Definition
A directional term meaning toward the centerline or longitudinal axis of an aircraft, or closer to the fuselage relative to another point on the wing or structure.
Plain English
Closer to the middle of the aircraft. If something is inboard, it is nearer to the body of the plane than something else.
Context Anchor
Seen when identifying parts on a wing, propeller blade, landing gear, flap, fuel tank, or engine location.
Derivation
From 'in' (toward the inside) plus 'board,' an old nautical term for the side of a ship. Sailors spoke of things being inboard (toward the middle of the vessel) or outboard (toward the edge). Aviation borrowed the term directly from ships.
Why Pilots Care
Correct use prevents mistakes when selecting engines for start-up, managing asymmetric thrust, or configuring control surfaces.
Intuition Check
Do not read inboard as simply “inside the airplane.” In aviation, it means closer to the aircraft’s centerline or main body compared with another point.
Example Sentence 1
On a four-engine jet, the inboard engines are the two closest to the fuselage.
Example Sentence 2
Inboard flaps extend first to increase lift without excessive roll.