For starters, if you are considering using uncertified ADS-B Out equipment, check your airworthiness certificate. You can install uncertified ADS-B Out systems only on amateur-built aircraft and light-sport aircraft with an experimental airworthiness certificate, as well as on special light-sport aircraft (with some restrictions on the installation end). Any type-certificated aircraft must use FAA-approved ADS-B Out equipment and obtain installation certification. Keep in mind that even if you are able to use an uncertified ADS-B Out system, it must still meet the performance requirements of the FAA Technical Standard Order for 1090 MHz equipment (TSO-C166b), or for Universal Access Transceiver (UAT) 978 MHz equipment (TSO-C154c).
This is important because, unless specifically authorized by ATC, uncertified ADS-B transmitters that do not meet the performance requirements of an ADS-B Out TSO are not permitted to operate in airspace requiring ADS-B Out after January 1, 2020.
Air Traffic Control (ATC) would not use the data from transmitters that do not meet most of the performance requirements listed in the regulations for ADS-B Out performance (Title 14 Code of Federal Regulations (14 CFR) section 91.227). This means ATC cannot provide flight-following services or separation services to these aircraft.
To qualify non-TSO equipment as compliant for operations in ADS-B airspace, the avionics manufacturer must provide a statement of compliance that indicates the equipment — when installed in accordance with the installation instructions — complies with all requirements of 14 CFR section 91.227, and with the performance requirements of the appropriate TSO. Manufacturers of uncertified ADS-B Out equipment are expected to perform the appropriate engineering efforts to ensure their systems meet the required specifications. They should also be able to provide product support to include design changes, equipment modifications (or instructions for performing them), and revisions to the installation, operating, and maintenance instructions.
Along with a statement of compliance, owners equipping with non-TSO systems should also obtain installation instructions from the applicable avionics manufacturer. These manufacturers should consider the guidance in AC 20-165, Airworthiness Approval of Automatic Dependent Surveillance - Broadcast OUT Systems when creating installation instructions.
For special light-sport aircraft (SLSA) owners, the installation of any ADS-B Out equipment (certified or non-certified) must be performed in accordance with an applicable consensus standard and authorized by the aircraft’s manufacturer. This installation authorization has presented a challenge for some LSA owners whose aircraft manufacturer either went out of business or decided not to support and approve an ADS-B Out installation process.