Introduction

1.1 FANS-1/A includes components of Communication, Navigation, and Surveillance (CNS).

1.2 IFATCA has clear policy against the proliferation of the communication elements of FANS1/A, namely FANS-1/A CPDLC.

1.3 It is considered that the important reasons behind this position are not clearly understood in the wider ATM community and there is a need to clearly state IFATCA’s rationale, starting from first principles.

Discussion

2.1 The Surveillance element of FANS-1/A is comprised of Automatic Dependent Surveillance-Contract (ADS-C), which relies upon aircraft navigation systems transmitting position and other navigational information to the ATC system via a datalink. FANS-1/A is an industry standardised implementation of ADS-C. ICAO has promulgated Standards and Recommended Practices (SARPs) for the full implementation of ADS-C using an Aeronautical Telecommunications Network (ATN) compliant datalink and communications component. ATN compliant datalink systems are not yet widely deployed.

2.2 Concerns have been identified with the proposed extension to the use of the communication elements of FANS-1/A. The main concerns are the following:

i There is no message order assurance in FANS-1/A;

ii There is no true end-to-end message delivery assurance;

iii FANS-1/A does not use the ICAO 24-bit aircraft address to ensure that messages are delivered to the correct aircraft;

iv FANS-1/A cannot append LAT/LONG coordinates with the Fix name in route clearance messages;

v Inconsistency with CPDLC message set as defined in the ICAO ATN SARPs

2.3 FANS-1/A utilises currently available technology to support the communications requirements. The standard Aircraft Communications Addressing And Reporting System (ACARS) protocol is enhanced to some extent (ARINC 622) to overcome some of the functional shortfalls identified with ACARS relative to the ICAO datalink SARPs.

2.4 A major reason for the continued use of FANS-1/A CPDLC is that it is offers improved controller pilot communications when compared to the use of HF voice. It is a fact that many more ATM systems with CPDLC are being delivered, and the number of aircraft equipped with FANS1/A is rising.

2.5 Current IFATCA policy on FANS-1/A states in part:

2.6 IFATCA has specific policy which deals with a situation where different types of datalink are in use:

2.7 The table below summarises the major differences between FANS-1/A and existing ATN CPDLC components:

2.8 ACARS was originally designed for airline use where applications were unlikely to have the same integrity requirements as ATC applications. In an attempt to overcome this problem the Airlines Electronic Engineering Committee (AEEC) has developed additional standards (AIRINC 745 and AIRINC 622) to be applied to ACARS when used in an ADS function.

2.9 The ATN is more sophisticated than the ACARS communication system. It contains more communications management features and quality of services options. Therefore, the ATN will be better suited to supporting CPDLC for Air Traffic Management purposes than the proposed use of FANS-1/A CPDLC.

2.10 Current IFATCA policy concentrates on one particular difference between FANS-1/A CPDLC and ATN CPDLC:

Conclusions

3.1 SC1, having reviewed existing policy on the surveillance elements of FANS-1/A, proposes no amendments.

3.2 The differences between the FANS-1/A implementation of CPDLC and that standardised by ICAO (ATN SARPs) are of a complex nature. Current IFATCA policy does not reflect all aspects of these differences.

3.3 Full availability in service of an ATN datalink is still be some way off. This delay may well be made longer by the proliferation of FANS-1/A applications.

3.4 IFATCA’s objective is the acceptance and implementation of global standards for ATC systems.

3.5 There is considerable confusion over terminology. It is only the CPDLC aspects of FANS-1/A that are causing difficulties at present. FANS-1/A is a bundle of ADS C and CPDLC. ARINC 622 Is enhanced ACARS and it is a datalink component (CPDLC). ARINC 745 defines the ADS application, airborne equipment requirements and interfaces to other airborne systems (e.g. navigation).

3.6 The problem is the usability of ACARS for safety critical air traffic management functions. ARINC 622, even with enhancements, does not currently meet the operational performance (reliability, availability, integrity, etc.) for CPDLC.

3.7 There is a need to review the current policy on FANS-1/A CPDLC and reinforce IFATCA’s support for an ATN compliant solution, in accordance with ICAO ATN SARPs.

Recommendations

It is recommended that;

4.1 Current IFATCA policy on FANS-1/A CPDLC, IFATCA Manual page 3 2 4 14, para 4.10., being:

“FANS-1/A CPDLC has limitations. Further these shortcomings must preclude further proliferation of this technology, into states of the world where it is not currently deployed. Once the Aeronautical Telecommunications Network (ATN) Datalink system is deployed, use of the FANS-1/A CPDLC shall be replaced by the ATN system and FANS-1/A systems shall not be accommodated in the ATN, as this would seriously degrade the operational suitability of the ATN.”

Be deleted.

4.2 New IFATCA policy is:

That the ICAO ATN SARPs and their progressive development form the definitive basis for any future CPDLC implementation.

Any future regional or global implementation of CPDLC (FANS-1/A included) must be supported by a safety case which demonstrates full compliance with ICAO ATN SARPs.