Back in January 2017 Airspace4All (then under the name of FASVIG) published a report entitled
Non-Certified GPS ADS-B ‘Quick Win’ Actions

One of the recommendations therein was:

Approval of Non-Certified GPS as position source for Mode S ES ADS-B Out in CofA aircraft
The CAA should make a public statement clearly stating the circumstance in which it is permitted to use non-certified GPS as position source for Mode S ES ADS-B Out in CofA aircraft and in CAA Annex II Permit-to-Fly aircraft.

This followed on from an extensive trial undertaken by NATS in 2015 that found ADS-B data from aircraft with non-certified GPS was just as accurate as that from aircraft with certified GPS. You can read the NATS trial report here:

Europe Air Sports, PPL/IR Europe, AOPA, CAA, NATS and Eurocontrol have been working with EASA behind the scenes to turn our recommendations into reality.

Today (6th March 2019) there is news of an update to the EASA CS-STAN documentation that will permit the use of non-certified GPS as a position source for Mode S ES ADS-B transponders in EASA CofA aircraft.

This is great news! See below for details.


There is good news for owners of GA aircraft on the EASA register that have a transponder, which is capable of ADS-B (extended squitter) but have not had a suitable GNSS position source.

Within the next month, EASA will be releasing an update to CS-STAN Standard Changes and Standard Repairs.  If everything goes well, the update should include CS-SC005a, which will authorise aircraft maintenance engineers to connect GNSS position sources to an ADS-B capable transponder to enable ADS-B OUT.

Three configurations will be permissible under this standard change:

  • Configuration 1
    • certified transponder + certified GNSS
    • conforms to AMC 20-24 but with (E)TSO-C166b unit for ADS-B OUT
    • reports SIL = 3 and SDA = 2
  • Configuration 2
    • certified transponder + ADS-B OUT + TABS GNSS[1]
    • reports SIL = 1 and SDA = 1
  • Configuration 3
    • certified transponder + ADS-B OUT + uncertified GNSS
    • reports SIL = 0 and SDA = 0 (for airborne traffic awareness only)

This SC is not suitable for the release to service of the aircraft by the Pilot-owner, it must be performed by a licensed aircraft maintenance engineer.  However, the engineer does not have to apply for a Minor modification, which significantly reduces costs and saves time.

Please note that the CS-STAN address the airworthiness aspect (installation on the aircraft). The operation of this devices might be subject to limitations imposed by the Competent Authorities.

[1] See (E)TSO-C199 A1.2.6 for GNSS position source function requirements (for TABS class B devices)

Stay tuned, more details will come soon…