MIL-DTL-62180F(AT)
Failure Definition and Scoring Criteria (FD/SC)) shall not exceed twelve man-hours
during the first 6000 miles of Product Qualification Test (PQT). This equates to a
Maintenance Ratio (MR) of no greater than 0.04 Maintenance Man Hours
(MMH)/Operating hour at 20 mph (NOTE: 20 miles of operation at 20 mph is
equivalent to one operational hour.)
b. The scheduled maintenance as recommended by the appropriate maintenance manual
shall be conducted throughout the test.
3.1.2.2 Maintainability requirements for assembly(ies) on each vehicle model.
a. The total active scheduled maintenance for the assembly(ies) on the semitrailers
(excluding crew checks and services in accordance with FD/SC) shall not exceed
3 man-hours, and the total active unscheduled maintenance shall not exceed 3 man-
hours during 100 hours of operation in accordance with the requirements specified
herein. This equates to each vehicle assembly(ies) MR of no greater than 0.06.
b. The scheduled maintenance intervals shall be as recommended by the appropriate
maintenance manual throughout the test.
3.1.3 Reliability. (See 4.4.4.)
3.1.3.1 Reliability semitrailer. The reliability of the semitrailer shall achieve not less
than 6000 Mean Miles Between Hardware Mission Failures (MMBHMF) when subjected to the
speed and slope limitations in table I.
TABLE I. Speed and slope limitations.
Mileage
Longitudinal
Course
Speed (mph)
Percentage 1/
slope, max.
Hard surface roads
45
0-50
10%
Gravel and dirt roads
25
0-35
10%
(Unimproved roads)
Level cross country
20
0-20
10%
Hilly cross country
8
0-15
10%
Belgian block course
2
0-10
10%
1/ 90 percent of mileage in each course shall be accomplished with full payload. The
remaining ten percent of mileage shall be performed without payload.
3.1.3.2 Assembly(ies) Mean-Time-Between Failure (MTBF). The engine pump, fuel
dispensing and filter separator assemblies shall have a minimum MTBF of 100 hours when
subjected to requirements specified in 3.3.4.
3.1.3.3 Cyclic testing of assemblies. The fuel loading/unloading system shall be
demonstrated every 500 miles during the 6000 miles of operation.
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