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Airway & Route Course Change

Introduction:

Adhering to Airways or Routes
Figure 1: Adhering to Airways or Routes

Federal Airway System:

  • The VOR and L/MF (non-directional radio beacons) Airway System consists of airways designated from 1,200' above the surface (or in some instances higher) up to but not including 18,000' 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;
    • Identified by a "V" (Victor) followed by the airway number (for example, V12)
    • Depicted in black on aeronautical charts;
      • 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

NOTE:
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 designated 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
  • 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

Jet Route System:

  • The jet route system consists of jet routes established from 18,000' MSL to FL 450 inclusive
    • These routes are depicted on Enroute High Altitude Charts
    • Depicted in black on aeronautical charts
    • 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
  • Operation above FL 450 may be conducted on a point-to-point basis. Navigational guidance is provided on an area basis utilizing those facilities depicted on the enroute high altitude 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

Area Navigation (RNAV) Routes:

  • Published RNAV routes, including Q-Routes and T-Routes, can be flight planned for use by aircraft with RNAV capability, subject to any limitations or requirements noted on en route charts, in applicable Advisory Circulars, or by NOTAM
  • RNAV routes are depicted in blue on aeronautical charts and are identified by the letter "Q" or "T" followed by the airway number (for example, Q-13, T-205)
  • Published RNAV routes are RNAV-2 except when specifically charted as RNAV-1
  • These routes require system performance currently met by GPS, GPS/WAAS, or DME/DME/IRU RNAV systems that satisfy the criteria discussed in AC 90-100A, U.S. Terminal and En Route Area Navigation (RNAV) Operations
    • AC 90-100A does not apply to over water RNAV routes (reference 14 CFR 91.511, including the Q-routes in the Gulf of Mexico and the Atlantic routes) or Alaska VOR/DME RNAV routes (“JxxxR”). The AC does not apply to off-route RNAV operations, Alaska GPS routes or Caribbean routes
    • Q-routes are available for use by RNAV equipped aircraft between 18,000 feet MSL and FL 450 inclusive. Q-routes are depicted on Enroute High Altitude Charts
    • Aircraft in Alaska may only operate on GNSS Q­routes with GPS (TSO­C129 (as revised) or TSO­C196 (as revised)) equipment while the aircraft remains in Air Traffic Control (ATC) radar surveillance or with GPS/WAAS which does not require ATC radar surveillance
    • T-routes are available for use by GPS or GPS/WAAS equipped aircraft from 1,200 feet above the surface (or in some instances higher) up to but not including 18,000 feet MSL. T-routes are depicted on Enroute Low Altitude Charts
    • Aircraft in Alaska may only operate on GNSS T­routes with GPS/WAAS (TSO­C145 (as revised) or TSO­C146 (as revised)) equipment
  • Unpublished RNAV routes are direct routes, based on area navigation capability, between waypoints defined in terms of latitude/longitude coordinates, degree-distance fixes, or offsets from established routes/airways at a specified distance and direction. Radar monitoring by ATC is required on all unpublished RNAV routes, except for GNSS- equipped aircraft cleared via filed published waypoints recallable from the aircraft’s navigation database
  • Magnetic Reference Bearing (MRB) is the published bearing between two waypoints on an RNAV/GPS/GNSS route. The MRB is calculated by applying magnetic variation at the waypoint to the calculated true course between two waypoints. The MRB enhances situational awareness by indicating a reference bearing (no−wind heading) that a pilot should see on the compass/HSI/RMI, etc., when turning prior to/over a waypoint en route to another waypoint. Pilots should use this bearing as a reference only, because their RNAV/GPS/GNSS navigation system will fly the true course between the waypoints

Radar Vectors:

  • Controllers may vector aircraft within controlled airspace for separation purposes, noise abatement considerations, when an operational advantage will be realized 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

Turns:

  • Some variables which must be considered are turn radius, wind effect, airspeed, degree of turn, and cockpit instrumentation
  • An early turn, as illustrated below, is one method of adhering to airways or 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 or route boundaries Figure 1:
  • Without such actions as leading a turn, aircraft operating in excess of 290 knots true air speed (TAS) can exceed the normal airway or 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 or 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 operate at low speeds. Consequently, the FAA expects pilots to lead turns and take other actions they consider necessary during course changes to adhere as closely as possible to the airways or route being flown
  • Turns that begin at or after fix passage may exceed airway or route boundaries
  • Without such actions as leading a turn, aircraft operating in excess of 290 knots true airspeed (TAS) can exceed the normal airway or 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 changeover
  • Minimum Turning Altitude:

    • 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
NOTE:
When not along an airway, consider 91.177(a) for minimum altitudes

Navigational Gap:

  • A navigational course guidance gap, referred to as an MEA gap, describes a distance along an airway or route segment where a gap in navigational signal coverage exists
    • The navigational gap may not exceed a specific distance that varies directly with altitude
    • Example:
      • A flight operating at 17,000' MSL with a TAS of 400 knots, a 25° AoB and a course change of more than 40° would exceed the width of the airway or route; i.e., 4nm each side of center line
      • However, in the airspace below 18,000' MSL, operations in excess of 290 knots, TAS are not prevalent and the provisions 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 operate at low speeds
      • Consequently, the FAA expects pilots to lead turns and take other actions they consider necessary during course changes to adhere as closely as possible to the airways or route being flown

Preferred Routes
Figure 2: Preferred Routes

Preferred IFR Routes:

  • Preferred IFR routes have been established between major terminals to guide pilots in planning their routes of flight, minimizing route changes, and aiding in the orderly management of air traffic on Federal airways
  • Low and high altitude preferred routes are listed in the Airport/Facility Directory (A/FD) Supplement
  • To use a preferred route, reference the departure and arrival airports; if a routing exists for your flight, then airway instructions are listed [Figure 2]
  • Preferred IFR routes exists for the low altitude stratum and the high altitude stratum
    • The high altitude list is in two sections; the first section showing terminal to terminal routes and the second section showing single direction route segments
    • Also, on some high altitude routes low altitude airways are included as transition routes
  • Terms/abbreviations used in the listing:
    1. Preferred routes beginning/ending with an airway number indicate that the airway essentially overlies the airport and flight are normally cleared directly on the airway
    2. Preferred IFR routes beginning/ending with a fix indicate that aircraft may be routed to/from these fixes via a Standard Instrument Departure (SID) route, radar vectors (RV), or a Standard Terminal Arrival (STAR)
    3. Preferred IFR routes for major terminals selected are listed alphabetically under the name of the departure airport
      • Where several airports are in proximity they are listed under the principal airport and categorized as a metropolitan area
      • Example: New York Metro Area
    4. Preferred IFR routes used in one direction only for selected segments, irrespective of point of departure or destination, are listed numerically showing the segment fixes and the direction and times effective
    5. Where more than one route is listed the routes have equal priority for use
    6. Official location identifiers are used in the route description for VOR/VORTAC NAVAIDs
    7. Intersection names are spelled out
    8. NAVAID and distance fixes (e.g., ARD201113) have been used in the route description in an expediency and intersection names will be assigned as soon as routine processing can be accomplished. NAVAID radial (no distance stated) may be used to describe a route to intercept a specified airway (e.g., MIV MIV101 V39); another NAVAID radial (e.g., UIM UIM255 GSW081); or an intersection (e.g., GSW081 FITCH)
    9. Where two NAVAIDS, an intersection and a NAVAID, a NAVAID and a NAVAID radial and distance point, or any navigable combination of these route descriptions follow in succession, the route is direct
    10. The effective times for the routes are in UTC. During periods of daylight saving time effective times will be one hour earlier than indicated. All states observe daylight saving time except Arizona, Puerto Rico and the Virgin Islands. Pilots planning flight between the terminals or route segments listed should file for the appropriate preferred IFR route
    11. (90–170 incl) altitude flight level assignment in hundred of feet
    12. The notations "pressurized" and "unpressurized" for certain low altitude preferred routes to Kennedy Airport indicate the preferred route based on aircraft performance
    13. High Altitude Preferred IFR Routes are in effect during the following time periods unless otherwise noted
      • Monday thru Friday: 0701–2259 local time
      • Saturday: 0701–1459 local time
      • Sunday: 1300–2259 local time
    14. Use current SIDs and STARSs for flight planning
    15. For high altitude routes, the portion of the routes contained in brackets [ ] is suggested but optional. The portion of the route outside the brackets will likely be required by the facilities involved. Separated into low and high altitude

Position Reports:

  • Reporting points are designated for VOR Airway/Jet Route Systems
    • Flights using Victor Airways/Jet Routes will report over these points unless advised otherwise by ATC

Climbs:

  • Airways are designed for aircraft to begin climging immediately after passing a point where a minimum enroute altitude increases
    • Obstacle clearance is ensured if climb at 150 ft/min (to 5,000' AGL), 120 ft/nm (5,000'-10,000' AGL), and 100 ft/nm (>10,000' AGL)
    • Example: you must begin your climb no later than COFFE if flying east on V244 [Figure 3]
  • ATC will inform you prior to crossing the fix at which the minimum altitude changes but failing that, request it
  • Note that minimum crossing altitudes require you to cross at or above the next segment minimum altitude

Minimum Crossing Altitude
Figure 3: Minimum Crossing Altitude

Changeover Points (COP):

Changeover Point
Figure 4: Changeover Point
  • COPs are prescribed for Federal airways, jet routes, area navigation routes, or other direct routes for which an 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 in 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 [Figure 4]
      • Example: in the referenced figure, if flying from the left to right, you switch from the NAVAID behind you at 130 NM from, and 108 NM to the next, as the airway is defined
  • 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

Federal Airway and Charted IFR Altitudes
Figure 5: Federal Airway and Charted IFR Altitudes

Course Lights:

  • The course light, which can be seen clearly from only one direction, is used only with rotating beacons of the Federal Airway System:
    • Two course lights, back to back, direct coded flashing beams of light in either direction along the course of airway

Aeronautical Light Beacons:

  • An aeronautical light beacon is a visual Navigational Aid (NAVAID) displaying flashes of white and/or colored light to indicate the location of an airport, a heliport, a landmark, a certain point of a Federal airway in mountainous terrain, or an obstruction
    • Coded flashes of the auxiliary lights, if employed, further identify the beacon site
  • The light used may be a rotating beacon or one or more flashing lights
  • The flashing lights may be supplemented by steady burning lights of lesser intensity
  • The color or color combination displayed by a particular beacon and/or its auxiliary lights tell whether the beacon is indicating a landing place, landmark, point of the Federal airways, or an obstruction
  • Code Beacons:

    • Code Beacons are omni-directional lights used to identify airports and landmarks
    • In the case of airports, they flash the 3 or 4 character airport identifier in Morse code 6 to 8 times a minute
      • Green flashes for land airports
      • Yellow for water airports
  • Course Lights:

    • Course lights, which can be seen clearly from only one direction, is used only with rotating beacons of the Federal Airway System: two-course lights, back to back, direct coded flashing beams of light in either direction along the course of airway
    • Airway beacons are remnants of the “lighted” airways which antedated the present electronically equipped federal airways system
    • Only a few of these beacons exist today to mark airway segments in remote mountain areas
    • Flashes in Morse code identify the beacon site

Obstruction Lights:

  • Obstructions are marked and lit to warn airmen of their presence during daytime and night-time conditions
  • Aviation Red Obstruction Lights:

    • During daylight hours, aviation orange and white paint is used for marking
    • During nighttime operation, a flashing red light bacon indicates the marking of an en-route obstruction (20 to 40 flashes per minute)
    • Steady red light indicates an obstruction in the terminal area
  • Medium Intensity Flashing White Obstruction Lights:

    • Medium intensity flashing white obstruction lights may be used during daytime and twilight with automatically selected reduced intensity for night-time operation
    • When this system is used on structures 500 feet (153m) AGL or less in height, other methods of marking and lighting the structure may be omitted
      • Aviation orange and white paint is always required for day time marking on structures exceeding 500' AGL
    • Not normally installed on structures less than 200' AGL
  • High Intensity White Obstruction Light:

    • Flashing high intensity white lights during daytime with reduced intensity for twilight and night-time operation
    • When this type of system is used, the marking of structures with red obstruction lights and aviation orange and white paint may be omitted
  • Dual Lighting:
    • A combination of flashing aviation red beacons and steady burning aviation red lights for night time operation, and flashing high intensity white lights for daytime operation
    • Aviation orange and white paint may be omitted
  • Catenary Lighting:

    Catenary Lighting
    Figure 4: Catenary Lighting
    • Lighted markers are available for increased night conspicuity of high-voltage transmission line catenary wires
    • Lighted markers provide conspicuity both day and night
  • Medium intensity omni-directional flashing white lighting system provides conspicuity both day and night on catenary support structures
    • The unique sequential/simultaneous flashing light system alerts pilots of the associated catenary wires
  • High intensity flashing white lights are being used to identify some supporting structures of overhead transmission lines located across rivers, chasms, gorges, etc.
    • These lights flash in a middle, top, lower light sequence at approximately 60 flashes per minute
    • The top light is normally installed near the top of the supporting structure, while the lower light indicates the approximate lower portion of the wire span
    • The lights are beamed toward the companion structure and identify the area of the wire span
  • High intensity flashing white lights are also employed to identify tall structures, such as chimneys and towers, as obstructions to air navigation
    • The lights provide a 360° coverage about the structure at 40 flashes per minute and consist of from one to seven levels of lights depending upon the height of the structure
    • Where more than one level is used the vertical banks flash simultaneously

Resume Own Navigation vs. On Course:

  • ATC may use several terms to convey lateral and vertical restrictions
  • Course, as defined by the pilot/controller glossary: The intended direction of flight in the horizontal plane measured in degrees from north
  • Resume own Navigation, as defined by the pilot/controller glossary: − Used by ATC to advise a pilot to resume his/her own navigational responsibility. It is issued after completion of a radar vector or when radar contact is lost while the aircraft is being radar vectored

Amended Clearances:

  • Amended clearances will be issued any time an air traffic controller deems it necessary to avoid conflictions
  • Clearances will require that a flight enter holding, change altitude, or alter course in order to facilitate the safe, more efficient flow of traffic
  • A pilot may wish an explanation of the handling of the flight at the time of occurrence; however, controllers are not able to take time from their immediate control duties nor can they afford to overload the ATC communications channels to furnish explanations
    • Pilots may obtain an explanation by directing a letter or telephone call to the chief controller of the facility involved
  • Pilots have the privilege of requesting a different clearance from that which has been issued by ATC if they feel that they have information which would make another course of action more practicable or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued
    • An example might be avoiding weather the pilot sees ahead but ATC has not yet warned them about

Conclusion:

  • Pilots of aircraft are required to adhere to airways or routes being flown
  • Special attention must be given to this requirement during course changes
    • If you get a lock on the next NAVAID along your route, you can always ask for direct to save time/gas
  • 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 is one method of adhering to airways or routes
  • The use of any available cockpit instrumentation, such as DME, may be used by the pilot to lead the turn when making course changes
  • This consistent with the intent of 91.181 which requires pilots to operate along the center line of an airway and along the direct course between navigational aids or fixes
  • Do not file through any special use airspace
  • When flying in Canadian airspace, pilots are cautioned to review Canadian Air Regulations

References: