ATM Modernization, Commercial

A Single Solution To ADS-B?

By Brian Evans | May 1, 2007
Send Feedback

The move by FAA to "performance-based" contracting, where the end product is the certifiable goal, and the means to reach it is not rigidly specified, has both advantages and disadvantages. The advantages include allowing suppliers to replace costly "gold plated" government manufacturing specifications with good commercial practices.

But FAA has found that while the approach can yield cheaper, workable solutions, it can bring unexpected implications.

This is the current situation with the agency’s $1.5 billion Automatic Dependent Surveillance-Broadcast (ADS-B) program. After reviewing preliminary offerings from potential bidders, FAA selected Lockheed Martin, ITT and Raytheon as final candidates for the program. Under the contract, the winner would finance, build, operate and maintain around 500 ground stations of its own design, with the primary FAA requirement being the provision of certifiable signals in space and their processing for a service fee.

Raytheon, Waltham, Mass., is taking an innovative approach to the program by countering years of accepted practice on ADS-B frequencies.

Since the mid-1990’s, FAA has focused on two different ADS-B frequencies — general aviation (GA) would use the FAA-developed 978 MHz Universal Access Transceiver (UAT); airliners and other large aircraft would use ICAO’s international standard 1090 MHz Extended Squitter (ES) frequency.

When UAT was developed in the 1990s, it was felt airline units would be too expensive and too large for small GA aircraft. As a result, it was commonly accepted in industry circles that FAA’s future ADS-B ground stations would have to handle both frequencies, "translating" incoming UAT signals into 1090 ES formats and instantly rebroadcasting them to airliners, and vice versa. In this way, all pilots would see all aircraft in their vicinity.

However, under the constraints of the performance-based concept, FAA could not specify the technical process to achieve the end product, but could only call for a product that meets its operational requirement, essentially that all aircraft and air traffic controllers can see each other.

To that end, bidders were encouraged by the agency to use innovative approaches to achieve that goal. Lockheed Martin and ITT designed and proposed dual frequency units for the program.

Raytheon’s approach

Raytheon, on the other hand, is taking a different path. At the ATC Maastricht convention in February, the company proposed that UAT be abandoned, and the relatively few GA aircraft already equipped be switched to 1090ES units, since technology advances would now allow these to be built at competitive cost and size to UAT avionics.

Raytheon argued GA pilots could benefit from ADS-B service anywhere in the world compared to UAT, which provides service only in the United States and is very unlikely to be offered even by neighboring Canada or Mexico.

Further, the 1090ES transponders would allow GA aircraft to remove their legacy Mode A/C transponders, which have limited capabilities and can often degrade 1090ES operation in higher density airspace.

Raytheon also proposed the weather reports and forecasts provided by ADS-B’s Flight Information Service-Broadcast (FIS-B), which is unique to UAT, would be provided free of charge to GA aircraft from the XM Radio satellite that covers the United States.

"The Raytheon team solution uses a single frequency that is becoming the standard around the world as opposed to utilizing two different frequencies," said Andy Zogg, vice president of Raytheon’s Airspace Management and Homeland Security business.

Raytheon’s approach may not have necessarily been the innovation the FAA had in mind, but it was balanced by the fact that the proposal eliminated the need for the fairly complex, dual-frequency ground stations, as Raytheon’s would only need to handle 1090ES data.

"The FAA asked industry to be innovative in its approach to the ADS-B challenge so that the government could enjoy earlier and increased user benefits as well as reduced investment," Zogg said. "Raytheon embraced that challenge and developed an innovative technological solution that far exceeds what would be possible in the conventional approach."

While Raytheon declined comment to Avionics on this point, industry sources suggested this potentially could save FAA more than $200 million in the design, development and production of new, dual-frequency ground stations and their attendant lifecycle costs.

FAA planned to call for final bids in late March and responses are expected in late April or early May, with the contract will be whether to accept Raytheon’s lower-cost bid or opt for the potentially higher cost, and more technically challenging, dual-frequency approach.

Avionics concern

A critical FAA concern about Raytheon’s proposal would appear to be the availability of certified GA 1090ES avionics units of comparable cost, size and power consumption to a UAT unit.

Under its nationwide ADS-B implementation schedule, FAA planned to have its first ground stations under the new contract commissioned and operating at several locations in the 2009-2010 period, with one of the most urgently needed networks being the Gulf of Mexico (Avionics, April 2007, page 36). If the avionics are delayed, the issue could turn on just how much delay FAA would tolerate.

In the Gulf, the system must support two different surveillance requirements. At very low altitudes, more than 650 helicopters support thousands of offshore oil and gas platforms, most of which are out of range of shore-based ATC VHF stations and unable to receive updated weather reports and forecasts. At high altitudes, airliners crossing the Gulf pass through an area beyond the coverage of shore-based radar, necessitating reversion to inefficient procedural separation standards.

For both user groups, the lack of full surveillance and, for the helicopter community, the lack of communications and weather in the Gulf, compared to FAA’s domestic service, have long been the source of industry complaints, and ADS-B is expected to answer these concerns.

Any potential delay in FAA’s firmly stated implementation schedule would not be well received by operators.

Therefore, avionics availability will be a critical factor in Raytheon’s approach.

However, small 1090 MHz transponders have been built in the past by Bendix-King and by Aviation Communication & Surveillance Systems, the L-3 and Thales joint venture. The technology is certainly well understood.

Comsoft of Germany and Kinetik Avionics Products of the United Kingdom also are reported to have an interest in this area, but none of the companies approached by Avionics was prepared to discuss plans.

According to industry sources, Lockheed Martin and ITT had each proposed dual-frequency solutions for the FAA’s 500 ground stations, and were surprised when FAA announced in late February that Raytheon was included in the final down-selection of bidders.

Until then, many felt that Raytheon’s proposal would fall outside FAA’s expectations, and would not be selected.

But in accepting it, FAA also tacitly endorsed the company’s approach, which likely raised concerns at Lockheed Martin and ITT. Neither of the latter companies was understood to have included single-frequency options in their proposals.

Consequently, some observers feel Lockheed Martin and ITT could be considering three possible courses of action.

First, by bid closing time, they may have been able to incorporate Raytheon-like options in their final offers.

Second, they could request that the bid closing date be extended while they revise their offers to include such options.

Third, should Raytheon win the contract, they could protest the award on the grounds that it was non-compliant with the generally understood requirement, and raised the risk of delaying FAA’s clearly specified operational schedule.

Performance-based contracting has obvious advantages. But as FAA has discovered in the case of the ADS-B program, it can also bring unexpected side effects.


Nav Canada Moves On ADS-B

Nav Canada in March awarded its national ADS-B program to Sensis Corp., Syracuse, N.Y., and installation of the first ground stations is underway.

Like FAA, Nav Canada sees the system as the foundation of its future air traffic management system. But while FAA is aiming at an exclusively ADS-B environment, Nav Canada is taking a building-block approach. The privatized Canadian air navigation service provider plans a mix of ADS-B and multilateration (Avionics, April 2007, page 30) to progressively meet its operational needs. The contract with Sensis includes up to 200 ground stations capable of handling both applications.

Nav Canada will initially install ADS-B stations around Hudson Bay where, as in the Gulf of Mexico, 1090ES-equipped airliners flying northern routes between Europe and Asia are currently forced to observe much wider, and much less efficient, "procedural" separations when beyond the coverage of shore-based radars. Because of the shorter weather window in Canada’s frigid north, the Hudson Bay systems are not expected to be operational before mid-to-late 2008.

Nav Canada had not announced where future ADS-B installations will be made, but it is expected they will be gradually introduced in areas that have specific needs, rather than the nationwide blanket coverage planned by FAA. Other areas in Canada’s far north are expected to be high on Nav Canada’s list of future ADS-B installations, to enhance surveillance of increasing intercontinental air traffic.

In other parts of the country, such as the Vancouver area and the oil exploration center of Fort St. John, British Columbia, Nav Canada is installing the Sensis units in multilateration configurations to monitor movements of lower altitude traffic carrying non-ADS-B transponders and which fly in areas where interrogation signals from local surveillance radars are blocked by intervening mountains. As the aircraft community transitions to widespread ADS-B equipage, these stations can be converted to full ADS-B operation. — Brian Evans

Receive the latest avionics news right to your inbox