Definition
The larger, outer ring of the concentric dual-rotation knob on a Flight Management System (FMS) or GPS control panel. Turning it moves the cursor between fields, pages, or characters on the display, allowing the pilot to select which item to edit. It works together with the inner knob, which changes the value within the selected field.
Plain English
The big outer ring of the two-part knob on the GPS or flight computer. You turn it to move from one box or letter to the next on the screen, like using a tab key.
Context Anchor
Seen in GPS and glass-cockpit procedures, including instructions for using the nearest airport function.
Derivation
FMS stands for Flight Management System. 'Outer' refers to its physical position — it is the larger ring surrounding a smaller inner knob, the two arranged concentrically on the same shaft.
Why Pilots Care
Allows rapid navigation through GPS pages so the pilot can access needed information with minimal head-down time.
Analogy
Think of a two-part knob like two controls sharing the same center. The outside ring makes bigger moves, and the inside knob makes smaller moves.
Intuition Check
Do not read “outer” as a separate knob located somewhere else. Here it means the outside ring of a combined inner-and-outer control.
Example Sentence 1
She turned the outer FMS knob to highlight the nearest airport field, then used the inner knob to scroll through the list.
Example Sentence 2
After reviewing the flight plan, the pilot turned the outer FMS knob to return to the moving map screen.