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Federal Aviation Administration
Radar Services

Introduction:

Flight Following:

  • Provided by controllers to give traffic advisories to IFR and participating VFR traffic
  • This is a secondary task for ATC and will be provided workload permitting
    • Radar/nonradar traffic advisories do not relieve the pilot of his/her responsibility to see and avoid other aircraft
  • You may contact the controlling agency (approach/center) yourself airborne, or if you intend to use flight following from takeoff, you should mention it with your initial request to ground
  • Example: "[Agency] [Callsign], [Location], request advisories"

Air Route Traffic Control Center (ARTCC):

  • In air traffic control, an Area Control Center (ACC), also known as a Center
  • Is a facility responsible for controlling instrument flight rules aircraft en route in a particular volume of airspace (a Flight Information Region) at high altitudes between airport approaches and departures

Terminal Radar Approach Control (TRACON):

  • It is usually located within the vicinity of an airport
  • Typically, the TRACON controls aircraft approaching and departing between 5 and 50 miles of the airport
  • Radar equipment allows an air traffic controller to "see" the aircraft even at that distance

Radar Traffic Information Service:

  • Pilots receiving this service are advised of any radar target observed on the radar display which may be in such proximity to the position of their aircraft or its intended route of flight that it warrants their attention
  • Traffic Information Service is not intended to relieve the pilot of the responsibility for continual vigilance to see and avoid other aircraft
  • Radar Traffic Information Service Purpose:

    • The issuance of traffic information as observed on a radar display is based on the principle of assisting and advising a pilot that a particular radar target's position and track indicates it may intersect or pass in such proximity to that pilot's intended flight path that it warrants attention
      • This is to alert the pilot to the traffic, to be on the lookout for it, and thereby be in a better position to take appropriate action should the need arise
    • Pilots are reminded that the surveillance radar used by ATC does not provide altitude information unless the aircraft is equipped with Mode C and the radar facility is capable of displaying altitude information
  • Radar Traffic Information Service Provisions:

    • Many factors, such as limitations of the radar, volume of traffic, controller workload and communications frequency congestion, could prevent the controller from providing this service
    • Controllers possess complete discretion for determining whether they are able to provide or continue to provide this service in a specific case
    • The controller's reason against providing or continuing to provide the service in a particular case is not subject to question nor need it be communicated to the pilot
      • In other words, the provision of this service is entirely dependent upon whether controllers believe they are in a position to provide it
    • Traffic information is routinely provided to all aircraft operating on IFR flight plans except when the pilot declines the service, or the pilot is operating within Class A airspace
    • Traffic information may be provided to flights not operating on IFR flight plans when requested by pilots of such flights

NOTE:
Radar ATC facilities normally display and monitor both primary and secondary radar when it is available, except that secondary radar may be used as the sole display source in Class A airspace, and under some circumstances outside of Class A airspace (beyond primary coverage and in en route areas where only secondary is available). Secondary radar may also be used outside Class A airspace as the sole display source when the primary radar is temporarily unusable or out of service. Pilots in contact with the affected ATC facility are normally advised when a temporary outage occurs; i.e., "primary radar out of service; traffic advisories available on transponder aircraft only." This means simply that only the aircraft which have transponders installed and in use will be depicted on ATC radar indicators when the primary radar is temporarily out of service

    • When receiving VFR radar advisory service, pilots should monitor the assigned frequency at all times
    • This is to preclude controllers' concern for radio failure or emergency assistance to aircraft under the controller's jurisdiction
    • VFR radar advisory service does not include vectors away from conflicting traffic unless requested by the pilot
    • When advisory service is no longer desired, advise the controller before changing frequencies and then change your transponder code to 1200, if applicable
    • Pilots should also inform the controller when changing VFR cruising altitude
    • Except in programs where radar service is automatically terminated, the controller will advise the aircraft when radar is terminated

NOTE:
Participation by VFR pilots in formal programs implemented at certain terminal locations constitutes pilot request. This also applies to participating pilots at those locations where arriving VFR flights are encouraged to make their first contact with the tower on the approach control frequency

  • Issuance of Traffic Information:

    • Traffic information will include the following concerning a target which may constitute traffic for an aircraft that is:
      • Radar identified:

        • Azimuth from the aircraft in terms of the 12 hour clock, or
        • When rapidly maneuvering civil test or military aircraft prevent accurate issuance of traffic as in (a) above, specify the direction from an aircraft's position in terms of the eight cardinal compass points (N, NE, E, SE, S, SW, W, NW). This method must be terminated at the pilot's request
        • Distance from the aircraft in nautical miles;
        • Direction in which the target is proceeding; and
        • Type of aircraft and altitude if known
        • Example: Traffic 10 o'clock, 3 miles, west-bound (type aircraft and altitude, if known, of the observed traffic). The altitude may be known, by means of Mode C, but not verified with the pilot for accuracy. (To be valid for separation purposes by ATC, the accuracy of Mode C readouts must be verified. This is usually accomplished upon initial entry into the radar system by a comparison of the readout to pilot stated altitude, or the field elevation in the case of continuous readout being received from an aircraft on the airport.) When necessary to issue traffic advisories containing unverified altitude information, the controller will issue the advisory in the same manner as if it were verified due to the accuracy of these readouts. The pilot may upon receipt of traffic information, request a vector (heading) to avoid such traffic. The vector will be provided to the extent possible as determined by the controller provided the aircraft to be vectored is within the airspace under the jurisdiction of the controller
      • Not radar identified:

        • Distance and direction with respect to a fix;
        • Direction in which the target is proceeding; and
        • Type of aircraft and altitude if known
        • Example: Traffic 8 miles south of the airport northeast bound, (type aircraft and altitude if known)
  • The examples depicted in the following figures [Figure 1/2]point out the possible error in the position of this traffic when it is necessary for a pilot to apply drift correction to maintain this track. This error could also occur in the event a change in course is made at the time radar traffic information is issued
Induced Error in Position of Traffic
Induced Error in Position of Traffic
    • Example: In Figure 1 traffic information would be issued to the pilot of aircraft "A" as 12 o'clock. The actual position of the traffic as seen by the pilot of aircraft "A" would be 2 o'clock. Traffic information issued to aircraft "B" would also be given as 12 o'clock, but in this case, the pilot of "B" would see the traffic at 10 o'clock
Induced Error in Position of Traffic
Induced Error in Position of Traffic
    • Example:
    • In Figure 2 traffic information would be issued to the pilot of aircraft "C" as 2 o'clock. The actual position of the traffic as seen by the pilot of aircraft "C" would be 3 o'clock. Traffic information issued to aircraft "D" would be at an 11 o'clock position. Since it is not necessary for the pilot of aircraft "D" to apply wind correction (crab) to remain on track, the actual position of the traffic issued would be correct. Since the radar controller can only observe aircraft track (course) on the radar display, traffic advisories are issued accordingly, and pilots should give due consideration to this fact when looking for reported traffic

Radar Assistance to VFR Aircraft:

  • Radar equipped FAA ATC facilities provide radar assistance and navigation service (vectors) to VFR aircraft provided the aircraft can communicate with the facility, are within radar coverage, and can be radar identified
  • Pilots should clearly understand that authorization to proceed in accordance with such radar navigational assistance does not constitute authorization for the pilot to violate CFRs. In effect, assistance provided is on the basis that navigational guidance information issued is advisory in nature and the job of flying the aircraft safely, remains with the pilot
  • In many cases, controllers will be unable to determine if flight into instrument conditions will result from their instructions. To avoid possible hazards resulting from being vectored into IFR conditions, pilots should keep controllers advised of the weather conditions in which they are operating and along the course ahead
  • Radar navigation assistance (vectors) may be initiated by the controller when one of the following conditions exist:
    • The controller suggests the vector and the pilot concurs
    • A special program has been established and vectoring service has been advertised
    • In the controller’s judgment the vector is necessary for air safety
  • Radar navigation assistance (vectors) and other radar derived information may be provided in response to pilot requests. Many factors, such as limitations of radar, volume of traffic, communications frequency, congestion, and controller workload could prevent the controller from providing it. Controllers have complete discretion for determining if they are able to provide the service in a particular case. Their decision not to provide the service in a particular case is not subject to question

Terminal Radar Services for VFR Aircraft:

  • Basic Radar Service:
    • In addition to the use of radar for the control of IFR aircraft, all commissioned radar facilities provide the following basic radar services for VFR aircraft:
      • Safety alerts
      • Traffic advisories
      • Limited radar vectoring (on a workload permitting basis)
      • Sequencing at locations where procedures have been established for this purpose and/or when covered by a Letter of Agreement
    • NOTE: When the stage services were developed, two basic radar services (traffic advisories and limited vectoring) were identified as "Stage I." This definition became unnecessary and the term "Stage I" was eliminated from use. The term "Stage II" has been eliminated in conjunction with the airspace reclassification, and sequencing services to locations with local procedures and/or letters of agreement to provide this service have been included in basic services to VFR aircraft. These basic services will still be provided by all terminal radar facilities whether they include Class B, Class C, Class D or Class E airspace. "Stage III" services have been replaced with "Class B" and "TRSA" service where applicable
    • Vectoring service may be provided when requested by the pilot or with pilot concurrence when suggested by ATC
    • Pilots of arriving aircraft should contact approach control on the publicized frequency and give their position, altitude, aircraft call sign, type aircraft, radar beacon code (if transponder equipped), destination, and request traffic information
    • Approach control will issue wind and runway, except when the pilot states "have numbers" or this information is contained in the ATIS broadcast and the pilot states that the current ATIS information has been received. Traffic information is provided on a workload permitting basis. Approach control will specify the time or place at which the pilot is to contact the tower on local control frequency for further landing information. Radar service is automatically terminated and the aircraft need not be advised of termination when an arriving VFR aircraft receiving radar services to a tower-controlled airport where basic radar service is provided has landed, or to all other airports, is instructed to change to tower or advisory frequency. (See FAA Order JO 7110.65, Air Traffic Control, Paragraph 5−1−13, Radar Service Termination)
    • Sequencing for VFR aircraft is available at certain terminal locations (see locations listed in the Chart Supplement U.S.). The purpose of the service is to adjust the flow of arriving VFR and IFR aircraft into the traffic pattern in a safe and orderly manner and to provide radar traffic information to departing VFR aircraft. Pilot participation is urged but is not mandatory. Traffic information is provided on a workload permitting basis. Standard radar separation between VFR or between VFR and IFR aircraft is not provided
      • Pilots of arriving VFR aircraft should initiate radio contact on the publicized frequency with approach control when approximately 25 miles from the airport at which sequencing services are being provided. On initial contact by VFR aircraft, approach control will assume that sequencing service is requested. After radar contact is established, the pilot may use pilot navigation to enter the traffic pattern or, depending on traffic conditions, approach control may provide the pilot with routings or vectors necessary for proper sequencing with other participating VFR and IFR traffic en route to the airport. When a flight is positioned behind a preceding aircraft and the pilot reports having that aircraft in sight, the pilot will be instructed to follow the preceding aircraft. THE ATC INSTRUCTION TO FOLLOW THE PRECEDING AIRCRAFT DOES NOT AUTHORIZE THE PILOT TO COMPLY WITH ANY ATC CLEARANCE OR INSTRUCTION ISSUED TO THE PRECEDING AIRCRAFT. If other "nonparticipating" or "local" aircraft are in the traffic pattern, the tower will issue a landing sequence. If an arriving aircraft does not want radar service, the pilot should state "NEGATIVE RADAR SERVICE" or make a similar comment, on initial contact with approach control
      • Pilots of departing VFR aircraft are encouraged to request radar traffic information by notifying ground control on initial contact with their request and proposed direction of flight
        • EXAMPLE-Xray ground control, November One Eight Six, Cessna One Seventy Two, ready to taxi, VFR southbound at 2,500, have information bravo and request radar traffic information
        • NOTE-Following takeoff, the tower will advise when to contact departure control
      • Pilots of aircraft transiting the area and in radar contact/communication with approach control will receive traffic information on a controller workload permitting basis. Pilots of such aircraft should give their position, altitude, aircraft call sign, aircraft type, radar beacon code (if transponder equipped), destination, and/or route of flight
  • TRSA Service (Radar Sequencing and Separation Service for VFR Aircraft in a TRSA):
    • This service has been implemented at certain terminal locations. The service is advertised in the Chart Supplement U.S. The purpose of this service is to provide separation between all participating VFR aircraft and all IFR aircraft operating within the airspace defined as the Terminal Radar Service Area (TRSA). Pilot participation is urged but is not mandatory
    • If any aircraft does not want the service, the pilot should state "NEGATIVE TRSA SERVICE" or make a similar comment, on initial contact with approach control or ground control, as appropriate
    • TRSAs are depicted on sectional aeronautical charts and listed in the Chart Supplement U.S.
    • While operating within a TRSA, pilots are provided TRSA service and separation as prescribed in this paragraph. In the event of a radar outage, separation and sequencing of VFR aircraft will be suspended as this service is dependent on radar. The pilot will be advised that the service is not available and issued wind, runway information, and the time or place to contact the tower. Traffic information will be provided on a workload permitting basis
    • Visual separation is used when prevailing conditions permit and it will be applied as follows:
      • When a VFR flight is positioned behind a preceding aircraft and the pilot reports having that aircraft in sight, the pilot will be instructed by ATC to follow the preceding aircraft. Radar service will be continued to the runway. THE ATC INSTRUCTION TO FOLLOW THE PRECEDING AIRCRAFT DOES NOT AUTHORIZE THE PILOT TO COMPLY WITH ANY ATC CLEARANCE OR INSTRUCTION ISSUED TO THE PRECEDING AIRCRAFT
      • If other "nonparticipating" or "local" aircraft are in the traffic pattern, the tower will issue a landing sequence
      • Departing VFR aircraft may be asked if they can visually follow a preceding departure out of the TRSA. The pilot will be instructed to follow the other aircraft provided that the pilot can maintain visual contact with that aircraft
    • VFR aircraft will be separated from VFR/IFR aircraft by one of the following:
      • 500 feet vertical separation
      • Visual separation
      • Target resolution (a process to ensure that correlated radar targets do not touch)
    • Participating pilots operating VFR in a TRSA:
      • Must maintain an altitude when assigned by ATC unless the altitude assignment is to maintain at or below a specified altitude. ATC may assign altitudes for separation that do not conform to 14 CFR Section 91.159. When the altitude assignment is no longer needed for separation or when leaving the TRSA, the instruction will be broadcast, "RESUME APPROPRIATE VFR ALTITUDES." Pilots must then return to an altitude that conforms to 14 CFR Section 91.159 as soon as practicable
      • When not assigned an altitude, the pilot should coordinate with ATC prior to any altitude change
    • Within the TRSA, traffic information on observed but unidentified targets will, to the extent possible, be provided to all IFR and participating VFR aircraft. The pilot will be vectored upon request to avoid the observed traffic, provided the aircraft to be vectored is within the airspace under the jurisdiction of the controller
    • Departing aircraft should inform ATC of their intended destination and/or route of flight and proposed cruising altitude
    • ATC will normally advise participating VFR aircraft when leaving the geographical limits of the TRSA. Radar service is not automatically terminated with this advisory unless specifically stated by the controller
  • Class C Service: This service provides, in addition to basic radar service, approved separation between IFR and VFR aircraft, and sequencing of VFR arrivals to the primary airport
  • Class B Service: This service provides, in addition to basic radar service, approved separation of aircraft based on IFR, VFR, and/or weight, and sequencing of VFR arrivals to the primary airport(s)
  • PILOT RESPONSIBILITY: THESE SERVICES ARE NOT TO BE INTERPRETED AS RELIEVING PILOTS OF THEIR RESPONSIBILITIES TO SEE AND AVOID OTHER TRAFFIC OPERATING IN BASIC VFR WEATHER CONDITIONS, TO ADJUST THEIR OPERATIONS AND FLIGHT PATH AS NECESSARY TO PRECLUDE SERIOUS WAKE ENCOUNTERS, TO MAINTAIN APPROPRIATE TERRAIN AND OBSTRUCTION CLEARANCE, OR TO REMAIN IN WEATHER CONDITIONS EQUAL TO OR BETTER THAN THE MINIMUMS REQUIRED BY 14 CFR SECTION 91.155. WHENEVER COMPLIANCE WITH AN ASSIGNED ROUTE, HEADING AND/OR ALTITUDE IS LIKELY TO COMPROMISE PILOT RESPONSIBILITY RESPECTING TERRAIN AND OBSTRUCTION CLEARANCE, VORTEX EXPOSURE, AND WEATHER MINIMUMS, APPROACH CONTROL SHOULD BE SO ADVISED AND A REVISED CLEARANCE OR INSTRUCTION OBTAINED
  • ATC services for VFR aircraft participating in terminal radar services are dependent on ATC radar. Services for VFR aircraft are not available during periods of a radar outage and are limited during CENRAP operations. The pilot will be advised when VFR services are limited or not available
    • NOTE-Class B and Class C airspace are areas of regulated airspace. The absence of ATC radar does not negate the requirement of an ATC clearance to enter Class B airspace or two way radio contact with ATC to enter Class C airspace

Safety Alerts:

  • A safety alert will be issued to pilots of aircraft being controlled by ATC if the controller is aware the aircraft is at an altitude which, in the controller’s judgment, places the aircraft in unsafe proximity to terrain, obstructions or other aircraft
  • The provision of this service is contingent upon the capability of the controller to have an awareness of a situation involving unsafe proximity to terrain, obstructions and uncontrolled aircraft
  • Safety Alerts are mandatory services and are provided to ALL aircraft
    • The actual issuance of a safety alert cannot be mandated, but it can be expected on a reasonable, though intermittent basis
      • Stated another way, you cannot expect ATC to see every possible hazard but when they do, they must say something
    • Once the alert is issued, it is solely the pilot’s prerogative to determine what course of action, if any, to take
    • This procedure is intended for use in time critical situations where aircraft safety is in question
      • Noncritical situations should be handled via the normal traffic alert procedures
  • Safety Alerts may also be received from aircraft systems such as Automatic Dependent Surveillance Broadcast (ADSB)
  • There are two types of Safety Alerts:
    • Terrain or Obstruction Alerts
    • Aircraft Conflict Alerts/Mode C Intruder Alert
    • Terrain or Obstruction Alerts:

      • A Terrain/Obstruction Alert is issued when, in the controller's judgment, an aircraft's altitude places it in unsafe proximity to terrain and/or obstructions
      • Issuance is contingent upon the controllers awareness
        • ATC: "Low altitude alert Cessna Three Four Juliet, check your altitude immediately. And if the aircraft is not yet on final approach, the MVA (MEA/MIA/MOCA) in your area is six thousand"
      • The controller will discontinue alerts if informed by the pilot that action is being taken or that the obstruction is in sight
      • This is intended for time critical situations
      • Minimum Safe Altitude Warning (MSAW):

        • Designed solely as a controller aid when a tracked mode C equipped aircraft under their control is within a potentially unsafe proximity to terrain/obstructions
        • Terminal Automated Radar Terminal System (ARTS) IIIA, Common ARTS (to include ARTS IIIE and ARTS IIE) (CARTS), Micro En Route Automated Radar Tracking System (MEARTS), and Standard Terminal Automation Replacement System (STARS) facilities have an automated function which, if operating, alerts controllers when a tracked Mode C equipped aircraft under their control is below or is predicted to be below a predetermined minimum safe altitude
        • The ARTS IIIA, CARTS, MEARTS, and STARS facility will, when MSAW is operating, provide MSAW monitoring for all aircraft with an operating Mode C altitude encoding transponder that are tracked by the system and are:
          • Operating on an IFR flight plan; or
          • Operating VFR and have requested MSAW monitoring
        • Terminal AN/TPX-42A (number beacon decoder system) facilities have an automated function called Low Altitude Alert System (LAAS)
          • Although not as sophisticated as MSAW, LAAS alerts the controller when a Mode C transponder equipped aircraft operating on an IFR flight plan is below a predetermined minimum safe altitude
          • Pilots operating VFR may request MSAW or LAAS monitoring if their aircraft are equipped with Mode C transponders
            • PILOT: "Apache Three Three Papa request MSAW/LAAS"
    • Aircraft Conflict Alerts:

      • Controllers will immediately issue an alert to the pilot of an aircraft under their control if they are aware of another aircraft which is not under their control, at an altitude which, in the controller’s judgment, places both aircraft in unsafe proximity to each other
      • With the alert, when feasible, the controller will offer the pilot the position of the traffic if time permits and an alternate course(s) of action
      • Any alternate course(s) of action the controller may recommend to the pilot will be predicated only on other traffic being worked by the controller
        • ATC: "American Three, traffic alert, (position of traffic, if time permits), advise you turn right/left heading (degrees) and/or climb/descend to (altitude) immediately"
      • The controller will discontinue alerts if informed by the pilot that action is being taken or the other aircraft is in sight

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