En Route Operations (Part Seven)

Composition of Designators

The prefix letters that pertain specifically to RNAV designations are included in the following list:

  1. The basic designator consists of one letter of the alphabet followed by a number from 1 to 999. The letters may be:
    • A, B, G, R—for routes that form part of the regional networks of ATS route and are not RNAV routes;
    • L, M, N, P—for RNAV routes that form part of the regional networks of ATS routes;
    • H, J, V, W—for routes that do not form part of the regional networks of ATS routes and are not RNAV routes;
    • Q, T, Y, Z—for RNAV routes that do not form part of the regional networks of ATS routes.
  2. Where applicable, one supplementary letter must be added as a prefix to the basic designator as follows:
    • K—to indicate a low level route established for use primarily by helicopters;
    • U—to indicate that the route or portion thereof is established in the upper airspace;
    • S—to indicate a route established exclusively for use by supersonic aircraft during acceleration/ deceleration and while in supersonic flight.
  3. Where applicable, a supplementary letter may be added after the basic designator of the ATS route as a suffix as follows:
    • F—to indicate that on the route or portion thereof advisory service only is provided;
    • G—to indicate that on the route or portion thereof flight information services only is provided;
    • Y—for RNP 1 routes at and above FL 200 to indicate that all turns on the route between 30° and 90° must be made within the tolerance of a tangential arc between the straight leg segments defined with a radius of 22.5 NM;
    • Z—for RNP 1 routes at and below FL 190 to indicate that all turns on the route between 30° and 90° should be made within the tolerance of a tangential arc between the straight leg segments defined with a radius of 15 NM.

Note: RNAV Q-routes require en route RNAV 2, corresponding NAV/E2 code and PBN/C1-C4 based on navigation system update source.

 

Use of Designators in Communications

In voice communications, the basic letter of a designator should be spoken in accordance with the International Civil Aviation Organization (ICAO) spelling alphabet. Where the prefixes K, U, or S, previously mentioned, are used in voice communications, they should be pronounced as:

K—Kopter
U—Upper, as in the English language
S—Supersonic

Where suffixes F, G, Y or Z specified in above, are used, the flight crew should not be required to use them in voice communications. Below is an example of how the letters and numbers are spoken.

A11—Alpha Eleven
UR5—Upper Romeo Five
KB34—Kopter Bravo Thirty Four
UW456—Upper Whiskey Four Fifty Six

The en route chart excerpt depicts three published RNAV jet routes: J804R, J888R, and J996R. [Figure 2-45] The R suffix is a supplementary route designator denoting an RNAV route. The overlapping symbols for the AMOTT intersection and waypoint indicate that AMOTT can be identified by conventional navigation or by latitude and longitude coordinates. Although coordinates were originally included for aircraft equipped with an inertial navigation system (INS), they are now a good way to cross check between the coordinates on the chart and in the flight management system (FMS) or global positioning system (GPS) databases to ensure you are tracking on your intended en route course. The AMOTT RNAV waypoint includes bearing and distance from the Anchorage VORTAC.

Figure 2-45. Published RNAV jet routes.

Figure 2-45. Published RNAV jet routes. [click image to enlarge]

Random RNAV Routes

Random RNAV routes are direct routes that are based on RNAV capability between waypoints defined in terms of latitude or longitude coordinates, degree-distance fixes, or offsets from established routes or airways at a specified distance and direction. Radar monitoring by ATC is required on all random RNAV routes. Random RNAV routes can only be approved in a radar environment. Factors that are considered by ATC when approving random RNAV routes include the capability to provide radar monitoring and compatibility with traffic volume and flow. ATC radar monitor each flight; however, navigation on the random RNAV route is the responsibility of the pilot.

 

Pilots flying aircraft that are equipped with approved area navigation equipment may file for RNAV routes throughout the NAS and may be filed for in accordance with the following procedures:

  1. File airport-to-airport flight plans.
  2. File the appropriate RNAV capability certification suffix in the flight plan.
  3. Plan the random route portion of the flight plan to begin and end over appropriate arrival and departure transition fixes or appropriate NAVAIDs for the altitude stratum within which the flight is conducted. The use of normal preferred DPs and STAR, where established, is recommended.
  4. File route structure transitions to and from the random route portion of the flight.
  5. Define the random route by waypoints. File route description waypoints by using degree distance fixes based on navigational aids that are appropriate for the altitude stratum.
  6. File a minimum of one route description waypoint for each ARTCC through whose area the random route is flown. These waypoints must be located within 200 NM of the preceding center’s boundary.
  7. File an additional route description waypoint for each turnpoint in the route.
  8. Plan additional route description waypoints as required to ensure accurate navigation via the filed route of flight. Navigation is the pilot’s responsibility unless ATC assistance is requested.
  9. Plan the route of flight so as to avoid prohibited and restricted airspace by 3 NM unless permission has been obtained to operate in that airspace and the appropriate ATC facilities are advised.

Note: To be approved for use in the NAS, RNAV equipment must meet the appropriate system availability, accuracy, and airworthiness standards. For additional guidance on equipment requirements, see Advisory Circular (AC) 20-138C, Airworthiness Approval of Positioning and Navigation Systems. For airborne navigation database, see AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System.

Pilots flying aircraft that are equipped with latitude/ longitude coordinate navigation capability, independent of VOR/ TACAN references, may file for random RNAV routes at and above FL 390 within the conterminous United States using the following procedures:

  1. File airport-to-airport flight plans prior to departure.
  2. File the appropriate RNAV capability certification suffix in the flight plan.
  3. Plan the random route portion of the flight to begin and end over published departure/arrival transition fixes or appropriate NAVAIDs for airports without published transition procedures. The use of preferred departure and arrival routes, such as DP and STAR where established, is recommended.
  4. Plan the route of flight so as to avoid prohibited and restricted airspace by 3 NM unless permission has been obtained to operate in that airspace and the appropriate ATC facility is advised.
  5. Define the route of flight after the departure fix, including each intermediate fix (turnpoint) and the arrival fix for the destination airport in terms of latitude/longitude coordinates plotted to the nearest minute or in terms of Navigation Reference System (NRS) waypoints. For latitude/longitude filing, the arrival fix must be identified by both the latitude/ longitude coordinates and a fix identifier as shown in the example below.
    • MIA1 SRQ2 3407/106153 3407/11546 TNP4 LAX5
      • 1Departure airport
      • 2Departure fix
      • 3Intermediate fix (turning point)
      • 4Arrival fix
      • 5Destination airport
    • Or:
    • ORD1 IOW2 KP49G3 KD34U4 KL16O5 OAL6 MOD27 SFO8
      • 1Departure airport
      • 2Transition fix (pitch point)
      • 3Minneapolis ARTCC waypoint
      • 4Denver ARTCC waypoint
      • 5Los Angeles ARTCC waypoint (catch point)
      • 6Transition fix
      • 7Arrival
      • 8Destination airport
  6. Record latitude/longitude coordinates by four figures describing latitude in degrees and minutes followed by a solidus and five figures describing longitude in degrees and minutes.
  7. File at FL 390 or above for the random RNAV portion of the flight.
  8. Fly all routes/route segments on Great Circle tracks.
  9. Make any in-flight requests for random RNAV clearances or route amendments to an en route ATC facility.