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:
1. Failure notification,
2. Recording data link messages,
3. CSP integrity,
4. Compliance with CSP allocations for Required Communication Performance (RCP)/Required Surveillance Performance (RSP), and
5. Adequate subnetwork coverage for the route flown.
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 4-1
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.
Table 4-1. RCP 240 Transaction Time and Continuity Allocations to CSP Transaction Time Parameter *ET (sec)
99.9% of messages less than:
(sec) **TT (sec) C = 95% of messages less than:
(sec) Compliance Means RCTPCSP 120 100 Contract/service agreement terms. See also paragraph 4.1.2.
*ET is Expiration Time **TT is Transaction Time Table 4-2. RCP 240 CSP Availability and Outages Parameters Availability Parameter Safety Compliance Means Availability – CSP (ACSP) 0.999 Contract/service agreement terms Unplanned outage duration limit (minutes) 10 Contract/service agreement terms Maximum number of unplanned outages 48 Contract/service agreement terms Maximum accumulated unplanned outage time (minutes/year) 520 Contract/service agreement terms Unplanned outage notification delay (minutes) 5 Contract/service agreement terms 4-2
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.
Table 4-3. RCP 400 Transaction Time and Continuity to CSP Allocation Transaction Time Parameter *ET (sec) C = 99.9% of messages less than:
(sec) **TT (sec) C = 95% of messages less than:
(sec) Compliance Means RCTPCSP 280 240 Contract/service agreement terms See also paragraph 4.1.2.
*ET is Expiration Time **TT is Transaction Time Table 4-4. RCP 400 Availability and Outages Parameters Availability Parameter Requirement Compliance Means Availability – CSP (ACSP) 0.999 Contract/service agreement terms Unplanned outage duration limit (minutes) 20 Contract/service agreement terms Maximum number of unplanned outages 24 Contract/service agreement terms Maximum accumulated unplanned outage time (minutes/year) 520 Contract/service agreement terms Unplanned outage notification delay (minutes) 10 Contract/service agreement terms 4-3
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.
Table 4-5. RSP 180 Data Delivery Time and Continuity Criteria Data Delivery Time Parameter *OT (sec) C = 99.9% of messages less than:
(sec) **DT (sec) C = 95% of messages less than:
(sec) Compliance Means RSTPCSP 170 84 Contract/service agreement terms. Pre-implementation demonstration.
*OT is data overdue time (associated with operational continuity) **DT is Delivery Time Table 4-6. RSP 180 Availability and Outages Parameters Availability Parameter Safety Compliance Means Availability – CSP (ACSP) 0.999 Contract/service agreement terms Unplanned outage duration limit (minutes) 10 Contract/service agreement terms Maximum number of unplanned outages 48 Contract/service agreement terms Maximum accumulated unplanned outage time (minutes/year) 520 Contract/service agreement terms Unplanned outage notification delay (minutes) 5 Contract/service agreement terms
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.
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Table 4-7. RSP 400 Data Delivery Time and Continuity Criteria Data Delivery Time Parameter OT (sec) C = 99.9% of messages less than:
(sec) DT (sec) C = 95% of messages less than:
(sec) Compliance Means RSTPCSP 340 270 Contract/service agreement terms. Pre-implementation demonstration.
*OT is data overdue time (associated with operational continuity) **DT is Delivery Time Table 4-8. RSP 400 Availability and Outages Parameters Availability Parameter Safety Compliance Means Availability – CSP (ACSP) 0.999 Contract/service agreement terms Unplanned outage duration limit (minutes) 20 Contract/service agreement terms Maximum number of unplanned outages 24 Contract/service agreement terms Maximum accumulated unplanned outage time (minutes/year) 520 Contract/service agreement terms Unplanned outage notification delay (minutes) 10 Contract/service agreement terms
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 4-5
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.
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Table 4-9. Data Communications Network Services (DCNS) Performance Baseline Performance Metric System Requirements Packet Error Rate (Network Service) 10(-5) Availability – Reliability, Maintainability, and Availability (Network Service)
0.9999 Mean Time Between Outages (MTBO) – Reliability, Maintainability, and Availability (Network Service) 1,344 Hours Network Service Restoral Time – Reliability, Maintainability, and Availability 30 Seconds* En Route Capacity 0.0010 bps per km3 One-Way Latency at 95% (uplink or downlink) < 10 sec One-Way Latency at 99% (uplink or downlink) < 45 sec *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.
1. The CSP uplink transfer delay must be less than or equal to 10 seconds for 95 percent of all ATSU data messages.
2. The CSP downlink transfer delay must be less than or equal to 10 seconds for 95 percent of all ATSU data messages.
3. The CSP uplink transfer delay must be less than or equal to 45 seconds for 99 percent of all ATSU data messages.
4. The CSP downlink transfer delay must be less than or equal to 45 seconds for 99 percent of all ATSU data messages.
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.
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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.
1. The service availability for each network service thread must be at least 0.9999.
2. The minimum calculated service availability must be measured over the latest 12-month period. Availability is calculated as follows:
• Available Time: Total time during the latest 12-month period the service was under contract.
• Total Outage Time: The total unapproved service interruption or degradation time during the Available Time. It includes any unapproved degradation in which the service failed to meet all performance requirements of this specification. It includes any length of time exceeding the duration of a FAA-approved interruption or degradation.
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.
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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.
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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.
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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:
1. Number of logon/notification attempts received from an aircraft exceeds the maximum allowable number within the adapted time period. This is to prevent denial of service attacks against the data link communication service.
2. Suspected duplicate aircraft registration. This is to prevent messages which are addressed by aircraft registration from going to the wrong aircraft.
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:
1. Aircraft identification (same as item 7 of the flight plan);
2. Aircraft registration, if applicable, and/or aircraft address (same as item 18 of the flight plan); and
3. Departure and destination airports, when required (same as items 13 and 16 of the flight plan).
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.
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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:
1. Logon/Notification information does not exactly match flight plan
(e.g., incorrect tail number and/or call sign/flight ID);
2. Ground or air system anomaly;
3. Data corruption;
4. Suspected duplicate aircraft registration;
5. Aircraft intentionally blocked from logging on/notifying (i.e., on blocked list due to problem reports with the aircraft); and/or
6. There is no flight plan for the flight or the flight plan did not transfer from one ATSU to the next.
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:
1. The logon/notification request was successful (e.g., could be correlated with a flight plan); or
2. The logon/notification request was unsuccessful (e.g., could not be correlated with a flight plan).
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:
1. When a MONITOR (UM120) message is received, the pilot should change to the specified frequency upon receipt of the instruction or at the specified time or position. The pilot should not establish voice contact on the frequency.
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