Section 3. Low/Medium Frequency and VOR Airways

20-3-1. NAVAID SPACING

a. VOR Federal airways are based on NAVAIDs which normally are spaced no farther apart than 80 NM. They may be based on more widely spaced NAVAIDs if a usable signal can be provided and frequency protection afforded for the distance required (see Order 9840.1, U.S. National Aviation Handbook for the VOR/DME/TACAN Systems).

b. NAVAID spacing for L/MF airways has no standard but is determined on an individual basis.

20-3-2. VERTICAL AND LATERAL EXTENT

The standard vertical and lateral extent of these airways is specified in FAAO 8260.3, TERPS, and FAAO 8260.19, Flight Procedure and Airspace. Nonstandard dimensions may be specified as required except as limited by any flight inspection limitations and by paragraph 20-1-7 of this order.

20-3-3. WIDTH REDUCTIONS

a. Width reductions are not applicable to L/MF airways.

b. For ATS routes other than L/MF, a reduced airway width of 3 NM on one or both sides of the centerline may be established from the NAVAID to the point where 4.5 degree intersecting lines equal 3 NM. Normally, lines perpendicular to the airway centerline determine the ends of the reduced portion. If required, the ends of the reduced portion may be defined differently. A reduced width is permissible to obtain additional traffic capacity and flexibility through the use of multiple routes and to avoid encroachment on special use airspace or other essential maneuvering areas. Width reductions are considered the exception rather than the rule and are approved only where adequate air navigation guidance and justification exist.