Japan's airspace, already among the most congested in the world, is facing new pressure as more flights are funneled into Tokyo airports. Airlines and aviation authorities are hoping that a far-reaching air traffic modernization effort can ease the bottleneck and allow additional service to the nation's capital without causing gridlock.

Traffic saturation at Tokyo's Narita International and Haneda airports has meant strict limits on new flights, which has been a bone of contention for overseas airlines in particular. But expansion at both facilities is enabling more slots for international service, as well as the rapid emergence of domestic low-cost airlines. Within five years, traffic at the two airports is expected to rise by 20%.

Accommodating more aircraft on the ground is only half the battle, though. “When we talk about airport development projects, people tend to focus on runways, aprons and passenger terminals, but one of the most significant challenges is increasing airspace capacity,” says Takeshi Imagome, who is director of the air traffic international affairs office for the Japan Civil Aviation Bureau (JCAB).

As Imagome notes, concentration of traffic at the two Tokyo airports “is one of the major issues for us. . . . To cater for the traffic increase we are forecasting, we need to do something” to improve traffic flows.

Solving the Tokyo problem has been one of the main drivers behind the Collaborative Actions for Renovation of Air Traffic Systems (Carats) program. Carats is similar in concept to the U.S. NextGen program and Sesar (Single European Sky ATM Research), featuring a long-term vision for introducing a range of new technologies and procedures. The plan extends to 2025, the same target date as NextGen. Airlines, other airspace users, research institutes and government agencies have all been involved in defining the plan.

Carats has other similarities to the U.S. and EU efforts. It is aimed at doubling capacity in congested airspace, reducing fuel consumption and emissions by 10% per flight, and halving accident numbers. The Japanese project is not just focused on Tokyo; it is also intended to increase safety and efficiency at other domestic airports, and provide greater flexibility for Japan's busy oceanic and overflight routes.

Airlines are supporting the Carats program and have been closely involved in planning, says Norio Tomine, director of route planning and flight operations at Japan Airlines (JAL). “We must have a more efficient ATM system to have the capability to [handle] more traffic,” he stresses. “If we face more congestion with the current system, there will have to be more delays or flow constraints, and we'd like to avoid that.”

Another reason for airlines to be involved in Carats is to ensure that industry concerns are considered. Whenever a new concept is discussed, airlines emphasize the need for a cost-benefit calculation, says Tomine. “To implement these measures, there will need to be avionics upgrades and pilot training that will cost the airlines a lot of money,” he notes. “So while the efficiencies provided by Carats are something we want to pursue, at the same time we have to look at the cost. We want to try to achieve minimum cost and maximum benefit.”

Airlines want to ensure that they have as much advance warning as possible for any new requirements. “If we have discussions [with JCAB], this will result in more reasonable program schedules,” says Tomine. “The lead time for implementing new measures will be something we can negotiate with them before they mandate what has to be done.”

Tomine stresses that international harmonization will be crucial. Coordinating closely with NextGen and Sesar will allow the same procedures and technologies to be used during international operations.

As with every major ATM modernization project, funding is a major issue, both for government and system users. It is very unlikely that the Japanese government will subsidize Carats equipage for airlines, says Tomine. So JAL is in favor of encouraging airlines to upgrade through a “best-equipped, best-served” approach, where they would gain prioritized access to preferred routes if they are equipped with appropriate technology.

However, Imagome cautions that this strategy could be complicated. It would need to be broadly accepted by the airline industry, and carriers have differing opinions on this issue. Those that are not as keen to invest in new avionics are naturally less impressed by the best-equipped, best-served concept.

JCAB could also face funding challenges. The Japanese government is spending huge amounts to restore areas devastated by the earthquake and tsunami in March, “so that means JCAB's budget will be severely affected,” says Imagome. Whether Carats can be developed according to plan is a big question. “We have to request our budget year-by-year, so we may have to modify the [Carats] road map year-by-year to reflect the [economic] situation,” says Imagome.

The government has asked for an overall cost of Carats, and JCAB is still working on that. A detailed estimate will be difficult, Imagome notes, because the plan could change owing to new requirements or emerging technology, particularly for projects that are still a decade away.

The Carats initiative began about five years ago, and a broad blueprint was completed last year by a study group. Seven major targets and their supporting technologies were defined. A draft of a more detailed plan has been completed, although it must be approved at the government level. This road map will be revised for every fiscal year, which begins in April.

A committee was formed last year to oversee Carats progress, with members from government and other stakeholders. It will meet twice a year, and technical working groups will meet more frequently. As well as system users, JCAB will have to cooperate with the military, local communities around airports and overseas ATM agencies.

Some significant modernization projects that will be important to Carats have already been completed, such as a redesign of the Tokyo airspace and the streamlining of high-altitude domestic flows using satellite-based area navigation (RNAV). But many more improvements are needed in technology and procedures.

Carats is intended to make better use of cockpit capabilities in the existing fleet, as well as advanced capabilities in new aircraft types. JAL's Tomine says that current avionics, particularly flight management systems (FMS), are more advanced than the air traffic control system. He believes that means current cockpit equipage should be sufficient for at least the first five years of the modernization program.

Trajectory-based operations (TBO) are one of the major elements of Carats. This means that instead of the current sector-by-sector approach to traffic control, the focus willbe on end-to-end flight paths. Aircraft will be required to cross certain points at precise times, taking advantage of their onboard FMS capabilities.

This will allow smoother traffic flows, with much less need for aircraft to be vectored off their flight paths owing to congestion. The ultimate goal is known as 4-D trajectories, with the fourth dimension representing time. Many countries are pursuing TBO as a vital element of their modernization efforts.

Japan's first step into TBO is a project called calculated fix departure time (CFDT), which is essentially time-based sequence management. About an hour away from arrival at an airport, an aircraft is given a precise time to cross a point where traffic flows merge.

So far, CFDT is being trialed only for Haneda approaches during busy periods. The intention is to expand it to Narita, and future phases will involve multiple merging and crossing points. In the long term, after 2025, the plan is for TBO to include real-time flight-path changes to avoid severe weather.

Japan is also pursuing continuous-descent operations (CDOs). These allow a steady predetermined approach to be flown from top-of-descent, rather than traditional stepped approaches. Because they are more efficient, CDOs reduce fuel consumption and emissions.

CDOs are currently being used at Osaka Kansai International Airport during night hours when traffic is less dense. JCAB plans to introduce them next at Hiroshima Airport, and then at other secondary facilities. CDOs will likely come to the Tokyo airports eventually, but this will be more complicated due to traffic saturation, says Imagome.

JAL's Tomine says some airlines have requested that JCAB introduce CDOs in Tokyo, but he agrees that this will be difficult. Not only is this airspace congested, it is also constrained to the west by metropolitan areas and military air bases.

Tomine also sees value in focusing on smaller airports first. They are important to airline domestic networks, but their airspace is less busy than the Tokyo's. “If it's easier to introduce [CDOs] at the smaller airports, then we could maybe get more benefit from earlier timing,” says Tomine. “This will also give JCAB experience with these kinds of procedures, and they will have more information about how it can be done at Haneda.”

Procedures categorized as performance-based navigation (PBN) will be important to Carats. These include the RNAV routes that have already been established between major domestic city pairs. In addition, JCAB is continuing to introduce airport arrival and departure routes enabled by RNAV and another form of PBN known as required navigation performance (RNP).

JCAB is in the early stages of introducing even more precise approaches known as RNP-authorization required (RNP-AR). These allow aircraft to fly curved approaches that are useful in mountainous terrain or in congested airspace.

So far, two RNP-AR approaches have been established at Noshiro Airport in northern Japan, and one at Haneda for night-time use.

However, Tomine notes that RNP-AR approaches are not a high priority for airlines. He says the procedures are of much more value for the government, as they can route traffic away from heavily populated areas for noise mitigation. Imagome says JCAB will have to talk to the airlines about how quickly RNP-AR will be introduced, because there are cost implications in equipping older aircraft.

Cost-benefit analysis has also caused Automatic Dependent Surveillance-Broadcast to slip down the priority list. ADS-B is a satellite-based system that many countries are using to augment radar coverage, or to bring surveillance to vast areas where radar is impractical or too expensive.

Japan already has an excellent radar network, says Imagome. “In Japan, what is the business case for ADS-B? Our domestic airspace has at least double coverage,” he says. “It's not that we're against ADS-B or anything, but we're not sure if it's justified from an investment and benefit perspective.” Tomine agrees that extensive radar coverage makes ADS-B for surveillance purposes much less attractive than in other countries.

Another surveillance technology known as wide-area multilateration (WAM) has been deployed in Japan. JCAB uses WAM to enable simultaneous parallel departures at Narita. Multilateration essentially relies on triangulating aircraft transponder signals to determine their positions, rather than GPS. An advantage of WAM is that it generally does not require new aircraft equipage. JCAB is considering the long-term possibility of using WAM for en-route surveillance.

Multilateration is also being used for ground surveillance programs that are included in Carats. Combined with radar data, multilateration will give controllers greater situational awareness of airport runway and taxiway movements. So far, it has been deployed at Haneda and Kansai airports.

Japan's Electronic Navigation Research Institute is examining ways to further optimize airport surface movements, says Imagome. One strategy involves calculating gate-pushback times in a more scientific manner, incorporating a range of factors such as average taxi speeds at specific airports.

Imagome says ground movement programs could actually yield more benefits than flight-phase improvements. “We're trying to save a few minutes in en-route, terminal and arrival-departure phases, and we have not been doing much about saving maybe 20 minutes of delay on the ground,” he asserts. “That doesn't make much sense.”

While airlines will have to make some avionics upgrades for Carats, JCAB is also improving its own infrastructure. The agency is beginning the procurement process for a new suite of ATC automation equipment, covering tower, terminal and en-route applications. This effort is still in the initial phases, and international companies such as Thales have expressed interest in bidding, says Imagome.

JCAB has launched important initiatives involving oceanic operations, recognizing the busy international traffic flows into and over Japan. User-preferred routes (UPRs), for example, allow airlines to generate their own routes before takeoff based on prevailing weather conditions.

UPRs have been introduced on flights between Japan and New Zealand, Australia and Hawaii, and on overflights from the U.S. to Hong Kong and Taipei. Trials have also begun on some routes between Japan and U.S. West Coast destinations.

Tomine says UPRs allow JAL to use up-to-date weather data to generate more efficient routes, with variations of up to 100 mi. and time savings of 5-10 min. per flight. As well as severe weather, expected areas of turbulence can also be avoided.

The next step is dynamic airborne rerouting procedures (DARP), which enable aircraft to change their routes while in flight. JAL is currently trialing DARP on one of its Japan-Hawaii flights.

In 2009, JAL and JCAB demonstrated these and many other advanced procedures—on the ground and in the air—during a Boeing 747-400 flight between Osaka and Honolulu. The demonstration was part of the Asia and South Pacific Initiative to Reduce Emissions (Aspire), which saw similar flights conducted by airlines and ATC agencies from other nations. JAL's Aspire flight resulted in savings of 10,663 lb. of fuel, and 15,247 kg (33,544 lb.) of emissions.

International cooperation is one of the key goals of Carats, from both the airline and government perspectives. To this end, JCAB has been heavily involved in regional and global ATM harmonization efforts.

The agency has regular meetings with the FAA aimed at synchronizing Carats with NextGen, and JCAB plans similar efforts with the European Commission regarding Sesar. On the regional level, Japan and several other Asian nations have agreed to form the Asia-Pacific Seamless ATM Planning Group (APSAPG) under the auspices of the International Civil Aviation Organization (ICAO). This group held its first meeting in January and is due to issue a final report in 2013. Imagome is a co-chair of APSAPG, which is scheduled to meet in Japan in August.

Japan already holds bilateral ATM coordination meetings with both China and South Korea. Japan will also be looking to increase its ATM collaboration with Russia, given its importance for European routes. The goal is to have similar procedures and technology requirements at both ends of international flights.

Tomine stresses that coordination is essential for timetables as well as technology. If a particular technology is introduced only in Japanese airspace, then the cost-benefit equation could be unfavorable. “But if it is introduced in Sesar or NextGen at the same time, there is three times the benefit,” says Tomine. “This will be one of the main advantages for us from Carats.”