

MILHDBK338B: Electronic Reliability Design Handbook 
 

5.6.2.2.1 Equipment Example
5.6.2.2.1 Equipment
Example
An equipment whose repair times are assumed to be normally
distributed was monitored and the following repair times were observed (in
minutes):
6.5, 13.25, 17.25, 17.25, 19.75, 23, 23, 24.75, 27.5, 27.5,
27.5, 32, 34.75, 34.75, 37.5, 37.5, 40.25, 42.5, 44.75,
52
Find the following parameters.
(1) The pdf of g(t) and its value at 30
minutes
(2) The MTTR and median times to repair
(3) The maintainability for 30 minutes
(4) The time within which 90% of the maintenance
actions are completed
(5) The repair rate, u(t), at 30
minutes
(1) Pdf of
g(t)
(2) MTTR and Median
Time to Repair
These are the same for the normal
distribution because of its symmetry, and are given by
(3) Maintainability for
30 Minutes
From the standard normal table (Table 5.33).
f(0.07) = 1  .4721 =
0.5279 = 0.53
\ M(30) = 0.53 or 53% probability of making a repair
in 30 minutes.
(4) Time within which
90% of the Maintenance Actions are completed
_{0.9} = _{ct} +
fS_{Mct
}f = 1.28 from Table
5.66
=
29.16 + (1.28)(11.5) = 43.88
minutes
(5) Repair Rate at 30
Minutes




 
 