FANS 1/A support at EDYY
Rationale for FANS 1/A discontinuation in ATS/5
After 26 years of service, MUAC is saying goodbye to FANS1/A CPDLC operations, with the last service planned for 24.8.2021. We have been proud to support our FANS customer base, so wish to explain why we are taking this decision now.
FANS1/A is not covered by the EU Data Link Service Implementing Rule 29/2009 nor supported by any other ANSP in central EU airspace. Never designed for high-density airspace, mostly neither meeting DLS-IR integrity nor latency requirements (ACAS with only 2.4 Kbits/Sec), the natural phase out of FANS 1/A legacy aircraft has also been accelerated due to fleet modernisations following the COVID-19 pandemic.
Generating less than 20% of the Data Link traffic, FANS 1/A contributed unfortunately to more than 80% of the issues, often not resolvable due to major FMS design flaws like missing DM99 or the proceed to … via … UL79, missing the essential via part. Technical mitigations at MUAC became increasingly complicated, lacking effectiveness, such as the implementation of the Maximum Up Link timer 300 Sec., which failed after more than 3 year lead in preparation, as 50% of the aircraft still do not, and probably will never support this important functionality, more than 2 decades after introduction.
Also in the cockpit FANS crews had increasing problems, reporting a too high succession of ULs, 6 ULs in 2 Min. (technical and operational messages), being too much in such a slow system, and contributing to loosing situational awareness.
Generating growing ATN compatibility issues, FANS 1/A was never ATCO’s first Data link choice. Not capable of supporting the main DL incentive, to increase capacity in high traffic loads, justification for continuing FANS 1/A support became difficult. After 8 years of excluding bad performing ATN avionics through a laborious Log On Listing process (150% Provider Abort rate in 250 CPDLC hours in 4 month), we can no longer justify to continue to support even worse performing FANS 1/A aircraft.
We consider that as a whole MUAC will benefit more from focussing its efforts on ATN and the next generation of CPDLC, ramping up for base line ADS-C 2 trajectory downlink operations. Our objective remains to enhance Data Link performance at MUAC, especially when higher traffic loads will demand performant and reliable CPDLC operations, for the benefit of ATCOs and pilots alike.