According to ICAO Annex 11 basic designators for ATS routes shall consist of a maximum of five, in no case exceed six, alpha/numeric characters in order to be usable by both ground and airborne automation systems. The designator shall indicate the type of the route, that means: high/low altitude, specific airborne navigation equipment requirements (RNAV), aircraft type using the route primarily or exclusively.
COMPOSITION OF DESIGNATORS a. The basic designator consists of one letter of the alphabet followed by a number from 1 to 999. The letters may be:
1. A, B, G, R — for routes which form part of the regional networks of ATS routes and are not area navigation routes;
2. L, M, N, P — for area navigation routes which form part of the regional net-works of ATS routes;
3. H, J, V, W — for routes which do not form part of the regional networks of ATS routes and are not area navigation routes;
4. Q, T, Y, Z — for area navigation routes which do not form part of the re-gional networks of ATS routes.
b. Where applicable, one supplementary letter shall be added as a prefix to the basic designa-tor as follows:
1. K — to indicate a low level route established for use primarily by helicopters;
2. U — to indicate that the route or portion thereof is established in the upper airspace;
3. S — to indicate a route established exclusively for use by super-sonic aircraft during acceleration/deceleration and while in su-personic flight.
c. Where applicable, a supplementary letter may be added after the basic designator of the ATS route as a suffix as follows:
1. F — to indicate that on the route or portion thereof advisory service only is provided;
2. G — to indicate that on the route or portion thereof flight information service only is provided;
ENROUTE DATA - GENERAL 249 DESIGNATORS OF ATS ROUTES AND IT
3. Y — for RNP1 routes at and above FL200 to indicate that all turns on the route between 30 and 90 degrees shall be made within the tolerance of a tangential arc between the straight leg seg-ments defined with a radius of 22.5 NM;
4. Z — for RNP1 routes at and below FL190 to indicate that all turns on the route between 30 and 90 degrees shall be made within the tolerance of a tangential arc between the straight leg seg-ments defined with a radius of 15 NM.