Definition
The visible, rounded or flush ends of the rivets that fasten the airplane's metal skin to its underlying structure. On a preflight inspection, rivet heads are checked to confirm they are present, tight, undamaged, and not showing signs of working loose, popping out, or smoking (a dark stain trailing from the rivet that indicates movement).
Plain English
The small metal bumps you can see all over the outside of the airplane. They are the tops of the fasteners holding the metal skin onto the airframe. During a walkaround, you look at them to make sure none are missing, loose, or leaving a dark smudge.
Context Anchor
Seen during preflight inspection of the wings, tail, and other outside surfaces of the airplane.
Derivation
A rivet is a metal pin used to join two pieces together; the 'head' is the wider end that sits on the surface and stops the rivet from pulling through. The word rivet comes from the Old French 'river,' meaning to fix or fasten.
Why Pilots Care
Protruding rivet heads increase parasite drag, which reduces cruise speed and fuel efficiency on any airplane.
Intuition Check
Do not think of rivet heads as decoration. They are visible parts of fasteners, and their condition can give clues about the condition of the structure underneath.
Example Sentence 1
While inspecting the wing, the pilot noticed a dark streak trailing from one of the rivet heads, suggesting the rivet had been working loose.
Example Sentence 2
The mechanic replaced several rivets so the new heads would sit flush with the outer wing surface.