An entire ADS-B system consists of a “datalink” (transmitting and receiving on 1090MHz or 978MHz), connected to a high-integrity GNSS (GPS) receiver. The reliability and performance assurance levels for the GNSS are extremely high; in most applications, the function must be filled by a certified SBAS (WAAS) receiver or a non-augmented GPS that essentially meets the specifications of a WAAS receiver. An SBAS receiver is typically referred to by its TSO (or ETSO) certification designation:

• an SBAS (or WAAS) receiver is designated “TSO-C145” for a receiver or “TSOC146” for a WAAS receiver imbedded in an FMS or Navigation Management System.
• an “ordinary” aircraft-quality GPS is referred to as a “TSO-C129” GPS.
  

Uncertified GPS receivers, such as hand-held devices or Class 2 or Class 3 Electronic Flight Bags, do not meet integrity levels required for aviation applications and often provide dangerously inaccurate information to the pilot. Uncertified ADS-B Out systems pose a similar hazard to safe flight operation.



As with GPS, the requirements for ADS-B certified datalinks also vary between jurisdictions. The most significant variation as mentioned previously, is the FAA’s optional 978 MHz data link. This option, while only available in the 50 US states (and Puerto Rico) offers so many advantages that we recommend using it for all US based aircraft. For aircraft that may need to operate in US and non-US airspace we would recommend addition of a certified ADS-B transponder so that these aircraft can take advantage of the 978 link while in the US and still be compliant when they “Cross the border”.

The advantages of 978 datalink in the 50 US states is that is offers enhanced capabilities in addition to radar coverage.

	Free weather. If your data radio incorporates a receiver (optional with the FreeFlight Systems product), you can receive free data services, including free graphical weather, which can be displayed on an MFD or a class II Electronic Flight Bag (EFB). The FAA does not provide this service on the 1090 MHz “Mode S” datalink.
	Figure 2 Current ADS-B Deployment in the Gulf
	Free traffic. With the same radio you can receive ADS-B traffic service that can be displayed on an MFD or a class III EFB. The FAA does provide this service on the 1090 MHz “Mode S” datalink but only the more expensive transponders can receive the data.
	Figure 4 TIS-B Depiction (Depiction may vary on different displays)
	Beacons. FreeFlight Systems offers a battery powered 978 MHz beacon that can be used to transmit ground locations (hazards, safe areas or “come here”) to a 978 MHz ADS-B equipped aircraft.
	Fleet Tracking. Also utilizing a FreeFlight Systems beacon, dispatch can track fleets out to 40 miles depending on the altitude of the aircraft. In addition, the 978 MHz service provider may also allow for wider fleet tracking coverage although it is still undetermined whether the service will be free. Sat Com can still be used as a back-up system when a helicopter is out of ADS-B coverage. This option will decrease current Sat Com usage for tracking and therefore save on recurring costs.

Imagies and some ADS-B Information courtesy of the Federal Aviation Administration.
For more information, visit FAA Surveillance and Broadcast Services (ADS-B).