Definition
An autopilot lateral mode that holds the aircraft at the bank angle present when the mode engages, keeping the wings at that bank until the pilot commands a change or selects another lateral mode such as heading or navigation tracking.
Plain English
A basic autopilot setting that locks in whatever bank you have at the moment you turn it on and holds it there. If the wings are level, it keeps them level. If you're banked 10 degrees, it holds 10 degrees of bank.
Context Anchor
Seen when using or monitoring the autopilot during instrument flight, including discussions of autopilot use during unusual attitude prevention or recovery.
Derivation
Roll' refers to rotation about the aircraft's longitudinal axis -- the motion that tilts the wings. 'Mode' means a specific operating setting of the autopilot. Together: the autopilot setting that controls the roll axis.
Why Pilots Care
Roll mode is often the default lateral mode when the autopilot is first engaged. If a pilot turns on the autopilot while the aircraft is already banked, the autopilot will hold that bank rather than level the wings. Knowing this prevents surprise and reinforces the habit of leveling the wings before engaging the autopilot, or selecting heading or navigation mode promptly.
Grounding Statement
When roll mode is active, think of the system as working on the wings’ tilt, not on altitude, power, or the route.
Intuition Check
Roll mode does not mean the airplane is rolling out of control. It means the automatic system is in a selected way of controlling bank left, bank right, or wings level.
Example Sentence 1
After engaging the autopilot, the pilot noticed it was in roll mode holding a slight left bank, so she selected heading mode to track her assigned course.
Example Sentence 2
In roll mode the autopilot maintained a shallow bank to follow the assigned heading.