Definition
A short rib installed at the inboard end of an aircraft wing where the wing meets the fuselage. The butt rib closes off the inboard end of the wing structure and provides the attachment surface where the wing joins the fuselage.
Plain English
The rib at the very root of the wing — the one that sits where the wing meets the body of the aircraft and forms the end-cap of the wing structure.
Context Anchor
Seen in aircraft structure, assembly, repair, and inspection discussions, especially around the wing root or wing panel joint.
Derivation
‘Butt’ here means ‘the end’ or ‘the base’ of something — as in ‘butt end of a rifle’ or ‘butt joint’ in carpentry. It refers to the end where two parts meet flush. So a butt rib is simply the end rib of the wing, where it butts up against the fuselage.
Why Pilots Care
A pilot may see this term in maintenance records or damage reports. Damage, corrosion, or looseness near a butt rib matters because it is part of the structure supporting the wing at a major joint.
Intuition Check
“Butt” does not refer to the rear of the airplane here. It means the end of a section where two parts meet.
Example Sentence 1
The mechanic inspected the butt rib for corrosion where the wing attaches to the fuselage.
Example Sentence 2
Mechanics reinforced the butt rib before installing the new wing spar.