Definition
Simplified drawings that represent a system, circuit, or process as a series of labeled boxes connected by lines, where each box stands for a component or function and the lines show how signals, fluids, or forces flow between them. Block diagrams show what connects to what and in what order, without showing the internal detail of each component.
Plain English
A simple picture made of boxes and lines that shows the parts of a system and how they are linked together, without showing what is inside each part.
Context Anchor
Seen in aircraft maintenance manuals, avionics descriptions, electrical system explanations, and troubleshooting material.
Derivation
From 'block,' meaning a solid chunk treated as a single unit, and 'diagram,' from the Greek 'diagramma' meaning a figure drawn out. So a block diagram is literally a drawing made of units. The word 'block' is the clue: each part of the system is shown as one self-contained block, with the inner workings left out on purpose.
Why Pilots Care
When troubleshooting or studying a system, a block diagram lets a technician quickly see the path of power, signal, or fluid flow and identify where a fault could interrupt it. It is often the fastest way to understand an unfamiliar system.
Intuition Check
Do not read a block diagram as a picture of where parts are physically installed. It is a simplified relationship map, not an exact layout drawing.
Example Sentence 1
The technician studied the block diagram of the starter-generator system to trace the path from the battery bus to the generator control unit.
Example Sentence 2
Using the block diagram, the maintainer quickly isolated which unit was interrupting power to the navigation equipment.