Unprecedented Challenges Face Implementation of New Air Traffic Control System

Wed, Oct 31, 2007 — David Evans


The promise of a dramatic transformation of the nation’s air traffic control system was betrayed by a computer glitch that prevented the legislators from seeing a video of the Federal Aviation Administration’s (FAA) concept.

At the 17 October hearing of the House Transportation and Infrastructure Subcommittee on Aviation, the computer screens stubbornly remained blank, prompting the FAA’s chief witness, Vincent Capezzuto, to proclaim in an effort at humor, “This wasn’t covered by the ADS-B contract.”

What he was referring to is the FAA’s plan to dramatically alter the way it provides air traffic control services. The agency hopes to decrease its reliance on ground radars, using instead a system based in satellite technology called ADS-B. The acronym stands for automatic dependent surveillance – broadcast. ADS-B is the linchpin to the Next Generation (NextGen) air traffic control system that is intended to reduce the separation between airplanes, thereby increasing capacity, smooth airport operations, and do so while enhancing safety.

That, at least, is the promise of ADS-B and NextGen. Whether these concepts will change the future requirement for slot allocation at major hub airports remains to be seen.

The hearing came on the heels of two developments, cited by subcommittee Chairman Jerry Costello (D – Il.): “Within the last 60 days the FAA awarded $1.9 billion in contracts to an ADS-B consortium, and earlier this month the FAA published a notice of proposed rulemaking requiring aircraft to be [ADS-B] equipped by 2020.” (See Significant Regulatory Action for the NPRM)

The FAA hopes the contract will cut five years off the time needed to get the NextGen system up and running, and save the agency about $820 million over 20 years, Costello announced.

The hearing was an attempt to sort out hype from likely fact.

Extracts of the witness remarks, presented below, indicate the scope of the NextGen task and some of the problems associated with system development, certification, and functioning.

To reap the benefits of NextGen, airplanes will have to be equipped with the linchpin technology, ADS-B.  For light planes, the cost could be upwards of $10,000. For transport category aircraft (airliners), the cost of the avionics ranges from $40,000 to $160,000 per aircraft. Corporate aircraft costs fall in between these figures.

Certifying the system as safe, functional and reliable will fall to a board made up of FAA and contractor officials. This arrangement does not meet the test of independent certification. As Rep. John Duncan (R – Tenn.) observed, “The government will oversee certification done by the contractor.”

As Calvin Scovel, the Department of Transportation Inspector General, explained, “The FAA will control the performance of ADS-B through the contract and through a performance control board.”

Data critical to NextGen will be provided by private contractors, who will manage the ADS-B ground stations. According to Tom Brantley, President of the Professional Airways System Specialists (PASS), should the FAA have to take over the ground stations, it won’t have the capability of doing so.

The new system is expected to enhance safety, especially in those areas where ground-based radar cannot improve situational awareness for pilots and controllers.

Rep. Robin Hayes (R – N.C.) summed up what the system will do. “This is not the answer to air traffic delays [but] it will dramatically improve safety.”

Well, maybe it will improve safety. However, it was apparent during the course of the hearings that the benefits of the system were couched in terms of greater throughput. Accidents and incidents avoided were apparently not considered in the system’s cost-benefit equation.

Whether the subcommittee deems it necessary to independently certify the system before it’s declared operationally suitable remains to be seen. One would hope that independent certification would be seen as valuable, if not essential, given the changes to air traffic control the FAA envisions. For example, ADS-B facilitates conversion of the existing rail-roaded (ATC-directed) system from running on rails (the air routes) to a “roadway” system where pilots will need to see and avoid other aerial vehicles electronically – and themselves be seen. At the reduced separations proposed, will NextGen be a conversion from commanded direction to perpetual avoidance? And at what point will traffic density or saturation bring chaos theory into play? Whether this aerial interaction will at some point translate into a raucous chorus of weak links, and the compromise of safe separation, remains to be seen.

Another potential vulnerability to NextGen is the integration of the current paper-chase of the NOTAM (Notice to Airmen) system into ADS-B. The data-stream should automatically present to the pilot in real-time any significant information relevant to his route of flight or destination. Pilots in preflight who presently review reams of pages of barely relevant NOTAM data, and then disastrously forget the salient detail when it really counts, would benefit from a real-time presentation of pertinent NOTAM items. This critical aspect was not discussed at the hearing, yet, as saying goes, threat briefings are always enhanced when they are timely.

In short, the legislators glossed over key points of NextGen and ADS-B vulnerability, and it appears that it now depends on the contractor and the FAA to self-certify that the system is truly safe.

The legislator’s reaction to the testimony they heard was, in many respects, remarkably passive. Rep. Tom Petri (R – Wisc.), the ranking subcommittee member, captured what seemed to be the prevailing attitude. “The transition to the new system will not be simple,” he declared.

Remember, the video of the new system could not be played; a bad omen.

FIGURE A: The concept for ADS-B application in the NextGen air traffic control system. Source: Mitre Corp., Center for Advanced Aviation System Development (CAASD)

The dazzling promise; testimony of the FAA’s Vincent Capezzuto, director of surveillance and broadcast services:

“As you know, this system [ADS-B] is vital to building the Next Generation Air Transportation System (NextGen). … [The] FAA has crafted an innovative and closely monitored contract with the ITT Corporation for the development of ADS-B. …

“ADS-B uses signals from the international Global Navigation Satellite System to provide air traffic controllers and pilots with much more accurate information that will help keep aircraft safely separated in the sky and on runways.  Aircraft avionics receive satellite signals and transmit the aircraft’s precise locations to air traffic controllers and [other] pilots.

“The avionics convert that position into a digital code and combine it with other unique data from the aircraft’s flight monitoring system – such as the type of aircraft, its speed, its flight number, and whether it’s turning, climbing or descending. The code containing all of this data is automatically broadcast from the aircraft’s avionics once a second or more, as compared to the current 5 to 12 second refresh from today’s radar. While a time saving of 4 to 11 seconds may seem brief to some, this savings actually allows for far greater accuracy in determining aircraft position. …

“When properly equipped with ADS-B, both pilots and controllers will, for the first time, see similar real-time displays of air traffic. Pilots will have much better situational awareness because they will know with greater accuracy where their own aircraft are, and their displays will show them all the aircraft in the air and on the ground around them. … At night and in poor visual conditions, pilots will also be able to see where they are in relation to the ground … In addition to improved safety in the sky, ADS-B can help reduce the risk of runway incursions. Both pilots and controllers will see the precise location on runway maps of each aircraft and [ADS-B] equipped ground vehicles, along with data that shows where they are in relation to one another. These displays are clear and accurate, even at night or during heavy rainfall.

“ADS-B also has the potential to increase capacity significantly, because more accurate tracking using satellite based positioning means aircraft will be able to fly safely with less distance between them. Because the better accuracy available with ADS-B also means greater predictability of aircraft movement, air traffic controllers will be able to manage the air traffic arriving and departing from congested airports with greater precision, resulting in even more gains in efficiency. …

“Although radar technology has advanced, it is essentially a product of World War II technology. Radar occasionally has problems discriminating airplanes from migratory birds and rain ‘clutter.’ Secondary surveillance radar systems can determine the identity of the aircraft because they interrogate transponders on-board the aircraft; however, both primary and secondary radars are very large structures that are expensive to deploy, need continuous maintenance, and require the agency to lease large plots of land on which to situate them. ADS-B, on the other hand, does not have problems with clutter because it receives data directly from aircraft transmitters rather than passively scanning for input as do radars.

“Also, ADS-B provides superior accuracy and timeliness of information in comparison to secondary radars. ADS-B ground stations are inexpensive compared to radar, and are the size of mini-refrigerators that can go essentially anywhere, so they minimize the required real estate. In addition, ADS-B also provides greater coverage, since ADS-B ground stations are much easier to place than radar. Remote areas where there is currently no radar, such as the Gulf of Mexico and parts of Alaska, will have precise surveillance coverage with ADS-B.”

The rain of skepticism on the dazzling promise; the view of Calvin Scovel, the Department of Transportation’s Inspector General:

“We recognize that ADS-B has potential to enhance capacity, improve safety, and fundamentally change the way air traffic is managed. However, a full disclosure of costs, expected benefits, and risks is needed. … Given FAA’s history with developing new technologies and its approach for ADS-B, we believe that an extraordinary level of oversight will be required.

“First, realistic expectations need to be set for what benefits ADS-B will deliver in terms of capacity and delay reduction.  ADS-B will not provide near-term capacity benefits or relief from record-level delays at the nation’s most congested airports. FAA’s plans call for ADS-B ground infrastructure to be in place by 2013, and airspace users are not expected to be equipped with new avionics until 2020. …

“It is important to note that FAA intends to mandate ‘ADS-B Out’ usage (the broadcast of position information from aircraft to ground systems), but the majority of benefits from the new satellite-based technology rely on ‘ADS-B In’ and the display of information in the cockpit. FAA is developing several air-to-air capabilities with United Parcel Service (UPS) that show considerable promise for enhancing pilot situational awareness. However, costs and other requirements for ‘ADS-B In’ and cockpit displays, which could shift more responsibility to the pilot, are not clear at this time. …

“Second, ADS-B has demonstrated important benefits in Alaska, where radar coverage is limited, but its implementation in the continental United States, which involves supplementing and ultimately replacing radar, is a complex undertaking. Before FAA even considers the more advanced capabilities (such as reducing distances between aircraft in congested airspace), ADS-B must demonstrate the same level of service that radar now provides.

“Our work shows that the widespread introduction of ADS-B faces a myriad of risks. These risks include user acceptance, frequency congestion concerns about the broadcast link for large transport aircraft, development and approval of air traffic procedures that can capitalize on ADS-B, and necessary adjustments to existing controller displays and related automation systems. All of these risks could materially affect the cost, schedule, and expected benefits of ADS-B.

“Finally, FAA has decided to rely on a service contract approach for ADS-B. This means that the Government will not own the ADS-B ground infrastructure but will pay for broadcast services. …

“An important oversight mechanism is the establishment of a performance control board for ADS-B. This board, comprised of FAA and contractor personnel, is expected o monitor ADS-B performance, review changes to the system and mutually resolve disagreements. This board is not yet in place, and its charter is not finalized. …

“We are concerned that FAA could find itself in a situation where it knows very little about the system that is expected to be the foundation of NextGen.”

A few more drops of rain on the dazzling promise; testimony of Dr. Agam Sinha, Mitre Corp., Center for Advanced Aviation System Development:

“One critical design element of the ADS-B system is a backup concept for ensuring continuity of surveillance during system outages. Since ADS-B depends on the aircraft’s navigation system, a potential point of failure is the navigation reference source – typically GPS [Global Positioning System, a satellite based system] augmented with WAAS [the FAA’s Wide Area Augmentation System, a ground-based technology that refines the GPS signal for greater navigational accuracy].

“The FAA, working with government and industry stakeholders, examined several alternative backup concepts to mitigate the negative impact on ADS-B caused by a GPS outage. It was determined that the best option was to keep about half of the existing radars – enough to provide coverage at the 40 busiest terminal areas and all en route airspace over 18,000 feet above mean sea level.”

Certifying the dazzling promise will not be independent according to Tom Brantley, President, Professional Airways Systems Specialists (PASS), the union of technicians who presently maintain the FAA’s air traffic control hardware:

“In our view, the approach being used by the FAA to deploy ADS-B is one that discounts decades of responsibly ensuring the safety of the flying public. … With the implementation of this system, ADS-B, unlike our current radar systems, will not be certified and all maintenance will be the responsibility of the contractor …

“PASS is especially disturbed by the elimination of FAA certification of the system, the decrease in system redundancy and the FAA’s troubled history of contract management …

“The FAA anticipates being able to ‘commission’ ADS-B services for use in the NAS [National Airspace System] by 2010 and by 2013 to have coverage everywhere there is currently radar coverage. The agency expects full implementation to take approximately 20 years, at which time primary radar will be eliminated and about half of the legacy secondary radars will be maintained to provide a back-up in case of an ADS-B outage …

“Since certification is an inherently governmental function, it can only be accomplished by FAA employees …

“In a recent update to the order [FAA Order 600.15D, General Maintenance Handbook for National Airspace System Facilities], effective October 1, 2007, the agency has ‘clarified’ the text to read, ‘FAA owned NAS systems, subsystems, and services directly affecting the flying public shall be certified’ (emphasis added). In other words, the FAA has not only re-interpreted the criteria to allow ADS-B to be deployed without requiring certification but actually prohibits full and appropriate certification of all systems it does not own.

“In addition, PASS has learned that the FAA intends to perform ‘service certification’ on ADS-B in order to give the pretense that the agency can oversee the safety and performance of the system.  Further changes the agency has made to its own orders reveal the agency’s true intentions of taking FAA employees out of the process …

“Since ADS-B is not a system owned by the FAA, and will therefore not be listed in Appendix 3, FAA employees will not be performing system certification; thus, the first two criteria above no longer apply [constituent systems and subsystems are certified by air traffic organization personnel of the FAA, and that indications on monitors and control consoles are normal]. The agency will then fall back to the newly added fourth criteria, ‘observation or knowledge of customer using the NAS Infrastructure Service.’ In essence, without a true certification of ADS-B, the controllers will have to rely on the users, i.e., pilots or the vendor, to tell the FAA that the service is wrong. Even the smallest inaccuracy will only be addressed if the ‘users’ report a problem. There will be no internal FAA quality checks as there are today.”

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