Automatic Dependent Surveillance-Broadcast In (ADS-B In)

There is no specific authorization to use ADS-B In for traffic situational awareness. Installation of ADS-B In equipment is not required for compliance with § 91.225 or § 91.227. However, aircraft owners and operators who choose to voluntarily equip with ADS-B In avionics will achieve greater benefit from the technology through improved traffic situational awareness on the ground and in the air.

Note: This AC only addresses ADS-B In systems installed consistent with AC 20-172, Airworthiness Approval for ADS-B In Systems and Applications, and meeting TSO-C195a (or later revision), Avionics Supporting Automatic Dependent Surveillance-Broadcast (ADS-B) Aircraft Surveillance Applications (ASA).

2.4.1 ADS-B In Systems. Most ADS-B In systems will include a flight deck traffic display depicting the relative position and related information of ADS-B-equipped aircraft presented on a plan view. This traffic display is only one component of the input and output devices collectively known as a Cockpit Display of Traffic Information (CDTI). The traffic display may be on a dedicated display or integrated into and presented on an existing display (e.g., navigation display (ND) or multifunction display (MFD)). The terms traffic display and CDTI are used interchangeably when the meaning is clear in context. In many installations, a moving map depicting key surface elements of the airport may be displayed when on the ground or within a predefined altitude/distance from an airport while airborne.

Note: ADS-B Traffic Advisory System (ATAS) is an ADS-B In application intended specifically for General Aviation (GA) use that will incorporate an audio traffic alerting capability. There is a configuration in which the display is optional for aircraft that cannot accommodate a display.

2.4.2 Operation. The CDTI will display nearby ADS-B Out traffic and may also display TIS-B traffic, depending on the installation and operating airspace. The display may have functionality to allow the pilot to select a target to obtain additional information that might not be automatically displayed, such as distance from own-ship and groundspeed (GS). The system will also provide range selection and declutter functionality. More advanced ADS-B In systems may also include certified functionality to perform ADS-B In procedures described in the appendices of this AC.

Note: For traffic situational awareness, pilots are encouraged to incorporate the display in their normal scan to aid in the early detection of nearby traffic when in visual conditions and to aid in understanding the flow and amount of nearby traffic when in instrument conditions. However, the traffic display is not intended to be used for self-separation or to deviate from an ATC clearance. Should questions arise about a potential conflict with traffic while on an instrument flight rules (IFR) clearance, the pilot should query ATC. Pilots are also cautioned to not allow the display to become a distraction from the primary task of flying the aircraft, or scanning outside for traffic. Finally, pilots are cautioned against unnecessarily communicating on the ATC frequency about traffic observed on the traffic display.

2.4.3 Limitations. Pilots should understand the proper use and limitations of their equipment and should adhere to the following:

2.4.3.1 Only use the traffic display to supplement what can be seen out the window (OTW), except when authorized to conduct ADS-B In operations described in the appendices of this AC. Pilots must always conduct OTW scans to see and avoid as required under § 91.113(b).

2.4.3.2 Unless specifically certified for the function, the traffic display is not intended for collision avoidance or self-separation.

2.4.3.3 Not all ground and airborne traffic will appear on the traffic display. The traffic display can only display properly equipped ADS-B Out traffic broadcasting on the received frequencies, and, depending on the operating location, ADS-SLR, ADS-R, TIS-B, and/or Traffic Alert and Collision Avoidance System (TCAS) (if installed) traffic. Additionally, the completeness of the traffic situational awareness information is affected by range, signal quality, and proper installation and function of the ADS-B Out system on the traffic aircraft.

2.4.3.4 Unless initiated by the controller, pilots should typically not use the call sign or Aircraft Identification (ACID) of observed traffic in radio communications, as this could create confusion for both ATC and pilots monitoring the frequency.

2.4.3.5 In multipiloted aircraft, establish and comply with crew coordination procedures on the use of the CDTI and ADS-B In information to minimize head-down time.

2.4.3.6 Use of the traffic display does not change pilot or controller responsibilities.

2.4.3.7 If at any time the presented information becomes unreliable, inoperative, or a distraction, disregard the information presented on the traffic display.

2.4.3.8 In TCAS-equipped aircraft, ADS-B In traffic display information does not change existing procedures for response to a traffic advisory (TA) and/or Resolution Advisory (RA).

AC 90-114, ¶2.4