SESAR’s benefits for GA need further study

 - May 18, 2008, 12:17 AM

The SESAR (Single European Sky ATM Research) program to define and implement a new air traffic management system for the Single European Sky (SES) presents an opportunity for all stakeholders to work together to develop a common concept of operations (ConOps, in Eurocontrol jargon). According to Serge Lebourg, a certification expert with Dassault Aviation’s technical department, this is one of the genuinely positive aspects of the long-awaited SESAR. However, he warned delegates to Eurocontrol’s recent business and general aviation forum in Brussels that many SESAR decisions are still “conditional on the results of cost-benefit analysis.”

Lebourg sees benefits in SESAR for business aviation in terms of safety, environment and operations. He said it will minimize the risk of collision in local airport TMAs.
For the management of airspace, it will provide a “virtual tower” capability and dynamic management of approaches and takeoff paths in airspace.

ASAS will allow pilots to maintain separation and avoid collisions in low aircraft density airspace (for example, above FL410, in desert areas and over Africa). It also promotes the development of “cooperative self-separation” ASAS mode (separation delegated by ATC to pilot) and the elimination of all nonprecision approaches.

CDAs Eliminate Level-offs

In terms of the environment, SESAR will allow real controlled descent approaches (CDA) in SBAS mode to eliminate all level-offs, and the development of SBAS special approaches will help to minimize noise nuisance to airport residents. For instance, bizjets can already fly steep and curved approaches at an airport such as Paris Orly, which reduces noise for neighbors and therefore the need for curfews.

In terms of operations, SESAR promises optimization of the complete flight from takeoff to landing. Other possible benefits include operating on free routes in “climbing cruise” in a unique sector all over Europe (above FL410) and performing “3-D pseudo ILS” approaches down to 200 feet on any runway down
to 100/50 feet for head-up display- and enhanced vision system-equipped aircraft. In fact, Lebourg actually admitted that Dassault’s U.S. rival Gulfstream is far more advanced in the HUD/EVS field.

However, Lebourg expressed concern that “due to a lack of time,” business and general aviation currently comprise no more than a limited part of the ConOps. He said, that as is often the case in aviation policy making, priority has been given to the needs and circumstances of airlines and their hub airports. According to Lebourg, business aviation’s interests have accounted for less than 0.3 percent of the total SESAR budget to date.

In the Dassault executive’s opinion, current SESAR technology recommendations simply do not cover all the requirements of general aviation and helicopters. “They need low-cost, low-power, integrated CNS [communication, navigation and surveillance] solutions,” he said.

The service delivery cost of future air traffic management (ATM) also remains a concern. “There is a need for public funding, since ATC charges will not cover all deployment costs,” said Lebourg. “This funding must first cover the needs of the users that have no revenues, such as GA.”

Other speakers at the forum said nontechnical considerations have driven technology recommendations. As a result of lobbying, there is a lack of common vision on the technology needed by and available to SES airspace users. Only the technological requirements of commercial air transport have been subject to a positive cost-benefit analysis, claimed Lebourg.

Satellite-based Nav Systems

For navigation, the main ingredients of SESAR will include satellite-based augmentation systems (or SBAS–EGNOS in Europe; WAAS in the U.S.), pseudo ILS approaches on any runway (decision height down to 200 feet). In the U.S., stressed Lebourg, 30,000 GA aircraft are equipped and more than 1,000 approaches are published. “This results in airliners making nonprecision approaches on the same runways where GA aircraft perform Cat 1 approaches,” he said.

Sole Means of Nav

According to Lebourg, among GNSS developments, Galileo and GPS III (expected to be in service at around 2012 to 2015) will provide better availability, accuracy, integrity and continuity of service. For light aviation, the combination of GPS and Galileo should be recognized as a sole means of navigation. “There will be no longer any need for ADF, VOR, ILS and markers,” he said.

For surveillance, Lebourg said that there is a need for a new safety concept that no longer should be passive and based on the “see-and-avoid” principle, but on advanced systems providing an aircraft’s position. “Each flying object should be able not only to report its position but also have access to positions of other aircraft,” he declared.

Lebourg said mode-S transponders are a good example of negative cost-benefit analysis since the costs are for GA, and the benefits are for airlines and business aviation. ADS-B could provide a solution adapted to local airport TMAs and GA applications, he added. The proposed Universal Access Transceiver (UAT), which will provide ADS-B “in and out,” flight information service (FIS) and traffic information service (TIS), seems the right solution, said Lebourg, and is recommended by the U.S. Federal Aviation Administration.

In the field of communication, the extension of the 8.33 kHz channel spacing for VHF radios in the lower airspace (below FL195) remains an open issue. Eurocontrol is preparing a revised business case, implementation plan and safety assessment. This work will take into account the results of a frequency usage study, which is a key concern for both general and military aviation.

The agency also plans to begin a consultation process next month with a view to seeking conclusions from consultants by year-end. Modifications to the European Commission’s implementation rule on this issue might follow later. “As usual,” predicted Lebourg, “GA will pay the bill and airlines will enjoy the benefits.”

Among datalink solutions, the VDL-2 option being considered for larger aircraft might not be the most efficient means for all GA aircraft, for which UAT is considered a more cost-effective solution. VDL-4, which the Nordic states are promoting, is also a possibility.

Lebourg said the selection and deployment of technology should be based on a plan accepted by all stakeholders. ADS-B should be advocated as a primary means of navigation to provide separation and collision avoidance. Aircraft should not be equipped with an ADS-B out system, which will not be used by the air navigation service providers (ANSPs) and thus would not permit development of airborne separation assurance systems (ASAS).

CNS Integration

CNS integration and safety issues have to be considered. If UAT provides a datalink capability, there is no need for VDL-2 on light aircraft. The selection of means of separation and collision avoidance must depend of the safety objective requirements, based on common points, such as baro-altitude and communication means, the 090 MHz extended squitter and TCAS.

According to Lebourg, there are reasons to remain optimistic about SESAR. “We will reach an agreement with airlines in the future, but when?” he asked rhetorically. With the next-generation air transportation system (NextGen) developed in the U.S., Europe’s SESAR will have to work on common solutions taking into account global interoperability needs of air transport.

The FAA’s proposed rules on ADS-B promotes SBAS, UAT and FIS-B. In Europe, both EGNOS (the GPS augmentation system) and Galileo (the civilian GNSS system) will continue to be developed despite the fact that SESAR has not touched upon these issues.

General and business aviation must help promote and develop their research-and-development needs and to finance the specific technology deployment, said Lebourg. “Eurocontrol has to take the lead, in cooperation with ANSPs, on these activities where public funding and adequate human resources will be needed,” he concluded.