ENR 3.5 Other Routes
Airways and Route Systems
- Three fixed route systems are established for air navigation purposes. They are the Federal airway system (consisting of VOR and L/MF routes), the jet route system, and the RNAV route system. To the extent possible, these route systems are aligned in an overlying manner to facilitate transition between each.
VOR and L/MF System
The VOR and L/MF (nondirectional radio beacons) Airway System consists of airways designated from 1,200 feet above the surface (or in some instances higher) up to but not including 18,000 feet MSL. These airways are depicted on IFR Enroute Low Altitude Charts.
The altitude limits of a victor airway should not be exceeded except to effect transition within or between route structures.
Except in Alaska, the VOR airways are: predicated solely on VOR or VORTAC navigation aids; depicted in black on aeronautical charts; and identified by a “V” (Victor) followed by the airway number (for example, V12).
Segments of VOR airways in Alaska are based on L/MF navigation aids and charted in brown instead of black on en route charts.
A segment of an airway which is common to two or more routes carries the numbers of all the airways which coincide for that segment. When such is the case, pilots filing a flight plan need to indicate only that airway number for the route filed.
A pilot who intends to make an airway flight, using VOR facilities, will simply specify the appropriate “victor” airway(s) in the flight plan. For example, if a flight is to be made from Chicago to New Orleans at 8,000 feet, using omniranges only, the route may be indicated as “departing from Chicago-Midway, cruising 8,000 feet via Victor 9 to Moisant International.” If flight is to be conducted in part by means of L/MF navigation aids and in part on omniranges, specifications of the appropriate airways in the flight plan will indicate which types of facilities will be used along the described routes, and, for IFR flight, permit ATC to issue a traffic clearance accordingly. A route may also be described by specifying the station over which the flight will pass but in this case since many VORs and L/MF aids have the same name, the pilot must be careful to indicate which aid will be used at a particular location. This will be indicated in the route of flight portion of the flight plan by specifying the type of facility to be used after the location name in the following manner: Newark L/MF, Allentown VOR.
- With respect to position reporting, reporting points are designed for VOR Airway Systems. Flights using Victor airways will report over these points unless advised otherwise by ATC.
The L/MF airways (colored airways) are predicated solely on L/MF navigation aids and are depicted in brown on aeronautical charts and are identified by color name and number; e.g., Amber One. Green and Red airways are plotted east and west. Amber and Blue airways are plotted north and south.
Except for G13 in North Carolina, the colored airway system exists only in the state of Alaska. All other such airways formerly so designated in the conterminous U.S. have been rescinded.
Use of adjacently located LF/VHF airways and routes - many locations just outside the contiguous 48 states have two separate airway structures. One structure is made up from VORs and the other from L/MF NAVAIDs (nondirectional radio beacons). In some instances, the different routes appear to overlie each other. The NAVAIDs are sometimes depicted so close to each other that they will have the appearance of being collocated, or nearly so. Substituting a VOR radial for a nondirectional radio beacon bearing could, in many circumstances, cause an excessive “off course” navigational error. Strict adherence to the color coding of the route structure and NAVAID in use should be maintained. Chart procedures provide an excellent means of route differentiation through the use of color which is defined and explained in the legend.
- The use of TSO-C145 (as revised) or TSO-C146 (as revised) GPS/WAAS navigation systems is allowed in Alaska as the only means of navigation on published air traffic service (ATS) routes, including those Victor, T-Routes, and colored airway segments designated with a second minimum en route altitude (MEA) depicted in blue and followed by the letter G at those lower altitudes. The altitudes so depicted are below the minimum reception altitude (MRA) of the land-based navigation facility defining the route segment, and guarantee standard en route obstacle clearance and two-way communications. Air carrier operators requiring operations specifications are authorized to conduct operations on those routes in accordance with FAA operations specifications.
- The VOR and L/MF (nondirectional radio beacons) Airway System consists of airways designated from 1,200 feet above the surface (or in some instances higher) up to but not including 18,000 feet MSL. These airways are depicted on IFR Enroute Low Altitude Charts.
Jet Route System
- The jet route system consists of jet routes established from 18,000 feet MSL to FL 450 inclusive.
These routes are depicted on En Route High Altitude Charts. Jet routes are depicted in black on aeronautical charts and are identified by a “J” (Jet) followed by the airway number; e.g., J12. Jet routes, as VOR airways, are predicated solely on VOR or VORTAC navigation facilities (except in Alaska).
Segments of jet routes in Alaska are based on L/MF navigation aids and are charted in brown color instead of black on en route charts.
- With respect to position reporting, reporting points are designated for Jet Route Systems. Flights using jet routes will report over these points unless otherwise advised by ATC.
- Controllers may vector aircraft within CONTROLLED AIRSPACE for separation purposes, noise abatement considerations, when an operational advantage will be realize by the pilot or the controller, or when requested by the pilot. Vectors outside of CONTROLLED AIRSPACE will be provided only on pilot request. Pilots will be advised as to what the vector is to achieve when the vector is controller initiated and will take the aircraft off a previously assigned nonradar route. To the extent possible, aircraft operating on RNAV routes will be allowed to remain on their own navigation.
Changeover Points (COPs)
- COPs are prescribed for Federal airways, jet routes, area navigation routes, or other direct routes for which an minimum en route altitude (MEA) is designated under 14 CFR Part 95. The COP is a point along the route or airway segment between two adjacent navigation facilities or waypoints where changeover navigation guidance should occur. At this point, the pilot should change navigation receiver frequency from the station behind the aircraft to the station ahead.
- The COP is normally located midway between the navigation facilities for straight route segments, or at the intersection of radials or courses forming a dogleg in the case of dogleg route segments. When the COP is NOT located at the midway point, aeronautical charts will depict the COP location and give the mileage to the radio aids.
- COPs are established for the purpose of preventing loss of navigation guidance, to prevent frequency interference from other facilities, and to prevent use of different facilities by different aircraft in the same airspace. Pilots are urged to observe COPs to the fullest extent.
Airway or Route Course Changes
- Pilots of aircraft are required to adhere to airways/routes being flown. Special attention must be given to this requirement during course changes. Each course change consists of variables that make the technique applicable in each case a matter only the pilot can resolve. Some variables which must be considered are turn radius, wind effect, airspeed, degree of turn, and cockpit instrumentation. An early turn, as illustrated in FIG ENR 3.5-1, is one method of adhering to airways/routes. The use of any available cockpit instrumentation, such as distance measuring equipment, may be used by the pilot to lead the turn when making course changes. This is consistent with the intent of 14 CFR Section 91.181 which requires pilots to operate along the centerline of an airway and along the direct course between navigational aids or fixes.
- Turns which begin at or after fix passage may exceed airway/route boundaries. FIG ENR 3.5-1 contains an example flight track depicting this, together with an example of an early turn.
- Without such actions, as leading a turn, aircraft operating in excess of 290 knots true airspeed (TAS) can exceed the normal airway/route boundaries depending on the amount of course change required, wind direction and velocity, the character of the turn fix, (DME, overhead navigation aid, or intersection), and the pilot's technique in making a course change. For example, a flight operating at 17,000 feet MSL with a TAS of 400 knots, a 25 degree bank, and a course change of more than 40 degrees would exceed the width of the airway/route; i.e., 4 nautical miles each side of centerline. However, in the airspace below 18,000 feet MSL, operations in excess of 290 knots TAS are not prevalent and the provision of additional IFR separation in all course change situations for the occasional aircraft making a turn in excess of 290 knots TAS creates an unacceptable waste of airspace and imposes a penalty upon the preponderance of traffic which operates at low speeds. Consequently, the FAA expects pilots to lead turns and take other actions they consider necessary during the course changes to adhere as closely as possible to the airways or route being flown.
Minimum Turning Altitude (MTA)
- Due to increased airspeeds at 10,000 ft MSL or above, the published minimum enroute altitude (MEA) may not be sufficient for obstacle clearance when a turn is required over a fix, NAVAID, or waypoint. In these instances, an expanded area in the vicinity of the turn point is examined to determine whether the published MEA is sufficient for obstacle clearance. In some locations (normally mountainous), terrain/obstacles in the expanded search area may necessitate a higher minimum altitude while conducting the turning maneuver. Turning fixes requiring a higher minimum turning altitude (MTA) will be denoted on government charts by the minimum crossing altitude (MCA) icon (“x" flag) and an accompanying note describing the MTA restriction. An MTA restriction will normally consist of the air traffic service (ATS) route leading to the turn point, the ATS route leading from the turn point, and the required altitude; e.g., MTA V330 E TO V520 W 16000. When an MTA is applicable for the intended route of flight, pilots must ensure they are at or above the charted MTA not later than the turn point and maintain at or above the MTA until joining the centerline of the ATS route following the turn point. Once established on the centerline following the turning fix, the MEA/MOCA determines the minimum altitude available for assignment. An MTA may also preclude the use of a specific altitude or a range of altitudes during a turn. For example, the MTA may restrict the use of 10,000 through 11,000 ft MSL. In this case, any altitude greater than 11,000 ft MSL is unrestricted, as are altitudes less than 10,000 ft MSL provided MEA/MOCA requirements are satisfied.