r T ё , •:, , Downloaded from https://www.everyspec.com AMCP 706-198 .camgl, No. 7 A helicopter inertial navigation system is tested (Ref. 11) and truncated at 4 failures, at which time 1500 hr of test time have elapsed. Estimate the mean life, the 2-sided (symmetrical) upper and lower &-confidence limits, and the 1-sided lower s-confidence limit on mean life for a a-confidence level of 0.95. Procedure Example 1. Tabulate the test results. I.. t a time elapsed at the k 0 -th failure 1500 hr kh 0 - number of failures= 4. 2. Compute the estimated 2. 8 . 1500 hr/4 - 375 hr mean life from t - I/k 0 o 1/0 - 2.67/1000-hr. (2-29) 3. Calculate the symmetri- 3. C -'95% cal levels.' - 97.
5%, 1 - CD - 2.5%. 4. Copy the appropriate data 4. Ratio a-.onfidenoe from Table 2-8, 2.2 2.5% 0.27 97.5% 1.94 5% 5, Compute s-confidence 5. Nu - 2.2h - 2.2 x 2.67/1000-hr - 5. 87/1000-hr limits for 95% symmetric 0 - - 170 hr levels. X,& = 0. 27% - 0. 27 x 2. 67/1000-hr 0. 72/1000-hr OU - 1/Xh w 1390 hr. 6. Compute the 1-sided 95% 6. )h - 1. 94h - 1. 94 x 2.67/1000-hr 8 -confidenve limit. = 3.18/1000-hr 9 L - 1/A - 193 hr. 7. Make the s-c, lice 7. Conf{170 hr % 0 5 1390 hrl - 95% statements. Conf {193 hr S•01 - 95%. . ,