South Pacific of FANS-1/A Datalink Communications

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South Pacific of FANS-1/A Datalink Communications

37TH ANNUAL CONFERENCE, Toulouse, France, 30 March – 3 April 1998

WP No. 82

South Pacific of FANS-1/A Datalink Communications


Since the implementation in the South Pacific of FANS-1/A datalink communications (i.e., CPDLC – Controller Pilot Data Link Communications), controllers and pilots have been seen not only increasing examples of operational problems associated with its usage, but also disturbing trends towards proliferating the technology into other regions of the world. It has become apparent that the Federation should consider whether we need policy specific to this datalink technology, in addition to our policy on datalink generally.

When FANS-1A CPDLC was deployed in the South Pacific less than two years ago it was hoped by states and airlines that this technology would deliver substantial benefits in the form of reduced oceanic separation standards. Since that time a substantial number of operational problems have prevented these benefits from being realised. Unfortunately until fairly recently these problems have had to be reported in an anecdotal and informal manner. Although there was an interoperability team in place up until the system was actually operational , for some reason this team was disbanded when the system was deployed. This left no formal central organisation tasked with collecting, analysing and addressing problems with the system.

The problems that have surfaced in this informal atmosphere have been troubling. They include datalink messages being delivered to the wrong aircraft, messages being lost entirely, connections between the aircraft and the ground system being broken despite automation indications to the contrary, aircrew difficulties with establishing a connection, and connections being terminated and response to situations that can routinely occur. These problems have seemingly resulted from various reasons, some technical , some procedural, some related to the human machine interface (HMI) , and some related to user training and currency. Additionally, United Airlines pilots have experienced an alarming increase in pilot deviations from clearances that were directly to attributed to the FANS-1/A datalink.

These problems have prompted IFALPA to conclude in a formal letter to ICAO that “these failings make it most unlikely that the Federation (IFALPA) will ever be in a position to accept FANS-1 CPDLC as a primary means of ATS communications.”

The reports of problems have also recently prompted the re-formation of a Fans interoperability team (FIT) composed of most of the concerned participants in FANS- 1/A CPDLC in the South Pacific. To date unfortunately, IFATCA has not been invited to participate although there are indications that this situation may change.

There are several technical areas where FANS-1/A CPDLC does not meet what have been specified as general operational requirements for any ATS datalink system and which IFATCA supports as requirements. The most crucial of these is in the area of a true end to end message assurance capability. FANS-1/A message assurance stops at the avionics MU box , which can return a positive delivery indication to the controller and still not deliver the message to the datalink application avionics. This situation can leave the flight crew unaware that a datalink message has even been delivered, while at the same time the controllers indication incorrectly reports that it has.

There has also been increasing pressure from states and airlines to force the FANS-1/A datalink equipped aircraft to be accommodated in the more robust Aeronautical Telecommunications Network (ATN) datalink system. This pressure has led ICAO to task the ADS Panel with developing a method whereby this accommodation can be accomplished. Although the panel supported by our IFATCA representative has nearly completed development of a technical and operational accommodation system , the document will present some unanswered operational considerations that States must take into account in deciding whether to field ATN systems that will do this accommodation. One of the most important ones involves the issue of end to end message assurance. It raises grave operational concerns when mixing aircraft that have no reliable message assurance capability into a system that is required to have such a feature.

To Conclude

IFALPA has already taken a strong position against the proliferation of the FANS-1/A CPDLC beyond regions where it is currently developed. Even in the areas where it is currently in use, they feel that it should be used for primary ATS communications.

Increasing numbers of Federation controllers are going to called upon to make use of the FANS- 1/A CPDLC. It is important that we make a clear and strong statement of our position regarding this technology.

If the recently formed FANS Interoperability Team (FIT) is successful in addressing and correcting the technical and operational problems with the FANS-1/A CPDLC, this policy re-evaluated in light of the assessed suitability of the system.

Last Update: September 28, 2020  

March 10, 2020   712   Jean-Francois Lepage    1998    

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