Data Link Communications

This advisory circular (AC) applies to all pilots, certificate holders, operators, and/or program managers conducting data link communication operations and to those providing data communication services on behalf of operators to meet Federal Aviation Administration (FAA) and International Civil Aviation Organization (ICAO) requirements. The AC provides an overview of data link communication operations for U.S. domestic operations and in oceanic and remote continental airspace. It includes operational use guidance, minimum performance and services of communication service provider (CSP), performance monitoring, training requirements, and discrepancy reporting.

Michael Zenkovich Deputy Executive Director, Flight Standards Service

CHAPTER 1. GENERAL

1.1 Purpose of this Advisory Circular (AC)

This AC provides guidance for aircraft eligibility and operational use of data link communications in the United States and in oceanic and remote continental airspace. This document also provides explanations of data link systems to inform those who may be new to using digital aircraft communication and surveillance systems. This AC provides new guidance associated with updated and/or new operational authorization. The regulatory source basis for this AC is Title 14 of the Code of Federal Regulations (14 CFR) part 91, § 91.123. For more information, see paragraph 1.11.

1.1.1 AC Terms. The term “must” is used in this AC to indicate a mandatory requirement driven by regulation or required for a system to operate properly. The term “should” is used to indicate a recommendation. The term “operator” refers to the certificate holder, program manager, and operator/company. Future Air Navigation System (FANS) 1/A(+) is used to denote both FANS 1/A and/or FANS 1/A+.

1.1.2 Alternative Method of Compliance. In lieu of following the guidance in this AC without deviation, operators may elect to follow an alternative method, provided the alternative method is found to be acceptable to the Federal Aviation Administration (FAA). This AC does not change, add, or delete regulatory requirements or authorize deviations from regulatory requirements.

1.2 Applicability

This AC applies to operators under 14 CFR parts 91, 91 subpart K (part 91K), 121, 125, 129, and 135 conducting data link communications operations in the United States or in oceanic and remote continental airspace. This AC also applies where the foreign authority has adopted International Civil Aviation Organization (ICAO) data link communication standards.

Note: Part 91 operators do not require operational authorization for the use of data link in the United States. For data link operations in oceanic and remote continental airspace and/or foreign countries requiring specific data link approval, part 91 operators may apply to their responsible Flight Standards office for a letter of authorization (LOA). Pilots using “J” codes for U.S. domestic data link en route require a data link authorization prior to entering oceanic and remote continental airspace. Part 91 operators filing J codes for U.S. domestic data link services must have a data link authorization to file J5–J7 in oceanic and remote continental airspace (see Appendix D, Flight Planning).

1.3 Where You Can Find This AC

You can find this AC on the FAA’s website at http://www.faa.gov/regulations_policies/advisory_circulars.

1.4 What This AC Cancels

AC 120-70C, Operational Authorization Process for Use of Data Link Communication System, dated August 3, 2015, is cancelled.

1.5 Scope

The scope of this AC is limited to the interoperability designators listed in Table 2-2, Interoperability Designators and Descriptions. Aeronautical Information Services (AIS) and Meteorological Information (METI) Services are excluded from the scope of this AC.

1.6 AC Format

Chapter 2, Data Link Communication Overview, is intended to inform those not familiar with data link communications. Chapters 3-8 provide aircraft eligibility and operational guidance with the following topics:

1.7 Version References

The most current version of a document is designated by parentheses “( )” placed at the end of the number designation. Specific versions are indicated by a letter. If no letter appears after the document designation, then all versions of the document are applicable. As a convenience, most references are hyperlinked to a website containing the most current document. The most current ACs or Technical Standard Orders (TSO) are available by clicking the following links:

1.8 FAA Document References

This AC, along with AC 20-140( ), provides all the information necessary for data link communication compliance in the United States and in oceanic and remote continental airspace and should be considered the “source documents” for the operational use of data link by U.S. operators and pilots. ICAO documents are referenced in this document as a convenience to the operator.

1.9 References (current editions)

3. TSOs:

5. RTCA and European Organization for Civil Aviation Equipment (EUROCAE) Documents:

6. Data Communications Network Service (DCNS) Alternative Media Description. The DCNS Alternative Media Description defines the qualification requirements for any media proposed to be used for domestic en route air traffic control (ATC) operations.

7. NAS Data Communications Guide. This document introduces operators to data link communications operations within the United States National Airspace. It discusses Controller-Pilot Data Link Communication–Departure Clearance (CPDLC-DCL) and outlines the roles of the Airline Operations Center, clearance delivery controllers, and pilots. The document describes the general procedures for logging on/notifying, loading the flight plan, receiving the CPDLC-DCL, responding to the CPDLC-DCL message, and disconnecting/logging off. Examples of different types of revised CPDLC-DCLs are provided with guidance for reviewing, processing, and responding to the clearances. Additionally, this guide provides general information on the use of data link communications during en route operations.

8. Data Link Communication Compliance Guide. This guide expedites the compliance process as it condenses into one location the information required for data link operations.

1.10 Airworthiness

For airworthiness guidance for new aircraft and systems, refer to AC 20-140( ).

1.11 Regulatory Basis for Data Link Communication

CPDLC is an acceptable method of delivering and accepting an ATC clearance in accordance with part 91, § 91.123. With data link communication technology, both digital and voice communication are available to ATC and the pilot. Depending on the operation, data link communication may be the most suitable method of communication as deemed necessary for ATC and pilot purposes.

1.11.1 CPDLC Compliance and Voice Communication. CPDLC is not sufficient as a means of compliance to the voice communication equipment requirements as per §§ 91.129, 91.130, 91.131, 91.135, 91.205, and 91.511; part 121, §§ 121.99 and 121.122; and part 135, § 135.165, and is not required by these rules. For data link communications, two-way radio voice communication or other means of communication approved by the FAA must also be available.

1.11.2 Flight Plan Filing and Data Link Communication Capability. Pilots and operators must file an accurate flight plan in accordance with §§ 91.169 and 91.153(a)(9). The Air Traffic Service Unit (ATSU) evaluates flight plan designator(s) to provide filed services. Pilots and operators should use the guidance in this AC and other appropriate documents to determine the data link communication designator(s) for their route (see Appendix D).

1.11.3 Cockpit Voice Recorder (CVR) and Flight Data Recorder (FDR). Operators must comply with the CVR and FDR requirements of §§ 91.609(j), 121.359(k), and 135.151(h), and part 125, § 125.227(i). FAA Information for Operators (InFO) 16004 provides additional guidance concerning the applicability of these regulations.

1.12 AC Feedback Form

For your convenience, the AC Feedback Form is the last page of this AC. Note any deficiencies found, clarifications needed, or suggested improvements regarding the contents of this AC on the Feedback Form.

CHAPTER 2. DATA LINK COMMUNICATION OVERVIEW

2.1 Introduction

This chapter is intended to be informative for those not familiar with data link communication. For those already knowledgeable, Chapters 3 through 8 of this AC are devoted to data link eligibility and use.

2.2 What Are Data Link Communications?

“Data link” is a generic term encompassing different types of data link systems and subnetworks. Figure 2-1, Overview Data Link System, provides an overview of a data link system, including subnetworks. While many data link capable aircraft have access to very high frequency (VHF) data link (VDL), not all aircraft have access to additional satellite and/or high frequency (HF) data link capability. Similarly, not all communication service providers (CSP) have HF data link capability.

2.2.1 Aircraft Communication Addressing and Reporting System (ACARS) and Aeronautical Telecommunications Network (ATN). There are ACARS-based applications and ATN-based applications. The VDL Digital Link Mode 2 subnetwork supports both ACARS-based and ATN-based applications. The other subnetworks listed in this section support ACARS-based applications only. Controller Pilot Data Link Communication (CPDLC) and Automatic Dependence Surveillance-Contract (ADS-C) can be Future Air Navigation System (FANS) 1/A(+) or ATN-based. The FANS 1/A-based services are used over the ACARS networks and the ATN-based services are used over the ATN networks. The ACARS and ATN networks are not compatible. This AC concentrates on CPDLC and ADS-C using FANS 1/A(+) unless specifically denoted as ATN.

2.2.2 Data Link Subnetwork. Data link systems send messages over several communication subnetworks:

2.2.3 Data Link Systems. Data link communications is a means of transmitting and receiving digital information. ATS data link systems include the following:

2.3 FANS

FANS 1/A is ACARS-based and provides direct data link communication between the pilot and the air traffic controller via FANS 1/A avionics and FANS 1/A ground end systems. In the early 1980s, International Civil Aviation Organization (ICAO) began an effort to establish data link architecture under its FANS structure. Boeing developed FANS 1 to DO-219 and ARINC 745 using ARINC 622 binary character data format followed by Airbus with its FANS A. These two systems are referred to as FANS 1/A. The “+” at the end of FANS 1/A indicates an updated system version that includes a message latency monitor to detect old messages that may no longer apply. FANS messages can be sent over a variety of subnetworks depending on:

2.4 CPDLC and ADS-C

2.4.1 CPDLC. CPDLC is a means of communication between controller and pilot, using data link for air traffic control (ATC) communications. Messages from an aircraft to the Air Traffic Service Unit (ATSU) may follow a standard format or may be free text. Messages from a controller normally follow a standard format and usually require a response from the pilot (see Appendix F, Controller Pilot Data Link Communication (CPDLC) Uplink and Downlink Tables, for uplink message (UM) and downlink message (DM) sets).

2.4.2 ADS-C. ADS-C is an automated surveillance information system that sends position and other flight reports to the ATSU. After initial logon/notification, a link is established between the ground system and the aircraft. Without pilot input, the oceanic ATSU/Aeronautical Operational Control (AOC) can establish a “contract” with the aircraft to receive reports of aircraft identification, aircraft position, altitude, Mach number, vertical rate, true track, magnetic heading, ground speed, navigation waypoints, and meteorological data.

2.4.2.1 ADS-C Contract Types. Depending on the aircraft type, there can be up to five separate connections to different ground facilities (i.e., ATSU/AOC) at any one time. Each connection can have one Periodic contract, one Event contract, and one Demand contract.

1. Periodic. The ATSU can set or alter the update rate or time interval as needed (a higher update rate is usually required in high traffic areas or associated with reduced separation).

2. Event. The aircraft system will communicate an event as established by the ATSU if there is a change in waypoint, vertical rate, lateral deviation or altitude. An event contract remains in effect until the ATSU cancels it or until the event(s) used to trigger the report occurs. The waypoint change event contract will trigger a report for all waypoint changes. All other event contracts will trigger a report on the first occurrence and then, if necessary, the ATSU will need to request a new event contract indicating all desired event types. (See Figure 2-2, ADS-C Event Sequence.)

3. Demand. The ATSU can request a single update as needed. This does not affect an existing contract preset rate.

2.4.2.2 ADS-C Emergency. An ADS-C emergency can be triggered by the pilot by the following means:

Note: Once an ADS-C emergency has been triggered, under normal circumstances, the avionics will continue to transmit ADS-C emergency periodic reports until the pilot de-selects the ADS-C emergency function.

2.5 ATN

ATN is an inter-network architecture permitting ground, air-ground, and avionics data subnetworks to exchange digital data for the safety of air navigation and for the regular, efficient, and economic operation of ATS. ATN is in limited use in Europe, but not available in U.S. domestic airspace. The system is terrestrial based and not available over oceanic and remote continental areas.

2.5.1 ATN B1. ATN B1 consists of the following:

2.6 B2

B2 is ATN-based and will enable extended capabilities not possible with ATN B1 or FANS 1/A(+) as shown in Table 2-2, Interoperability Designators and Descriptions. The FAA plans to implement the B2 CM, CPDLC, and ADS-C ATN-based applications over the Internet Protocol Suite. B2 will provide additional services such as:

1. CPDLC:

2. ADS-C:

2.7 FANS 1/A(+) and ATN

Some avionics implementations support both the FANS 1/A(+)-based applications and associated protocols and the ATN-based applications and protocols. Depending on the system used by the ATSU, pilots may be required to logoff/disconnect any existing CPDLC or ADS-C session(s) and reestablish contact to another ground system when seamless transfer is not possible.

2.8 ACARS ATS

ACARS is a digital data link system for transmitting short, relatively simple messages between aircraft and ground stations via VHF, HF, or satellite.

Note: The ACARS network also carries FANS 1/A(+) messages.

2.8.1 Background. ARINC designed the ACARS protocol to replace VHF voice service in 1978. Later, Société International de Télécommunications Aeronautiques (SITA) added additional radio stations to augment this service. Airlines introduced ACARS in the late 1980s to reduce crew workload and improve data integrity. Although the term ACARS is often thought to encompass only a single data link system installed on the aircraft, it actually refers to a complete air and ground system.

2.8.2 Aircraft and Ground ACARS Systems. The aircraft portion of ACARS system consists of an avionics computer called an ACARS management unit (MU) and a control display unit (CDU). On the ground, the ACARS system is made up of a network of radio transceivers to receive (or transmit) data link messages and route them to various airlines on the network.

2.8.3 ACARS ATS Supported Applications Include:

2.9 Tower Data Link System (TDLS)

The TDLS automates tower-generated information for transmission to aircraft via data link communication for both CPDLC-DCL and Pre-Departure Clearance (PDC). The TDLS interfaces with sources of local weather data and flight data in order to provide pilots with PDC, D-ATIS, and CPDLC-DCL services.

Note: The term PDC refers to the U.S. ATS of DCL. The DCL includes flight plan route, climb via, and/or initial/requested altitude, beacon code assignment, and departure frequency.

2.10 CPDLC-DCL

CPDLC-DCL is available at various airports in U.S. domestic airspace using FANS 1/A(+) via VDL Mode 0/A and/or Mode 2 for departure clearance services.

2.10.1 Dispatch or Flight Following Systems. For operators with a dispatch center, flight following system, or other base of operations, copies of all data link communications may be routed to, and stored by, the operator. Contact the FAA Data Communications Program Office (refer to their website) to coordinate.

2.10.2 CPDLC–Departure Clearance Service (CPDLC-DCL). CPDLC-DCL provides a means for requesting and delivering initial and revised DCLs. These CPDLC messages include departure procedure, flight plan route, initial and requested altitude, beacon code, departure frequency, and other non-route information.

Note 1: CPDLC-DCL is different than international DCL operations. International systems use the ACARS ATS DCL application via ARINC 623/European Organization for Civil Aviation Equipment (EUROCAE) ED-85A, not the FANS CPDLC application.

Note 2: At participating airports, PDC services may be available for non-FANS equipped aircraft.

2.10.3 CPDLC Specified on the Airport Diagram. To differentiate what communication services are available at each facility, refer to the airport diagram, Standard Instrument Departures (SID), and other terminal procedures pages. See Figure 2-3, Data Link Communication Services on Departure Procedure, for the CPDLC annotation on a departure procedure.

2.10.3.1 CPDLC-DCL logon/notification (see paragraph 5.3). “KUSA” is the National Single Data Authority (NSDA) for all CPDLC logons/notifications in the United States. Pilots activate the data link communication system anytime during preflight by logging on to/notifying KUSA with ATC. Within 30 minutes of the proposed departure time, an “ATC Connection Established” message will be received if the following conditions are met:

2.10.3.2 Once a successful ATC connection has been established and the CPDLC-DCL has been approved by the controller, the CPDLC-DCL will be automatically sent to the aircraft. Pilots do not have to request a clearance. After the clearance is received and verified, pilots should:

(DM1)) the message.

Note 1: If it becomes necessary to revert to voice after receiving a clearance, pilots should respond with Reject/Unable to the uplinked clearance.

Note 2: For CPDLC-DCL ground operations only, pilots can expect an automated ATC-initiated logoff/disconnect 5 to 10 minutes after takeoff.

2.10.3.3 If changes in tower or en route conditions occur (e.g. weather) the ATSU may amend the clearance information and transmit a revised CPDLC-DCL. Pilots should follow the same procedure for revised clearances.

2.11 PDC

PDC is a subscriber based service to provide an effective and efficient means of delivering a text-based electronic departure clearance prior to taxi. Data link communication technologies are utilized via a PDC in which ATC clearances are sent to a subscriber’s dispatch center, flight followers, or base of operations. The clearance is made available to the pilot with the following formats:

2.11.1 PDC Communication. It is not necessary for an aircraft to be equipped with data link communication avionics for a flight to participate in the PDC service. It is only necessary for the pilot to be able to obtain a printed or electronically displayed copy of the PDC message prior to taxi (may be printed at the FBO terminal, the airline gate, etc.). The contents of the PDC message are relayed to the aircrew without modification, omission, or alteration. PDC is at the discretion of the clearance delivery controller. If the controller determines that issuing a PDC could introduce confusion, the controller will issue a verbal clearance to the aircrew. If the pilot is uncertain of the clearance, the PDC must not be used and the pilot must contact clearance delivery via voice (telephone or radio) and obtain their clearance.

2.11.2 PDC vs. CPDLC-DCL. The primary difference between the PDC and CPDLC-DCL services is the PDC service depends on the operator or other third party to deliver the PDC to the aircraft whereas CPDLC-DCL service is a direct connection after logon/notification from the tower automation to the flight deck avionics of FANS-equipped aircraft. See Table 2-1, PDC vs. CPCLC-DCL, below for a side-by-side comparison.

2.12 Data Authority

“KUSA” is the national data authority for all U.S. domestic CPDLC logons/notifications. Figure 2-12, Data Communication Services Strategy, describes the current and planned data communication services to be available in the domestic en route environment. CPDLC en route operations in U.S. domestic airspace will use FANS 1/A(+) equipped aircraft with multi-frequency VDL Mode 2 radios. For an alternate subnetwork, see paragraph 4.6.2.

2.12.1 Current Data Authority (CDA). When an aircraft system accepts a CPDLC connection, this active connection initiates the exchange of messages between the ATSU and the aircraft as the ATSU becomes the CDA. The CDA typically initiates address forwarding to permit a downstream or adjacent ATSU (next data authority (NDA)) to establish an inactive CPDLC connection and/or an Automatic Dependent Surveillance (ADS) contract for monitoring purposes.

2.12.2 Data Authority Transfer. When the active CPDLC connection is terminated, the aircraft will activate any inactive connection. In this case, the next data authority becomes the CDA and is now able to exchange CPDLC messages with the aircraft. Figure 2-4, Next Data Authority Notification, illustrates the transfer from the CDA to the NDA.

2.13 ATSUs and Aircraft Interoperability

Figure 2-5, Air Traffic Service Unit (ATSU) and Aircraft Interoperability Designators, shows different ATSU ground systems and interoperable aircraft systems. The diagram shows the CSP and its Centralized ADS-C System (CADS). CSP’s CADS enables an ATSU without FANS 1/A capability to receive ADS-C reports from any FANS 1/A, FANS 1/A(+) or FANS 1/A ADS-C aircraft. A designator is assigned to each type of ATSU and aircraft data link system. Explanations of each interoperability designator are provided below in Table 2-2. Table 2-3, Types of Data Link Systems and Operations, provides an overview of the operational capabilities that are supported by each of the different data link systems.

Note: B2 will be included at a later date.

2.14 Performance-Based Communication and Surveillance (PBCS) Concept

The PBCS concept provides objective operational criteria to evaluate different and emerging communication and surveillance technologies and is intended for evolving Air Traffic System Management (ATM) operations. Once these criteria have been set and accepted, a specific implementation of an ATM operation including its technical and human performance may have its viability assessed against these operational criteria. ATS system changes based on communication and/or surveillance performance align with the PCBS concept (refer to ICAO Doc 9869).

2.14.1 Aligned with Performance-Based Navigation (PBN). The PBCS concept is aligned with the concept of PBN. While the PBN concept applies RNP and RNAV specifications to the navigation element, the PBCS concept applies required communication performance (RCP) and required surveillance performance (RSP) specifications to communication and surveillance elements, respectively. Each RCP/RSP specification includes allocated criteria among the components of the communication and surveillance systems involved.

2.14.2 Communication, Navigation, and Surveillance (CNS)/ATM Model. Where beneficial, RCP, RNP/RNAV, and RSP specifications are applied to communication, navigation, and surveillance elements to ensure the operational system and its components perform in accordance with the specifications. Figure 2-6, Performance-Based CNS/ATM Model, provides an overview of the performance-based CNS/ATM model, which characterizes the relationship of the performance-based specifications among CNS elements supporting an ATM operation.

Note: Similar to the PBN concept, security is beyond the scope of the PBCS concept. However, in some cases, the RCP and RSP specifications may include criteria to support mitigations from security threats.

2.14.3 PBCS and PBN Differences. There are some differences between the PBCS concept and PBN concept:

Note: PBCS includes real-time alerts (e.g., when a communication transaction expires or a position report is overdue) that are conceptually different than the PBN alerts (e.g., RNP UNABLE).

2.15 RCP and RSP Specifications Supporting ATM Operations

To perform ATM operations within a performance-based airspace, the standards specify functional, safety and performance criteria for the applicable CNS elements. RCP and RSP specifications, in conjunction with RNP/RNAV specifications, provide these criteria and are intended to facilitate the development of standards for ATM operations. This approach is essential to the evolution of operational concepts that use emerging technologies. For example, within the organized track system (OTS) in North Atlantic High Level Airspace (NAT HLA), the Reduced Lateral Separation Minima (RLatSM) include the following requirements:

2.15.1 RCP Specifications. An RCP specification represents operational parameters for the complete communication transaction. It is identified by a designator (e.g., RCP 240 or RCP 400) in order to simplify the designator naming convention and to make the RCP Expiration Time (ET) readily apparent to airspace planners, aircraft manufacturers, and operators. The designator represents the value for the communication ET after which the initiator is required to revert to an alternative procedure. The RCP specifications are applied to achieve the performance required of the communication process and may support aircraft separation minima.

2.15.2 RCP Parameters. The following describes the RCP parameters:

1. RCP Transaction Time. An RCP parameter that specifies the maximum time for the completion of a proportion of operational communication transactions after which the initiator should revert to an alternative procedure. Two values are specified:

2. RCP Continuity (RCP C). The minimum proportion of operational communication transactions to be completed within the specified RCP transaction time, given the service was available at the start of the transaction.

3. RCP Availability (RCP A). The required probability that an operational communication transaction can be initiated.

4. RCP Integrity (RCP I). The required probability that an operational communication transaction is completed with no undetected errors.

Note: While RCP I is defined in terms of the “goodness” of the communications capability, it is specified in terms of likelihood of occurrence of malfunction on a per flight hour basis (e.g., 10⁻⁵), consistent with RNAV/RNP specifications.

2.15.3 RCP Framework and Actual Communication Performance (ACP). In Figure 2-7, Actual Communications Performance (ACP), the combined uplink and downlink performance of ground systems, communication service, and aircraft systems is the Actual Communication Technical Performance (ACTP). Pilots and controllers should respond as soon as possible as part of the overall human performance. Human performance combined with ACTP results in ACP. ACP is an indicator of the operational performance of a communication system which includes the human and technical components. Human performance considers such factors as training, procedures, and human-machine interface (HMI). Technical performance comprises the installed elements of communication performance operating together to meet the intended function. ACP is assessed in the same terms and parameters as an RCP specification, its allocations, and other relevant operational criteria provided by an RCP specification. Operationally, an appropriate level of communication performance is required for aircraft systems, communications networks, and ground systems.

Note: In ICAO documentation, pilot response time is called Pilot Operational Response Time (PORT).

2.15.4 RCP 240 Illustration. As illustrated in Figure 2-8, RCP 240 Illustration, the controller sends a data link communication message through the ATSU via the CSP to the aircraft. The Required Communication Technical Performance (RCTP) is the overall time for the communication to travel from the ATSU to the flight deck and return excluding human response time. RCTP should be less than or equal to 150 seconds for 99.9 percent of the operational time (ET) and must be less than or equal to 120 seconds for 95 percent of the nominal time (TT). The message arrives at the flight deck and the pilot should respond as soon as possible (i.e., ROGER (DM3)/WILCO (DM0), UNABLE (DM1), or STANDBY (DM2)). The pilot responds to the message and it travels back to the ATSU.

2.15.5 RCP 240 Specification Tables. Table 2-4, RCP 240 Transaction Time and Continuity Allocations–CPDLC, shows Transaction Time and Continuity allocations from the sender (controller) to responder (pilot) and back to sender (controller). RCTP consists of the ATSU system, network, and the aircraft system. Table 2-5, RCP 240 Availability Criteria (Aircraft System), provides the aircraft system availability criteria. Table 2-6, RCP 240 Integrity Criteria (Aircraft System), provides the integrity criteria for the aircraft system.

2.15.6 RCP 400 Illustration. As illustrated in Figure 2-9, RCP 400 Illustration, the controller sends a data link communication message through the ATSU through the CSP to the aircraft. The RCTP is the overall time for the communication to travel from the ATSU to the flight deck and return excluding human factors. RCTP should be less than or equal to 310 seconds for 99.9 percent of the operational time (ET) and must be less than or equal to 260 seconds for 95 percent of the nominal time (TT). The message arrives at the flight deck and the pilots should respond as soon as possible (i.e., ROGER (DM3)/WILCO (DM0), UNABLE (DM1), or STANDBY (DM2)). The pilot responds to the message and it travels back to the ATSU.

2.15.7 RCP 400 Specification Tables. Table 2-7, RCP 400 Transaction Time and Continuity Allocations—CPDLC, shows Transaction Time and Continuity allocations from the sender (controller) to responder (pilot) and back to sender (controller). RCTP consists of the ATSU system, network, and the aircraft system. Table 2-8, RCP 400 Availability Criteria (Aircraft System), provides the availability criteria for the aircraft system. Table 2-9, RCP 400 Integrity Criteria (Aircraft System), provides the integrity criteria for the aircraft system.

2.16 Required Surveillance Performance (RSP)

2.16.1 Background. In the past, surveillance over oceanic and remote continental areas was limited to pilot position reports via HF radio. When crossing a compulsory reporting point, the pilot would contact the ATSU via a radio operator and report: identification, position, time, altitude, next PR point, name of succeeding reporting point, and remarks. Once the aircraft entered a radar environment, pilot reports were eliminated. Today, along with voice pilot position reports, surveillance in oceanic and remote continental airspace is accomplished much more accurately through the use of ADS-C. As with CPDLC, ADS-C requires certain performance requirements for operational surveillance in support of specific ATM functions. This includes the transmission of aircraft position, velocity and intent with a specified precision, accuracy and update rates. In combination with RCP and RNP, RSP enables the efficient use of airspace by allowing reduced lateral and along-track separation of aircraft by supplying accurate and frequent updates of aircraft position.

2.16.2 RSP Concept. The concept of RSP relates to the surveillance component and complements RNP and RCP. A collective set of performance measures are established to ensure overall communication transactions and surveillance data deliveries are suitable for certain surveillance related goals. For example, the surveillance goal may be to achieve 30 nautical miles (NM) lateral and 30 NM along-track separation in oceanic airspace. RSP is operationally derived and not based on any specific techniques, aircraft technologies, or architecture.

2.16.3 RSP Specification. An RSP specification is identified by a designator (e.g., RSP 180) in order to simplify the designator naming convention and to make the RSP Data Operational Overdue Time (OT) readily apparent to airspace planners, aircraft manufacturers and operators. The designator represents the value for the surveillance data delivery time when the surveillance data delivery is considered overdue. RSP specifications are applied to airspace based on specific objectives (e.g., the performance required of the surveillance process used to support particular separation minima). The RSP specification is a set of requirements/operational parameters for ATS provision and associated ground equipment, aircraft capability, and operations needed to support performance-based surveillance. Surveillance performance requirements are included and allocated to system components (Required Surveillance Technical Performance (RSTP)). It includes surveillance data delivery time, continuity, availability, integrity, and safety. A specified RSP specification is intended to define the surveillance performance required of a surveillance process to support a particular ATM function. RSP specification is applied to the airspace, route, or procedure based on the most stringent RSP specification of the required ATM functions.

2.16.4 RSP Parameters. RSP include the accuracy of the reported position, the latency in reporting the position to the controller, and the integrity, availability, and continuity of the surveillance data. The following describes the RSP parameters:

1. RSP Surveillance Data Transit Time. The maximum time for the reception of the surveillance data after which the controller should revert to an alternative procedure.

2. RSP Continuity. The minimum proportion of surveillance data delivery to be completed within the specified RSP surveillance data delivery time, given the service was available at the start of the delivery.

3. RSP Availability. The required probability that surveillance data can be provided.

4. RSP Integrity. The required probability that surveillance data delivery is completed with no undetected errors.

2.16.5 RSP 180 Illustration. In Figure 2-10, RSP 180 Illustration, the ATSU establishes an event contract with the aircraft with specific allocations described below:

1. From 1 to 2 (Aircraft). The aircraft reaches the particular event and is required to respond within 5 seconds or less 99.9 percent of the operational time (OT) and less than or equal to 3 seconds 95 percent of the nominal delivery time (DT).

2. From 2 to 3 (CSP). The signal is then transmitted through the communication service provider (CSP) network. This action must occur within 170 seconds or less for 99.9 percent of the OT and less than or equal to 84 seconds 95 percent of the DT.

3. From 3 to 4 (ATSU). From the (CSP) this message is sent through the ATSU which has a required performance of less than or equal to 5 seconds for 99.9 percent of the time and less than or equal to 3 seconds for 95 percent of the time. The total communication from the event to the controller must be less than or equal to 180 seconds with 99.9 percent probability (OT) and less than or equal to 90 seconds with 95 percent probability (DT).

2.16.6 RSP 180 Specification Tables. Table 2-10, RSP 180 Surveillance Data Delivery and Continuity Allocations—ADS-C, shows allocations for Required Surveillance Monitoring Performance/Required Surveillance Technical Performance (RSMP/RSTP) consisting of the aircraft system, network and ATSU. Table 2-11, RSP 180 Availability Criteria (Aircraft System), provides the availability criteria for the aircraft system.

Table 2-12, RSP 180 Integrity Criteria (Aircraft System) provides the integrity criteria for the aircraft system.

2.16.7 RSP 400 Illustration. In Figure 2-11, RSP 400 Performance, the ATSU establishes an event contract with the aircraft with specific allocations described below.

1. From 1 to 2 (Aircraft). The aircraft reaches the particular event and is required to respond within 30 seconds or less 99.9 percent of the OT and less than or equal to 15 seconds 95 percent of the DT.

2. From 2 to 3 (CSP). The signal is then transmitted through the CSP network. This action must occur within 340 seconds or less for 99.9 percent of the OT and less than or equal to 270 seconds 95 percent of the DT.

3. From 3 to 4 (ATSU). From the CSP this message is sent through the ATSU which has a required performance of less than or equal to 30 seconds for 99.9 percent of the time and less than or equal to 15 seconds for 95 percent of the time. The total communication from the event to the controller must be less than or equal to 400 seconds with 99.9 percent probability (OT) and less than or equal to 300 seconds with 95 percent probability (DT).

2.16.8 RSP 400 Specification Tables. Table 2-13, RSP 400 Surveillance Data Delivery and Continuity Allocations—ADS-C, shows allocations for Required Surveillance Monitoring Performance/Required Surveillance Technical Performance (RSMP/RSTP) consisting of the aircraft system, network and ATSU. Table 2-14, RSP 400 Availability Criteria (Aircraft System), provides the availability criteria for the aircraft system. Table 2-15, RSP 400 Integrity Criteria (Aircraft System), provides the integrity criteria for the aircraft system.

2.17 High Frequency Data Link (HFDL)

Over the past few decades HF has provided an effective means of voice communication over long distance in oceanic and remote continental airspace. HF communication is no longer restricted to voice and provides another means of sending and receiving digital communication. HFDL augments existing VHF and satellite communications (SATCOM) (i.e., CPDLC and ADS-C) data link communication systems. A subnetwork of 15 HFDL ground stations extends worldwide communication coverage beyond that of VHF data link communication subnetworks.

2.17.1 HFDL Applications. HFDL subnetwork provides communication to both ATSU and AOC in oceanic and remote continental airspace and can be used for:

2.17.2 Ionosphere HF Disturbance and Reliability. HF is subject to temporary signal distortion due to changes in the ionosphere layer shape and density. Because of multiple HFDL ground stations, ionosphere disturbances are less frequent than in the early days of HF voice. Modern aircraft HFDL systems automatically search for the best available frequency from all HFDL operational ground station frequencies. Once a suitable frequency is found, the aircraft establishes a connection by sending a logon/notification message to the ground station. A logon/notification confirmation uplink is established enabling the pilot to send data.

Note: Monitoring data have shown that HFDL does not meet RCP 240/RSP 180.

2.18 Future U.S. Domestic Airspace Data Link Communication Services

Figure 2-12 depicts future plans for data link communication services. Though this planning diagram is subject to change, it generally provides a preview of expanding data link services in the next few years. This is added to the AC to enable operators planning upgrades in pace with future technology and upcoming data link communication services.

2.19 Data Communication Services Strategy

Segment 1 in Figure 2-12 consists of two phases.

2.19.1 Tower Services and En Route Services. Segment 1, Phase 2 (S1P2) services will be delivered in two stages, “initial” services and “full” services. S1P2 en route services are expected to begin in 2019 and are planned to leverage existing Phase 1 FANS 1/A aircraft and expand Phase 1 infrastructure to deliver CPDLC services in the U.S. domestic en route airspace. Listed below are en route initial and full services:

1. En Route Initial Services. The initial services in S1P2 will include the following:

2. En Route Full Services. With the continuation of S1P2, en route full services will include (see the following paragraphs for descriptions of some initial and full service features):

Note: The full services of speed, stuck microphone, adapted arrivals, and beacon codes are deferred until further notice.

2.19.2 Speeds.

1. Initial Services. The controller can issue UM61 CROSS (position) AT AND MAINTAIN (altitude) AT (speed).

2. Full Services (Deferred). The controller will be able to:

2.19.3 Crossing Restrictions. Initially, the controller will be able to use two crossing restriction message elements to instruct the pilot to cross a specific fix at a specific altitude and, if desired, at a specific speed. With full service, the controller will have considerably more flexibility in composing crossing restriction clearances. For example, the controller will be able to clear an aircraft to cross a specific fix at a specific time and have the option of entering a crossing restriction.

2.19.4 Routes. Initially, the pilot will be able to DM22 REQUEST DIRECT TO (position). The controller will be able to issue route clearances, such as UM74 PROCEED DIRECT TO (position), UM79 CLEARED TO (position) VIA (route clearance), UM80 CLEARED (route clearance), and UM83 AT (position) CLEARED (route clearance). With full service, the controller’s workstation will be enhanced to support entry from the Radar (R) and Radar Associate (RA) positions and permit entry of route offsets with additional message elements.

2.19.5 Advisory. Air Traffic personnel issue advisory messages to aircraft on a routine basis. Examples include dynamic airport information (runway closures, runway visual range, braking action, etc.), convective significant meteorological information (SIGMET), Central Weather Advisories (CWA), Pilot Weather Reports (PIREP), weather displayed on the controller’s scope, and current ride reports. CPDLC will allow the controller to send a limited set of advisory messages to the aircraft on a case-by-case basis or to all aircraft with which the controller has a CPDLC connection. Advisory messages such as SIGMETs and CWAs, which must be broadcast to all aircraft on frequency, will still need to be verbally broadcast in a mixed equipage environment. However, advisory messages that are issued to individual aircraft, such as dynamic airport information, displayed weather, PIREPS, and current ride reports are excellent candidates for automating. S1P2 CPDLC services will only support ride reports and free text messages created at the sector. The messages will be provided to the controller to send to the appropriate aircraft. In addition to freeing the controller from verbally delivering the advisory, CPDLC also allows positive confirmation that affected aircraft have received the information.

2.19.6 Holding Instructions. The controller may be directed to hold all arrivals for a particular airport. With full service, the controller will be able to send a CPDLC message UM91 HOLD AT (position) MAINTAIN (altitude) INBOUND TRACK (degrees) (direction) TURN LEG TIME (leg type).

2.19.7 Stuck Microphone (Deferred). With full service, the controller will be able to instruct the pilot to check their microphones.

2.19.8 Adapted Arrivals (Deferred).With full service, the controller and pilot will be able to use CPDLC to execute adapted arrival procedure. The adapted procedure contains both lateral and vertical aircraft maneuvers and provides greater efficiency for users.

2.19.9 Beacon Codes (Deferred). As aircraft transition in U.S. domestic airspace from one facility to another, there is the possibility of beacon code duplication. Often this happens when there is significant traffic and/or delays in the system. It is also prevalent at facilities which border foreign airspace. Today, when this conflict occurs, En Route Automation Modernization (ERAM) will assign the aircraft a new code and notify the controller, who then verbally issues it to the pilot. With CPDLC, the FAA ground system will automatically send a UM with the new code to the aircraft at the appropriate time with no controller involvement. The controller will also be able to manually compose and send a beacon code message if needed.

CHAPTER 3. AIRCRAFT ELIGIBILITY

3.1 Introduction

This chapter provides guidance on how operators can determine if their aircraft data link system is compliant and eligible for operational use. This AC does not address design approval or installation of data link systems. For airworthiness guidance, refer to AC 20-140( ), Guidelines for Design Approval of Aircraft Data Link Communication Systems Supporting Air Traffic Services (ATS).

3.2 Aircraft Eligibility

The Airplane Flight Manual (AFM) should identify the following for data link communication eligibility:

Note: Descriptions of the data link services are provided for a given airspace or operation. For example, in the United States, departure clearance (Controller-Pilot Data Link Communication–Departure Clearance (CPDLC-DCL)) service requires the aircraft to be interoperable with Future Air Navigation Systems (FANS)-1/A(+), to use either the Very High Frequency (VHF) Data Link (VDL) Mode 0/A or VDL Mode 2 subnetwork, and to not have any prescribed aircraft performance requirements. Operators should refer to the requirements defined by the Air Traffic Service Unit (ATSU) for each operation. A summary of typical operational requirements is provided in Chapter 5, Operational Use of Data Link Communications, of this AC.

3.3 Statement of Compliance (SOC)

Due to the complexity of the criteria to determine eligibility, the operator must obtain a statement of compliance from the entity that owns the design approval for their data link installation. This may be the aircraft manufacturer, the operator, the manufacturer of the data link system, or another party. The statement of compliance should be provided in the AFM, AFM Supplement, or other acceptable document. Table C-3, Preferred Original Equipment Manufacturer Annotation, provides an example of a statement of compliance. The statement of compliance must indicate the aircraft data link system meets the aircraft-allocated requirements of Required Communication Performance (RCP) and Required Surveillance Performance (RSP) specifications.

Note: For a FANS 1/A CPDLC and Automatic Dependent Surveillance-Contract (ADS-C) aircraft system, RTCA DO-306/European Organization for Civil Aviation Equipment (EUROCAE) ED-122, Safety and Performance Standard for Air Traffic Data Link Services in Oceanic and Remote Airspace (Oceanic SPR Standard), is equivalent to RCP 240, RCP 400, RSP 180, and RSP 400 specifications. For an Aeronautical Telecommunications Network (ATN) Baseline 1 (B1) or FANS 1/A CPDLC aircraft system, RTCA DO-290/ED-120, Safety and Performance Requirements Standard for Air Traffic Data Link Services in Continental Airspace (Continental SPR Standard), provides performance criteria for the EUR Region.

3.3.1 Alternate Means of Compliance for No SOC. In lieu of the SOC stated in the AFM, AFM Supplement, or other acceptable documentation, operators may provide a detailed submission to the FAA validating that the aircraft’s current system meets the RCP/RSP applicable requirements. As a minimum, this submission should include information on avionics continuity, integrity, availability, and safety and monitoring/alerting requirements (refer to RTCA DO-306/ED-122). Equipment manufacturer support should be solicited to acquire suitable documentation.

3.3.2 Interoperability. The operator must confirm the interoperability of their aircraft data link system (interoperability requirements standards (INTEROP) designators are described in Table 2-2, Interoperability Designators and Descriptions). The statement of compliance must indicate the INTEROP and a reference to the definition of that INTEROP. Aircraft Communications Addressing and Reporting System (ACARS) ATS, FANS 1/A, FANS 1/A+, and ATNB1 INTEROP designators, and/or the compliance statement, must reference AC 20-140 or later revision. For the ATN Baseline 2 (B2) INTEROP designator, the compliance statement must reference AC 20-140C or later revision.

3.3.2.1 In U.S. domestic en route airspace, for operations supported by FANS 1/A(+) data link communication systems, the avionics system must have “push to load” capability into the navigation system whenever a routing change (e.g., uplink message (UM)79, UM80, and UM83) is received.

Note: Operators using an alternate means of compliance for “push to load” will not be permitted once full services are implemented. “Full services” require fully integrated (“push to load”) avionics. For a description of “Full Services,” see Figure 2-12, Data Communication Services Strategy.

3.3.3 Subnetwork. The operator must confirm the subnetwork capability of their aircraft (subnetworks are described in paragraph 2.2.2). The statement of compliance must indicate the subnetworks that are supported and a reference to the definition of the subnetworks. The compliance statement must reference AC 20-140 or later for any of the following subnetworks:

Note: For aircraft utilizing Inmarsat (SwiftBroadband (SBB)), the SOC must reference AC 20-140C or later.

3.3.4 VDL M2 Requirements for U.S. Domestic En Route. The VDL M2 requirements include aircraft that are equipped with VDL Mode 2 equipment approved to Technical Standard Order (TSO)-C160a, Very High Frequency (VHF) Digital Link (VDL) Mode 2 Communications Equipment, (see Note 1 below for details) or later that is capable of tuning to more than one VDL M2 channel.

Note 1: Minimum performance standard of TSO-C160 does not include the capability for the Communications Management Unit (CMU) (Avionics Architecture Class W and Z) or VDL M2 Radio (Avionics Architecture Class X) to tune to more than one VDL M2 channel. The above equipment is capable of tuning to only one VDL M2 channel (i.e., 136.975 MHz). The minimum performance standard of TSO-C160 for VDL M2 Radio (Avionics Architecture Class V or Y) contains the capability to support VDL Mode 2 multi-frequency operation when integrated with a CMU (Avionics Architecture Class W and Z) that supports VDL M2 multi-frequency according to TSO-C160a.

Note 2: The FAA accepts the use of VDL M0/A en route when VDL M2 communications are lost, if the aircraft is equipped with a properly functioning VDL M2 radio before starting the flight or dispatching. An alternate subnetwork may be used provided it complies with paragraph 4.6.2. Table C-1, Summary of Airspace Requirements, provides a summary of airspace requirements.

3.3.5 Performance Data for Compliance. The operator should evaluate the demonstrated performance of their aircraft data link system as provided by the FAA and other Air Navigation Services Providers (ANSP) as part of the ANSP monitoring programs. FAA monitoring data is available for initial and continuous compliance and operator data may be acceptable for initial data link eligibility. Actual Communications Performance (ACP) of the CPDLC two-way communications and Actual Surveillance Performance (ASP) of the ADS-C are evaluated against respective RCP and RSP specification standards. This data should be included to quantify support of the aircraft performance portion of the data link eligibility. If no performance data is available, then initial compliance for applicable airspace will be based on the SOC with performance being monitored as data is collected. (See Chapter 6, Performance Monitoring.)

Note 1: For fleet aircraft, records for every tail number are not necessary provided that all the aircraft have the same data link communication configuration. Operators with a single aircraft may meet the above requirement using records of other aircraft with the same make, model, and series (M/M/S) and the same data link communication configuration.

Note 2: RCP and RSP performance data is not required for aircraft operating only in U.S. domestic airspace.

3.4 Configuration Control

Operators should maintain their aircraft in an avionics configuration which has been shown to provide acceptable data link communication performance. A list of recommended avionics is available at http://dcis.harris.com/new-operator-documents.

3.5 Maintenance

The operator is responsible for all maintenance of data link communication systems. Maintenance procedures for data link communications are approved or accepted as part of an operator’s initial maintenance manual approval or as a revision to that manual.

Note: Maintenance facilities conducting Supplemental Type Certificate (STC) modifications must coordinate Master Minimum Equipment List (MMEL)/minimum equipment list (MEL) changes that include all data communications equipment with the Aircraft Evaluation Group (AEG). The Original Equipment Manufacturer (OEM) or the holder of installation approval for the aircraft (e.g., STC holder) must demonstrate compliance with the criteria in this AC. An STC for additional installed items must document any applicable MEL relief.

3.5.1 System Alteration (Including Software Updates). Operators must evaluate alterations to the aircraft and identify any changes to aircraft eligibility. The owner of the design approval for the alteration must confirm the alteration did not affect the data link system. If the alteration affected the data link system, the owner of the design must provide a statement of compliance to the associated INTEROP, subnetworks and performance standards. Operators must determine aircraft eligibility after each alteration.

3.5.2 Subnetwork Configuration for Route Coverage. The operator must ensure communication coverage capability of their aircraft’s subnetwork for the route to be flown (see paragraph 4.1.3). For adequate coverage, operators may have to adjust their aircraft’s media management parameters (e.g., where the system automatically switches from VDL to SATCOM). Operators have experienced unacceptable performance transitioning airspace with marginal VDL coverage because the aircraft tries to maintain or reestablish a VDL connection. Some States may also limit the subnetworks that can be used for operation.

CHAPTER 4. COMMUNICATION SERVICE PROVIDERS (CSP)

4.1 CSP for Oceanic and Remote Continental Operations

For oceanic and remote continental operations using data link communications, operators are responsible for ensuring their CSP meets the minimum specifications of this chapter. The operator/CSP agreement must include these requirements in addition to monitoring their performance as addressed in Chapter 6, Performance Monitoring.

4.1.1 Substandard Performance. If a CSP fails to satisfy the allocated requirements, the operator should not file or use the associated performance standard until the problem is resolved. An exception is allowed for performance below the 99.9 percent operational transaction time which permits the operator to continue to operate at the 95 percent nominal transaction time or greater while investigating the issue for corrective action.

4.1.2 CSP and Operator Arrangements. Operators must ensure the services they have arranged with their CSP(s) include:

4.1.2.1 Failure Notification. The CSP should notify the operator and any affected Air Traffic Service Units (ATSU) of any failure condition that may impact data link communication operations (such as coverage or performance). This includes when a CSP holds an agreement with an aircraft operator but not with the affected ATSU.

4.1.2.2 Recording Data Link Messages. The operator should ensure that they have access to communication and surveillance data sent or received to their aircraft for at least 30 days. The CSP(s) should retain records for at least 30 days to allow for accident/incident investigation purposes. The operator or CSP should make these records available for air safety investigative purposes on request.

4.1.2.3 CSP Integrity. The CSP must pass messages without manipulating the information protected by error detection codes used by the aircraft system and the ATSU. In particular, the CSP must not reconstitute or regenerate any of the error detection codes.

4.1.2.4 RCP Allocation Requirements. The operator must ensure the CSP satisfies the allocated requirements for any RCP used by the operator. The CSP has two points of demarcation with an ATSU domain consisting of ground router to ground router interface and two signal in space points of demarcation with aircraft’s data link communication system. The downlink message enters the CSP domain at the first emission of the first bit of the first frame from the aircraft’s data link communication system. For uplink message (UM), it exits the CSP domain at the last emission of the last bit of the last frame to the aircraft’s data link communication system. The Required Communication Technical Performance (RCTP)CSP is the two-way transfer delay from when a message (e.g., UM) is received from the ATSU at the CSP point of demarcation (e.g., enters from the ground domain) until its successful arrival at the CSP’s signal in space point of demarcation. When the message is answered, it arrives at the signal in space CSP point of demarcation and continues the CSP’s ground router to ground router interface back to the ATSU. It includes delay such as propagation delay and retransmissions, as well as subnetwork delays resulting from queueing/flow control, segmentation, processing, ground-network transmission, routing, etc.

4.2 RCP 240 CSP Allocations

The CSP must meet the performance requirements described in Table 4-1, RCP 240 Transaction Time and Continuity Allocations to CSP, and Table 4-2, RCP 240 CSP Availability and Outages Parameters, where RCP 240 has been prescribed on the routes flown by the operator.

*ET is Expiration Time **TT is Transaction Time

4.3 RCP 400 CSP Allocations

The CSP must comply with the performance described in Table 4-3, RCP 400 Transaction Time and Continuity to CSP Allocation, and Table 4-4, RCP 400 Availability and Outages Parameters, along the route to be flown by the operator.

*ET is Expiration Time **TT is Transaction Time

4.4 RSP Allocation Requirements

The operator must ensure the CSP satisfies the allocated requirements for any RSP used by the operator. The Required Surveillance Technical Performance (RSTP)CSP is the one-way transfer delay from when a message is received at the CSP’s signal in space point of demarcation until its successful arrival at the other CSP’s ground router to ground router point of demarcation to the ATSU. It includes delay such as propagation delay and retransmissions, as well as subnetwork delays resulting from queueing/flow control, segmentation, processing, ground-network transmission, routing, etc. Delay is measured from the first bit emission of the first bit of the first frame/data packet from the aircraft’s Data Link Radio to the last bit exiting the CSP domain when it is received by the ground domain (ATSU).

4.4.1 RSP 180 CSP Allocations. The CSP must comply with the performance described in Table 4-5, RSP 180 Data Delivery Time and Continuity Criteria, and Table 4-6, RSP 180 Availability and Outages Parameters.

*OT is data overdue time (associated with operational continuity) **DT is Delivery Time

4.4.2 RSP 400 CSP Allocations. The CSP must comply with the performance described in Table 4-7, RSP 400 Data Delivery Time and Continuity Criteria, and Table 4-8, RSP 400 Availability and Outages Parameters.

*OT is data overdue time (associated with operational continuity) **DT is Delivery Time

4.5 Alternate Means of Compliance

A Performance-based Communication and Surveillance (PBCS) Charter is available as an alternate means of compliance to validate the operator/CSP agreement for performance and services stated in this AC. Operators and CSPs need only to become charter members by following the instructions at http://www.fans-cra.com/. Operators who are seeking an Operations Specification (OpSpec)/Management Specification (MSpec)/Letter of Authorization (LOA) A056, Data Link Communications, authorization and are charter members satisfy their responsibility of ensuring their CSP meets the minimum specifications of this chapter provided that their CSP is also a charter member. Charter members using this alternate means of compliance must remain as charter members or notify their responsible Flight Standards office of their change in status.

Note: A change of charter membership status will affect operational authorization.

4.6 CSP for U.S. Operations

The FAA provides Very High Frequency (VHF) Data Link (VDL) Mode 2 for all data link operations within the domestic United States (except oceanic and remote continental areas, which fall under paragraph 4.1). In addition, the FAA has authorized the use of VDL M0/A for CPDLC-DCL application. Operators can use the VDL Mode 2 subnetwork or may participate in CPDLC-DCL using VDL M0/A with no additional responsibilities. If the operator’s aircraft is equipped with a properly-functioning VDL M2 radio before starting the flight or dispatching, the FAA accepts the use of VDL M0/A en route when VDL M2 communications are lost.

4.6.1 Initial CSP Qualification. A CSP planning to offer an alternate subnetwork for data link communications in the United States should contact the FAA Data Communications Program Office. The CSP needs to provide substantiating information to demonstrate their subnetwork satisfies the requirements allocated to the CSP and will need to enter into an agreement with the FAA on the sharing of data, notification of outages, security of communication, and other detailed characteristics. For further information refer to the Data Communications Network Services (DCNS) Alternative Media Description.

4.6.2 Alternate Subnetworks. The FAA allows operators to select an alternate subnetwork other than VDL M2, provided the subnetwork satisfies the required performance allocation and the operator/CSP enters into an agreement to ensure the performance is achieved and maintained. The FAA identifies accepted alternate subnetworks by listing on the Performance-Based Flight Systems Branch (AFS-470) Data Communications (DataComm) website. CSPs will be notified of changes to this list. CSPs must comply with the alternate media performance specifications for VDL Mode 2 shown in Table 4-9, Data Communications Network Services (DCNS) Performance Baseline.

*Reliability, maintainability, and availability restoral time applies except for catastrophic processor failures and force major events, in which case the maximum restoration time must be within 3 minutes.

4.6.3 Operator Agreement with CSP. Operators using an alternate subnetwork qualified by the FAA have similar responsibilities as when using data link communications for oceanic and remote continental operations. The CSP must meet the specifications in paragraphs 4.6.3.1 through 4.6.3.3.

4.6.3.1 Transfer Delay.

4.6.3.2 Data Integrity. The Packet Error Rate at the CSP Network Service Delivery Point (SDP) must be less than 1x10⁻⁵. The packet error rate is the number of incorrectly received data packets divided by the number of received packets. A packet is declared incorrectly received if at least one bit is erroneous or if it is delivered to an incorrect recipient. This metric excludes packets lost in transmission due to connection failure or excessive latency, as those are accounted by other metrics.

4.6.3.3 Reliability, Maintainability, and Availability. The reliability, maintainability, and availability performance requirements presented in this section apply to the specific CSP subnetwork seeking qualification and should not take into account the availability of additional subnetworks in order to achieve the required performance levels. A network service thread includes all equipment between the CSP SDP and aircraft users, excluding any aircraft components. This would include the relevant emitting or receiving ground station antenna(s) as well as transmitting/receiving the necessary radio frequency (RF) signal levels across the entire ordered service volume in question. Signal levels need to account for terrain impacts, as applicable to the service volume in question. For the purposes of availability, utilization of diverse ground station sites and other means of redundancy are included to provide the required level of availability for the ordered service volume.

4.7 CSP Monitoring

For oceanic and remote continental operations and for the use of alternate subnetworks for U.S. data communications, the operator must be aware of their CSP performance. The operator and CSP agreement should address performance monitoring and the performance data as necessary to remain in compliance.

4.7.1 U.S. Domestic Data Communications. If the CSP performance fails to satisfy the allocated requirements, the FAA will notify the CSP and operators. In this case, the alternate subnetwork authorization for operations is suspended and the operator should not file or use the associated performance standard (if prescribed) until the FAA indicates the alternate subnetwork performance is compliant.

CHAPTER 5. OPERATIONAL USE OF DATA LINK COMMUNICATIONS

5.1 Operational Use

5.1.1 Application Process. Operators must contact their principal operations inspector (POI) to begin the application process for an OpSpec/MSpec/LOA A056 authorization. A compliance guide is available at: https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afx/afs/afs400/afs470/datacomm/. This guide expedites the compliance process as it condenses into one location the information required for data link operations.

5.1.2 Minimum Equipment List (MEL) and Master Minimum Equipment List (MMEL). MELs and MMELs must include any revisions necessary for data link communication operations. These provisions must be approved by the FAA. Operators must specify the required dispatch conditions. A sample MEL is provided in Appendix B, Data Link Communications Minimum Equipment List (MEL) and Master Minimum Equipment List (MMEL) Provisions.

5.1.2.1 MEL procedures, limitations, and requirements should consider the system as a whole and also may consider subfunctions and other system interdependencies. Communications Management Unit (CMU) inoperative may render all Controller-Pilot Data Link Communication (CPDLC) virtually inoperative, while loss of Very High Frequency (VHF) Data Link (VDL) Mode 2 (M2) may render the system unacceptable for KUSA domestic but may be acceptable for en route oceanic operations provided satellite communications (SATCOM) or alternate media is available and meets performance requirements. Other systems with inter-relations such as Global Positioning System (GPS) function inoperative may not affect CPDLC operations, but depending on airplane design may affect Future Air Navigation Systems (FANS) Automatic Dependent Surveillance-Contract (ADS-C) operations. MMEL and Operator MELs should consider all functions and system relationships to the greatest extent possible.

5.1.2.2 For operations where communication equipment is required to meet a Required Communication Performance (RCP)/Required Surveillance Performance (RSP) specification, the performance must be included in the MEL.

5.1.3 Flight Plans. Dispatchers and pilots intending to conduct operations using data link communication must file an accurate flight plan (see Appendix D, Flight Planning). Air Traffic Service Unit (ATSU) automation relies on correct flight plan codes to determine aircraft and operator data communication eligibility for various services (e.g., reduced separation). If operators defer data link equipment before flight, a new flight plan must be filed reflecting the revised capability codes. The flight plan must always accurately reflect the aircraft’s current capabilities.

Note: Part 91 operators filing “J” codes for U.S. domestic data link services must have a data link authorization to file J5–J7 in oceanic and remote continental airspace (see Appendix D).

5.2 Data Link Operational Guidance

Pilots must be proficient with the equipment and procedures used for data link communication. Training must be based on operating guides from the manufacturer or approved operational procedures for operators with a FAA certificate. The NAS Data Communications Guide is available to provide general data communication procedure guidance in the United States but is not a substitute for Original Equipment Manufacturer (OEM)/Airplane Flight Manual (AFM) procedures. For international operations, operators should reference International Civil Aviation Organization (ICAO) Doc 10037, Global Operational Data Link (GOLD) Manual, ICAO Doc 9869, Performance-Based Communication and Surveillance (PBCS) Manual, and state Aeronautical Information Publications (AIP).

5.2.1 Crew Resource Management (CRM). When operating aircraft with more than one pilot, the pilot flying and pilot monitoring (not flying) should individually review each CPDLC uplink message (UM) prior to responding to and/or executing any clearance and individually review each CPDLC downlink message (DM) prior to transmission. Reading a message individually is a key element to ensuring that each pilot does not infer any preconceived intent different from what is intended or appropriate. Reading the message aloud would bias the other pilot and could lead to the error of “reading” what was read aloud as opposed to what was actually displayed.

5.2.1.1 UMs. Some UMs, such as complex or conditional clearances, require special attention to prevent the pilot from responding to a clearance with ROGER (DM3)/WILCO (DM0) but not complying with that clearance. To minimize errors, when responding to a clearance with ROGER (DM3)/WILCO (DM0), each pilot should read the UM individually (silently) before initiating a discussion about whether and how to act on the message.

5.2.1.2 DMs. In a similar manner, each pilot should individually review CPDLC DMs before the message is sent.

5.3 Logon/Notification

5.3.1 Departing U.S. Domestic Airports. The logon/notification should be approximately 30 minutes prior to proposed departure time. Pilots should maintain KUSA until logged off/disconnected by air traffic control (ATC). If leaving U.S. domestic airspace, the automatic transfer from KUSA to the next data authority (NDA) may not be possible. In such cases, the pilot must terminate the CPDLC connection(s) and then initiate a logon/notification to prompt the new Current Data Authority (CDA) to establish a CPDLC connection.

Note: Intermittent NO COMM annunciations may occur and do not necessarily mean the ATC connection is lost. Pilots should delay logging off/disconnecting to allow the annunciation to end as the system may reestablish the connection.

Logging off/disconnecting and logging back on/notifying will cause the ATC connection to end and may block future connections.

5.3.2 Blocked List. In rare instances for security and safety reasons, an aircraft may be blocked from any logon/notification attempt until it is manually removed by the Flight Data Communications Specialist (FDCS). This occurs automatically via the system or manually by the FDCS. The following reasons may cause an aircraft to be blocked from logon/notification:

5.3.2.1 Pilot Action. The pilot experiencing a blocked logon/notification should either contact clearance delivery or their Aeronautical Operational Control (AOC) to resolve the issue.

5.3.3 Outside Data Link Airspace. The pilot should initiate a logon/notification 10 to 25 minutes prior to entry into airspace where data link communication services are provided or prior to entering oceanic and remote continental airspace.

Note: Departing from a foreign airport close to or within oceanic and remote continental airspace may require the logon/notification to be initiated prior to departure.

5.3.4 Required Data for Logon/Notification. To perform an initial logon/notification request, the pilot enters the four character ICAO identifier of the ATSU and enters/verifies the following flight-specific information:

Note 1: When the aircraft identification includes a numeric component, this component must exactly match what is listed on the flight plan. In other words, “ABC3” does not match “ABC003.”

Note 2: While the ATSU identifier is only four characters, Aeronautical Telecommunications Network (ATN) Baseline 1 (B1) is capable of supporting up to eight characters.

Note 3: If applicable, ensure ADS-C is on or armed prior to logon/notification.

5.3.5 Data Must Match Flight Plan. To avoid an automatic rejection of the logon/notification request, the pilot must ensure the flight-specific information entered into the aircraft system is the same as the corresponding details filed in the flight plan.

5.3.6 Possible Reasons for Failed Logon/Notification. The following are possible reasons for receiving an indication of logon/notification failure:

5.3.7 Failure of Data Link Communication Connection. When failure of a data link communication connection is detected (downlink message fails to send), the pilot should terminate the connection and then initiate a new logon/notification with the current ATSU. If another failure occurs, revert to voice communication.

5.3.8 Logon/Notification Response. The logon/notification response message provides information to the aircraft system concerning whether:

5.4 En Route

Normally, response to CPDLC messages should be via CPDLC and response to a voice message should be via voice. However, if a CPDLC message is unclear or conflicting, always clarify with voice and then close the CPDLC dialog.

5.4.1 Contact or Monitor Message. A CONTACT (UM117) or MONITOR (UM120) message instructs the pilot to change to the specified frequency and may include a position or time for when to change to the new frequency. Use of a CONTACT or MONITOR message is as follows:

5.4.2 Waypoint Sequencing. The pilot should ensure waypoints are sequenced correctly. If an aircraft passes abeam a waypoint by a distance greater than the aircraft flight management system (FMS) waypoint automatic sequencing parameter, the pilot should manually sequence the waypoints in the FMS. If the pilot does not sequence the waypoints, incorrect information will be contained in ADS-C reports and CPDLC position reports; the next waypoint in these reports will actually be the waypoint that the aircraft has already passed. This may result in a timing error or out of conformance indication on the Air Navigation Services Providers (ANSP) ground system.

5.4.3 Multi-Part Messages. If pilots are unable to comply with any portion of a multi-part message, “UNABLE” (DM1) the entire message. Additionally, pilots should avoid sending multiple requests to the ATSU in a single message.

5.4.4 CPDLC Connection Failure. If a CPDLC dialogue is interrupted by a data link service failure, expect the controller to recommence the entire dialogue by voice communication. When the controller recognizes a failure of the CPDLC connection, the controller will instruct the pilot to terminate the connection and then initiate another logon/notification. See Table 5-1, CPDLC Connection Failure Responses, for the voice phraseology in response to a connection failure.

Note: Additional voice phraseology is available in Appendix E, Voice Phraseology.

5.5 Voice Monitoring

Pilots must continuously monitor VHF or high frequency (HF) as appropriate and/or maintain a Selective-Calling System (SELCAL) watch.

5.5.1 Pilot Response. As with voice communication, pilots should respond as soon as possible to all data link communication messages (e.g., ROGER (DM3)/WILCO (DM0), UNABLE (DM1), or STANDBY (DM2)). If more time is needed to make a decision and respond, select standby (“STBY”).

5.6 Free Text Messages

Free text messages should only be used when a standard message element does not exist or is inadequate. When sending a free text message, use standard ATSU phraseology and avoid using non-standard abbreviations. (See Appendix E.)

Note 1: For FANS 1/A implementations, the pilot cannot respond to the free text message element with ROGER (DM3)/WILCO (DM0), UNABLE (DM1), or STANDBY (DM2).

Note 2: When the controller uses free text to ask the crew affirmative/negative questions, the pilot can only respond with ROGER (DM3)/WILCO (DM0), which means they have read and understood the message, but does not answer the question affirmatively. In these cases, the pilot should respond to the question with a separate message (see Appendix E).

5.7 Data Link Communication Failures

The pilot must notify the ATSU as soon as practical of any indications of degraded performance resulting from a failure or loss of connectivity in accordance with 14 CFR part 91, § 91.187. For example, reportable events include:

Note: Timely notification is appropriate to ensure the ATSU has time to assess the situation and apply a revised separation standard, if necessary.

5.7.1 Failure of Automatic Transfer. If an automatic transfer of the CPDLC connection does not occur at the boundary (CDA to NDA), the pilot should contact the transferring ATSU by sending a CPDLC TRANSFER FAILURE (DM 67) message or voice equivalent, advising them the transfer has not occurred. If this does not resolve the situation, the pilot should logoff/disconnect and logon/notify the NDA. Revert to voice if still unable to logon/notify NDA.

5.7.2 Actions and Phraseology for Data Link Communication Failure. In the event of an aircraft data link communication system failure, the pilot should revert to voice and notify the ATSU of the situation. For example, for a CPDLC failure, the pilot should use the voice phraseology, “CPDLC failure, continuing on voice,” as shown in Table E-1, Voice Phraseology Related to Controller-Pilot Data Link Communication (CPDLC) From Pilot. The pilot continues to use voice until the functionality of the aircraft system can be reestablished.

5.8 ADS-C

Normally, the pilot should leave ADS-C armed for the entire flight. However, in airspace where ADS-C is available, if the pilot switches ADS-C off for any reason, or they receive indication of avionics failure leading to loss of ADS-C, the pilot should advise ATC and follow alternative procedures.

5.8.1 Airspace Where ADS-C Is Not Available. In airspace where ADS-C is not available, the pilot may switch ADS-C off to cancel inadvertent ADS-C connections. In such cases, the pilot should ensure the ADS-C is armed when reentering airspace where ADS-C is again available.

5.8.2 Emergencies. The pilot may activate the ADS-C emergency mode, which changes all existing ADS-C periodic contracts from normal mode to emergency mode and creates emergency mode ADS-C periodic contracts on any ADS-C connections that do not have a periodic contract already in place. The pilot may also activate ADS-C emergency mode by sending a “MAYDAY MAYDAY MAYDAY” (DM56) or “PAN PAN PAN” (DM55) CPDLC message. ADS-C emergency mode may be deactivated by the ATSU or by the pilot sending a “CANCEL EMERGENCY” (DM58) CPDLC message. In emergencies, pilots may revert to voice communication when able.

5.9 Exiting CPDLC and ADS-C Areas

The ATSU should automatically logoff/disconnect data authority approximately 15 minutes after exiting CPDLC and/or ADS-C areas. After 15 minutes, if aircraft equipment permits, the pilot should ensure there are no active CPDLC or ADS-C connections. Ensuring connections are not active eliminates the possibility of inadvertent or inappropriate use of the connections.

5.9.1 Contact Current ATSU. The pilot should contact the current ATSU unit prior to the manual termination of any ADS-C contract. This applies even when outside the applicable ATSU and the pilot logs off/disconnects ADS-C because it did not logoff/disconnect 15 minutes after leaving ADS-C airspace.

5.9.2 Connection Termination Failed. In the event the connection termination has failed, the pilot should contact the ATSU via voice or any other appropriate means.

5.10 Logoff/Disconnect

Prior to logoff/disconnect, the pilot should ensure there are no unresolved or open messages. The pilot will logoff/disconnect and confirm CPDLC connection is terminated and continue with voice communication.

Note: Pilots should wait at least 10 minutes after landing before initiating a CPDLC-Departure Clearance (DCL) logon/notification to ensure En Route Automation Modernization (ERAM) and Tower Data Link Services (TDLS) have enough time to clear previous flight information.

5.10.1 U.S. Domestic Logoff/Disconnect. Logoff/disconnect should automatically occur approximately 5 minutes after departure for DCL services. Do not logoff/disconnect until ATC terminates the session. If proceeding to international or oceanic and remote continental airspace and CPDLC services are not terminated, then manually logoff/disconnect prior to a new logon/notification.

Note: When KUSA is active as the domestic U.S. single data authority, CPDLC services will not automatically terminate after departure. Aircraft leaving U.S. airspace must logon/notify the next appropriate NDA.

5.10.2 International and Oceanic and Remote Continental Logoff/Disconnect. The ATSU should automatically logoff/disconnect data authority approximately 15 minutes after exiting CPDLC and/or ADS-C areas.

Note: For transitions between data link communication systems (i.e., FANS to ATN), follow OEM procedures for logon/notification/logoff/disconnect requirements specific to your avionics system.

CHAPTER 6. PERFORMANCE MONITORING

6.1 Performance Monitoring

With the implementation of performance based systems, monitoring of those systems ensures compliance. Monitoring provides a higher level of confidence the operational system will continue to meet the Required Communication Performance (RCP)/Required Surveillance Performance (RSP) specification. Operators should incorporate a performance monitoring process and must participate in performance monitoring which includes reporting and addressing problems. The goal of monitoring data link communication performance is to:

Note: There are no established RCP/RSP standards in U.S. domestic airspace as of the publication date of this AC. As Controller-Pilot Data Link Communication (CPDLC) is introduced into en route operations for U.S. domestic airspace, RCP standards will be published.

6.2 Oceanic and Remote Continental Airspace

6.2.1 FAA Data Collection. The FAA, along with other Air Traffic Service Units (ATSU), has been monitoring CPDLC and Automatic Dependent Surveillance-Contract (ADS-C) transactions since 2009. Analysis of Actual Communications Performance (ACP) for the CPDLC transactions and Actual Surveillance Performance (ASP) for the ADS-C downlink messages (DM) are accomplished on a semi-annual basis with an emphasis on the nominal continuity (95 percent) requirements associated with safety.

6.2.2 RCP Performance Analysis. Data analysis of ACP, including the Actual Communication Technical Performance (ACTP), is compared against RCP standards (see Tables 2-4 through 2-9) to determine whether the CPDLC performance is adequate.

6.2.3 RSP Performance Analysis. ASP is compared against RSP standards (see Tables 2-10 through 2-15) to determine whether surveillance performance is adequate. ASP analysis is based on the calculation of delivery time of the ADS-C periodic and event reports between the aircraft and the ATSU ground system.

6.2.4 Evaluating Operational and Nominal Transaction Times. ACP and ASP are evaluated using operational (99.9 percent) and nominal (95 percent) continuity criteria. Observed ACP and ASP must meet or exceed the nominal 95 percent continuity requirements.

Note 1: If ACP/ASP does not meet the nominal continuity, the operator will be notified and should not continue data link operations at the associated performance level until the issue is resolved (see paragraphs 6.4 and 6.5).

Note 2: If ACP/ASP does not meet the operational continuity 99.9 percent, the operator is notified to investigate and initiate corrective action. The nominal performance 95 percent is still sufficient for data link communication performance.

6.3 Performance Website

Operators may obtain a Pass/Fail/insufficient data monitoring performance report for their aircraft from the FAA Performance-based Communication and Surveillance (PBCS) Monitoring website.

6.4 Substandard Performance

Operators must address substandard performance whether the source of that report is from the operator’s own monitoring process, Communication Service Provider (CSP), FAA, or a foreign authority. Operators can view aggregate performance observed within FAA oceanic airspace from the PBCS monitoring website in the above paragraph. If the result of the report is “Fail,” the operator should follow the directions on the website to request further details and a corrective action plan. With a “Fail” report, operators may continue to operate at a less stringent performance level (i.e., RCP 240 to RCP 400) provided they file the appropriate performance flight plan designator.

6.5 Corrective Aircraft Action

The operator may return to the performance stated in their statement of compliance (SOC) provided the corrective action plan is completed.

6.6 Data Link Performance Eligibility

As stated in paragraph 3.3.5, RCP and RSP performance monitoring data should be included to quantify data link eligibility. If performance monitoring data is insufficient, then the SOC will be the initial basis for compliance with continued monitoring.

6.7 Procedures to Report Problems

The operator should establish procedures to report problems to the regional PBCS monitoring entities identified in Aeronautical Information Publications (AIP) (or equivalent publications) associated with the route of flight on which the problem occurred (see Chapter 8, Reports).

6.8 Performance Monitoring in U.S. Domestic Airspace

Reserved.

CHAPTER 7. TRAINING

7.1 Training Documentation

7.1.1 Part 91 Operator Training. Part 91 operators must be proficient with the procedures and operations associated with the use of data link communication systems in accordance with their Airplane Flight Manual (AFM) and AFM Supplement if applicable. Part 91 operators should be knowledgeable with the procedures and operations as shown in paragraphs 7.4 and 7.5.

7.1.2 Parts 91 Subpart K (Part 91K), 121, 125, and 135 Operator Training. Part 91K, 121, 125, and 135 operators should have a training program addressing the operational practices, procedures, and training items related to data link communication operations (e.g., initial, upgrade, or recurrent training for pilots, operational control personnel, and maintenance personnel). If criteria for training or checking are other than as specified in this AC, the criteria may be found in Flight Standardization Board (FSB) reports applicable to a particular aircraft type.

Note: A separate training program is not required if data link communication training is integrated in the current training program. However, the applicant must identify the training elements from this AC within the existing training program.

7.2 Objectives

Operators should include the following objectives to ensure appropriate pilot data link communications qualification:

7.3 Ground and Flight Training

7.3.1 Pilot Knowledge/Training. Parts 91K, 121, 125, and 135 operators should maintain training syllabi (e.g., initial, upgrade, or recurrent) and other appropriate materials including operational practices and procedures. Training for other personnel must be included where appropriate (e.g., operational control personnel or maintenance).

7.3.2 Pilot Training. Parts 91K, 121, 125, and 135 operators should ensure their process contains training for pilots on equipment requirements, normal and non-normal operations and procedures, and limits of their data link communication capability. Pilots must receive data communications training specific to the avionics suite they will be operating. A common type rating does not guarantee the pilot has received training on the data communications equipment installed on a particular aircraft.

7.3.3 Regulatory Basis. All training must be in accordance with the following where applicable:

1. Part 91K:

7.4 Pilot Knowledge Subject Areas

The minimum following subjects should be addressed in an approved curriculum of data link communications academic training during the initial introduction of data link communication systems:

ROGER (downlink message (DM) 3)/WILCO (DM0), UNABLE (DM1), or STANDBY (DM2) of a data link communication message;

Note: For subsequent ground training, only the new, revised, or emphasized items need be addressed.

7.5 Pilot Procedural Training Items

As a minimum, procedural training should include:

9. CRM. Independent message verification, discussion, and action (see paragraph 5.2.1).

7.5.1 Credit for Training. Operators may receive credit for existing data link communications training already approved in a different application. For example, an operator may receive credit for training based on previous use of data link communication services, such as on different routes, for a different type of operation, or training conducted by another operator (except for part 121 or 135), training center, or manufacturer. The principal operations inspector (POI) will determine whether and how much credit an operator should receive, considering whether the training is used in another FAA-approved application and whether the operator has demonstrated the training is relevant to the new application.

7.5.2 Pilot Currency. Once pilots have completed initial data link communication training, pilot currency programs/training should include data link communication elements.

7.6 Dispatcher Training

An aircraft dispatcher, flight follower, or other operational control personnel should not be assigned to duty unless he/she has demonstrated satisfactory data link communication knowledge to the operator. Training should include:

7.7 Maintenance Training

Operators should ensure all maintenance personnel receive training on their airplane’s data link communication equipment. Operators unsure of required maintenance procedures for data link communication-related equipment should contact their aircraft manufacturer field service representatives.

CHAPTER 8. REPORTS

8.1 Introduction

Operators and manufacturers must develop reporting procedures to ensure effective identification, tracking, and followup of data link-related events. Procedures should provide the following to the Regional Monitoring Agency (RMA).

8.2 Common Reasons to Report

Common reasons for submitting a problem report are:

8.3 Oceanic and Remote Continental Problem Reporting

For Future Air Navigation Systems (FANS) 1/A(+) problem reporting in oceanic and remote continental airspace, notify the FANS Central Reporting Agency (CRA) at http://www.fans-cra.com/. This site is maintained by Airways New Zealand as a service to the global FANS community and includes the:

8.4 U.S. Domestic Airspace Problem Reporting

For data link communication problems in U.S. domestic airspace, an Operational Problem Report (OPR) should be filed with the FAA by downloading the Data Comm Operational Problem Report Ticket. The completed information should be faxed or emailed as shown on the form. Harris Corporation is contracted by the FAA to process problem reports.

8.5 Problem Reporting Process

The following is the problem reporting process:

3. Operator is notified of the results.

APPENDIX A. FOREIGN OPERATORS

A.1 General

Foreign operators may use data link communications when operating in U.S. airspace. In order to take advantage of Air Traffic Service Unit (ATSU) data communication services, foreign operators must be properly equipped and file the appropriate flight plan designator codes (see Chapter 3, Aircraft Eligibility, and Appendix D, Flight Planning).

A.2 Title 14 CFR Part 129

The FAA does not approve data link communications installations, training programs, minimum equipment lists (MEL), or maintenance programs for foreign operators operating non-U.S.-registered aircraft. Such authorizations are addressed as specified by the State of the Operator or State of Registry, as appropriate. However, since compatibility of data link communications within U.S. airspace is essential, part 129 operations guidelines for data link communications are provided by this AC. Compliance with these data link communications provisions ensures both data link communication system and procedural compatibility. The FAA issues authorization to foreign operators for data communications operations in U.S. airspace via operations specification (OpSpec) A003. Outside the United States, in international waters wherein U.S. air traffic (i.e., New York and Oakland air route traffic control centers (ARTCC)) is tasked by the International Civil Aviation Organization (ICAO) with traffic separation for all aircraft, the foreign operator needs to have their Civil Aviation Authority’s (CAA) approval for data communications. The FAA does not issue an OpSpec for operations outside the United States. See Appendix B, Data Link Communications Minimum Equipment List (MEL) and Master Minimum Equipment List (MMEL) Provisions, for further details on MELs and MMELs when the FAA is the State of Registry of a foreign operator’s aircraft. More details will be provided in future revisions of the AC as they become available.

A.3 Application Process

Foreign operators should contact their FAA principal operations inspector (POI) to obtain application information for part 129 data link communications authorization in U.S. airspace. When a foreign operator submits the necessary information to the responsible principal inspector (PI), showing its aircraft are in compliance, the PI approves data communications via OpSpec A003 or an amendment. Although not mandatory, foreign operators should comply with the provisions of this AC or equivalent provisions specified by the State of the Operator or by ICAO.

A.4 Unique Address

An appropriate data link communication system must be installed and operated on suitable frequencies specified by the ATSU during flight in U.S. airspace if procedures are predicated on its use. A unique and specific address, the ICAO 24-bit aircraft identification, must be assigned to the airplane and the data link communication must recognize this address. When properly set, the unique address may not be altered, set to a duplicated address, or set to an address that potentially interferes with the ATSU or data link communication safety functions.

A.5 U.S. Interoperability Requirements

The operator must confirm the interoperability of their aircraft data link system (interoperability requirements standards (INTEROP) designators are described in Table 2-2, Interoperability Designators and Descriptions).

The data link communication system must be operated in accordance with the U.S. airspace interoperability requirements, except as provided for by the MEL provisions acceptable to the State of the Operator.

A.6 Training

Training and procedures for use of data link communication as specified by ICAO, this AC, or other equivalent criteria acceptable to the FAA should be used when operating in U.S. airspace.

A.7 Unsafe Performance or Conditions

Unsafe performance or conditions related to data link communication operations which potentially could affect continued safe operations in U.S. airspace (a data link communication event) should be reported to their International Field Office (IFO) (refer to the FAA’s IFO website). Operators should also follow the problem reporting procedures in Chapter 8, Reports.

A.8 U.S. Domestic Airspace

For a summary of U.S. domestic (Controller-Pilot Data Link Communication–Departure Clearance (CPDLC-DCL) service and U.S. en route data communication service) airspace requirements, see Appendix C, Summary of Airspace Requirements.

APPENDIX B. DATA LINK COMMUNICATIONS MINIMUM EQUIPMENT LIST (MEL) AND MASTER MINIMUM EQUIPMENT LIST (MMEL) PROVISIONS

B.1 Inoperative Equipment

Each operator intending to have authority to dispatch an aircraft with a data link communication system or component temporarily inoperative must do so in accordance with provisions of a minimum equipment list (MEL). For U.S.-registered aircraft, MELs are approved for each operator and type aircraft, within provisions of the FAA Master Minimum Equipment List (MMEL) for that type. When proposed MEL provisions are consistent with the FAA MMEL, principal operations inspectors (POI) may approve the MEL. Enhanced features (those above and beyond the basic data link communication system) may be inoperative, provided the inoperative features do not degrade the system (e.g., data link communication printers).

Note: Title 14 CFR part 91, § 91.213 does not provide MMEL relief should equipment fail that is not included in the MMEL/MEL. Also refer to 14 CFR part 121, § 121.628; part 125, § 125.201; part 129, § 129.14; and part 135, § 135.179.

Note 1: The provisions and repair category intervals are intended to grant the operator sufficient relief during the initial stages of the data link communication implementation. This is intended to promote the installation process, as well as support the use of a partial system. Both equipment reliability and operational experience will dictate, what, if any, revision to this MMEL relief should be considered after the installation phase is completed.

Note 2: Operators are responsible for entering the number in the “Number Installed” column of the MEL.

Note 3: Operators are responsible for entering alternate procedures in the MEL comment section or referencing the location of such procedures in their manual system.

Note 4: If MMEL has not been updated for Controller-Pilot Data Link Communication (CPDLC) equipment for aircraft that are issued a Supplemental Type Certificate (STC), the operator is reminded that they must adhere to § 91.213.

Note 5: Special Condition: The MMEL does not provide relief for inoperative data communications equipment at this time and is being reviewed at the Aircraft Evaluation Group (AEG). Should any of the equipment/software fail relative to data link communications, the data equipment/software must be replaced/repaired before the aircraft can take off according to § 91.213(a).

APPENDIX C. SUMMARY OF AIRSPACE REQUIREMENTS

C.1 Summary of Airspace Requirements

(Table C-1, Summary of Airspace Requirements.) Each Air Traffic Service Unit (ATSU) providing data link services defines the requirements for their operations (refer to International Civil Aviation Organization (ICAO) Doc 4444, Procedures for Air Navigation Services - Air Traffic Management; ICAO Doc 7030, Regional Supplementary Procedures; ICAO Doc 10037, Global Operational Data Link (GOLD) Manual, ICAO Global Guidelines for Data Link Operations; Aeronautical Information Publications (AIP); and flight information region (FIR) specific bulletins for additional information).

Note: Table C-1 asterisks:

* An approval is required to use VDL M0/A for U.S. en route data communications and the operator assumes responsibility for the Communication Service Provider (CSP). The allocation of performance requirements to the CSP is more stringent than the RCP 240 allocation, which is used only to identify the aircraft allocation. See Chapter 4, Communication Service Providers. ** Aircraft typically use VDL M0/A or VDL M2 when in range of ground radios, which is also acceptable. However, an aircraft with only these subnetworks would not be eligible for the oceanic and remote continental operations due to coverage limitations.

*** See ICAO Doc 4444 for more information.

**** Must be tunable (Technical Standard Order (TSO)-C160a or later, Very High Frequency (VHF) Digital Link (VDL) Mode 2 Communications Equipment) with “push to load” capability into the navigation system whenever a routing change is received for operations supported by Baseline 2 (B2) and Future Air Navigation Systems (FANS) 1/A(+) data link communication systems.

Table C-3. Preferred Original Equipment Manufacturer Annotation “The FAA has approved the aircraft data link system to the criteria in AC 20-140C for the following data link capabilities:

• Interop Designators: FANS 1/A+ (with automation) ATN B1
• B2
• ACARS ATS
• Subnetworks: VDL M0/A/2
• SATCOM (Classic Aero, SBD, SBB)
• HFDL

ACARS ATS Aircraft-Allocated Performance CPDLC: RCP 130, RCP 240, RCP 400 ADS-C: RSP 160, RSP 180, RSP 400 This design approval does not constitute operational authorization.”

APPENDIX D. FLIGHT PLANNING

D.1 Filing Required Communication Performance (RCP)/Required Surveillance Performance (RSP) Capabilities

When filing RCP/RSP capabilities, operators must ensure the planned use of associated communication and surveillance capabilities for the flight will be in accordance with regulations, policies, and procedures in control areas for the flight, as published by the applicable States in Aeronautical Information Publications (AIP) (or equivalent publications). Operators should ensure the proper information to denote Performance-based Communication and Surveillance (PBCS) capabilities is included in the International Civil Aviation Organization (ICAO) flight plan.

D.1.1 The following are determinations for proper filing:

D.2 Regulatory Basis

Flight planning must be in accordance with the following where applicable:

1. Part 91:

D.2.1 Flight Plan Descriptors:

Note 1: Refer to ICAO Doc 4444, Procedures for Air Navigation Services – Air Traffic Management, Appendix 2, for flight plan requirements. Also, refer to the FAA Flight Planning Information website.

Note 2: The inclusion of PBCS capability in the filed flight plan indicates that the relevant aircraft equipment comprising the aircraft system is approved and serviceable, the pilot is appropriately trained and qualified, and the operator holds applicable authorization to use the equipment for PBCS operations. If these conditions are not met, then PBCS capability should not be included in the flight plan.

D.3 Example

As a flight plan example, use the following:

If Actual Communications Performance (ACP) meets at least RCP 240 at 95 percent and Actual Surveillance Performance (ASP) meets at least RSP 180 at 95 percent, then the operator approved for RCP 240/RSP 180 may file the following:

D.3.1 If ACP does not meet RCP 240 at 95 percent, then the operator may file for RCP 400 by entering P1 and/or P3 in field 10. If ASP does not meet RSP 180 at 95 percent, then the operator may file for RSP 400 by entering “SUR/RSP400” in field 18.

D.4 Item 10a Descriptors

In Item 10a of the flight plan, operators should insert one of the descriptors, P1-P2, as appropriate, listed in Table D-1, to identify an aircraft’s RCP capability.

Note: Part 91 operators filing “J” codes for U.S. domestic data link services must have a data link authorization to file J5–J7 in oceanic and remote continental airspace.

D.5 Item 10b Descriptors

In Item 10b of the flight plan, operators should insert one of the descriptors, D1 and G1, as appropriate, listed in Table D-2, to identify an aircraft’s RSP capability:

D.6 Item 18 RSP Specification

In Item 18 of the flight plan, the aircraft operator should file the RSP capability by inserting the indicator “SUR/” followed by the appropriate RSP specification (e.g., RSP400 or RSP180).

Note: The ATSU unit uses the flight plan information to determine when to apply particular Air Traffic System Management (ATM) operations that are dependent on the capability and to configure the system (e.g., set timer threshold values) for efficient operation when RCP and/or RSP varies.

D.7 Field 18/DAT for CPDLC or Pre-Departure Clearance (PDC)

The proposed data link communication “codes” in Field 18/DAT are an optional mechanism for the user to notify FAA automation to generate a CPDLC or PDC.

* No spaces in actual DAT/ codes.

** No ICAO flight plan change required if user currently gets PDC and does not want DCL. Current PDC designation will be the default.

* No spaces in actual DAT/ codes.

* No spaces in actual DAT/ codes.

* No spaces in actual DAT/ codes.

APPENDIX E. VOICE PHRASEOLOGY

APPENDIX F. CONTROLLER-PILOT DATA LINK COMMUNICATION (CPDLC) UPLINK AND DOWNLINK TABLES

APPENDIX G. TERMINOLOGY AND ACRONYMS

G.1 Terminology

1. Aeronautical Telecommunications Network (ATN). A global inter-network architecture that allows ground, air-ground, and avionic data subnetworks to exchange digital data for the safety of air navigation and for the regular, efficient, and economic operation of Air Traffic Services (ATS).

2. Air Navigation Services Provider (ANSP). An organization responsible for the provision of ATS.

3. Air Traffic Data Link Service. A data communication capability comprising air/ground and ground/ground data network services, specified data link message sets and protocols, aircraft equipment, Air Traffic Service Unit (ATSU) facility equipment, and operational procedures intended to provide primary or supplemental ATSU communications.

4. Air Traffic Service Unit (ATSU). This domain includes the controller and the ATSU system which consists of an end system where data communications applications reside, a ground to ground router, a ground to ground communication network, and human-machine interface (HMI).

5. Aircraft Communications Addressing and Reporting System (ACARS). ACARS is a digital data link system for transmission of short messages between aircraft and ground stations via airband radio or satellite. ACARS as a term refers to the complete air and ground system, consisting of a service provider and aircraft/ground equipment.

6. Allocations. For approval, design, and monitoring purposes, performance requirements are provided against allocated human and technical Air Traffic System Management (ATM)/Communication, Navigation, and Surveillance (CNS) elements (i.e., the aircraft system, aircraft operator, ANSP, and Communication Service Provider (CSP)) of the data communications transaction.

7. Automatic Dependent Surveillance-Contract (ADS-C). ADS-C is a surveillance information system using automated reports. An agreement is established between the ground system and the aircraft via a data link. Without pilot input, the ATSU can establish a “contract” to provide reports of aircraft position, altitude, speed, elements of navigational intent, and meteorological data. The system can generate the following types of reports:

8. Availability. The probability that an operational communication transaction can be initiated when needed.

9. Communication Transaction Time. The maximum time for the completion of the operational communication transaction, after which the initiator should revert to an alternative procedure.

10. Continuity. The probability that an operational communication transaction can be completed within the communication transaction time.

11. Controller-Pilot Data Link Communications (CPDLC). CPDLC is a two-way data-link communication system by which controllers can transmit digital text messages to an aircraft as an alternative to voice communications. Messages from an aircraft to the ATSU may follow a standard format or may be free text. Messages from a controller normally follow a standard format and usually require a response from the pilot.

12. Current Data Authority (CDA). The designated ground system through which a CPDLC dialogue between a pilot and a controller currently responsible for the flight is permitted to take place.

13. Data Link Communication System. A data link communication system is a means of transmitting and receiving digital information. “Data link” is a generic term that encompasses different types of data link communication systems and subnetworks.

14. Departure Clearance (DCL). DCL (CPDLC-DCL) is the initial phase of U.S. domestic airspace implementation of data communication and is limited to tower services. CPDLC-DCL provides automated assistance for requesting and delivering initial and revised DCLs using CPDLC. The DCL includes flight plan route, climb via and/or initial/requested altitude, beacon code assignment, and departure frequency.

15. Downlink Message (DM). A CPDLC message sent from an aircraft.

16. Future Air Navigation System (FANS). FANS is an avionics system which provides direct data link communication between the pilot and the air traffic controller. The communications include air traffic control (ATC) clearances, pilot requests, and Position Reporting (PR).

17. Integrity. The probability of one or more undetected errors in a completed communication transaction.

18. Maximum Accumulated Unplanned Outage Time. A value that defines the acceptable accumulated duration of unplanned outages that exceed the unplanned outage duration limit in a specified time period.

Note: Unplanned outages that are less than the unplanned outage duration limit are considered against the criterion for continuity.

19. Maximum Number of Unplanned Outages. A value that defines the acceptable number of unplanned outages that exceed the unplanned outage duration limit in a specified time period.

Note: Unplanned outages that are less than the unplanned outage duration limit are considered against the criterion for continuity.

20. Minimum Equipment List (MEL). A list which provides for the operation of aircraft, subject to specified conditions, with particular equipment inoperative, prepared by an operator in conformity with, or more restrictive than, the Master Minimum Equipment List (MMEL) established for the aircraft type.

21. Next Data Authority (NDA). The ground system so designated by the CDA through which an onward transfer of communications and control can take place.

22. Performance-Based Communication and Surveillance (PBCS). PBCS is a concept that applies required communication performance (RCP) and required surveillance performance (RSP) specifications to ensure appropriate performance levels for relevant ATM operations (e.g., application of a reduced separation minimum).

23. Pre-Departure Clearance (PDC). A PDC is a clearance that is issued in a text format rather than being issued audibly over a clearance delivery frequency. This text clearance is issued through the use of a data link communication computer system and is relayed from a dispatch system to the pilot via an ACARS message or a terminal gate printer.

24. Required Communication Performance (RCP). A set of requirements for ATS provision, aircraft capability, and operations needed to support performance-based communication within a defined airspace.

25. Required Surveillance Performance (RSP). A statement of the performance requirements for operational surveillance in support of specific ATM functions.

26. Satellite Communication (SATCOM). The Aviation SATCOM is a worldwide mobile communications system providing voice and data communications services between aircraft subnetworks and ground subnetworks.

27. Secondary Surveillance Radar (SSR). A type of radar used by ATSU to transmit and receive data on transponder equipped aircraft. This data includes barometric altitude and identification codes.

28. Supplemental Type Certificate (STC). An STC is a type certificate (TC) issued when an applicant has received FAA approval to modify an aeronautical product from its original design.

29. Surveillance Transaction Time. The surveillance transaction time specifies the maximum time for the completion of the operational surveillance process. This parameter is an indication of time criticality.

30. Type Certificate (TC). A TC is issued by the FAA when the airworthiness of an aircraft manufacturing design has been determined to be acceptable. Once issued, the design cannot be changed without approval from the FAA.

31. Uplink Message (UM). A CPDLC message sent from a ground system.

G.2 Acronyms

Acronym Meaning

4-D Four-Dimensional 4DTRAD Four-Dimensional Trajectory Data Link 14 CFR Title 14 of The Code of Federal Regulations AC Advisory Circular ACARS Aircraft Communications Addressing and Reporting System ACL Air Traffic Control Clearance ACM Air Traffic Control Communication Management ACP Actual Communications Performance ACTP Actual Communication Technical Performance AD Airworthiness Directive

ADS Automatic Dependent Surveillance ADS-C Automatic Dependent Surveillance-Contract AEG Aircraft Evaluation Group

AFM Airplane Flight Manual AFN Air Traffic Service Facilities Notification AIP Aeronautical Information Publication AIS Aeronautical Information Service AMC Air Traffic Control Microphone Check ANSP Air Navigation Service Provider

AOC Aeronautical Operational Control

ASP Actual Surveillance Performance

ATC Air Traffic Control ATIS Automatic Terminal Information Service ATM Air Traffic System Management ATN Aeronautical Telecommunications Network ATN B1 Aeronautical Telecommunications Network Baseline 1 ATS Air Traffic Service

ATSU Air Traffic Service Unit

• Acronym Meaning
• B2 Baseline 2
• CADS Centralized ADS-C System
• CDA Current Data Authority
• CDU Control Display Unit
• CFR Code of Federal Regulations
• CM Context Management

CNS Communication, Navigation, and Surveillance CPDLC Controller-Pilot Data Link Communication

• CRA Central Reporting Agency
• CRD Clearance Request and Delivery
• CRM Crew Resource Management
• CSP Communication Service Provider
• CVR Cockpit Voice Recorder

CWA Central Weather Advisory D-ATIS Digital Automatic Terminal Information Service D-TAXI Data Link Taxi

• DCL Departure Clearance
• DCNS Data Communications Network Service
• DLIC Data Link Initiation Capability
• DLMA Data Link Monitoring Agency
• DM Downlink Message
• DRNP Dynamic Required Navigation Performance

DSC Downstream Clearance DT RSP Data Delivery Time (associated with nominal continuity – 95 percent) EPP Extended Projected Profile

ERAM En Route Automation Modernization

ET Expiration Time EUROCAE European Organization for Civil Aviation Equipment FAA Federal Aviation Administration

FANS Future Air Navigation System

• Acronym Meaning
• FBO Fixed-Base Operator
• FDR Flight Data Recorder
• FIR Flight Information Region
• FMS Flight Management System
• GA General Aviation

GOLD Global Operational Data Link (GOLD) Manual (Doc 10037) GPS Global Positioning System

HF High Frequency (radio)

HFDL High Frequency Data Link

HMI Human-Machine Interface ICAO International Civil Aviation Organization IER Information Exchange and Reporting

IFO International Field Office

IM Interval Management INTEROP Interoperability Requirements Standards ISPACG Informal South Pacific Air Traffic Services Coordinating Group ITP In-Trail Procedures

• LOA Letter of Authorization
• MEL Minimum Equipment List
• METI Meteorological Information
• MMEL Master Minimum Equipment List

M/M/S Make, Model, and Series MOPS Minimum Operational Performance Standard MSpec Management Specification

• MTBO Mean Time Between Outages
• MU Management Unit
• NAT North Atlantic
• NDA Next Data Authority
• NM Nautical Mile
• NSDA National Single Data Authority

• Acronym Meaning
• OCD Oceanic Clearance Delivery
• OCL Oceanic Clearance
• OEM Original Equipment Manufacturer
• OPR Operational Problem Report
• OpSpec Operations Specification

OT RSP data overdue time (associated with operational continuity) PANS Procedures for Air Navigation Service Part 91K Part 91 Subpart K PBCS Performance-Based Communication and Surveillance PBN Performance-Based Navigation

• PDC Pre-Departure Clearance
• PI Principal Inspector
• PIREP Pilot Weather Report
• POI Principal Operations Inspector
• PORT Pilot Operational Response Time
• PR Position Reporting
• RA Radar Associate
• RCP Required Communication Performance
• RCP AAIR RCP Availability – Aircraft
• RCP ACSP RCP Availability – CSP
• RCP C RCP Continuity

RCP I RCP Integrity RCTP Required Communication Technical Performance RF Radio Frequency

• RLatSM Reduced Lateral Separation Minima
• RMA Regional Monitoring Agency
• RNAV Area Navigation

RNP Required Navigation Performance RSMP Required Surveillance Monitored Performance RSP Required Surveillance Performance

• Acronym Meaning
• RSP AAIR RSP Availability – Aircraft
• RSP ACSP RSP Availability – CSP
• RSP C RSP Continuity
• RSP I RSP Integrity
• RSTP Required Surveillance Technical Performance RTF Radio Telephone
• SATCOM Satellite Communication
• SBB SwiftBroadband
• SBD Short Burst Data
• SDP Service Delivery Point
• SELCAL Selective-Calling System

SID Standard Instrument Departure SIGMET Significant Meteorological Information SITA Société International de Télécommunications Aeronautiques SOC Statement of Compliance SPR Safety and Performance Requirements SSR Secondary Surveillance Radar

• STC Supplemental Type Certificate
• TC Type Certificate
• TDLS Tower Data Link Services

TSO Technical Standard Order TWIP Terminal Weather Information for Pilots UM Uplink Message

VDL Very High Frequency Data Link

VHF Very High Frequency (radio)

Advisory Circular Feedback Form

If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by contacting the Flight Technologies Division (AFS-400) at 9-AWA-AFS400-Coord@faa.gov or the Flight Standards Directives Management Officer at 9-AWA-AFS-140-Directives@faa.gov.

Subject: AC 90-117, Data Link Communications

Date: _____________________

Please check all appropriate line items:

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Recommend paragraph _____________ on page __________ be changed as follows:

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In a future change to this AC, please cover the following subject:

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