Bearings, radials, and mileages

This regulation establishes the standard measurement conventions used throughout Part 71, which defines controlled airspace in the United States.

When you see bearings and radials in airspace descriptions, they're always referenced in true direction (not magnetic), measured from the point of origin—typically a navigation facility like a VOR. All distances are in nautical miles.

This matters because airspace boundaries are legally defined using these measurements. For example, if Class D airspace extends "within a 4-mile radius of the airport" or Class E airspace begins "along the 090° radial," you know exactly what those numbers mean: nautical miles and true bearings from the specified point.

In practice, you'll usually work with magnetic directions when flying, so you'll need to apply magnetic variation when correlating published airspace boundaries with your navigation instruments. Understanding this convention ensures you correctly interpret airspace charts and descriptions.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*