Definition
An instrument cross-check technique in which the pilot's eyes return to the attitude indicator after looking at each of the other flight instruments, treating the attitude indicator as the hub of a wheel and the surrounding instruments as the spokes. The pattern is attitude-instrument-attitude-instrument-attitude, rather than scanning from one peripheral instrument directly to another.
Plain English
A way of checking your instruments where you always come back to the attitude indicator in the middle between every other instrument you look at. Eyes go: middle, outside, middle, outside, middle.
Context Anchor
Used in instrument flying when learning or practicing how to check the flight instruments in an organized way.
Derivation
Radial comes from the Latin radius, meaning the spoke of a wheel or a ray extending out from a center. The scan is called radial because the eyes move outward from a central point (the attitude indicator) and back, like spokes radiating from a hub.
Why Pilots Care
Prevents instrument fixation and supports continuous awareness of attitude, airspeed, altitude, and heading.
Analogy
Think of the attitude indicator as the hub of a wheel and the other instruments as points around the rim. Your eyes move out along one spoke, back to the hub, then out along another spoke.
Intuition Check
Radial does not mean a radio navigation radial here. It means the eye movement goes outward from a center point and back; scan means a deliberate checking pattern, not a casual glance.
Example Sentence 1
During straight-and-level flight, the instructor had the student use a radial scan, returning to the attitude indicator after each glance at the altimeter, heading indicator, and airspeed indicator.
Example Sentence 2
Switching to a radial scan kept the pilot from staring at one instrument during the approach.