- What is ADS-B?
Automatic Dependent Surveillance Broadcast (ADS-B) is part of a comprehensive transformation of air traffic control (ATC) practices that leverages emerging GPS, satellite and computer processing capabilities to gradually phase out the reliance on radar that has been an aviation cornerstone for decades. ADS-B compliance requires each pilot to automatically self-report their GPS position, using networking technology to make this information available to controllers and other pilots. The acronym ADS-B is therefore based on this Automatic reporting, Dependency on GPS and ADS-B Out transmitters, improved Surveillance capability created for ATC and Broadcasted positional data.
Each ADS-B system includes two essential avionics components. The satellite navigation source (GPS) and the transmitter (transponder) that communicates the essential aircraft information in frequent intervals to a network of ground stations. This transmitted data includes the position as well as the speed, heading, altitude and call sign. Emergency codes can also be activated and broadcast using ADS-B.Although the term NextGen is sometimes used interchangeably with ADS-B, the Next Generation Transportation System is actually an all-encompassing air transportation modernization effort, including ADS-B as well as other innovations like Performance Based Navigation (PBN) and System Wide Information Management (SWIM), which will continue to roll out over the next decade and beyond.
- ADS-B Benefits
The precise positional information imparted by ADS-B compliance leads to greater efficiency and improvement in many categories, including optimized aircraft spacing, more direct routing and better situational awareness for air traffic controllers and pilots.
The enhanced level of shared data allows pilots to more accurately assess the position of other aircraft and receive real-time warnings or redirection. This creates a significantly improved safety profile with callouts no longer subject to latency constraints and error levels minimized. Unlike radar, ADS-B can also monitor air traffic at very low altitudes or on the ground, so inadvertent runway incursions become appreciably less likely.
In addition to real-time weather reporting, ADS-B In also provides other supplementary information to pilots, such as runway closures, flight restrictions and terrain maps for low visibility areas, all of which further augment safety and efficiency.
Ground stations are cheaper and easier to place than radar deployments, so the amount of coverage provided can be easily expanded. The technology shift from radar to GPS also provides inherent benefits in navigation and fuel efficiency, since flying over ground-based radar stations to support ATC check points will no longer be necessary and more direct routing can be implemented.
- ADS-B Compliance
ADS-B capability has been mandated by the FAA for aircraft flying within controlled airspace over the continental United States and select class E airspace over the Gulf of Mexico. Controlled airspace is defined as class A, B and C airspace or class E airspace above 10,000 feet. Class A airspace is characterized primarily by altitude, while class B, C and E airspace zones are further defined by airport proximity and location.
ADS-B compliance is required by January 1, 2020, unless an ATC deviation has been approved in advance. In addition to airliners, helicopters, turboprops and private jets must also be equipped with ADS-B transponders. The FAA has provided financial assistance in the form of rebates to offset some of the conversion cost burden on individual operators.
Complete details of the FAA’s ADS-B compliance rules can be found in released Code of Federal Regulations (CFR) publications. ADS-B regulation 14 CFR § 91.225 provides specifics on the impacted airspace and regulation 14 CFR § 91.227 defines the performance standards for the ADS-B transponder and positioning device (GPS).
International ADS-B compliance regulations are rolling out at a complementary pace. Most Asian nations with significant air traffic already require 1090ES (Extended Squitter), while Europe and Canada are also mandating compliance, although at a slightly less aggressive pace.
- Difference Between ADS-B In and ADS-B Out
ADS-B technology includes two distinct communication paths. ADS-B Out refers to the transmission of GPS data from the aircraft to ground-based ATC stations. ADS-B In is an optional deployment of inbound communication technology that furnishes pilots with weather, traffic and other valuable information. Only ADS-B Out capability is mandated by FAA regulations.
The ADS-B Out equipment is what the aircraft uses to continuously transmit precise position information and other flight data. This unidirectional dissemination is required for ADS-B compliance with data broadcasted once per second. Either a 1090 MHz extended squitter (ES) or a dedicated 978 MHz universal access transceiver (UAT) can be installed to suit this application, along with a WAAS enabled GPS device.
All aircraft flying in class A airspace are required to operate on the 1090ES MHz frequency, making this the logical choice for commercial airliners, and all ADS-B Out equipment must be permanently (panel) installed.
As the name suggests, ADS-B In technology allows the pilot to receive subscription-free information including air traffic and weather from ground stations or other pilots. ADS-In capability is optional and therefore not included in the ADS-B compliance regulations published by the FAA.
The ADS-B In receiver can also enable the pilot to view the ADS-B Out information of other aircraft, using a computer screen or portable tablet. Although ADS-B In is not mandated, the benefits garnered from this option can greatly enhance situational awareness and safety levels. Portable ADS-B In only devices are available, along with comprehensive ADS-B In/Out products that integrate both communication modes.
- ADS-B Testing Requirements
Without adequate testing, the safety and efficiency benefits of ADS-B cannot be fully realized. The FAA’s public ADS-B PAPR (Performance Report) tool is used to verify ADS-B compliance of an airborne deployment simply by providing basic aircraft information online and requesting the test.
The FAA report details any specific areas that failed to meet performance requirements and any incorrect avionics settings that are detected. Some of the more common issues observed include missing barometric pressure altitude, flight ID issues and position “jumping” errors.
Before this airborne testing is performed, it is a recommended practice to utilize an ADS-B test set on the ground to ensure a passing result will be obtained during the official certification testing. This includes testing the transponder and receiver separately, then again at the system level to verify compatibility. ADS-B test equipment is versatile enough to suit all levels of manufacturing and deployment is an invaluable element of this ground testing.
For testing at the R&D, factory test, or return-to-service level, ADS-B test equipment with flexible emulation capabilities can facilitate robust testing of avionics components prior to installation. The ATC-5000NG, for commercial applications, and the IFF-45TS, for military applications, either a ground transponder or an airborne interrogator, making this powerful platform an industry-wide standard for avionics OEMs.
- ADS-B Test Equipment
Transponder testing for extender squitter and UAT equipment types is an essential element of ADS-B compliance testing. Comprehensive test coverage includes sensitivity, frequency and power as well as transponder performance in the simulated airborne environment.
The IFR6000 flight line test set is the industry standard for testing installed systems and can provide confidence that the transponder, GPS and antennas are functioning as intended. The exceptional user interface enables most test processes to be performed without leaving the main user screens.
The GPS-1000 portable satellite simulator is an easy-to-use test device that can create 3D WAAS GPS simulations to support ADS-B testing. The GPS-1000 allows the user to simulate a position in lieu of using unreliable repeaters or moving the aircraft outside or to a surveyed location. In addition to providing a GPS source, the GPSG-1000 can be used to test the aircraft’s GPS receiver and to support testing of any other airborne system that requires a GPS input. The GPS-1000 features upgradable software and unlimited simulated navigation plan storage.
Although the IFR6000 provides for an easy ADS-B test to AC 20-165 requirements, when combined with the ADS-B INTEGRITY Test App, the user can now perform cross checks to assure the installed transponder is properly configured. Improper configuration is the cause of most non-performing equipment (NPI) issues identified by the FAA. By including the GPSG-1000 as part of the test, a dynamic not found in any other test solution is added. The GPSG-1000 will allow the user to ‘test in place’, meaning not having to move the aircraft outside, to a surveyed location, or rely on repeaters that can be problematic or cause interference with nearby aircraft. The GPSG-1000, with the ADS-B INTEGRITY Test App, can simulate a flight path and provide a full performance report of AC 20-165B requirements, including latency analysis and positional error, which otherwise can only be accomplished by flying the aircraft.
Using Antenna Couplers will enhance safety by shielding RF Transmissions, meaning that your aircraft will not be visible on others’ radars. VIAVI offer various Antenna Coupler options – F-16 IFF Antenna Coupler Kit, UC-584 Series Transponder Antenna Coupler, and the TC-201A TCAS/Transponder Directional Antenna Coupler.
ADS-B Takes Off
After a decade of discussion, development and refinement, ADS-B compliance is no longer just a convenient integration of modern technology to improve air traffic safety and throughput. It has become the mandated ATC communication mode for commercial flights in the U.S and ultimately worldwide. Radar technology established an exceptional track record for safety and reliability over the past century, yet the preeminence of satellite GPS and modern networking architecture can no longer be denied.
Aviation industry growing pains have underscored a remarkable opportunity for safer, more efficient air travel through ADS-B Out regulation and an information bonanza for pilots through this new technology. Throughout this transition, industry leading ADS-B test equipment will play a pivotal role in the overall success of ADS-B from the engineering lab to the skies.