Air Traffic Control Reform Newsletter #72
Photo 91183491 © Stefano Carnevali -

Air Traffic Control Reform Newsletter

Air Traffic Control Reform Newsletter #72

April 2010

In this issue:

  • NextGen and New Types of Planes
  • FAA Faulted on New-Controller Training
  • Winglets and Wake Turbulence
  • ATC Performance: Europe vs. USA
  • Questions about BEBS
  • News Notes

NextGen Will Facilitate New Aircraft Options

We all know (or at least believe) that NextGen will significantly increase airspace capacity, but everything I’ve seen suggests that the smallest (albeit significant) increase will be in runway throughput. And in the largest metro airports where adding new runways can be hugely expensive (if not politically impossible), that is a serious constraint on aviation growth. But a new study, funded by NASA, suggests that the tools provided by NextGen will make it feasible to provide short-haul service from 3,000-foot runways, thereby opening up important new metro-area capacity.

Besides several news releases, I have read the 18-page executive summary of the report, “Advanced Vehicle Concepts and Implications for NextGen,” produced under NASA Ames contract #NNA08BA64C. (To the best of my knowledge, the full study is not yet available online.) It was produced by a 21-member team, drawn from Sensis Corp., Georgia Tech, MIT, University of North Carolina, Honeywell, CSSI, Inc., ATAC Corp., and Engility Corp. They reviewed five new aircraft types, using generic performance specs, and a generic model of the NextGen ATC system, along with a number of other models to assess safety, environmental impacts, etc. The five aircraft types were:

  • Cruise-efficient short takeoff and landing (CESTOL);
  • Large commercial tilt-rotor (LCTR);
  • Unmanned aerial system (UAS);
  • Very light jet (VLJ);
  • Supersonic transport (SST).

Since, in my judgment (based on the study’s findings), by far the most significant impact on air transportation would come from the CESTOL, my comments here are limited to that vehicle type.

As modeled for the study, the CESTOL would be a hundred-passenger plane able to land and take off using 3,000-ft. runways. Thus, it could serve reliever airports in the same metro area as a congested major hub (e.g., Briscoe Field in Gwinnett County in the Atlanta metro area) as well as using underutilized short runways at major hubs. What NextGen does to make this feasible is to provide precise independent approach/departure paths in the metro area’s terminal airspace. For example, the CESTOL could fly steep and/or spiral approach paths. Since STOL capability generally comes at some cost, part of the study’s purpose was to assess whether the gains in capacity outweigh those increased costs. (I note in passing that the tilt-rotor that was also studied would fill nearly the same market niche, but at significantly greater cost than the CESTOL.)

CESTOL was modeled as substituting for conventional (e.g., 737) flights in those metro areas where demand exceeded capacity, for flights up to 600 nm in length. In addition to generic studies of CESTOL (and the others) in the overall National Airspace System, the study team did two detailed analyses, for the New York and Washington, DC metro areas. In each case, they redesigned the entire airspace using RNAV and RNP procedures, and assuming continuous descent approaches (CDAs) for conventional aircraft but curved arrival and departure paths for the CESTOLs. As the New York metro area summary explains, “The CESTOL scenario showed a substantial reduction in delay compared to the baseline, primarily due to the offloading of flights from Newark International Airport (EWR) to satellite airports. . . . Spiral departure procedures combined with midfield takeoff procedures help mitigate the negative impact CESTOLs have on departure throughput. Furthermore, the use of underutilized runways for CESTOL operations contributes to an overall increase in the metroplex arrival throughput.” For the Washington, DC area, the results “again reveal that CESTOL aircraft have the potential to increase throughput and reduce delay when used with reliever airports and underutilized runways.” And on a systemwide basis, “The CESTOL scenario (which shifts many flights to less congested regional airports) shows a substantial reduction in delay compared to the baseline scenario.”

These are important and powerful results. They offer commercial aviation a way to compete with poorly justified proposals to spend hundreds of billions of taxpayer dollars to create inter-city high-speed rail systems on routes up to 600 nautical miles (nm). One of the arguments made by HSR proponents is that it is either impossible or more costly to expand short-haul air service in those markets, so government must step in with a new modal alternative. What’s left out of that argument, in addition to new approaches like CESTOL, is that commercial aviation is self-supporting, covering the full cost of its airport and ATC infrastructure via aviation user taxes. In stark contrast, 100% of the enormous capital costs of HSR (vehicles plus guideway plus stations) and very likely a portion of its operating costs would come from general taxpayers, whether or not they ever use the rail systems.

It was already outrageous for the federal government to use general-fund tax money to create a new mode in competition with commercial aviation. HSR’s environmental benefits over driving and flying are negligible, and the cost per ton of CO2 eliminated by shifting trips from those modes to HSR is many thousands of dollars per ton. But in addition to those arguments, aviation can now counter the “we can’t add airport capacity” claim by responding, “Yes we can!”

FAA Criticized on Controller Screening and Placement

While the FAA has made major progress in the last several years hiring large numbers of new recruits to replace the post-strike generation of controllers who’ve begun retiring, its process of screening and placing new hires leaves much to be desired. That’s the conclusion of an audit by the DOT Office of the Inspector General, released the first of this month. (“Review of Screening, Placement, and Initial Training of Newly Hired Air Traffic Controllers,” AV-2010-049).

The main problem is as follows. Would-be controllers must pass a basic aptitude test (called AT-SAT) prior to being allowed to begin training at the FAA Academy in Oklahoma City. Those who pass that hurdle take two to three months of training at the academy and then go on to an ATC facility for what typically amounts to several years of on-the-job training. But facility managers told the OIG auditors that “candidates arrive after passing Academy training unprepared to begin facility training, often requiring additional time and resources to refresh them on subjects previously taught at the Academy.” Those defects in Academy training were identified in an internal FAA study in 2007, “but more than 2 years since its completion, changes have not been implemented.”

More serious than that shortcoming is the way in which the FAA decides which facility to send trainee controllers to. Air traffic control facilities differ enormously in their complexity and traffic levels, designated as Levels 4 through 12, with the busiest and most complex (e.g., Southern California TRACON, Chicago O’Hare Tower) having the highest numbers. Given this fact, you would think the agency would try to match the applicant’s knowledge and abilities to the facility level, for his or her on-the-job training. Wrong. According to the OIG audit, the FAA uses neither the AT-SAT score nor the candidate’s Academy results to decide on facility assignments. Instead, it assigns candidates to facilities before they enter the Academy, and does so based on where openings exist and the candidate’s geographical preference. As a result, “new controller candidates are being assigned to some of the busiest air traffic control facilities in the Nation with little consideration of whether they have the knowledge, skills, and abilities necessary to become certified controllers in those locations.”

That might sound overly dramatic, but consider these additional points brought out in the audit. First of all, in contrast to even a few years ago when only 7% of new hires had no prior ATC experience (generally from the military), in FY 2009 that lack of experience extended to 72% of those hired. AT-SAT was designed to screen out those with lower probability of becoming certified as capable controllers, and was predicted by its designers to average a 67.5% pass rate. But today FAA declares 93% to be passing, “primarily because FAA reweighed elements from the original test, based on concerns of possible adverse impacts, which ultimately reduced focus on specific air traffic control aptitudes.” And the Performance Verification test given at the Academy, which is graded on a Pass/Fail basis, enables 95% to receive a grade of “Pass.” The auditors point out that “Scores [on the PV] are based strictly on the subjective assessment of the designated examiners, which we found can vary extensively.”

This lack of rigor in testing, when combined with facility assignment that does not take aptitude into account, is leading to serious problems. According to the audit, in FY 2008 some 58% of all new hires with no prior ATC experience were placed at Level 10 through 12 facilities-since that’s where the most openings were. And of the 233 new controllers with no prior ATC experience who completed training during that year, nearly half (109) did not certify at their assigned location. Since the beginning of FY 2008, FAA had to reassign more than 300 new controllers to lower-level facilities, and another 227 new controllers requested reassignment. In other words, you can dumb down the “aptitude” and classroom tests so nearly everybody passes, but you can’t fake the on-the-job training.

This flawed process produces top-level numbers that look good to Congress: enough new controllers are being hired and trained to fill in for those in the process of retiring. But it’s costly and wasteful to accept people into training who can’t ultimately hack it, and to place people with middling skills into the most-demanding ATC facilities raises real safety concerns. In its response, the FAA “partially concurs” with all three OIG recommendations for change. That’s better than rejecting them, but I hope OIG revisits this issue in a year or two to see what improvements FAA has made.

Winglets and Wake Turbulence

One of the biggest challenges for NextGen (and comparable ATC modernization efforts in other countries) is increasing runway throughput. A big constraint on runway throughput today is wake turbulence. Planes that are landing or taking off generate a swirling vortex of turbulent air off each wingtip, strong enough in many cases to upset a plane that attempted to land or take off close behind. In general, vortices are larger and more dangerous the larger the plane, but since aircraft show up for landing in a random sequence, the general rule is to maintain a constant spacing between them, based on the worst-case wake turbulence.

Considerable ATC research is going on to find ways around this constraint. If NextGen provides automation that better sequences arrivals and departures, it may be feasible to tailor the spacing to the specifics of each pair-e.g., a 747 landing after a regional jet would need less than the worst-case spacing. Another idea is real-time monitoring of cross-winds, based on the idea that a good cross-wind can blow the offending vortex away from the runway.

Until recently, I have not seen winglets referred to as a potentially significant factor in reducing wake turbulence and thereby reducing the spacing between landings and takeoffs. But when I saw a news item a couple of weeks ago about a new winglet testing program by Aviation Partners, Inc. (API), a light bulb went off. Let me explain.

API is the world’s leading winglet producer, developing the “blended winglet” that has been retrofitted to hundreds of 737s and 757s over the past decade, as well as many business jets. Airlines opt for winglets because they reduce fuel consumption by about 5%, and fuel these days is the largest single component of direct operating cost. And how do winglets do this? By reducing the size and intensity of the vortex behind the wingtip. Apparently, as it first spins off the wingtip, the vortex hits the winglet surface, generating a force vector pointing slightly forward. This imparts some additional energy to the aircraft in the forward direction, and the resulting energy loss to the vortex makes it smaller and less damaging to anything in the wake of the aircraft-including a following plane. (Go to Wikipedia, under “wingtip device,” for a detailed explanation and illustration.)

The news item, appearing in several places, announced that API will soon resume testing on a winglet concept it first developed a number of years ago-the spiroid winglet. Instead of just being an upward-canted wingtip, the spiroid is a complete loop. Testing on a Falcon 50 business jet will begin in early June, partly funded a grant from the U.S. DOT’s Volpe Transportation Systems Center. I first heard about spiroid winglets about three years ago at an Air Traffic Control Association conference-not a presentation, just lunch-table conversation. The context was not reduced fuel burn but reduced wake turbulence. API estimates that the spiroid winglet will reduce fuel burn by 6 to 10%–i.e., potentially up to double what a blended winglet does. If that translates into cutting the strength of the vortex in half, compared with a conventional winglet, that would be important progress on further reducing the runway wake turbulence problem.

Reducing fuel burn by 10%, if this pans out, would be reason enough for all jet aircraft to be equipped with winglets, based on sheer economics. And that will be an important step toward reducing the runway wake turbulence problem and increasing runway throughput.

Comparing ATC Performance in Europe and the United States

We all know that on a cost-effectiveness basis, air traffic control is more productive in the United States than in Europe. The fragmented European system, with 38 different air navigation service providers (ANSPs), employs a total of 56,000 staff compared with 35,000 for the FAA, and 16,800 controllers compared with our 14,000 (as of 2008). And due to everything in Europe being defined by national borders, there are 65 en-route centers compared with just 20 here, in a geographical area that’s about the same size. The U.S. system handles about 70% more IFR (instrument flight rules) flights and about 80% more flight hours, yet does so with fewer people.

These figures come from a recent report produced jointly by Eurocontrol and the FAA, “U.S./Europe Comparison of ATM-related Operational Performance,” dated October 2009 (and received by me in hard copy in December). The figures in the previous paragraph were provided for context, since the thrust of the report is to compare operational performance of the two systems. It’s a detailed, 64-page report, and I confess to having digested only the nine-page (but very well-done) Executive Summary. Here are a few highlights.

The report focuses on IFR operations, which is where most of the ATC activity is. Second, it also focuses mostly on flights to and from the 34 busiest airports in Europe and the USA, respectively. There are important differences in ATC flow management. Europe regulates airport operations based largely on their IFR capacity, in contrast to U.S. practice of unlimited operations at most airports, which means scheduling them to VFR (good-weather) capacity. So most flow-control in Europe is “strategic,” in that it is decided months in advance at the airport level, while in the United States it is “tactical,” imposed on the day of operations, and first applied to the en-route portion but extended (via ground holds) to airports when necessary.

In terms of on-time performance, the general trend was downward in both regions from 2004 to 2007, with an upturn in 2008. In Europe, on-time arrival figures are almost identical with on-time departure figures, but in the USA, arrivals are less punctual than departures. From 2000 to 2008, scheduled block times remained about the same in Europe, while creeping upward in the United States. And the variability of flight times is considerably higher in this country.

Ground delays are more frequent in Europe, but when they happen in this country they average twice as long as in Europe. Taxi-out times are consistently longer in this country, too. The extra miles flown due to less than optimal routings in the en-route phase, surprisingly, are only 1% lower in the United States, despite the far more convoluted airspace in Europe. And for arrival delays (due to sequencing and metering), these average about the same in both places, with a major outlier in London Heathrow (whose arrival delays are much higher than anywhere else).

The researchers also estimate how much of an “inefficiency pool” is actionable by improved air traffic management, coming up with 6 to 8% of total fuel burn, for both regions. That’s a smaller number than some have expected, and the report qualifies this by saying that “more work is needed to draw a more complete picture” of this important benefit from implementing NextGen and the Single European Sky.

Kudos to the Performance Review Unit at Eurocontrol and the FAA Air Traffic Organization’s Strategy and Performance business unit.

Questions About “Best-Equipped/Best-Served”

My recent article about the “best-equipped/best-served” concept, as an incentive for aircraft operators to equip their planes with the equipment needed for NextGen, brought several responses. The most interesting was from human factors scientist Ashley Nunes, who has worked on ATC issues for a number of government agencies. Nunes raised some important points regarding how prepared the Air Traffic Organization and its controllers are to implement something like BEBS.

Nunes writes that “prioritization of aircraft based on specific attributes does not enter the mental ‘model’ of the air traffic controller,” or at least there is no evidence that this is the case. “I believe this is due in large part to training, namely the fact that controllers are trained to push traffic [instead of] worrying about the nuances of equipage (versus performance characteristics which controllers must monitor for traffic management purposes).” At recent meeting of ATC researchers and controllers, Nunes tells me, this subject came up and “the controllers at the table were all in agreement that as proposed currently this really could not be done, given current training parameters. Why? Because we would be asking controllers to change their mindset from moving traffic efficiently to only moving SOME traffic efficiently.”

Elaborating further, Nunes cites my articles lauding the operational benefits of continuous descent approaches (CDAs) but says “we have observed spikes in controller workload when they are asked to manage traffic executed where there is a mix in operations, i.e., some of the traffic executed [CDAs] and some did not. Why? Because the cognitive [requirements] of the controller, while reduced for handling the better-equipped aircraft, actually increase when he/she is forced to move non-equipped aircraft around.”

These are important questions, and I look forward to hearing from other readers working on this problem. While I have observed operations (once) in a TRACON and (once) in a Center, I’m not a human factors expert, nor an expert on NextGen. My initial response to Nunes’ points is that obviously controller training needs to change, in a whole variety of ways, given the paradigm shift that NextGen represents. And also that initial cases of de-facto BEBS (such as the use of CDAs at selected airports today, and Nav Canada’s forthcoming preferred altitudes for ADS-B-equipped planes) need careful monitoring with these kinds of human factors points in mind.

News Notes

Wide-Area Multilateration in the United Kingdom
The UK air navigation service provider NATS will test a wide-area multilateration (WAM)/ADS-B system in the greater London area encompassing the airspace of Heathrow, Gatwick, Stansted, Luton, and London City airports. Its performance will be compared with that of the current radar surveillance system in meeting the current 3 nm. separation requirement in London-area terminal airspace. Prime contractor is Thales UK.

JPDO Tests Advanced Weather System
The Joint Planning & Development Office is demonstrating its NextGen concept of advanced probabilistic weather information, by means of a demonstration called JPDO Storm Desk. While not an official weather forecast, it is offering alternative, probabilistic weather scenarios for the Washington, DC metro area. The site can be accessed via the JPDO blog (

Follow-up re FAA Forecast
An aviation economist wrote in response to my article last month about the lower aviation growth in the 2010 FAA forecast report. He points out one reason for the change: a higher estimated price for fuel than used in last year’s forecast. And he adds, “This 2010 assumption about future fuel prices-which naturally would constrain the growth of demand somewhat compared to the fuel price scenario used in 2009-is [also] more consistent with the forecast that the Energy Information Administration has produced for the same period.”

Follow-up re Facility Consolidation
An airports expert whom I’ve known for many years provided another possible reason for controller opposition to facility changes. Controller pay in a combined (tower/TRACON) facility increases if the controller remains current at both operations. “This leads to controllers putting in the minimum number of hours per month needed to remain current at their secondary workplace, usually during a low-traffic period. This raises concerns about the difference between ‘currency’ and ‘proficiency,’ especially if a minimally proficient tower controller ends up working during busy shifts with complicated intersecting operations.” He also notes that the safety of different facility configurations depends on hard data, and that claims that larger facilities having more operational errors “may simply reflect their larger size, not a higher rate of operational errors.”

Remote Tower in Australia, Next
Airservices Australia has signed a memorandum of understanding with Swedish ANSP Luftfartsverket (LVF) and Saab to bring their award-winning remote tower technology to Australia. Airservices plans a trial of the system, under which a single tower could control several small or medium-size airports (which would be equipped with various sensors). Any decision to roll out the technology would require consultation with aviation users and regulatory approval from Australia’s Civil Aviation Authority.

Wide Area Multilateration (WAM) in the North Sea
Another geographical area that now has wide-area multilateration surveillance is the Netherlands portion of the North Sea. The air navigation service provider, LVNL, has implemented the system featuring Era’s MSS multilateration and ADS-B surveillance system. It handles both overflights in that airspace and flights to offshore oil platforms.