The FAA announced in August that it expects to award its ADS-B ground station contract (estimated to be for up to 500 ground stations) next July. The agency will use a “performance-based” contracting approach for the project, which will reportedly cost around $2 billion over its lifetime.

Under this approach, the contract winner will finance, build, own and operate the ground station networks, and sell their ADS-B signals to the FAA. The first stations, destined for Louisville, Ky., and the Gulf of Mexico, are scheduled to be operational in late 2009; 2013 is the target date for stations to be operational across the continental U.S.

The FAA made the announcement at the second of two Industry Day meetings on ADS-B held this summer. The first meeting was in June. Despite their support of the introduction of the technology, NBAA, AOPA and RAA at the August meeting expressed concerns about its introduction into the National Airspace System (NAS). Among their concerns are the full availability of system capabilities, the cost of avionics, the likelihood of equipage mandates and, for commercial users, the investment payback in operational benefits.

Less discussed, but clearly an underlying concern, was some attendees’ apprehension that the program, though apparently well founded, might meet the same fate as earlier projects such as MLS, LAAS and CPDLC, whose promises were never realized.

The FAA is concerned about user and manufacturer acceptance of the system plan. As FAA program manager Vincent Capezzuto stated in his opening presentation, the highest risk to the program is “if NAS users demonstrate active opposition to avionics-related mandates, there may be delays in required rulemaking activities and/ or the program may experience a reduction in benefits.”

He added that a medium risk to the program is that “if avionics suppliers are unwilling to accept investment risks, and/or unable to ramp up ADS-B equipment production, certification and installation, then the avionics ‘industrial base’ will lag user demand for ADS-B capabilities and make it difficult to meet the requirements of airspace mandates, and there will be a delay in benefits accrued to the program.”

ADS-B out and ADS-B in
While NBAA, AOPA and RAA gave formal presentations at the August meeting, the Air Transport Association (ATA), which represents the major passenger airlines, did not. This may have underscored the difference between ATA and the other groups regarding the two fundamental aspects of ads-b operations– called ads-b out and ads-b in–that affect the key issue of full availability of the system’s capabilities.

In ads-b, an airplane’s onboard unit transmits its ID, position, altitude, speed, heading and intent data every second, and these signals– known as ads-b out–are received by all other equipped airplanes within range, as well as the ADS-B ground stations. The ground station sends the airplane data to the nearest ARTCC, where it appears as a target on the controller’s screen. This is particularly valuable when an aircraft is flying at low altitude far from ATC’s radar, where it would otherwise not be detected.

In turn, the ARTCC sends to the ground station two sets of data for retransmission to aircraft within range. These are the separate Traffic Information Service and Flight Information Service Broadcasts (TIS-B and FIS-B, pronounced Tizbee and Fizbee).
TIS-B allows those low-flying aircraft to appear on an airplane’s cockpit display, along with any non- ADS-B but transponder-equipped aircraft the controllers see on their screens, but you can’t see on yours. And FIS-B delivers current weather charts, forecasts, notams and related data, which are equally valuable.

The aircraft’s reception of this data is called ads-b in but to accomplish this the ground stations must be equipped to transmit the TIS-B and FIS-B signals. Unfortunately, FAA planners–perhaps focusing more on benefits to controllers than users–appeared to have felt that getting everyone’s basic ADS-B returns on the radar screens was the primary goal, and that additional system features like TIS-B and FIS-B could come later.

From a strictly traffic surveillance point of view, this was probably logical. After all, the major airlines–ATC’s biggest customer– didn’t really need TIS-B and FIS-B since they already had TCAS to see other aircraft, and most were well supported with weather from their company dispatchers over their own datalinks. Perhaps as a consequence, the FAA’s implementation plan downplays the need for ads-b in.

The non-airline community, however, felt differently. NBAA director of air traffic services Bob Lamond told agency officials that while his association “absolutely supported” the eventual transition from surveillance radar, most of the ads-b out benefits went to the FAA. But most of the operator benefits come with ads-b in, he stated, and those must be achievable concurrent with equipage.

AOPA vice president Andy Cebula echoed Lamond’s view, stating that ADS-B’s traffic and flight information services provided the incentive for general aviation to equip. He emphasized AOPA’s position that an eight- to 10-year equipage transition must precede any installation mandate and noted that the transition period should not begin before the nationwide infrastructure–including TIS-B and FIS-B–was fully in place.

Avionics costs were also of concern to the two pilot associations and to the RAA. Lamond called for the FAA to have a firm plan for certification of equipment “that is affordable and makes sense to OEMs and operators,” while Cebula flatly stated that today’s equipment “is too expensive.” (Currently, Garmin’s GDL-90 ADS-B transceiver retails for $7,995, not including installation.)

Like NBAA and AOPA representatives, RAA vice president Scott Foose lauded the FAA’s moves to modernize today’s ATC system but pointed out that his association members would find it difficult to invest in new equipment unless there is a positive business case for it. Understanding the costs and benefits was critical, he said.

At another industry meeting attended by AIN, Foose made the intriguing suggestion that since FAA Administrator Marion Blakey had told Congress that the agency expected to save more than $1 billion by replacing secondary radar with ADS-B, part of that saving might be used to subsidize equipment purchases by operators, thereby speeding the transition process. Manufacturers have informally told AIN that avionics prices should fall once demand increases and production quantities can be ramped up.

The major passenger airlines have not made an issue about the cost of ADS-B avionics, possibly because current airline transponders are built to automatically send out so-called “extended squitter” signals identical to those transmitted by ADS-B units, and many earlier airline transponders can be modified to do so fairly inexpensively.

On the other hand, freight carrier UPS has made substantial pioneering investments–reportedly, around $100 million–in evaluating system benefits, well beyond the basic cost of the avionics. The company’s fleet is almost fully equipped, and UPS for several years has been testing novel applications, such as pilot self-separation, en route merging and spacing and operating “virtual VFR” approach sequencing in marginal IFR during the late-night “rush hours” at its Louisville base.

Presentations by avionics manufacturers at the Industry Day–including Garmin, Honeywell and Rockwell Collins–made it clear that the industry has the technology and is more than ready to meet the market demand–when it arrives. But as Rockwell Collins stated, “ads-b out is a hard sell.” The company also pointed out that there were significant differences in the emphasis placed on the system by the FAA, Eurocontrol and Airservices Australia.

In fact, while the FAA was emphasizing the prominent role ADS-B would play, Eurocontrol saw it being required for less than 50 percent of its future ATC improvements, and Australia was looking at it mainly as a source of ads-b out messages to controllers. These differences had to be resolved in the near future, Rockwell Collins felt, since the lack of clearly defined user operational benefits and payback “was challenging how ADS-B will develop.”

Honeywell expressed similar thoughts and asked whether there will be sufficient motivation, either through operational advantages or mandates, for users to invest in equipment, while Garmin, the major general aviation supplier so far, acknowledged that low production volumes inevitably mean high prices for the small number of users who adopt it early.

The Backup Question
The FAA recognizes that ADS-B dependence on GPS requires a backup positioning source, should problems arise with satellite reception, and the agency has established a team of experts in various candidate systems to evaluate and recommend solutions. The team’s report is expected later this year, with a final recommendation due next month.

But the FAA’s initial assessment was puzzling to many attendees, and appeared to underscore the agency’s controller-centric outlook. According to the assessment, the three backups that meet all the minimum criteria are secondary radar, primary radar and transponder multilateration, to be discussed later.

Ignoring the fact that secondary radar is intended to be replaced by ADS-B eventually, none of these candidates provides pilots with navigation information should GPS fail, although they do provide a target on a controller’s screen. Also, as one attendee pointed out, primary “skin paint” radar shows only a number of unidentified blips on the screen, and keeping track of which blip represents which aircraft could be hazardous in high-density terminal airspace.

The FAA’s second tier, which meets most of the criteria, included DME/DME/ IRU, scanning DME/DME, eLoran and satellite navigation. Of these, the first two are almost exclusive to high-end corporate airplanes, while satellite navigation alternatives, such as Europe’s Galileo, share interference vulnerability with GPS.

Excluded from consideration as backups were IRU only, VOR/DME and two very curious navigation systems LOC/ DME and MLS/Rnav. One attendee expressed concern to AIN about the apparent lack of system understanding at the FAA that led to those two even being listed as navigation backups in the event of GPS failure.

AIN has reported on the fact that computer hackers armed with a laptop, a low-cost ADS-B avionics unit and a small antenna are reportedly capable of producing as many as 50 false ADS-B targets that move across a controller’s screen. Industry sources have confirmed that such “spoofing” is indeed possible, and most companies have investigated countermeasures, although for obvious reasons these techniques are classified.

On a recent visit to ADS-B ground station builder Sensis, based in Syracuse, N.Y., AIN saw one counter-measures approach, where signals from a pre-encrypted airborne unit, when linked with a pilot’s individual security code, provided the controller with a clear indication that it was a valid target. For its major system procurement, the FAA will require bidders to demonstrate that their systems have total anti-spoofing protection and other security measures.

ADS-B and Multilateration
The FAA’s current ground station specification does not include a requirement for a multilateration capability, although this technique is now becoming a common ADS-B adjunct. Multilateration uses a number of small, widely spaced, unmanned ground receivers that listen for transponder responses to interrogations by secondary radars and TCAS-equipped aircraft in the vicinity. The position of each individual transponder–and thus its parent aircraft–is then calculated once per second by using a triangulation technique based on each incoming signal’s time of arrival, and the resulting aircraft position appears on the controller’s screen.

Multilateration is not ADS-B, and it provides no cockpit information. It is a newer-technology alternative to today’s secondary radar, offering the same effective range but providing better accuracy at significantly lower cost, and from much simpler equipment than large rotating radar antennas. It is a valuable complement to ADS-B in adding coverage of non-ADS-B traffic, for a substantially lower investment.

Both Sensis and Rannoch, of Alexandria, Va.–a separate ADS-B ground station provider–have installed multilateration systems at a number of U.S. and overseas airports, sometimes with and sometimes without accompanying ADS-B ground stations. At some locations, the multilateration installation can include several “passive,” or listen-only, stations, in addition to one or more “active” stations that transmit secondary radar-like interrogations, but at one-second intervals, compared with the radar’s 4.7-second sweep.

In Mongolia, where overflying airline jet traffic has rapidly increased, authorities have reportedly dropped plans to install secondary radar, and instead have opted for the much less costly, but equally effective, ADS-B/wide-area multilateration solutions from Rannoch.

At press time, Sensis, which also has a number of overseas installations, was beginning a similar ADS-B/wide-area multilateration system linking Tasmania with the Australian mainland. Transponder multilateration is also used in the FAA’s ASDE-X program, and its associated displays like the Sensis Safety Logic (see AIN, September, page 49).

Unquestionably, ADS-B will be a major step forward in aviation safety and efficiency, and the FAA is to be commended for launching the program under an innovative contract arrangement that shouldn’t break the agency’s strained capital budget.

At the same time, program officials appear to have been unprepared for the only modest enthusiasm of the non-airline user community, faced with what are seen as high avionics costs and uncertainty about benefits. Jeff Brabender, president of Coherent Solutions, of Salt Lake City, who has been involved in virtually all domestic ADS-B programs, told AIN that “As the FAA’s national program gets under way, it will be vital to get a critical mass of users to change the current cost/benefit imbalance. ads-b out provides them no new capability, but when combined with ads-b in the system opens up a whole new way of managing and sharing airspace more efficiently for everyone.”

The FAA certainly got the message about the importance of ads-b in from users at the most recent event. The next step is lowering the cost of avionics. One approach could be the method used by the agency’s WAAS office earlier this year where companies not traditionally in avionics were invited to apply for federal development grants to stimulate innovation and competition. Without such initiatives, Brabender’s critical mass might be hard to achieve.