MIL-DTL-24784/18B (SH)
complete coverage of equipment functions for fault-isolation by shipboard maintenance
technicians using test equipment and tools available aboard ship. The diagrams shall always lead
to a corrective action or to information required by the technician to correct the malfunction in
minimum time. Based upon the list of equipment output functions developed by the maintenance
analysis and the approved manual outline, the following shall apply:
a. Every output function shall be shown in a signal flow diagram. Associated functions may be
included on one diagram.
b. Every output function, except noncritical voltages for relay closure and lamp illumination in
other equipment of the weapon system or associated equipment, shall be displayed in a
separate detail pyramid. Associated functions may be included on one diagram.
c. Primary power distribution diagrams shall illustrate ships power from the first terminal board,
breaker box, or fuse box outside the subject equipment to the various terminal boards and
jacks within the equipment where each supply voltage is being distributed. Secondary power
distribution diagrams shall illustrate complete internal distribution of each supply voltage, and
extend back only to the nearest point where the transformer or dc power supply primary input
can be correlated to the appropriate primary power distribution diagram.
d. The ladder diagram technique shall be used primarily to show all relay coils within an
equipment and the path of energizing current for each. However, coils that are in series with
the main path of signal flow and that appear on signal flow diagrams or on power distribution
diagrams shall not be repeated in relay ladder diagrams. The same technique shall be used for
such items as indicating lamps, solenoids, and control mechanisms, as applicable.
3.6.6.3.1 Sequencing of troubleshooting diagrams. The sequence of trouble-shooting diagrams
in a manual shall be as follows:
a. For Case A, each signal flow diagram shall be followed by the detailed pyramid(s) for the
output functions depicted on it. Each complex multisheet detailed pyramid shall be preceded
by its summary pyramid if one is required. The ladder diagrams shall follow all the signal flow
diagrams and pyramids. The power distribution diagrams shall follow the ladder diagrams.
Deviations from this arrangement shall be approved by the Government.
b. For Case B, summary block diagrams shall precede the signal flow or group of signal flow
diagrams encompassed by each. The ladder diagrams shall follow all the signal flow diagrams.
The power distribution diagrams shall follow the ladder diagrams. Deviations from this
arrangement shall be approved by the Government.
3.6.6.3.2 Cross-referencing maintenance documents. Documents shall be cross-referenced to
save time required for troubleshooting and to reduce bulk. Point-to-point referencing shall be
used within any one type of document, and document references may be used across types where
applicable. Point-to-point reference is required in detail pyramids and in signal flow diagrams.
Document-to-document reference is to be used when referencing from one category of PMS
material to another, as from a detail pyramid to an MRC. The overall criterion for referencing in
the maintenance documents requires that the technician shall never be dead-ended during
maintenance actions.
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