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Automatic Dependent Surveillance Broadcast

Introduction:

  • Automatic Dependent Surveillance-Broadcast (ADS-B) is surveillance technology being deployed throughout the National Airspace System [Figure 1]
  • Position reports are based on satellite navigation systems (aircraft to aircraft)
  • ADS-B broadcasts once per second with the aircrafts position, velocity, identification and other information
  • Also receives this information from other aircraft
  • The ADS-B system is composed of aircraft avionics and a ground infrastructure
    • On-board avionics determine the position of the aircraft by using the GNSS and transmit its position along with additional information about the aircraft to ground stations for use by ATC and other ADS-B services
    • This information is transmitted at a rate of approximately once per second

Frequencies:

  • In the United States, ADS-B equipped aircraft exchange information is on one of two frequencies:
    • 978 or 1090 MHz
  • The 1090 MHz frequency is associated with Mode A, C, and S transponder operations
  • 1090 MHz transponders with integrated ADS-B functionality extend the transponder message sets with additional ADS-B information
  • This additional information is known as an "extended squitter" message and referred to as 1090ES
  • ADS-B equipment operating on 978 MHz is known as the Universal Access Transceiver (UAT)
  • ADS B avionics can have the ability to both transmit and receive information
  • The transmission of ADS-B information from an aircraft is known as ADS-B Out
  • The receipt of ADS-B information by an aircraft is known as ADS-B In
  • On January 1, 2020, all aircraft operating within the airspace defined in 14 CFR part 91, 91.225 will be required to transmit the information defined in 91.227 using ADS-B Out avionics
  • In general, operators flying at 18,000' and above will require equipment which uses 1090 ES
  • Those that do not fly above 18,000 may use either UAT or 1090ES equipment (Refer to 14 CFR 91.225 and 91.227)
  • While the regulation will not require it, operators equipped with ADS-B In will realize additional benefits from ADS-B broadcast services:

ADS-B Certification and Performance Requirements:

  • ADS-B equipment may be certified as a surveillance source for air traffic separation services using ADS-B Out
  • ADS-B equipment may also be certified for use with ADS-B In advisory services that enable appropriately equipped aircraft to display traffic and flight information
  • Refer to the aircraft's flight manual supplement or Pilot Operating Handbook for the capabilities of a specific aircraft installation

ADS-B Capabilities & Procedures:

  • ADS-B enables improved surveillance services, both air-to-air and air-to-ground, especially in areas where radar is ineffective due to terrain or where it is impractical or cost prohibitive
    • Initial NAS applications of air-to-air ADS-B are for "advisory" use only, enhancing a pilot's visual acquisition of other nearby equipped aircraft either when airborne or on the airport surface
    • Additionally, ADS-B will enable ATC and fleet operators to monitor aircraft throughout the available ground station coverage area
  • An aircraft’s Flight Identification (FLT ID), also known as registration number or airline flight number, is transmitted by the ADS-B Out avionics
    • The FLT ID is comprised of a maximum of seven alphanumeric characters and also corresponds to the aircraft identification annotated on the ATC flight plan
    • The FLT ID for airline and commuter aircraft is associated with the company name and flight number (for example, AAL3342)
    • The FLT ID is typically entered by the flightcrew during preflight through either a Flight Management System (FMS) interface (Control Display Unit/CDU) or transponder control panel
    • The FLT ID for General Aviation (GA) aircraft is associated with the aircraft’s registration number
    • The aircraft owner can preset the FLT ID to the aircraft’s registration number (for example, N235RA), since it is a fixed value, or the pilot can enter it into the ADS-B Out system prior to flight
    • ATC systems use transmitted FLT IDs to uniquely identify each aircraft within a given airspace and correlate them to a filed flight plan for the provision of surveillance and separation services
    • If the FLT ID is not entered correctly, ATC automation systems may not associate surveillance tracks for the aircraft to its filed flight plan
    • Therefore, Air Traffic services may be delayed or unavailable until this is corrected
    • Consequently, it is imperative that flightcrews and GA pilots ensure the FLT ID entry correctly matches the aircraft identification annotated in the filed ATC flight plan
  • ADS B systems integrated with the transponder will automatically set the applicable emergency status when 7500, 7600, or 7700 are entered into the transponder
    • ADS B systems not integrated with the transponder, or systems with optional emergency codes, will require that the appropriate emergency code is entered through a pilot interface
    • ADS-B is intended for in-flight and airport surface use
    • ADS-B systems should be turned "on" -- and remain "on" -- whenever operating in the air and moving on the airport surface
    • Civil and military Mode A/C transponders and ADS-B systems should be adjusted to the "on" or normal operating position as soon as practical, unless the change to "standby" has been accomplished previously at the request of ATC

ATC Surveillance Services using ADS-B - Procedures and Recommended Phraseology - For Use In Alaska Only:

  • Radar procedures, with the exceptions found in this paragraph, are identical to those procedures prescribed for radar in AIM Chapter 4 and Chapter 5
  • Preflight:
    • If a request for ATC services is predicated on ADS-B and such services are anticipated when either a VFR or IFR flight plan is filed, the aircraft's "N" number or call-sign as filed in "Block 2" of the Flight Plan must be entered in the ADS-B avionics as the aircraft's flight ID
  • In-flight:
    • When requesting ADS-B services while airborne, pilots should ensure that their ADS-B equipment is transmitting their aircraft's "N" number or call sign prior to contacting ATC
    • To accomplish this, the pilot must select the ADS-B "broadcast flight ID" function

NOTE:
The broadcast "VFR" or "Standby" mode built into some ADS-B systems will not provide ATC with the appropriate aircraft identification information. This function should first be disabled before contacting ATC

Aircraft with an Inoperative/Malfunctioning ADS-B Transmitter or in the Event of an Inoperative Ground Broadcast Transceiver (GBT):

  • ATC will inform the flight crew when the aircraft's ADS-B transmitter appears to be inoperative or malfunctioning:
    • PHRASEOLOGY: YOUR ADS-B TRANSMITTER APPEARS TO BE INOPERATIVE/MALFUNCTIONING. STOP ADS-B TRANSMISSIONS
  • ATC will inform the flight crew when the GBT transceiver becomes inoperative or malfunctioning, as follows:
    • PHRASEOLOGY: (Name of facility) GROUND BASED TRANSCEIVER INOPERATIVE/MALFUNCTIONING
    • (And if appropriate) RADAR CONTACT LOST
NOTE:
An inoperative or malfunctioning GBT may also cause a loss of ATC surveillance services
  • ATC will inform the flight crew if it becomes necessary to turn off the aircraft's ADS-B transmitter
    • PHRASEOLOGY: STOP ADS-B TRANSMISSIONS
  • Other malfunctions and considerations:
    • Loss of automatic altitude reporting capabilities (encoder failure) will result in loss of ATC altitude advisory services
    • Loss of automatic altitude reporting capabilities (encoder failure) will result in loss of ATC altitude advisory services

ADS-B Limitations:

  • The ADS-B cockpit display of traffic is NOT intended to be used as a collision avoidance system and does not relieve the pilot's responsibility to "see and avoid" other aircraft [Figure 2]
  • ADS-B must not be used for avoidance maneuvers during IMC or other times when there is no visual contact with the intruder aircraft
  • ADS-B is intended only to assist in visual acquisition of other aircraft
  • No avoidance maneuvers are provided nor authorized, as a direct result of an ADS-B target being displayed in the cockpit
  • Use of ADS-B radar services is limited to the service volume of the GBT

NOTE:
The coverage volume of GBTs are limited to line-of-sight

Reports of ADS-B Malfunctions:

  • Users of ADS-B can provide valuable assistance in the correction of malfunctions by reporting instances of undesirable system performance
  • Since ADS-B performance is monitored by maintenance personnel rather than ATC, it is suggested that malfunctions be reported in any one of the following ways:
    1. By radio or telephone to the nearest Flight Service Station (FSS) facility
    2. By reporting the failure directly to the FAA Safe Flight 21 program at 1-877-FLYADSB or http://www.faa.gov/nextgen/programs/adsb/
  • Reporters should identify:
    1. Condition observed
    2. Date and time of observation
    3. Altitude and location of observation
    4. Type and call sign of the aircraft
    5. Type and software version of avionics system
Broadcast Services Architecture
Figure 1: Broadcast Services Architecture
Terminal Service Ceilings and Floors
Figure 2: Broadcast Services Architecture
Enroute Service Ceilings and Floors
Figure 3: Enroute Service Ceilings and Floors

Limitations:

  • Limited to the service volume of the ground based transmitter
  • Report all malfunctions to the nearest FSS, Form 8740-5, or the FAA Safe Flight 21 program at 1-877-FLYADSB or http://www.faa.gov/nextgen/programs/adsb/

Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment and use:

  • After January 1, 2020, and unless otherwise authorized by ATC, no person may operate an aircraft in Class A airspace unless the aircraft has equipment installed that:
    • Meets the requirements in TSO-C166b, Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Service-Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz); and
    • Meets the requirements of 91.227
  • After January 1, 2020, and unless otherwise authorized by ATC, no person may operate an aircraft below 18,000' MSL and in the following airspace unless the aircraft has equipment installed that meets the requirements above but substitute TSO-C166B for TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B) Equipment Operating on the Frequency of 978 MHz
    • Class B and Class C airspace areas;
    • Within 30 NM of an airport listed in appendix D, section 1 to this part from the surface upward to 10,000' MSL;
    • Above the ceiling and within the lateral boundaries of a Class B or Class C airspace area designated for an airport upward to 10,000' MSL;
    • Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000' MSL, excluding the airspace at and below 2,500' above the surface; and
    • Class E airspace at and above 3,000' MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles
  • Operators with equipment installed with an approved deviation under 21.618 are considered in compliance
  • The requirements of do not apply to any aircraft that was not originally certificated with an electrical system, or that has not subsequently been certified with such a system installed, including balloons and gliders
    • These aircraft may conduct operations without ADS-B Out within 30 NM of an airport listed in appendix D, section 1 to this part from the surface upward to 10,000' MSL and Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000' MSL, excluding the airspace at and below 2,500' above the surface
    • Operations authorized by this section must be conducted:
      • Outside any Class B or Class C airspace area; and
      • Below the altitude of the ceiling of a Class B or Class C airspace area designated for an airport, or 10,000' MSL, whichever is lower
  • Each person operating an aircraft equipped with ADS-B Out must operate this equipment in the transmit mode at all times
  • Requests for ATC authorized deviations from the requirements must be made to the ATC facility having jurisdiction over the concerned airspace within the time periods specified as follows:
    • For operation of an aircraft with an inoperative ADS-B Out, to the airport of ultimate destination, including any intermediate stops, or to proceed to a place where suitable repairs can be made or both, the request may be made at any time
    • For operation of an aircraft that is not equipped with ADS-B Out, the request must be made at least 1 hour before the proposed operation

Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment performance requirements:

  • Definitions:
    • ADS-B Out is a function of an aircraft's on-board avionics that periodically broadcasts the aircraft's state vector (3-dimensional position and 3-dimensional velocity) and other required information as described in this section
    • Navigation Accuracy Category for Position ( NAC P ) specifies the accuracy of a reported aircraft's position, as defined in TSO-C166b and TSO-C154c
    • Navigation Accuracy Category for Velocity ( NAC V ) specifies the accuracy of a reported aircraft's velocity, as defined in TSO-C166b and TSO-C154c
    • Navigation Integrity Category (NIC) specifies an integrity containment radius around an aircraft's reported position, as defined in TSO-C166b and TSO-C154c
    • Position Source refers to the equipment installed on-board an aircraft used to process and provide aircraft position (for example, latitude, longitude, and velocity) information
    • Source Integrity Level (SIL) indicates the probability of the reported horizontal position exceeding the containment radius defined by the NIC on a per sample or per hour basis, as defined in TSO-C166b and TSO-C154c
    • System Design Assurance (SDA) indicates the probability of an aircraft malfunction causing false or misleading information to be transmitted, as defined in TSO-C166b and TSO-C154c
    • Total latency is the total time between when the position is measured and when the position is transmitted by the aircraft
    • Uncompensated latency is the time for which the aircraft does not compensate for latency
  • 1090 MHz ES and UAT Broadcast Links and Power Requirements:
    • Aircraft operating in Class A airspace must have equipment installed that meets the antenna and power output requirements of Class A1, A1S, A2, A3, B1S, or B1 equipment as defined in TSO-C166b, Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Service-Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz)
    • Aircraft operating in airspace designated for ADS-B Out, but outside of Class A airspace, must have equipment installed that meets the antenna and output power requirements of either:
      • Class A1, A1S, A2, A3, B1S, or B1 as defined in TSO-C166b; or
      • Class A1H, A1S, A2, A3, B1S, or B1 equipment as defined in TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B) Equipment Operating on the Frequency of 978 MHz
  • ADS-B Out Performance Requirements for NAC P, NAC V , NIC, SDA , and SIL:
    • For aircraft broadcasting ADS-B Out as required under 91.225 (a) and (b):
      • The aircraft's NACP must be less than 0.05 NM;
      • The aircraft's NACV must be less than 10 meters per second;
      • The aircraft's NIC must be less than 0.2 NM;
      • The aircraft's SDA must be 2; and
      • The aircraft's SIL must be 3
    • Changes in NACP , NACV , SDA, and SIL must be broadcast within 10 seconds
    • Changes in NIC must be broadcast within 12 seconds
  • Minimum Broadcast Message Element Set for ADS-B Out. Each aircraft must broadcast the following information, as defined in TSO-C166b or TSO-C154c. The pilot must enter information for message elements listed in paragraphs (d)(7) through (d)(10) of this section during the appropriate phase of flight
    • The length and width of the aircraft;
    • An indication of the aircraft's latitude and longitude;
    • An indication of the aircraft's barometric pressure altitude;
    • An indication of the aircraft's velocity;
    • An indication if TCAS II or ACAS is installed and operating in a mode that can generate resolution advisory alerts;
    • If an operable TCAS II or ACAS is installed, an indication if a resolution advisory is in effect;
    • An indication of the Mode 3/A transponder code specified by ATC;
    • An indication of the aircraft's call sign that is submitted on the flight plan, or the aircraft's registration number, except when the pilot has not filed a flight plan, has not requested ATC services, and is using a TSO-C154c self-assigned temporary 24-bit address;
    • An indication if the flight crew has identified an emergency, radio communication failure, or unlawful interference;
    • An indication of the aircraft's "IDENT" to ATC;
    • An indication of the aircraft assigned ICAO 24-bit address, except when the pilot has not filed a flight plan, has not requested ATC services, and is using a TSO-C154c self-assigned temporary 24-bit address;
    • An indication of the aircraft's emitter category;
    • An indication of whether an ADS-B In capability is installed;
    • An indication of the aircraft's geometric altitude;
    • An indication of the Navigation Accuracy Category for Position (NACP );
    • An indication of the Navigation Accuracy Category for Velocity (NACV );
    • An indication of the Navigation Integrity Category (NIC);
    • An indication of the System Design Assurance (SDA); and
    • An indication of the Source Integrity Level (SIL)
  • ADS-B Latency Requirements:
    • The aircraft must transmit its geometric position no later than 2.0 seconds from the time of measurement of the position to the time of transmission
    • Within the 2.0 total latency allocation, a maximum of 0.6 seconds can be uncompensated latency. The aircraft must compensate for any latency above 0.6 seconds up to the maximum 2.0 seconds total by extrapolating the geometric position to the time of message transmission
    • The aircraft must transmit its position and velocity at least once per second while airborne or while moving on the airport surface
    • The aircraft must transmit its position at least once every 5 seconds while stationary on the airport surface
  • Equipment with an approved deviation. Operators with equipment installed with an approved deviation under 21.618 of this chapter also are in compliance with this section.

Reference Standards:

  • The standards required are incorporated by reference with the approval of the Director of the Office of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. All approved materials are available for inspection at the FAA's Office of Rule making (ARM-1), 800 Independence Avenue, SW., Washington, DC 20590 (telephone 202-267-9677), or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. This material is also available from the sources indicated in paragraphs (h)(1) and (h)(2) of this section
    • Copies of Technical Standard Order (TSO)-C166b, Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Service-Broadcast (TIS-B) Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz) (December 2, 2009) and TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B) Equipment Operating on the Frequency of 978 MHz (December 2, 2009) may be obtained from the U.S. Department of Transportation, Subsequent Distribution Office, DOT Warehouse M30, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20785; telephone (301) 322-5377. Copies of TSO -C166B and TSO-C154c are also available on the FAA's Web site, at http://www.faa.gov/aircraft/air_cert/design_approvals/tso/. Select the link "Search Technical Standard Orders"
    • Copies of Section 2, Equipment Performance Requirements and Test Procedures, of RTCA DO-260B, Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B) and Traffic Information Services-Broadcast (TIS-B), December 2, 2009 (referenced in TSO-C166b) and Section 2, Equipment Performance Requirements and Test Procedures, of RTCA DO-282B, Minimum Operational Performance Standards for Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B), December 2, 2009 (referenced in TSO C-154c) may be obtained from RTCA, Inc., 1828 L Street, NW., Suite 805, Washington, DC 20036-5133, telephone 202-833-9339. Copies of RTCA DO-260B and RTCA DO-282B are also available on RTCA Inc.'s Web site, at http://www.rtca.org/onlinecart/allproducts.cfm

Automatic Dependent Surveillance-Rebroadcast (ADS-R):

  • ADS−R is a datalink translation function of the ADS−B ground system required to accommodate the two separate operating frequencies (978 MHz and 1090 ES)
  • The ADS−B system receives the ADS−B messages transmitted on one frequency and ADS−R translates and reformats the information for rebroadcast and use on the other frequency
  • This allows ADS−B In equipped aircraft to see nearby ADS−B Out traffic regardless of the operating link of the other aircraft
  • Aircraft operating on the same ADS−B frequency exchange information directly and do not require the ADS−R translation function
  • Reports of ADS−R Malfunctions:

    • Users of ADS−R can provide valuable assistance in the correction of malfunctions by reporting instances of undesirable system performance
    • Since ADS−R performance is monitored by maintenance personnel rather than ATC, report malfunctions to the nearest Flight Service Station (FSS) facility by radio or telephone
    • Reporters should identify:
      • Condition observed
      • Date and time of observation
      • Altitude and location of observation
      • Type and call sign of the aircraft
      • Type and software version of avionics system

References: