Definition
The supporting frame or structural base of a piece of equipment, on which the working components are mounted. In aviation, the term most often refers to the metal frame inside an electronic unit (such as a radio, transponder, or instrument) that holds the circuit boards, wiring, and components in place and provides a common electrical ground.
Plain English
The frame or skeleton of a device that everything else is built onto and bolted to.
Context Anchor
Seen in aircraft maintenance, landing gear discussions, and descriptions of how aircraft parts or equipment are mounted and supported.
Derivation
From the French chassis, meaning frame or framework, which itself comes from the Latin capsa, meaning a box or case. The original idea is a structural box that holds and protects what is inside it — exactly what a chassis still does today.
Why Pilots Care
Many aircraft electrical systems use the chassis itself as the ground return path. A loose or corroded chassis connection can cause intermittent radio, instrument, or lighting problems that are difficult to trace.
Intuition Check
Do not think of chassis only as a car term. In aviation, it means the supporting frame or ground-supporting structure of an aircraft or equipment.
Example Sentence 1
The technician removed the radio cover and found a cracked solder joint between the circuit board and the chassis.
Example Sentence 2
All major flight loads are transferred through the chassis to the wings and landing gear.