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|  MIL-S-18471G(AS)
3.2.1.7 Reliability.
3.2.1.7.1 Probability of success. As a minimum, the escape system shall
achieve the reliability levels specified for the following operational modes:
a.
Aircrew automated escape reliability, expressed as the
probability that the escape system shall perform as required
in 3.3.2, shall be at least 0.98.
Non-emergency reliability, expressed as the probability
b.
that the escape system shall successfully perform the
requirements of this specification and the aircraft
mission requirements specified in the aircraft detail
specification, shall be at least that specified in the
applicable subsystem allocation for the aircraft in
which the escape system will be installed.
3.2.1.7.2 Design redundancy. System components, whose proper functioning
is critical to the successful operation of the escape system or to the safety
of the aircrewmember(s), shall be redundant or shall be provided with redundant
actuation means.
3.2.1 .7.3 Fail-safe operation. Critical functional components or subsystems
which have two or more modes of operation shall be designed to ensure that any
failure of the sensing, command, or control means to properly select the
intended mode of operation shall result in the system functioning in the
least hazardous mode. The selection of the least hazardous mode shall be
acceptable to the procuring activity (see 6.2.2).
3.2.1.8 Maintainability. If more stringent maintainability requirements
are specified by the aircraft detail specification subsystem allocations, they
shall be achieved. As a minimum, the escape system shall achieve the following
maintainability levels:
Based upon a flying hour rate of 35 hours/monthf the direct
a.
maintenance man hour/flight hour (DMMH/FH) at the organiza-
tional and intermediate maintenance levels for corrective
and preventive maintenance including the preparation of
items to be installed in the escape system, shall be not
greater than 0.05 for a single seat escape system. (A
different value of the DMMH/FH may be designated in the
contract for application to a multiple seat system. In
addition, the procuring activity may also adjust the DMMH/FH
for different flying rates to assure that the total DMMH/
month/aircraft does not exceed 1.75 hours.)
b. The mean time to repair (MTTR) shall be not greater than
0.40 hours.
c. The maximum corrective maintenance time (Mmax) for the
95th percentile individual maintenance action, ranked on
the basis of corrective times, shall be not greater than
2.5 hours including time for parachute packing, and time
for system removal and reinstallation in the crew station,
if required.
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