

 at the 0.5, 0.7, and 0.9 radial positions. Table 9 lists the offsets of Blade C 

 at the 0.7 radius. Each figure shows the section properly proportioned, and expanded 

 to allow a more detailed comparison. In all cases, the general measured section 

 shape matches the design shape quite well. The expanded section views indicate a 

 tendency for the measured section to be thicker than design over most of the section 

 except at the leading edge where the measured section is thinner. This could be 

 indicative of the manufacturing process, where extensive hand finishing at the lead- 

 ing edge is necessary. The largest measured deviation in offset was approximately 

 0.006 in. on the suction side of Blade B at the 0.7 radius, as shown in Figure 34d. 



A possible error could have occurred, influencing the offset measurement 

 uniformly across the chord. An error in the measurement of the reference axis of 

 the blades would have increased the offsets on both sides of the blade, thus explain- 

 ing the extra thickness measured. A thicker leading edge would result, perhaps 

 obscuring a critical problem with leading-edge shape. It is doubtful that this error 

 occurred. 



A variety of localized irregularities in blade shape were also measured over 

 most of the sections. Where surface pressures were measured, roughness was caused 

 by gage cover plates protruding above the surrounding blade surface. This was most 

 prevalent at the 0.9 radius where the coverplate gage configuration was used 



46 



