Avionics News September 2021 - 33

Figure 2: A schematic representation of
some of the circuitry shown in Figure 1
complete understanding of the
individual components shown in
Figure 2. As you may guess, it
takes some time before someone
is ready to get into such detail.
the figure. Now we have a single symbol, which can be
placed among all the other symbols of a radio receiver
as shown in the top left of the same figure. In class, we
can discuss the functions of the various circuits within
the radio receiver and discuss how they are connected
together.
We can still simplify further. Figure 5 shows a
remote-mounted communication system. All of the
symbols shown in Figure 4, and more, are all within
the communications transceiver. When we teach
communication systems, we start with this diagram
since we can discuss how many separate components
are included and where we may locate them in the
airframe. For clarification, I call these types of block
diagrams external, and the blocks in Figures 3 and 4
internal. I ask students to memorize block diagrams
similar to the one shown in Figure 5. As a result, any
time an avionics communication system is discussed,
the student will have a picture in his or her head of
what components are involved and where they might be
in the aircraft.
Once a student has memorized the external block of a
system, we can begin to discuss the theory behind how
the system works using internal block diagrams. For
those not planning to become a component level repair
technician, the block diagram in Figure 4 would be
sufficient. For those going deeper into system repair or
design, the block in Figure 3 could be used as a prelude
to schematics as shown in Figure 2.
Component level technicians and engineers need a
Most likely, they started with block diagrams.
If a technician intends to make measurements within
the system, the schematic, such as that in Figure 2,
along with a photo or drawing of component location,
becomes necessary.
When teaching systems, I'll start with the system's
purpose, and if it involves radio, the modes,
frequencies, and channels used, when applicable. Next,
I'll introduce the block diagram. Once the students
have the block in memory, we can have intelligent
conversations about where in the aircraft we can find
components and the different variations of system
design. For many systems, I'll require memorization
down to the level shown in Figure 4.
Students who do not memorize the block diagrams
will slowly begin to feel lost as the class continues. The
longer we discuss a system, the more lost they will feel.
As a result, even though the memorization process may
seem tedious, there is much value to it.
Fortunately, there is a relatively non-tedious way to
memorize these blocks, the various formulae we must
learn, and even phone numbers or names. It only takes
a few minutes per day, and in less than a week, you can
have the diagram committed to memory.
This technique is based on the proven close
connection between hand movements and the brain,
especially the memory portion. This connection is so
tight that there are some things we can do only once
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Figure 3: Functionality becomes apparent with a block diagram of the circuitry shown in Figure 2.
avionics news * september 2021 33
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Avionics News September 2021

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