Definition
A circle drawn around a polygon so that every corner (vertex) of the polygon touches the circle. In aviation drafting and design, it is used to define the outer reach of a shape — for example, the diameter of the smallest circle that fully contains a propeller, rotor disc, or aircraft footprint.
Plain English
A circle drawn around a shape so it just touches every outside corner of that shape. It tells you the total space the shape takes up.
Context Anchor
Seen in aircraft drawings, layout work, and geometry used to describe or check the shape of parts.
Derivation
From Latin circum- meaning 'around' and scribere meaning 'to draw' or 'to write.' Literally 'drawn around.' That matches what the circle does — it is drawn around the outside of the shape.
Why Pilots Care
When you see a circumscribed circle on a diagram or specification, it is showing you the maximum reach of a part — useful for clearance, ground handling, and understanding how much space something sweeps through.
Intuition Check
Circumscribed does not mean “restricted” here. It means drawn around the outside so the circle touches the shape’s outer points.
Example Sentence 1
The propeller's circumscribed circle defines the total disc area swept by the blades during rotation.
Example Sentence 2
Using the circumscribed circle on the triangle formed by the waypoints gave the exact radius needed for the turn.