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Page Title:
Reliability, availability, maintainability, durability (RAM-D) |
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|  MIL-T-62531(AT)
3.4.8 Lighting. All vehicle lights, reflectors, and wiring shall be as specified herein and shall
conform to MIL-STD-1179. Lights and reflectors shall not be mounted on vehicle bumpers. Rear
lighting shall be mounted in a protective location to preclude damage when interfacing with other
vehicles or ancillary equipment. Vehicles shall be equipped with a blackout and marker lighting
system. Front and rear turn signal lamps shall be provided. Turn signal operating units shall have
visible and audible flash indicators and shall be mounted on the steering column (see 4.4.8).
3.5 Reliability, availability, maintainability, durability (RAM-D). The RAM-D requirements
shall be demonstrated by operating _____ vehicles, each for ______ kilometers for a total of
______ kilometers in accordance with the distance schedule specified in 3.6.1. For RAM-D
calculations, ______ kilometers shall equal one operating hour (see 4.6).
3.5.1 Reliability (mission). The mission reliability of the vehicle system shall be not less than
______ percent at ______ percent confidence level and shall be demonstrated under the conditions
stated herein. The mission duration shall be ______ kilometers for a total of missions. The number
of mission failures shall not exceed ______ failures. A mission failure is a failure which precludes
the completion of a mission, once started, and which cannot be corrected by the crew with material
and equipment provided for crew level of maintenance (see 4.5.1).
3.5.2 Availability (inherent). The inherent availability of the vehicle system shall be not less
than ______ percent and shall be determined based on the following relationship (see 4.5.2):
A=
MTBF
X 100
MTBF + MTTR
where
A=
Inherent availability.
MTBF = Meantime (hours) between failures.
MTTR = Meantime (hours) to repair; the MTTR is the summation of all active repair
times used to isolate a malfunction, effect repair and restore the vehicle
system to operational status divided by the total number of mission failures.
Active repair time does not include supply downtime, waiting administrative
downtime and preventive maintenance.
3.5.3 Maintenance ratio. The maintenance ratio is an index which establishes a relationship
between the total time required to perform maintenance and the total mission operating time in hours.
The maintenance ratio shall not exceed ______ and shall be based on the following relationship
(see 4.5.3):
MR =
T
M
where MR =
Maintenance ratio.
T=
Total maintenance time (hours) expended to perform scheduled and
unscheduled maintenance covering the total vehicle system operating time
period.
M
=
Total mission time (hours).
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