Definition
A course displacement measured as an angle from the desired track rather than as a fixed distance. With VOR navigation, the course deviation indicator (CDI) shows angular deviation, so each dot of needle deflection represents a set number of degrees off course (typically 2° per dot). Because the displayed error is angular, the actual distance off course grows wider the farther the aircraft is from the station, and shrinks as the aircraft gets closer.
Plain English
How far off course you are, measured in degrees from the line you wanted to fly — not in miles or feet. The same needle swing means a bigger sideways gap when you’re far from the station and a smaller gap when you’re close.
Context Anchor
Seen in VOR/DME RNAV discussions when interpreting course guidance and how far off course the aircraft may be at different distances from the navigation reference.
Derivation
‘Angular’ comes from the Latin angulus, meaning ‘corner’ or ‘angle.’ The term simply means the deviation is measured as an angle opening out from the station, like a slice of pie — which is why the same angular error covers more ground the farther you are from the point of the slice.
Why Pilots Care
It shows the precise heading correction needed to rejoin the desired course and stay within protected airspace or approach limits.
Analogy
Think of two lines spreading out from the same point. Close to the point, the gap between them is small; farther away, the gap is much wider, even though the angle between the lines has not changed.
Grounding Statement
Picture two lines spreading out from the VOR station like a slice of pie — narrow at the station, wider farther away. The CDI shows the angle of the slice, not the width.
Intuition Check
Do not read “deviation” here as a fixed number of feet or miles off course. “Angular deviation” means the error is measured in degrees, and the actual sideways distance depends on how far you are from the reference point.
Example Sentence 1
Approaching the VOR, the pilot noticed the CDI becoming more sensitive because angular deviation tightens as distance to the station decreases.
Example Sentence 2
While tracking the VOR radial inbound, the pilot noted increasing angular deviation and adjusted the heading to maintain the airway centerline.