Definition
The metal frame or structure of an aircraft (or piece of equipment) used as the common return path for electrical current. Instead of running a separate return wire from every electrical component back to the battery's negative terminal, the metal airframe itself carries the current back, completing the circuit.
Plain English
The aircraft's metal body is used as one giant wire to carry electricity back to the battery, so each component only needs one wire running to it instead of two.
Context Anchor
Seen in aircraft electrical system descriptions, wiring diagrams, radio installations, and electrical troubleshooting.
Derivation
Chassis' comes from the French chassis, meaning 'frame.' 'Ground' in electrical use means the common reference point that completes a circuit. Together: the frame itself acts as the electrical return path.
Why Pilots Care
Ensures all electrical equipment shares the same reference point, preventing voltage differences that could cause instrument or radio malfunctions.
Intuition Check
Chassis ground does not mean a connection to the dirt or the airport surface. In an aircraft, it usually means a connection to the metal structure of the aircraft or equipment.
Example Sentence 1
The mechanic traced the flickering nav light to a corroded chassis ground at the wing root.
Example Sentence 2
Loose chassis ground connections can cause intermittent avionics failures during flight.