Navigational tolerance for LOC/VOR is defined as which?

• A. Full scale deflection
• B. Half scale deflection
• C. 1 degree
• D. +/- 5 degrees

Answer: (B)

The main idea is how closely you must stay on the intended path when using LOC or VOR. The navigational tolerance is defined by the amount of deflection allowed on the course deviation indicator (CDI) before you’re considered off course. This tolerance is half of the CDI’s full-scale deflection. In typical LOC/VOR indicators, full-scale deflection corresponds to about 10 degrees of deviation, so half-scale equals roughly 5 degrees. That 5-degree limit is what determines acceptable tracking errors, making half-scale deflection the best description of the tolerance.

Full-scale deflection would mean a much larger deviation and isn’t the standard tolerance. A 1-degree tolerance is too tight for routine navigation, given signal and aircraft dynamics. Saying “±5 degrees” describes a numeric range, which aligns with the same practical limit, but the formal definition is stated as half-scale deflection.