Theoretical percentage of truncation = 13.9 percent(from Table II of Reference 7, 

 corresponding to s = - 1.087). 



Mean value of a; = -ss = 1.087 (0.3898) = 0.4237 = x. 



Mean value of A = 0.6990 + i = 0.6990 + 0.4237 = 1.1227, Q = 13.26 



Mean value of = antilog of 1.1227 = 13.26 



Therefore tiie mean value of tiie pitch angle = 13.26 t 10 = 1.326° 



The value of the variate A corresponding to a probability of 97.5 percent is 1.96 stand- 

 ard deviations greater than the mean value of A. Let Uiis value be A._ . Then A _ = 

 log ((9gy j) = 1.1227 + 1.96 (0.3898) = 1.8867, ^g^g = 77.0. Therefore the pitch angle corres- 

 ponding to a probability of 97.5 percent is 7.7 deg. The two sets of values of pitch angle and 

 probability (1.326 deg, 0.50), (7.7 deg, 0.975) define the straight line in Figure 7 which 

 represents the log-normal distribution of pitch angle. 



36 



