PERCENTAGE OF TIME THE VALUES EXCEED THE ORDINATE 



Fig. 4-17 Cumulative Amplitude Distribution of B-45 Echo; Larger Range of 

 Aspect Angle. 



Rayleigh line fitted to the lower levels. This is attributed to reflections 

 from the propeller, which, for a rather large range of angles, are stronger 

 than from the remainder of the aircraft. This is shown by the original 

 pulse-to-pulse photographs shown in Fig. 4-19. Here every fifth pulse 

 (repetition rate 120 cps) is much larger (on all three frequencies) than the 

 intervening ones. The dominance of the propeller echo was found to be 

 especially marked at oblique aspects of the aircraft between head-on and 

 broadside, corresponding to the region where a portion of the blade is nearly 

 normal to the line from the radar. 



To depict the gross aspect variation of cr, the median values over roughly 

 5° of azimuth were plotted against azimuth angle. Figs. 4-20 to 4-22 show 

 the results for the B-36, B-45, and F-51, respectively. In averaging over an 

 angular range of this amount, sharp peaks of the aspect dependence are 

 largely smoothed out. In all cases, however, a prominent and rather broad 

 maximum occurs in the neighborhood of the broadside aspect. This is 

 especially true in the case of the B-36 (which has a rather flat fuselage) as 

 shown by the 9380-Mc plot in Fig. 4-20 (broadside data for 1250 and 2810 

 Mc were saturated and so are absent from this figure). The F-51 has its 

 broadside maximum at an azimuth of about 98°, probably owing to the 

 tapered tail section of the fuselage. 



