Thailand's Aerothai has launched initiatives that will mean major upgrades in all facets of its air traffic management (ATM) system—including the first steps toward a nationwide satellite-based navigation network.

The ATM provider is one of the many in Southeast Asia that has automatic dependent surveillance-broadcast (ADS-B) projects and other modernization efforts underway. Thailand is particularly significant from an ATM perspective because Bangkok is one of Asia's most important air travel gateways. Suvarnabhumi Airport is among the world's top 10 for international passenger movements, and the fourth-busiest in Asia under this measure.

Unlike some nations adopting ADS-B, Thailand already has extensive radar surveillance, so ADS-B will supplement and improve the existing en route and terminal coverage rather than filling in vast gaps. Its other major ATM projects involve replacement of its backbone ATM operating systems, an ongoing effort to implement performance-based navigation procedures, and further ahead, the expansion of wide-area multilateration networks. The Thai organization also has a lead role in several key regional initiatives.

Aerothai currently has a single ADS-B ground station, located on a VHF tower at its Bangkok headquarters. It has contracted with Saab Sensis for another four ADS-B stations to be located elsewhere in the country.

Radar coverage is already provided by six secondary surveillance radars (SSRs), and another six will be installed at additional locations by year-end. This will ensure complete coverage across the Bangkok Flight Information Region (FIR).

The existing ADS-B station in Bangkok is primarily being used on a trial basis to assess the technology and monitor aircraft equipage levels, says Choosit Kuptaviwat, senior director of Aerothai's engineering bureau. With a range of 200 nm, this station can cover the terminal airspace for the two major airports serving Bangkok.

ADS-B signals are being detected in about 70% of airline traffic. The Bangkok station uses the DO 260/260A standard, but it will be upgraded to be compliant with the more advanced DO-260B standard when the four new stations are installed by year-end.

The five stations will initially be used for additional test and validation with a view to gaining certification from Thai regulator DCA, says Kuptaviwat. Aerothai intends to use SSR to verify ADS-B.

Kuptaviwat stresses that Aerothai's aim is to “go step-by-step, and not jump into ADS-B right away.” The air navigation service provider (ANSP) is “in no hurry” to bring ADS-B to operational use, as it has full coverage thanks to its radar network.

While there are no plans to replace any SSR sites, certifying ADS-B will give Aerothai this option in the future, Kuptaviwat says. ADS-B ground stations are much cheaper to procure than new radars.

The upgrade of the ATM operating systems will allow ADS-B and radar data to be fused, meaning an increase in positional accuracy on controllers' displays.

Aerothai officials say the improved tracking enabled by ADS-B will increase the effectiveness of controller-decision support tools such as an arrival and departure manager, boosting both safety and efficiency. The network will also provide an additional surveillance source in case of radar outage.

The ADS-B program is initially aimed at enhancing en route operations, but Aerothai is considering using it to supplement radar in the approach control environment. Some extra ground stations would probably be needed, but these could be installed much more easily than radars. The likelihood of this step would depend on future operational requirements, stresses Kuptaviwat.

In addition to ADS-B, Aerothai intends to procure wide-area multilateration (WAM) systems to improve approach- and ground-movement surveillance. There is already a Saab Sensis multilateration system at Suvarnabhumi, and the organization wants to install them at the busy Phuket and Chiang Mai airports.

Many of the technological and procedural improvements planned by Aerothai rely on the upgrade of its primary ATM automation systems. It has selected Thales equipment to replace the operating system at its main area control center in Bangkok, as well as at its six approach control facilities and many of its airport towers.

This initiative is called the Thailand Modernization CNS/ATM System Project (TMCS). It will give controllers new capabilities for handling air traffic, and the system will be able to process data from multiple sources such as WAM and ADS-B. TMCS will significantly improve many aspects of Aerothai's operation, including airspace management, flow and capacity control, and the provision of air traffic control. Facilities at the Bangkok headquarters complex have been renovated and extended to accommodate the new equipment for the area control center.

The prime contractor for TMCS is Thailand's Samart Corp., which has diverse business interests, including operating the Cambodian ATM system under contract.

Thales also has a major role in the TMCS team, and will provide a system based on its TopSky range of products. In addition, Thales will supply an arrival/departure manager and an ATM simulation system.

Installation will begin in parallel at the Bangkok area control center and the Bangkok approach control, followed by the approach facilities covering airports at Chiang Mai, Hat Yai, Phuket, Phitsanulok and Hua Hin and at towers at more remote provincial airports. The project is due for completion by 2017.

One of the major benefits for Aerothai is that it will have a fully integrated ATM system for the first time, Kuptaviwat says. Currently it has automation systems at various facilities supplied by different manufacturers, including Thales and Selex. This means it cannot take advantage of full system-wide automation.

Aerothai is looking to improve its cooperation with the Royal Thai Air Force regarding airspace use. Under the TMCS project, a working position compatible with the new ATM systems will be installed at a military base to enhance civil/military coordination.

The new flow control capabilities introduced with TMCS will also complement a regional flight management program administered by Aerothai. Known as the Bay of Bengal Cooperative Air Traffic Flow Management System (Bobcat), this coordinates westbound flights from South Asian cities to Europe to prevent bottlenecks as they enter Afghanistan's airspace.

Bobcat uses a software system created and hosted by Aerothai, but also involves neighboring air navigation service providers. Airlines request to use the routes covered by Bobcat, and based on these requests flights are assigned time slots and altitude levels to enter congested airspace. Most major carriers serving the region use Bobcat, with flights originating from hub cities such as Bangkok, Singapore, New Delhi, Kuala Lumpur, Hong Kong and Hanoi.

The Bobcat system is an example of how Aerothai has an important regional role in ATM. It is active in many ICAO working groups, task forces and panels, and coordinates with other Asia-Pacific ANSPs.

ADS-B is helping Aerothai in another of its regional responsibilities. The ANSP has been designated as the regional monitoring agency for Asia, assisting the International Civil Aviation Organization with the safety assessment program for reduced vertical separation minima (RVSM) and other monitoring activity. RVSM allows aircraft to use more flight levels, although airlines must prove that their aircraft instruments are accurate enough to maintain the correct levels.

Aerothai is using the Bangkok ADS-B ground station to monitor the height-keeping performance of aircraft as they pass through its coverage area. This is much more cost-effective than deploying the dedicated height-monitoring systems that would otherwise be required. Some other ANSPs that have installed ADS-B—such as Airservices Australia—are also using the technology for RVSM compliance monitoring.