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U.S. Department of Transportation Federal Aviation Administration
Advisory
Circular
Subject: Data Link Communications Date: 10/3/17 AC No: 90- Initiated by: AFS-400 Change:
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
CONTENTS
- Chapter 1. General 1- Paragraph Page
- 1.1 Purpose of this Advisory Circular (AC) 1-
- 1.2 Applicability.................................................................................................................. 1-
- 1.3 Where You Can Find This AC 1-
- 1.4 What This AC Cancels 1-
- 1.5 Scope 1-
- 1.6 AC Format..................................................................................................................... 1-
- 1.7 Version References 1-
- 1.8 FAA Document References 1-
- 1.9 References (current editions) 1-
- 1.10 Airworthiness 1-
- 1.11 Regulatory Basis for Data Link Communication 1-
- 1.12 AC Feedback Form 1-
- Chapter 2. Data Link Communication Overview 2-
- 2.1 Introduction 2-
- 2.2 What Are Data Link Communications? 2-
- 2.3 FANS 2-
- 2.4 CPDLC and ADS-C 2-
- 2.5 ATN 2-
- 2.6 B2 2-
- 2.7 FANS 1/A(+) and ATN 2-
- 2.8 ACARS ATS 2-
- 2.9 Tower Data Link System (TDLS) 2-
- 2.10 CPDLC-DCL 2-
- 2.11 PDC 2-
- 2.12 Data Authority 2-
- 2.13 ATSUs and Aircraft Interoperability......................................................................... 2-
- 2.14 Performance-Based Communication and Surveillance (PBCS) Concept 2-
- 2.15 RCP and RSP Specifications Supporting ATM Operations 2-
- 2.16 Required Surveillance Performance (RSP) 2-
- 2.17 High Frequency Data Link (HFDL) 2-
- 2.18 Future U.S. Domestic Airspace Data Link Communication Services 2-
- 2.19 Data Communication Services Strategy 2-
- Chapter 3. Aircraft Eligibility 3-
- 3.1 Introduction 3-
- 3.2 Aircraft Eligibility 3-
- 3.3 Statement of Compliance (SOC)................................................................................... 3-
- 3.4 Configuration Control 3-
- 3.5 Maintenance 3-
- Chapter 4. Communication Service Providers (CSP) 4-
- 4.1 CSP for Oceanic and Remote Continental Operations 4-
- 4.2 RCP 240 CSP Allocations............................................................................................. 4-
- 4.3 RCP 400 CSP Allocations............................................................................................. 4-
- 4.4 RSP Allocation Requirements 4-
- 4.5 Alternate Means of Compliance 4-
- 4.6 CSP for U.S. Operations 4-
- 4.7 CSP Monitoring 4-
- Chapter 5. Operational Use Of Data Link Communications 5-
- 5.1 Operational Use............................................................................................................. 5-
- 5.2 Data Link Operational Guidance 5-
- 5.3 Logon/Notification 5-
- 5.4 En Route........................................................................................................................ 5-
- 5.5 Voice Monitoring 5-
- 5.6 Free Text Messages 5-
- 5.7 Data Link Communication Failures 5-
- 5.8 ADS-C 5-
- 5.9 Exiting CPDLC and ADS-C Areas 5-
- 5.10 Logoff/Disconnect 5-
- Chapter 6. Performance Monitoring 6-
- 6.1 Performance Monitoring 6-
- 6.2 Oceanic and Remote Continental Airspace 6-
- 6.3 Performance Website 6-
- 6.4 Substandard Performance 6-
- 6.5 Corrective Aircraft Action 6-
- 6.6 Data Link Performance Eligibility 6-
- 6.7 Procedures to Report Problems 6-
- 6.8 Performance Monitoring in U.S. Domestic Airspace 6-
- Chapter 7. Training 7- - 7.1 Training Documentation 7- - 7.2 Objectives...................................................................................................................... 7- - 7.3 Ground and Flight Training 7- - 7.4 Pilot Knowledge Subject Areas 7- - 7.5 Pilot Procedural Training Items 7- - 7.6 Dispatcher Training....................................................................................................... 7- - 7.7 Maintenance Training 7-
- Chapter 8. Reports 8- - 8.1 Introduction 8- - 8.2 Common Reasons to Report 8- - 8.3 Oceanic and Remote Continental Problem Reporting 8- - 8.4 U.S. Domestic Airspace Problem Reporting 8- - 8.5 Problem Reporting Process 8-
- Appendix A. Foreign Operators A-
- A.1 General A-
- A.2 Title 14 CFR Part 129 A-
- A.3 Application Process A-
- A.4 Unique Address A-
- A.5 U.S. Interoperability Requirements A-
- A.6 Training A-
- A.7 Unsafe Performance or Conditions A-
- A.8 U.S. Domestic Airspace A- - Master Minimum Equipment List (MMEL) Provisions ........................................B- Appendix B. Data Link Communications Minimum Equipment List (MEL) and
- B.1 Inoperative Equipment ..................................................................................................B-
- Appendix C. Summary of Airspace Requirements .....................................................................C-
- C.1 Summary of Airspace Requirements ............................................................................C-
- Appendix D. Flight Planning D- - Performance (RSP) Capabilities D- D.1 Filing Required Communication Performance (RCP)/Required Surveillance
- D.2 Regulatory Basis D-
- D.3 Example D-
- D.4 Item 10a Descriptors D-
- D.5 Item 10b Descriptors D-
- D.6 Item 18 RSP Specification D-
- D.7 Field 18/DAT for CPDLC or Pre-Departure Clearance (PDC) D-
- Appendix E. Voice Phraseology E- - Downlink Tables.................................................................................................... F- Appendix F. Controller-Pilot Data Link Communication (CPDLC) Uplink and
- Appendix G. Terminology and Acronyms................................................................................. G-
- G.1 Terminology................................................................................................................. G-
- G.2 Acronyms G-
- Figure 2-1. Overview Data Link System 2- List of Figures
- Figure 2-2. ADS-C Event Sequence 2-
- Figure 2-3. Data Link Communication Services on Departure Procedure 2-
- Figure 2-4. Next Data Authority Notification 2-
- Designators 2- Figure 2-5. Air Traffic Service Unit (ATSU) and Aircraft Interoperability
- Figure 2-6. Performance-Based CNS/ATM Model 2-
- Figure 2-7. Actual Communications Performance (ACP) 2-
- Figure 2-8. RCP 240 Illustration 2-
- Figure 2-9. RCP 400 Illustration 2-
- Figure 2-10. RSP 180 Illustration 2-
- Figure 2-11. RSP 400 Performance 2-
- Figure 2-12. Data Communication Services Strategy 2-
- Table 2-1. PDC vs. CPDLC-DCL 2- List of Tables
- Table 2-2. Interoperability Designators and Descriptions...................................................... 2-
- Table 2-3. Types of Data Link Systems and Operations 2-
- Table 2-4. RCP 240 Transaction Time and Continuity Allocations—CPDLC 2-
- Table 2-5. RCP 240 Availability Criteria (Aircraft System).................................................. 2-
- Table 2-6. RCP 240 Integrity Criteria (Aircraft System) 2-
- Table 2-7. RCP 400 Transaction Time and Continuity Allocations—CPDLC 2-
- Table 2-8. RCP 400 Availability Criteria (Aircraft System).................................................. 2-
- Table 2-9. RCP 400 Integrity Criteria (Aircraft System) 2-
- Table 2-10. RSP 180 Surveillance Data Delivery and Continuity Allocations—ADS-C........ 2-
- Table 2-11. RSP 180 Availability Criteria (Aircraft System) 2-
- Table 2-12. RSP 180 Integrity Criteria (Aircraft System) 2-
- Table 2-13. RSP 400 Surveillance Data Delivery and Continuity Allocations—ADS-C........ 2-
- Table 2-14. RSP 400 Availability Criteria (Aircraft System) 2-
- Table 2-15. RSP 400 Integrity Criteria (Aircraft System) 2-
- Table 4-1. RCP 240 Transaction Time and Continuity Allocations to CSP 4-
- Table 4-2. RCP 240 CSP Availability and Outages Parameters 4-
- Table 4-3. RCP 400 Transaction Time and Continuity to CSP Allocation.............................. 4-
- Table 4-4. RCP 400 Availability and Outages Parameters 4-
- Table 4-5. RSP 180 Data Delivery Time and Continuity Criteria 4-
- Table 4-6. RSP 180 Availability and Outages Parameters 4-
- Table 4-7. RSP 400 Data Delivery Time and Continuity Criteria 4-
- Table 4-8. RSP 400 Availability and Outages Parameters 4-
- Table 4-9. Data Communications Network Services (DCNS) Performance Baseline............. 4-
- Table 5-1. CPDLC Connection Failure Responses 5-
- Table B-1. Minimum Equipment List Example....................................................................... B-
- Table B-2. Example of a Data Link Communication MMEL Provision B-
- Table C-1. Summary of Airspace Requirements C-
- Table C-2. Subnetwork Designators C-
- Table C-3. Preferred Original Equipment Manufacturer Annotation C-
- Table D-1. Item 10a Flight Plan COM Descriptors D-
- Table D-2. Item 10b Flight Plan Descriptors for Surveillance Equipment D-
- Table D-3. Voice, PDC, DCL D-
- Table D-4. DCL and En Route Data Link Clearances D-
- Table D-5. PDC Only and En Route Data Link D-
- Table D-6. En Route Data Link Clearances Only D-
- (CPDLC) From Pilot...............................................................................................E- Table E-1. Voice Phraseology Related to Controller-Pilot Data Link Communication
- Table E-2. Voice Phraseology Related to CPDLC From the ATSU ........................................E-
- Table F-1. Color Key F-
- Table F-2. Response Attribute of CPDLC Message Element for Uplink Messages F-
- Table F-3. Response Attribute of CPDLC Message Element for Downlink Messages F-
- Table F-4. Route Uplink Message Elements (RTEU) F-
- Table F-5. Route Downlink Message Elements (RTED) F-
- Table F-6. Lateral Uplink Message Elements (LATU) F-
- Table F-7. Lateral Downlink Message Elements (LATD) F-
- Table F-8. Level Uplink Message Elements (LVLU) F-
- Table F-9. Level Downlink Message Elements (LVLD) F-
- Table F-10. Crossing Constraint Uplink Messages (CSTU) F-
- Table F-11. Speed Uplink Messages (SPDU) F-
- Table F-12. Speed Downlink Messages (SPDD) F-
- Table F-13. Air Traffic Advisory Uplink Messages (ADVU) F-
- Table F-14. Air Traffic Advisory Downlink Messages (ADVD) F-
- Table F-15. Voice Communication Uplink Messages (COMU) F-
- Table F-16. Voice Communication Downlink Messages (COMD) F-
- Table F-17. Spacing Uplink Messages (SPCU) F-
- Table F-18. Spacing Downlink Messages (SPCD) F-
- Table F-19. Emergency/Urgency Uplink Messages (EMGU) F-
- Table F-20. Emergency/Urgency Downlink Messages (EMGD) F-
- Table F-21. Standard Response Uplink Messages (RSPU)...................................................... F-
- Table F-22. Standard Response Downlink Messages (RSPD) F-
- Table F-23. Supplemental Uplink Messages (SUPU) F-
- Table F-24. Supplemental Downlink Messages (SUPD) F-
- Table F-25. Free Text Uplink Messages (TXTU) F-
- Table F-26. Free Text Downlink Messages (TXTD) F-
- Table F-27. System Management Uplink Messages (SYSU) F-
- Table F-28. System Management Downlink Messages (SYSD) F-
- Table F-29. FANS 1/A Uplink Messages Not Recommended for Use F-
- Table F-30. FANS 1/A Downlink Messages Not Recommended for Use F-
- Table F-31. ATN B1 Uplink Messages Not Recommended for Use F-
- Table F-32. ATN B1 Downlink Messages Not Recommended for Use F-
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:
- Chapter 3 , Aircraft Eligibility,
- Chapter 4 , Communication Service Providers (CSP),
- Chapter 5 , Operational Use of Data Link Communications,
- Chapter 6 , Performance Monitoring,
- Chapter 7 , Training, and
- Chapter 8 , Reports.
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:
- ACs.
- TSOs.
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).
- Title 14 CFR Parts 21 , 23 , 25 , 27 , 29 , 43 , 91 , 91K, 121 , 125 , 129 , and 135.
- ACs:
- AC 20-140, Guidelines for Design Approval of Aircraft Data Link Communication Systems Supporting Air Traffic Services (ATS).
- AC 20-160, Onboard Recording of Controller Pilot Data Link Communication in Crash Survivable Memory.
- TSOs:
- TSO-C160a, Very High Frequency (VHF) Digital Link (VDL) Mode 2 Communications Equipment.
- TSO-C177( ), Data Link Recorder Equipment.
- ICAO Documents:
- Annex 6 , Operation of Aircraft, Part I, International Commercial Air Transport.
- Annex 6 , Operation of Aircraft, Part II, International General Aviation.
- Annex 10 , Aeronautical Telecommunications, Volume II, Communication Procedures including those with PANS status.
- Annex 10 , Aeronautical Telecommunications, Volume III, Communication Systems, Part 1, Digital Data Communications Systems.
- Annex 11 , Air Traffic Services.
- Annex 15 , Aeronautical Information Services.
- Annex 19 , Safety Management.
- Document 4444 , Procedures for Air Navigation Services - Air Traffic Management.
- Document 7030 , Regional Supplementary Procedures.
- Document 8400 , Procedures for Air Navigation Services, ICAO Abbreviations and Codes.
- Document 8585 , Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services.
- Document 9694 , Manual of Air Traffic Services Data Link Applications.
- Document 9869 , Performance-Based Communication and Surveillance (PBCS) Manual.
- Document 10037 , Global Operational Data Link (GOLD) Manual, ICAO Global Guidelines for Data Link Operations.
- Document 10063 , Manual on Monitoring the Application of Performance-Based Horizontal Separation Minima.
- North Atlantic Document 007 , North Atlantic Operations and Airspace Manual. This document is published on behalf of the North Atlantic Systems Planning Group by the European and North Atlantic Office of ICAO and includes data link material.
- North Atlantic Oceanic Errors Safety Bulletin (OESB).
and responding to the clearances. Additionally, this guide provides general information on the use of data link communications during en route operations.
- 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.
Figure 2-1. Overview Data Link System
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
(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.
- 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).
- 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.)
- Demand. The ATSU can request a single update as needed. This does not affect an existing contract preset rate.
Figure 2-2. ADS-C Event Sequence
2.4.2.2 ADS-C Emergency. An ADS-C emergency can be triggered by the pilot by the following means:
- Manually, by selecting the ADS-C emergency function;
- Indirectly, by triggering another type of emergency alerting system (e.g., transmission of a CPDLC emergency message or selection of a Secondary Surveillance Radar (SSR) emergency code); and
- Covertly (The availability of that functionality may vary between aircraft types).
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:
- Context management (CM) application for Data Link Initiation Capability (DLIC) service; and
- CPDLC application for ATC Communication Management (ACM), ATC Clearance (ACL), and ATC Microphone Check (AMC) services.
2.6 B2. B2 is ATN-based and will enable extended capabilities not possible with ATN B 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:
- CPDLC:
- Initial Four-Dimensional (4-D) Trajectory Data Link (4DTRAD),
- Dynamic Required Navigation Performance (DRNP), and
- Advanced flight Interval Management (IM).
- ADS-C:
- Extended Projected Profile (EPP) information provided in ADS-C reports supporting Information Exchange and Reporting (IER), 4DTRAD, and DRNP services.
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.
Figure 2-3. Data Link Communication Services on 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:
- Logon/notification information was correctly formatted;
- An ATC-filed flight plan is on file;
- Flight plan indicates the aircraft is CPDLC-DCL capable; and
- ATC controller has approved the DCL.
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:
- Review the clearance and verify that no clarification from ATC is required (Reject/Unable);
- Confirm the appropriate runway, if assigned, departure procedure, and transition with no discontinuities; and then
- Acknowledge (ROGER (DM3)/WILCO (DM0) or UNABLE (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:
- Internet access,
- Airline gate terminal,
