May 4, 2018
ADS-B : what does it do for you?
Several years ago, the Federal Aviation Administration (FAA) recognized that the US air transportation system and the tools it uses needed a significant review and upgrade in order to keep pace with the growing air traffic density and the demands of the industry and the public in general. This realization lead to what we know now as NextGen. I recall my attendance at an FAA meeting more than 20 years ago reviewing the early progress of NextGen and my amazement at the magnitude of the project and its ambitious objectives. According to the FAA website, NextGen is the modernization of the US air transportation system. Its overall goal is to increase the safety, capacity, predictability, and resiliency of American aviation. This overhaul brings together dozens of innovative technologies, capabilities, and procedures that will improve how the US public flies from departure to arrival. While the deployment of NextGen is still in its early years relatively speaking, the program has already achieved tremendous improvements across the US. This link presents a short video on the initiative and some of its achievements to date: https://www.faa.gov/nextgen/what_is_nextgen/ The FAA recognized very early on that ADS-B is one of these innovative technologies and it constitutes a critical cornerstone of NextGen. The FAA also recognized that as much as Automatic Dependant Surveillance – Broadcast (ADS-B) is necessary to the success of NextGen, ADS-B would not, on its own, greatly increase or decrease the overall safety of their air transportation system. The U.S. have ground-based ADS-B systems across the country. No such thing is planned in Canada.
ADS-B Out offers some very significant benefits to the users it was originally intended for and it is rapidly expanding around the world. The USA have mandated ADS-B to be effective in 2020 in its airspace. Canada does not yet have an ADS-B mandate and Transport Canada Civil Aviation (TCCA) does not consider mandating the deployment of this technology, as far as COPA understands at the time of this writing. Conversely, Nav Canada has made significant progress in planning the deployment of this technology in Canadian airspace. It serves Nav Canada both from a financial aspect on radar reduction and elimination in some parts of the country, to being able to provide better service to those with the (still expensive) equipment.
ADS-B is a space-based (satellite) Surveillance system that will track all suitably equipped aircraft anywhere, in real time, globally, without the need for radar stations. ADS-B is a surveillance system that offers very high accuracy and real-time knowledge of these aircraft in flight, thus enabling highly precise monitoring of the skies and optimal aircraft separation and routing for improved efficiency while maintaining flight safety for high altitude, high speed, long-range flights, more precisely heavy transport aircraft operators and major carriers. This level of accuracy is Dependant on the on-board certified WAAS-GNSS sensor. ADS-B is a Broadcast system. The fundamental ADS-B mandates around the world, current or future, are for ADS-B Out. In other words, a compliant aircraft equipped with ADS-B Out will broadcast its flight parameters; it will not receive any information of any kind. The flight crew will be in exactly the same situation as one operating in today’s transponder environment: the aircraft broadcasts its position and the crew does not receive anything back. The significant difference is that today’s transponder (typically Mode C) replies to radar interrogations while the ADS-B Out transponder broadcasts twice every second Automatically, without interrogation or input of any kind. ADS-B Out operates on frequency 1090 MHz Extended Squitter (1090ES) via the Aireon Iridium Next satellite constellation. There is no ground station except those required to collect return signals from the satellites and route these to the relevant Air Traffic Control Units. Figure 1 illustrates the concept of Aireon Iridium Next satellite constellation and the ASD-B data link communication channels.
Figure 1 – ADS-B within the Aireon Iridium Next Satellite Constellation
In similar fashion to a Mode C transponder today, the ADS-B Out transponder must be aircraft mounted and certified. This remains an expensive proposition for GA at this time. The industry has been working seriously to bring out newer and better models and prices are gradually coming down. As of this writing, the costs for a GA aircraft installation still hovers around $5000US to $6000US installed. The debate about Diversity antenna (top and/or bottom antenna) is still going strong and these costs will increase if the installation requires both top and bottom antennae.
From the pilot’s perspective, ADS-B Out is a transmit only system, the aircraft, hence the pilot, does not receive anything. ADS-B In is the counterpart to ADS-B Out in this technology deployment. ADS-B In receives the transmissions from ADS-B Out equipped aircraft within radio range. ADS-B In is not part of any mandate but it is certainly a good idea if your aircraft is equipped ADS-B Out as this feature completes the circle of traffic information for all suitably equipped aircraft airborne in one’s given sector of airspace. ADS-B In is Line-Of-Sight to ADS-B Out sources and requires that a screen be available in the cockpit to display the traffic information received by ADS-B In. Since ADS-B In equipment is not mandated, it does not require certification and can be portable. This can be as simple as having a Stratus 2 and an iPad with ForeFlight for example. The FlightBox by Open Flight Solutions and the tiny, very low cost Scout (www.flywithscout.com) are other great examples. Garmin also offers similar products. The industry offers several variations on that theme and mostly at very attractive prices. Figure 1 also illustrates this aircraft-to-aircraft data link.
Benefits to GA of equipping for ADS-B
The ADS-B technology as described above represents what Nav Canada plans to deploy in Canadian Airspace. The deployment of this technology, as currently proposed, offers very limited benefits to GA and that at a relatively steep cost for installation, maintenance, and regular recertification. But one cannot really dispute the safety value of better awareness of aircraft traffic around us. In that perspective, one must also recognize the difference in airborne traffic density around Pearson International for instance, and similar locations, where Mode C is currently (and will remain) mandatory, and flying just about anywhere further than 200 km north of the US/Canada border or 49th parallel. Nav Canada states that an ADS-B mandate will not negate the need for a Mode C transponder in airspace where it is currently required. Nav Canada also states the current Mode C areas will remain effective after ADS-B deployment. For now, COPA cannot identify any further benefits to the Canadian GA owner and/or pilot from the Nav Canada planned ADS-B deployment than the one described in this article: awareness of air traffic in your area, if you are equipped ADS-B Out and ADS-B In.
ADS-B in the US
COPA does recognize that the ADS-B concept is valuable and could offer numerous other benefits to GA if the proposed deployment was reconsidered in that light. The FAA approach to deploying ADS-B recognizes the necessity of the technology in their NextGen program and the limited contribution of ADS-B to the important element of safety in GA. In-cockpit information such as traffic awareness, weather, and other flight information features all constitute the vital information any pilot should have in flight. Consequently, ADS-B in the US supports two different datalinks: the 1090ES system as described here is mandated above 18,000ft, and using ground-based 978UAT below 18,000ft. 978 UAT stands for 978 Mhz Universal Access Transceiver, and it must be certified and installed. The FAA is deploying 978UAT to provide GA with the in-cockpit information identified here. The US system provides both Traffic Information Services – Broadcast (TIS-B) and Flight Information Services – Broadcast (FIS-B).
TIS-B provides a custom traffic report from ground stations to aircraft equipped with ADS-B Out (on 1090ES). This custom traffic report covers a volume 30NM in diameter and 3000ft high, centered on the intended recipient aircraft. Aircraft with ADS-B In can also see this custom report if they are in that area, as well as other aircraft if these other aircraft are equipped with ADS-B Out. TIS-B broadcasts from ground stations only in response to ADS-B Out aircraft. As most GA aircraft will not have ADS-B Out, the full extent of this particular benefit will be limited. Single-band ADS-B In receives only 1090ES air-to-air, dual band ADS-B In receives both 978 and 1090. Figure 2 shows your scenario if you are equipped with ADS-B In only such as a Stratus 2 (which is dual band) for instance and no ground station. You receive only air-to-air traffic from aircraft equipped with ADS-B Out (1090ES).
Figure 2 – Basic configuration: your aircraft with a Stratus 2 only
Figure 3 illustrates your same scenario, but you are now close to an aircraft equipped with ADS-B Out (1090ES). Through your Stratus 2, you will receive the traffic report sent out to that ADS-B Out aircraft, but take note that this report is centered on that aircraft, so it does not provide you full accuracy of the traffic around you.
Figure 3 – Basic configuration, your aircraft with Stratus 2 only, but close to an ADS-B Out aircraft
Figure 4 illustrates your same aircraft again but now also equipped with ADS-B Out (1090ES). You now receive a custom traffic report tailored to you and centered on your aircraft. This report is highly accurate and complete, in real time.
Figure 4 – Same basic configuration with Stratus 2 plus ADS-B Out
In the US system, ground stations broadcast TIS-B. This allows the Air Traffic Control Units to blend in the traffic information from Mode C transponder equipped aircraft and to provide the pilot with a complete picture of all the air traffic in that pilot’s immediate environment. The quality of traffic information provided within the US system configuration is far more complete and accurate than will ever be provided in Canada with the current ADS-B proposal. The US system provides its GA owners, pilots, and operators a real safety benefit, measurable and quantifiable.
FIS-B operates in constant broadcast mode and provides text weather (METARs, TAFs, PIREPs), graphical weather (radar), airspace status (TFRs, NOTAMs). The ADS-B deployment planned by Nav Canada does not include any provision for FIS-B as ADS-B 1090ES cannot accommodate this level of information. The FAA has clearly recognized the value of accurate and complete air traffic information in their national airspace and the impact this technology deployment imposes on their GA community. The FAA has consequently taken steps to address these issues in a positive and constructive manner. The FAA does not mandate ADS-B 1090ES below 18,000ft but rather relies on 978UAT and encourages GA owners and operators to equip with a suitable solution that achieves the objective. Canadian GA pilots equipped ADS-B In dual-band can take advantage of the US FIS-B datalink when flying within range of US stations but the information received is limited to US airspace data.
For GA in Canada, the Aireon Iridium Next constellation ADS-B solution does offer a relative safety perspective but nothing more for now. This solution primarily focuses on airlines and heavy carriers who will unquestionably gain from it. GA owners and pilots who feel more secure and comfortable with ADS-B in their aircraft can equip at their discretion as some have done so far. Nonetheless, we feel that an indiscriminate mandatory ADS-B mandate for all aircraft in all of Canadian Airspace is not an appropriate nor a necessary technological deployment, nor an obvious solution to a problem yet to be completely defined and agreed. See and avoid is an important consideration, but so is weather and other elements of the Flight Information Servive (FIS-B) and these are totally ignored in this technology deployment. We do believe Nav Canada needs to introduce more valuable features into this equation to make ADS-B more palatable to GA and thus enhance its acceptance in that milieu.