FAR 73.5 — Bearings and Distances
FAR 73.5 explains how bearings, radials, and distances are measured in special use airspace: true bearings from origin and statute miles by default.
FAR 73.5 sets the measurement conventions used throughout Part 73 (Special Use Airspace, including Restricted and Prohibited Areas). It's a short but important rule because it tells you how to interpret the numbers describing the boundaries of these areas on charts and in regulations.
- Bearings and radials referenced in Part 73 are true (referenced to true north), not magnetic, and are measured from the point of origin.
- Mileages in Part 73 are stated in statute miles unless the regulation specifically says otherwise — not nautical miles, which is what pilots usually work in.
Why it matters operationally: when you're plotting or avoiding a Restricted or Prohibited Area, you need to know that the published boundaries use true bearings and statute miles. If you mistakenly apply magnetic variation or convert to nautical miles, you could end up inside protected airspace. Always cross-check chart depictions and apply the correct convention when reading the legal description of a special use area.