primary area

primary area

[′prī‚mer·ē ′er·ē·ə] (navigation) In terminal operations, an area within a segment in which full obstacle clearance is applied.

primary area

A defined area symmetrically disposed about the nominal flight track in which full obstacle clearance is provided (ICAO). When track guidance is provided in the design of an instrument approach procedure, each of the five segments of the approach constitutes a specified volume of airspace, the vertical cross section of which is an area symmetrically about the centerline of each segment. The vertical cross section is broken down into a primary and secondary areas. At any point, the width of the primary area is equal to one-half of the total width. The width of each secondary area is equal to one-quarter of the total width. Where no track guidance is provided during a turn specified by the procedure, the total width of the area is considered the primary area. See also secondary area.