NextGen vs. Legacy Aviation NAVAIDs: Cost-Benefit Analysis

Introduction

When deciding whether to upgrade airport navigational systems, it is important to perform a cost-benefit analysis in order to determine which course — to upgrade or not to upgrade — is the better option (FAA, 2011). Upgrading from legacy systems can be expensive in terms of implementation and training, while the added value of the Next Generation Air Transportation System (NextGen) aviation terminal navigation systems (NAVAIDs) is, as yet, unknown aside from the projected estimates supplied by the FAA (Materna, Mansfield, & Walton, 2015).

Following the FAA's 2011 request for feedback in the Federal Register on its proposal to upgrade legacy NAVAIDs such as VORs to NextGen's GPS/WAAS RNAV, over 300 comments were provided from the public. These ranged from trepidation about safety ("The elimination of the VOR system and reliance solely on GPS for navigation would be a grave mistake") to concern for environmental issues (Bello, 2012). Congressman Eliot L. Engel (2012) of the U.S. House of Representatives wrote to the FAA:

"While I agree the modernization of our aviation system is necessary to bring it into the 21st century, it must also keep pace with the increased number of flights and maintain our technological advancements by implementing new equipment to keep our system the safest in the world. I do have several concerns as the transition takes place. The first concern is that the combination of the NextGen implementation and the airspace redesign will put an undue burden on the residents of Rockland County. These two changes will direct more flights, closer together, over this suburban community. This will directly lead to increased noise and increased pollution. My other concern is that some aspects of the NextGen implementation may be exempted from the proper environmental review. I strongly object to this. While it is claimed that NextGen will lower overall pollution, Rockland County should not be the test case for this. The increase in flights will add to pollution and could exacerbate the already too-high childhood asthma rate." (Engel, 2012)

The concerns expressed by the Congressman regarding the update are not directly related to safety for pilots and passengers, but rather to noise pollution — upgraded systems could mean more flights being flown over residential communities — and environmental pollution, which could detrimentally affect the health of children and adults. These are, in other words, safety issues that impact stakeholders on the ground, and as a result, they bear directly on the decision about whether or not to upgrade systems. As GPS systems will alter routes and raise political, social, and environmental issues (as Engel's letter — one among many — to the FAA demonstrates), the NextGen upgrades are not as clear-cut or as simple as the FAA's initial proposal appeared to suggest.

While these concerns may be valid, the cost-benefit analysis in this study focuses not only on such issues but also on whether NextGen systems will provide meaningfully better safety features and mechanisms than legacy NAVAIDs already in place. For example, Jan and Kao (2013) assessed the tracking performance of the GPS NextGen system and identified the "major concern to aviation authorities" regarding its use — namely, that the GPS signal could be jammed by radio-frequency interference (p. 6636). As Sueki and Kim (2016) point out, "many vulnerabilities of NextGen stem from the increased interconnection of systems through wireless networks" (p. 201). The fact that security measures still need to be addressed in these interconnected systems indicates that the upgrade may present more cost and less benefit in terms of safety. Jan and Kao (2013) also note that with simple algorithmic retrofitting, current legacy systems could be enabled to track aircraft in real time — just as the proposed GPS NextGen systems would do — without the added cost.

This study tests the hypothesis that the cost-benefit ratio of upgrading NAVAIDs to NextGen systems justifies the expense when compared to continuing to use existing legacy systems. The null hypothesis is that the cost-benefit ratio of upgrading NAVAIDs to NextGen systems does not rationalize the expense when compared to continuing to use existing legacy systems. To test this hypothesis, a literature review was conducted of reports in the National Transportation Safety Board database, journal reports, and correspondence between agencies regarding NextGen upgrades. The Federal Register's Proposed Provision of Navigation Services for the Next Generation Air Transportation System (NextGen) Transition to Performance-Based Navigation (PBN), along with its 366 public comments, provided ample material for examination of going concerns. The literature review also includes descriptions of legacy and NextGen systems, current articles and reports, and federal aviation regulations.

Background and NextGen Overview

As Karp (2016) notes, the FAA is currently in the middle of completing "an 18-year ATC modernization initiative encompassing a variety of technologies and procedural changes, all coming under the umbrella of NextGen." With mega-contracts awarded to companies like Lockheed Martin — tasked with producing an infrastructural piece of equipment called the Terminal Flight Data Manager (TFDM) at a price tag of $344 million — the FAA is spending a substantial amount of money on upgrades that many critics do not see the value of (Karp, 2016). The FAA has stated that a full sense of the benefits of upgrading to NextGen will not be felt until 2030, when all the components of the system have come together.

The problem is that critics already see the picture that is emerging and believe the costs associated with NextGen outweigh the benefits (Public Submission, 2015). While supporters can point to technological upgrades that make the industry safer, opponents can point to problems that make the whole initiative seem like little more than an unnecessary exercise in contracting work to companies like Lockheed Martin — routinely and historically known for obtaining lucrative contracts from the federal government (Karp, 2016).

In 2007, the FAA released a Fact Sheet explaining its approach to upgrading airport navigation systems. NextGen was described as a "wide-ranging transformation of the entire national air transportation system — not just certain pieces of it — to meet future demands and avoid gridlock in the sky and in the airports" (FAA, 2007, p. 1). NextGen was designed as a deliberate and total shift away from legacy ground-based systems, which would be replaced by a "more dynamic satellite-based technology" using GPS to show where aircraft are at every second, as opposed to the seconds-long intervals of legacy radar sweeps that leave gaps in real-time knowledge of an aircraft's position (FAA, 2007, p. 1). With GPS and a number of other navigation tools installed, NextGen would allow aircraft to fly more closely together on more streamlined routes.

Some of the major elements of NextGen include Automatic Dependent Surveillance-Broadcast (ADS-B) — described as the "backbone of the NextGen system" due to its GPS technology and real-time continuous surveillance capability (FAA, 2007, p. 1). As of 2007, the FAA's President's Budget request for ADS-B had reached $564 million.

Other components of the NextGen upgrades included the System Wide Information Management system (SWIM), which the FAA identified as providing "infrastructure and services to deliver network-enabled information access across the NextGen air transportation operations" (FAA, 2007, p. 1). By 2007, its budget request total stood at $173 million. The NextGen Data Communications system was promoted as an improvement on the voice-only communications of legacy systems, allowing aircraft that are "data-link equipped" to exchange "routine controller-pilot messages and clearances via data," enabling traffic controllers to better and more safely monitor traffic (FAA, 2007, p. 1). Its budget request total had reached $126 million by that year. Other features identified in the Fact Sheet included the NextGen Network Enabled Weather system, the NAS Voice Switch, and NextGen Demonstrations and Infrastructure Development.

According to the FAA (2007), NextGen would also promote more collaborative air traffic management, reduce weather impacts, "improve airport surface movements" at high-density airports by reducing "spacing and separation requirements," and more effectively manage "flows into and out of busy metropolitan airspace" (p. 2). However, as Materna, Mansfield, and Walton (2015) showed nearly ten years after the FAA's Fact Sheet was published, even high-density airports would be unable to effectively utilize NextGen upgrades without further physical expansion of the airports themselves (p. 137).

Regardless of whether the upgrades would have a beneficial or costly effect on the industry and the U.S. economy, at the outset of the initiative, more than $1 billion had already been allocated to the FAA's upgrading plan. The FAA advised in 2015 that this plan would save the industry more than $11 billion through 2030, with savings expected from En Route Automation Modernization (ERAM), ADS-B, Datacomm, and Performance-Based Navigation (FAA, 2015). In the same FAA (2015) Fact Sheet, it was revealed that estimates for NextGen upgrade costs had reached more than $32 billion — a projected budget covering the years 2007 to 2030 — with nearly half of that going to private-sector contract costs.

Within the scope of this project, the term benefit may be understood in terms of safety, strategy, and cost-efficiency. Safety encompasses all stakeholders — not just industry leaders, but also those within communities under flight paths and those working within the industry. The study draws primarily on the NTSB federal database and its affiliated links, such as the FAA Aviation Safety Information Analysis and Sharing (ASIAS) database, as well as Airlines for America (A4A), the Flight Safety Foundation, and IATA for statistical data. As the data indicate, U.S. aviation currently provides the safest form of transportation in the nation according to the NTSB (A4A, 2015), meaning that safety statistics alone cannot determine the cost-benefit ratio regarding NextGen upgrades. A broader approach addressing cost and benefit across multiple dimensions must therefore be employed.

Accidents and Safety

Research on accidents and safety by Ho and Burns (2003) indicates that navigation systems do play a part in reducing the risk of catastrophe. However, accidents are isolated incidents, and part of the risk of crashes comes from the fact that there are too many instruments for pilots to choose from. Midair collisions are infrequent; nonetheless, the 2002 collision of a DHL cargo jet with a Russian airliner revealed the extent to which navigation system complications can prevail. The Russian plane was alerted to the risk of impending collision by both the ATC and the onboard TCAS systems — yet, had only one navigation instrument been in use, the confusion that ensued might have been avoided. The Russian pilot chose to follow ATC directives while ignoring TCAS maneuver recommendations, and a crash occurred. Human factors were certainly an element — and today's NextGen systems are being implemented in part to reduce the role of human error in navigation. In this sense, NextGen is designed to take human-error risk out of the equation. The TCAS's worldwide usage and the up-and-coming ACAS X indicate that the technology to limit human-factor risk already exists (Kochenderfer et al., 2012).

However, TCAS systems are more than 40 years old, and NextGen systems such as ACAS X have been designed to update the logic "used to select pilot advisories" and control navigation options made more complicated by the introduction of surveillance information from new sources (Holland et al., 2013). As Jeannin et al. (2014) note, ACAS X is a NextGen system currently being installed in planes around the world, and tests have shown that it is able to reduce the likelihood of collision by 59%, reduce the need for alerts by the same proportion, and cut the frequency of disruptive alerts by nearly 30% (Holland et al., 2013).

In terms of ground navigation, the FAA's push for ADS-B NextGen systems is viewed as highly impactful on industry safety and efficiency. Airplanes outfitted with ADS-B transponders work with GPS satellites to give a precise indication of location every second — unlike legacy radar. The ADS-B system can also couple location information with data relating to the plane's flight number, trajectory, speed, and maneuvers, all signaled within a 150-mile radius. As The Economist (2016) reported: "By knowing at any instant exactly where they are relative to other aircraft in the sky, planes so equipped can travel closer together without fear of colliding. They can also take more direct routes to their destinations, instead of zig-zagging their way from one control tower to the next. That saves fuel and time, while minimizing aerial congestion." In this regard, NextGen systems maximize airspace, reduce time in the sky, and conserve fuel. Opponents argue, however, that the reduction in emissions is relative: with airspace and flight paths condensed, NextGen allows more flights to take place, which puts more — not fewer — emissions into the atmosphere and concentrates them over tighter regions rather than dispersing them across a range of routes.

Sueki and Kim (2016) point out that the ADS-B system, a critical part of NextGen, "is an easy target for attackers" precisely because it "transfers essential information via wireless network without encryption" (p. 201). In an era of persistent cyber threats, if this information can be hacked or manipulated, the consequences could be catastrophic. Thus, even for passengers, crew, and the industry as a whole, NextGen risks associated with cybersecurity could be assessed as far greater than the profits foreseen from streamlining routes and increasing the number of planes in the sky at any given time.

Jan and Kao (2013) assert that radar tracking remains a necessary backup in the event of a GPS outage — whether caused by an attack on satellites or by radio-frequency interference. They note that in order for the current radar system to meet ATM system performance standards, it would need to be enhanced with a special tracking algorithm. This would allow the legacy system to remain a viable navigation option in the event of a GPS blackout. Using the Kalman filter as a baseline for evaluating their algorithm, the researchers find that the legacy system can meet surveillance standards should NextGen GPS fail. This finding indicates not only that legacy systems are still relevant, but that they may be necessary — and that a total navigation overhaul is not required when a relatively simple algorithmic enhancement could bring legacy systems up to contemporary ATM standards.

Approach and Landing Accident Reduction (ALAR) has been a focus of the Flight Safety Foundation for years. Approach and landing accidents have been reduced in recent years thanks to safety products and international workshops geared toward educating pilots and controllers about these types of accidents (FSF, 2015). In 2009, there were 17 major aircraft accidents involving aircraft weighing 5,700 kg or more, and 9 of those were ALAR-related — fewer than half the number recorded the previous year. The issues related to ALAR are thus largely rooted in human factors, where education, training, and safety products have significantly reduced incident numbers, rather than in technological systems failures.

Among the 366 respondents to the FAA's request for comments, Schmidt (2013) identified several safety issues related to GPS technology in aviation and the abandonment of VORs. Schmidt (2013) argued that "a primary component of safety is redundancy. Eliminating a large percentage of the nation's primary air navigation system eliminates a primary component of safety. Eliminating VORs is a bad idea." He acknowledged the benefits of GPS and WAAS but argued that "GNSS navigation is susceptible to many forms of failure, ranging from scheduled outages, to unavailability of satellites, to interference, to intentional sabotage. These failure modes are not hypothetical. GNSS systems often fail" (Schmidt, 2013). He further argued that "as GNSS evolves into the primary navigation mode for U.S. airborne navigation, it is imperative that the current primary system (VORs) be available as a failsafe" and noted that "many aircraft are not yet and may never be equipped with GPS receivers. Eliminating the VOR airway system will render these aircraft debilitated or useless for IFR and even some VFR flight" (Schmidt, 2013).

Bowman's (2012) letter to the Docket Operations, M-30, U.S. Department of Transportation, representing FedEx, provides additional perspective on going concerns about the FAA's NextGen policy proposal. The letter identifies several technical problems: the update proposal would "mandate equipage that is not offered by major airline airframe manufacturers"; the approach is "inconsistent with the concept of PBN to stipulate a specific sensor solution"; and GBAS should be identified as a suitable replacement for CAT III Instrument Landing System (ILS) approach operations. Most critically, Bowman (2012) argued that companies like FedEx, which operate globally and must equip aircraft to interact with systems worldwide, are already spending millions on RNP AR technology that yields accuracy similar to WAAS CAT I minima — the same standard targeted by the FAA's proposal. As Vice President of Flight Operations at FedEx, Bowman's letter carries significant weight: it encompasses technical, business, pragmatic, and safety considerations. The issues demonstrate that upgrading to NextGen systems is essentially inevitable, but that the upgrade should be performed in a manner that provides cohesion and uniformity rather than creating additional problems for carriers, pilots, and airports operating within a global context.

Testimony before the Subcommittee on Aviation, Committee on Transportation and Infrastructure, House of Representatives, published by the United States Government Accountability Office (2011), revealed that "delays have resulted in increased costs and reduced benefits" for stakeholders and that "going forward, FAA must focus on delivering systems and capabilities in a timely fashion to maintain its credibility with industry stakeholders" (p. 3). However, the timeliness of acquisitions and implementations has not been adequately upheld, and the FAA has not been forthcoming in ensuring that new flight routes meet environmental safety requirements (Wills, 2013). Noise pollution has negatively impacted several cities where new routes have been adopted as a result of NextGen, including Boston, New York, Baltimore, Phoenix, San Jose, Santa Cruz, and San Francisco. Low-flying aircraft have also created problems in Palo Alto, where Dremann (2014) reports that four-fifths of flights over the region are in violation of the 8,000-foot elevation rules governing aircraft approaches.