Hello,
Garmin is always happy to share information we have about the requirements of ADS-B Out compliance, and as others have pointed out, we have done so many times in the past. Here is one example.
2013 ADS-B Out Thread
Those that have equipped their aircraft for IFR operation with certified GPS/GNS/GTN WAAS GPS navigators have a relatively simple path to ADS-B Out compliance in 2020 (add an appropriate 1090ES transponder like the GTX23ES), and most are already fully compliant.
All of us equipping for and flying VFR, the focus of this thread, have significantly different challenges and may be frustrated that our excellent non-certified WAAS GPS receivers that we use to navigate VFR anywhere in the world are not considered sufficient to provide the position source data for ADS-B Out. These units are so accurate that we even render the center-line of runways in synthetic vision as we takeoff and land. The positional accuracy of these units can be as high as 3 meters 95% of the time.
These WAAS GPS receivers employ features such as fault detection and exclusion (FDE) to identify and exclude data received from poorly performing satellites to safeguard against a corrupted position solution, but admittedly, there are fewer safeguards and notifications of degraded accuracy than available in say, a GTN 650 WAAS GPS receiver used to fly an IFR LPV approach to minimums which has very strict and well defined integrity monitoring requirements.
Many in industry have pointed out to the regulatory authority that VFR only aircraft are only operating in see-and-avoid conditions and ATC does not provide traffic separation between IFR and VFR aircraft in these conditions.
The following is from the Airman's Information Manual (AIM), Chapter 4, Section 4:
When weather conditions permit, during the time an IFR flight is operating, it is the direct responsibility of the pilot to avoid other aircraft since
VFR flights may be operating in the same area without the knowledge of ATC. Traffic clearances provide standard separation only between IFR
flights.
As such, perhaps there is little reason, if any, for the high hardware and software design assurance requirements of FAR 91.227 for VFR equipage and operation.
One potential exception is VFR operation in Class B airspace. As specified in the AIM, an ATC clearance is required for all aircraft to operate in this area, and all aircraft that are so cleared receive separation services within the airspace. The cloud clearance requirement for VFR operations is “clear of clouds.” Since relatively few of us operate our VFR only aircraft in/out of Class B airspace, we would probably accept some additional operational restrictions in Class B if required to allow us to continue to use our non-certified position sources for ADS-B Out.
Don't forget that we are continuously squittering SDA=0 and notifying ATC that we are using a lower design assurance position source (but not necessarily lower accuracy), so ATC could take this into account when providing Class B separation services if they chose to.
Safety is certainly served by having all VFR aircraft providing ADS-B Out, and the path to achieving this is affordability. Many of us hope for a rule change that would allow us to continue to use our presently non-compliant non-certified position source in combination with our certified 1090ES transponder past January 1, 2020. In the absence of such a rule change, all of us will make the best of the ever increasing number of equipage choices for compliance.
Thanks,
Steve
