Definition
The capacity of an aircraft's ailerons to produce enough rolling moment to counter an opposing rolling force and keep the wings level or recover the desired bank angle. When the rolling force acting on the aircraft exceeds what full aileron deflection can correct, roll-control authority has been lost.
Plain English
How much power the pilot has, through the ailerons, to stop the aircraft from rolling or to roll it back upright. If something is twisting the aircraft harder than the ailerons can push back, the pilot runs out of control.
Context Anchor
Seen in wake turbulence discussions, especially when a wake vortex may try to roll the airplane faster than the pilot can correct.
Derivation
"Authority" here comes from its older sense of "power to act or command." In aviation, a control surface has "authority" when it has enough power to make the aircraft do what the pilot is asking. Roll-control authority is specifically the aileron's power to command roll.
Why Pilots Care
Loss of roll-control authority during a wake encounter can produce an uncommanded roll from which recovery is impossible.
Grounding Statement
Picture a wake vortex lifting one wing and dropping the other; roll-control authority is the airplane’s ability to fight that motion when the pilot commands it.
Intuition Check
Authority does not mean legal permission here. It means the real physical effectiveness of the airplane’s roll controls.
Example Sentence 1
A light trainer that flies into the wake vortex of a heavy jet can lose roll-control authority and be rolled inverted before the pilot can recover.
Example Sentence 2
A light aircraft may lose roll-control authority when rolled by the wake of a heavy jet on approach.