Unleashing the future potential of ADS-B technology

There’s a lot of interest and discussions today within the aerospace industry about ADS-B and the future potential applications that can derive from this technology. Can you explain what ADS-B is exactly?

ADS-B is a surveillance technology that enables large amounts of information about the equipped aircraft to be transmitted to air traffic controllers or to any system equipped to receive and decode this information broadcasted on the 1090 MHz frequency. This frequency is already used by current transponders on board aircraft to transmit a more limited range of parameters, but saying that ADS-B is a simple evolution of the existing Mode S transponders would be an understatement. It is a real breakthrough in the world of surveillance.

ADS-B stands for Automatic Dependent Surveillance - Broadcast.

• Automatic because it periodically transmits information with no pilot or operator involvement required (Mode S requires interrogation by ground secondary radar or aircraft’s TCAS).
• Dependent, because the position and velocity vectors are derived from the Global Positioning System (GPS) or other suitable Navigation Systems (Mode S do not transmit aircraft position).
• Surveillance, because it provides a method of determining 3 dimensional position and identification of aircraft, vehicles, or other assets (without using ground radars unlike what is required today).
• Broadcast, because it transmits the information available to anyone with the appropriate receiving equipment.

Those properties make ADS-B superior to the traditional combination ground radar/Mode S transponder. Information is richer, update rate is about 10 times faster (which is critical in congested airspaces) and positional information much more accurate. Also, from an ATM perspective, ADS-B ground stations are a fraction of the cost of a radar station, both from installation and maintenance perspective.  This allowed some countries with limited surveillance capability to suddenly get a full picture of their airspace at a much more reasonable cost.

ADS-B has become mandatory in many world regions. What is the current situation?

ADS-B started slowly (we were already offering solutions ten years ago) but, in recent years, ANSPs (Air Navigation Service Providers) around the world have realized the potential of this technology. There are two main reasons why a country or a region is mandating ADS-B:

• Air traffic in this region is getting so dense that traditional radar technology is reaching its limits: this is the case for United States, Europe and China for example where massive modernization programs such as NextGen and SESAR included pretty early ADS-B technology in their roadmaps.
• Complicated geography (mountains, deserts, vast bodies of water) and/or budget limits of this region did not allow installation of ground radar stations hence limiting the surveillance capability and forcing aircraft to fly under procedural separations, which is, in most cases, very inefficient. Australia for their central deserts areas, Canada for the Hudson Bay, a large part of East Asians countries, South Africa, Colombia and Mexico.

The main problem for airlines today is that many countries have chosen a very similar timeframe to mandate ADS-B, namely between 2020 and 2022, which is a short period to have to retrofit tens of thousands of aircraft. In addition, ADS-B translates into two different standards (DO-260 and DO-260B) and mandates can request one or the other, with occasional side effects on other items of equipment such as the GNSS source. This is causing a lot of confusion for some operators who don’t necessarily have the workforce and time to go into this kind of detail.
In addition, some regions of the world like United States are seeing a gridlock at many MRO (Maintenance and Repair and Operations) as airlines and operators are waiting the last minute to retrofit their fleet.

Can you explain a bit more in detail those two different ADS-B standards and how it applies to the different regions?

Today, there are indeed two standards: DO-260 (a.k.a version 0) and DO-260B (a.k.a version 2). You can forget about the DO-260A (version 1), it was an intermediate standard that was never published. And since you are probably already wondering, yes, there is a DO-260C that is being considered.

In general, DO-260 (version 0) is requested for the case of complicated geography aforementioned. It can be used when traffic is not overly dense and gives a much improved situational awareness to the air traffic controller, hence allowing more efficient routes and separations between aircraft.

DO-260B (version2) is the latest and greatest for ADS-B. This standard, compared to DO-260, adds information within the message broadcasted that gives the air traffic controller means to provide better services is extremely dense areas like over the US, Europe and China.
We also have countries that are anticipating the traffic growth by already mandating DO-260B like New Zealand, Mexico, South Africa, Saudi Arabia or the UAE. DO-260B is of course backward compatible with DO-260, and if you are DO-260 compliant, you won’t be in a DO-260B mandated area.

What can you tell us more about those two mandates in the US and Europe?

Those two mandates apply to all aircraft flying inside the EU or US airspace, not just the aircraft registered in the EU or US. So it pretty much impacts all the long range fleet in the World too.

The European mandate is applicable June 7th 2020 with very limited exemptions possible (the date has been recently confirmed at ADS-B SPI Workshop in Brussels on July 4th 2018). Aircraft will need to comply with DO-260B standard by this date but there is no requirement on the GNSS source.

The US mandate is applicable Jan 1st 2020 to all aircraft (from GA to Commercial aviation) and refers to the DO-260B standard. In addition to broadcast a DO-260B compliant message, GNSS receiver (GPS) will need to provide a position with the correct level of integrity (SIL) and accuracy (NACp). Without them, the aircraft will either need to request to be controlled through an airspace still having radar coverage (radar coverage will be maintained in all class B airports but removed in the vast majority of Class C ones) or, in the worst case, be denied to fly in the US airspace. From a probabilistic point of view, this situation is not likely to happen 89% of the time with a SA ON GPS receiver, 99% with a SA Aware GPS receiver and 99.9% of the time with an SBAS (Space Based Augmentation system, a.k.a WAAS over the US) capable GPS receiver.

There is a lot of confusion about this GNSS requirement and it is often understood as a mandate for a SBAS GNSS receiver along with DO-260B compliant transponders. This is not true. You can fly after 2020 with an SA ON GPS receiver, but the probability for your aircraft to be grounded because of the wrong GPS constellation configuration at a given date and time is one out of 10 which is of course not acceptable for any commercial operators. Hence the race to have the commercial fleet equipped with SBAS compliant MMR (Multi Mode Receiver which includes a GPS receiver).

What solutions is Thales offering operators today?

Thales and its sister company ACSS were the first to certify DO-260B compliant transponders (the NXT-800 family) on aircraft such as the B-737NG and the A320/A330. On regional aircraft, the younger brother of the NXT-800, the NXT-600, is available on ATR x2-600 and Bombardier Q400. We are also offering a range of retrofits based on the new NXT-800 transponder or the older XS-950 family that can be modified to be DO-260B compliant. Along with the transponders, the DO-260B mandates require a modified ATC control panel able to inform the flight crew of a possible ADS-B failure (independent from the transponder failure message).

Thales ATC control panel is certified on Airbus for this requirement. We are not offering an SBAS solution though for our existing MMR, but we do offer SBAS compliant standalone GPS receiver for ATR and Q400 aircraft. Depending on the platform, some wiring modifications are required that can lengthen the retrofit, but it is the case for all equipment manufacturers.

What is the future of ADS-B?

As already mentioned, ADS-B has an impact on transponders. This is what we are calling ADS-B OUT because the ADS-B message is broadcast outside the aircraft by the transponder. But now it is a given that the vast majority of the worldwide fleet is about to be equipped with ADS-B transponders, so authorities and equipment manufacturers (including Thales) are actively working on ADS-B IN. ADS-B IN is the capability for an aircraft to receive and decode ADS-B OUT information received from other aircraft. It is commonly integrated into the TCAS (Traffic Alert and Collision Avoidance System).

By having access to such improved situational information, we are looking at providing the flight crew with ways of optimizing the flight by reducing separations, flight time and fuel burn in ways that were impossible before. This is where the business case really makes sense for airlines (as ADS-B OUT alone is more justified for ATC). We are also working of applications to address some safety issues such as runway incursions by using ADS-B as a mean to display aircraft traffic on the airport directly on the pilot displays.