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:
1. Interoperability,
2. Subnetwork, and
3. Aircraft performance.
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 3-1
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:
• VDL M0/A,
• VDL M2,
• High Frequency Data Link (HFDL),
• Inmarsat, and
• Satellite communications (SATCOM) Iridium (Short Burst Data (SBD)).
Note: For aircraft utilizing Inmarsat (SwiftBroadband (SBB)), the SOC must reference AC 20-140C or later.
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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/newoperator-documents.
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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.
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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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