MIL-DTL-24784 / 21B (SH)
Diagrams, secondary FBDs, FCDs, and so forth, as required to support the system maintenance
concept. All diagram notes (general, apron, multiple page, and so forth), except for FBDs and
FCDs, shall be developed in accordance with 3.5.1 and MIL-DTL-24784.
3.6.6.9.1 Maintenance concept flowchart. The flowchart shall illustrate the basic methodology
of troubleshooting casualties. The philosophy or concept behind the troubleshooting method will
be shown by depicting generalized maintenance actions rather than specific tasks performed.
Overall format of the flowchart shall be divided into Operational, Detection, Localization, and
Isolation and Repair sections by use of labelled dashed lines. Each block of the flowchart shall
contain a circled number that corresponds to a paragraph number of an accompanying narrative
text that describes the content of that block. Block numbers shall be assigned sequentially and
shall follow the top-to-bottom, left-to-right flow pattern used by the flowchart. The flowchart
shall illustrate typical operations performed during the troubleshooting process in the sequence
that they were performed. The flowchart shall represent sufficient examples of the hardware and
software used with the equipment to illustrate the underlying troubleshooting philosophy. All
inherent or built-in troubleshooting aids shall be illustrated. However, to minimize complexity,
the flowchart shall not attempt to show all of the possible troubleshooting operations for every
hardware and software combination. (see 3.5.1.2).
3.6.6.9.2 Maintenance concept flowchart definitions. This section shall describe each of the
blocks of the maintenance concept flowchart and their content by use of narrative text presented
in tabular form. The table shall consist of paragraphs referenced to the numbered block of the
flowchart that is described. The table shall contain a separate sequentially numbered description
for each block appearing on the maintenance concept flowchart.
3.6.6.9.3 Fault logic diagrams (FLDs). The FLDs shall be prepared in accordance with
MIL-DTL-24784.
3.6.6.9.4 Sequenced switching diagrams (SSDs). SSDs may be used to step the technician
through a sequence of events to support troubleshooting. SSDs are generally used when normal
monitoring of events will miss symptoms that are significant to the troubleshooting process. This
can be due to the speed that the events take place, the need for controlling operator actions or
other circumstances that make a step-by-step monitoring of events useful to the troubleshooting
process. SSDs are often used to monitor weapon control functions, ensuring that the technician
zeros in on the correct symptom rather than a symptom indirectly resulting from the actual
problem.
3.6.6.9.5 Troubleshooting dependency diagrams. FLDs (see 3.6.6.9.3) shall be provided to
augment the troubleshooting procedures. Supporting information required to explain the use of
the diagrams shall be provided in the text or general note.
3.6.6.9.6 FCDs. FCDs shall be the most detailed part of the system of diagrams used to depict
the functional divisions of the equipment. The FCDs shall be directly linked to the lowest level of
FBDs contained in Chapter 3. This reference shall be by the hardware reference designator.
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