Definition
The center of gravity of an aircraft when it contains only the items specified in the aircraft's empty weight — typically the airframe, engines, all permanently installed equipment, unusable fuel, and full operating fluids such as hydraulic fluid and (for some aircraft) full engine oil. It does not include usable fuel, crew, passengers, baggage, or cargo. It is expressed as a distance (in inches) from the aircraft's reference datum.
Plain English
It's the balance point of the airplane when it's stripped down to just the aircraft itself and its built-in fluids — no people, no fuel you'd burn, no luggage. Mechanics and loaders use this as the starting point before adding everything else.
Context Anchor
Seen in aircraft weight-and-balance records, especially after weighing an aircraft or after equipment is installed, removed, or moved.
Derivation
Center of gravity means the point where an object's weight acts as if it were concentrated. Empty-weight narrows that idea to the aircraft's official empty condition, not to a completely stripped aircraft.
Why Pilots Care
It provides the fixed starting reference needed to calculate where the balance point will move once passengers, baggage, or fuel are added.
Analogy
Think of balancing a model airplane on one fingertip before adding anything to it. The fingertip location is like the empty-weight center of gravity; every item added later can move that balance point.
Intuition Check
Empty does not mean the aircraft has nothing in it. It means the aircraft is in its officially recorded empty condition. Center does not mean the middle of the airplane. It means the point where the aircraft balances.
Example Sentence 1
After installing the new avionics package, the technician recalculated the empty-weight center of gravity and updated the aircraft's weight and balance records.
Example Sentence 2
Using the empty-weight center of gravity, the pilot calculated where to seat passengers so the loaded aircraft stayed within limits.