5°  NBD  4.34 NM  49.66 NM  NBD 5°  5°  5°  4.5°  4.5°  4.5°  4.5°  51  51  4 NM  4 NM  Primary obstacle clearance area  V214  Figure 2-36. Zanesville VOR/Victor Airway 214.  Figure 2-37. LF/MR airway width.  Figure 2-38. Primary obstacle clearance area.  2-19  Primary and Secondary En Route Obstacle  Clearance Areas  43  50 29  3000  3000 SABGE  090°  109  334  12  9  12  147  347  183  N40° LORES  276  15  15 209  22  3000 2500  ZANDR  MUNCE  HISOM 5  V214  263  272  224 158  300 59-115  Barnesville Brodfield (6G5) 1312  4D L  [2P7] 1187 L*28  Cambridge Muni (CDI) 799  43 L  Zoneville Muni (ZZV) 900  50 L  ZANESVILLE  111.4 ZZV 51  N42°34.15' W99°59.38'  A  CLEVELAND  122.5 122.2 122.1R  BELLAIRE  117.1AIR 118  N40°31.00' W99°49.04'  A  CLEVELAND  122.1R  CLEVELAND Bolonl 120.4  257.975  21  33  34  17  factor. The pilot/aircraft information component of these  criteria includes pilot ability to track the radial and the flight  track resulting from turns at various speeds and altitudes  under different wind conditions. The navigation system  information includes navigation facility radial alignment  displacement, transmitter monitor tolerance, and receiver  accuracy. All of these factors were considered during  development of en route criteria. From this analysis, the  computations resulted in a total system accuracy of ±4.5°  95 percent of the time and ±6.7° 99 percent of the time.  The 4.5° value became the basis for primary area obstacle  clearance criteria, airway and route widths, and the ATC  separation procedures. The 6.7° value provides secondary  obstacle clearance area dimensions.  The primary obstacle clearance area has a protected width  of 8 NM with 4 NM on each side of the centerline. The  primary area has widths of route protection based upon  system accuracy of a ±4.5° angle from the NAVAID. These  4.5° lines extend out from the NAVAID and intersect the  boundaries of the primary area at a point approximately  51 NM from the NAVAID. Ideally, the 51 NM point is where  pilots would change over from navigating away from the  facility, to navigating toward the next facility, although this  ideal is rarely achieved. [Figure 2-38] 