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|  MIL-C-62135 A(AT)
3.1.2 Durability (minimum). When installed on the M520 cargo vehicle the crane assembly
shall have a .90 probability of not requiring removal from the vehicle for repair during 125 hours
of crane operation (125 crane missions, see 6.4) without requiring replacement of motors or crane
brake.
3.1.3 Maintainability. When maintenance procedures shown in the technical manuals are
followed and the crane is subject to endurance testing, or operation on the vehicle as defined in
the mission statements the demonstrated maintainability shall be as follows:
(a) Means Operator Preventive Maintenance Time shall not exceed .50 manhours per
mission. This time shall not be included in scheduled maintenance time.
(b) Maximum Operator Corrective Maintenance Time shall not exceed .15 manhours per
mission without being classified as a mission failure.
(c) The ratio of total corrective and scheduled maintenance manhours to operating hours
shall not exceed .12.
(d) The ratio of total scheduled maintenance manhours to total operation hours shall not
exceed .10.
(e) The ratio of total corrective maintenance manhours to operating hours shall not
exceed .02.
(f) Mean manhours to perform a corrective maintenance action (MTTR) shall not
exceed 1.00.
(g) The specified mean cycles between maintenance actions (MCBMA) shall not be less
than 21 cycles.
3.1.3.1 Maintainability Failure. A maintainability failure is defined as any unscheduled
adjustments, repair or replacement. To calculate MCBMA, consult definitions in MIL-STD-721.
3.1.4 Interchangeable components. The electric motor assemblies provided for turntable,
cable hoist, and boom lift shall be identical.
3.2 Materials. Materials specified herein in referenced drawings, specifications, and standards
shall be free from all defects and imperfections that might affect the serviceability and function of
the finished product.
3.3 Crane assembly. The crane assembly shall be in accordance with 11651265. The
assembly shall include winches, wire rope, load block, lifting hook, sheaves, controls, wiring, and
all items necessary for its complete adaptation. All direct load carrying components of the crane
shall have a safety factor of not less than two, based on the yield point of the material used. The
liftoff weight of the complete crane assembly shall not exceed 875 pounds. The crane liftoff
configuration shall include features of removal from the truck as a separate unit, bolts securing the
crane to the vehicle, with waterproof electrical connections between the truck and crane.
3
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