Definition
In aircraft sheet-metal work, the act of holding a heavy steel block (a bucking bar) firmly against the protruding shank of a solid rivet while the opposite (manufactured) head is struck by a rivet gun. The mass of the bucking bar resists the gun's blows and forces the rivet shank to deform into a properly shaped shop head, locking the joint together.
Plain English
Holding a solid metal block against the back side of a rivet while someone hammers the front, so the rivet squashes into shape and stays in place.
Context Anchor
Seen in aircraft maintenance and construction when installing solid rivets in metal skins, ribs, and other sheet-metal parts.
Derivation
From the verb 'to buck,' meaning to push back or resist. The bucking bar's job is to push back against the rivet gun's hammering force, so the action of holding it became known as bucking.
Why Pilots Care
Uncorrected bucking can quickly turn into loss of control, especially close to the ground during takeoff or landing.
Analogy
It is like holding a heavy block behind a small metal pin while someone taps the other side. The backing support lets the pin spread instead of simply moving away.
Intuition Check
Bucking does not mean the aircraft is jumping, resisting, or moving roughly here. In sheet-metal work, it means backing up a rivet firmly while it is being formed.
Example Sentence 1
The apprentice was bucking rivets on the wing skin while the senior mechanic worked the rivet gun from the other side.
Example Sentence 2
On short final the airplane started bucking from the crosswind gusts, requiring the pilot to relax back pressure and let the nose settle.