Click for next page ( 223


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 222
9 Air Traffic Congestion: Problems and Prospects THOMAS CRAIG Each year, hundreds of millions of passengers are flown all over the United States. They rely on air travel to conduct their businesses and maintain ties with friends and family. Although the airline industry orig- inated more than 50 years ago, it is still a growth industry, with a rate of increase faster than the growth rate of the nation's gross national product (GNP). Moreover, air travel is likely to develop its dominant position because no projected mode of transportation could displace it as the quick- est and most efficient way of moving people from city to city. Nor are more exotic forms of communication, such as video conferencing, ex- pected to displace it. By any yardstick, air travel is a success. Yet this very success has created problems. Because so many people are flying on so many planes, the airports and airways of the United States are no longer adequate to move them smoothly to their preferred desti- nations. Airport congestion has many causes airline marketing policies, airport layout, and noise considerations are examples but one principal effect: delay. The dollar amount of the cost of annual air travel delay is difficult to state with precision, but it is certainly large (Table 9-1~. This cost would be even larger if it were possible to quantify the frustration of millions of travelers who are experiencing more and more delays in an ever more crowded system. The problems of relieving congestion in the air and in airports do not have simple solutions. The authority and responsibility for tackling them clearly lie with the Federal Aviation Administration (FAA). But the au 222

OCR for page 222
AIR TRAFFIC CONGESTION TABLE 9-1 Estimated Annual Cost of Air Traffic Delay, 1984 ~223 Cost of Delays Amount Aircraft Average delay per operation (minutes) Air camer operations (thousands) Total delay (thousands of hours) Average cost of delay per hour Total cost of delay to aircraft (millions of dollars) Passengers Passenger hours lost (millions) Value of passenger time lost (dollars per hour) Total cost of delay to passengers (millions of dollars) Total cost of delay (passengers plus aircraft) (millions of dollars) . SOURCE: Transportation Systems Center. Airport Capacity Enhancement Plan. 1986. Cambridge, Mass. 6.8 10,839.5 1,228.5 1,647.0 2,023.0 1 17.9 22.3 2,629.3 4,652.3 thority for relieving congestion on the ground is divided among many entities and is thus a controversial and highly politicized issue. Conse- quently, constructing new airports and improving old ones are slow, pain- ful processes. Under the circumstances, there is little hope that many, if any, new airports will be built in the United States during the rest of this century. Although its authority is clear, the FAA still faces a difficult task in tackling the problems of delay due to congestion in the air because so- lutions require federal funding and the cooperation and agreement of various parties. Congress, faced with extremely high deficits, is slow to provide adequate funding to upgrade the air traffic control (ATC) system. Moreover, most of the proposed solutions are technical, and controversy and delay surround the implementation of each new proposed piece of advanced technology. In many cases the parties involved cannot concur because they genuinely disagree on the technical merits of alternative systems. Improvements are also delayed because the various factions in- volved take divergent stances on the merits of the National Airspace Plan, which is the overall FAA blueprint for reaching multibillion-dollar partial solutions to the congestion problem. Although the FAA is the sole des- ignated authority for operating and improving the federal airways system, it is still subject to the wishes of Congress and the public as expressed in federal legislation. The FAA administers the law; it does not create it. CAUSES OF AIRPORT CONGESTION Airline marketing policies, which are driven by passengers' preference for prime-time flying, contribute significantly to the problem of air travel

OCR for page 222
224 120 a) Q o ._ a, Q o o me 180 160 140 100 80 60 40 20 THOMAS CRAIG Arrivals 0 2 4 6 8 10 Noon 2 4 6 8 10 Tlme Midnight FIGURE 9-1 Scheduled operations at Atlanta's Hartsfield International Airport. demand exceeding supply. As a result the number of planes scheduled to arrive and depart almost simultaneously at an airport can overwhelm the system (Figure 9-1 and Table 9-21. For example, as shown in Table 9-2, 41 aircraft operations are scheduled for the first 10 minutes of the hour at Atlanta's Hartsfield Airport; unscheduled flights raise the number even higher. Such situations can generate backups and cause delays that last throughout the day. A New York area airport official, in summing up the problem of schedule bunching, stated, "When there are delays, they (the airlines) say, 'Others will blink first.' Well, nobody is going to blink." Aircraft weight classes and differences in speeds contribute to conges- tion because these variations affect air traffic control processing. Within the terminal area, radar separation that must be maintained between planes is established at 3 nautical miles (NM). Arriving aircraft that are following a heavy jet, however, must be separated by 4, 5, or 6 NM, depending on the weight class of the subsequent flights. All departing planes following the heavy jet are under the same constraints. Consequently, as the number of heavy jet operations increases, an airport's actual arrival and departure capacity can be significantly reduced, thus increasing congestion and delay (Figure 9-21. Because of these variations in terminal area and approach speeds, controllers must ensure that initial spacings exceed the required

OCR for page 222
225 no as o Ad ._ so o Ed EM as C) Cry _4 U: Cal Cal _ ~ To ~ ~ _ I_ ._ Ct 3 3 Ct Cal Ct .b <: . Ct _ Cal Ct .> Em 0 ~ ~ ~ rat ~ ~ 0 0 ~ of Do oo oo oo Go Do ~ ~ oo ~ ~ Go as 0 ~ ~ To to a, ~ ~ ~ ~ ~ oo Do ~ ~ ~ as ax cry ~ ox ~ as 0 0 0 - ~ ~ - car ~ ~ ~ ~ C'I _____________ ~ ~ ~ l_ ~ _ _ _ ~t ~ ~ _ 0 - ~ ~ ~ ~ ~ ~ oo ~ O - c~ ~ ~ ~ ~ ~ oc a~ 0 - ~ ~ ~ ~ ~ ~ oo ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ u~ ~ ~ ~ ~ ~ u~ .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ____________4__________4________ _______ _____~ ______ ________ c~ c~ ~ ~ ~ _____ aN C~ ~) - C~ ~ ~ 00 0 0 0 - ~ ~ o0 ON O ~ ~ ~ ~ U~ C~ CN ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ u~ ~ U~ ~ ~ \0 ~ ~ ~ ~D oo - - - ( ~_ c-~ (~) (~) _ c~] _ _ (~] _ _ _ c~] g a~ ~: c: ct .= ~:5 OCR for page 222
a) - Q ._ - a, - t~s 40 ._ - 60 30 - - - - - - 0 20 40 60 80 100 Percentage of Heavy Jets FIGURE 9-2 Influence of heavy jets on arrival throughput. The figure assumes the airplane mix is composed of large and heavy jets. distance when a slower aircraft is leading so that the distance between the planes is not less than the allowed minimum when the leading aircraft crosses the landing threshold. The resulting spacings can double the target minimum separation as aircraft are vectored to the final approach course at various distances on the landing runway. When the trailing aircraft is slower, separation increases at the threshold to more than the minimum and throughput is lost. The same is true when planes with different climb speeds depart consecutively. One obvious way of reducing congestion lies in increasing the size of airplanes so that more passengers travel on each flight. This stratagem can succeed, provided allowance is made for the increased wake vortex separation required when the maximum gross weight of the airplane ex- ceeds 300,000 pounds (see Figure 9-3~. The layout of an airport can also affect congestion, either positively or negatively. Runway spacings, the point of intersection of the runways, the location and turnoff angle of exits, and runway length are all relevant factors when considering an airport's capacity. Figures 9-4 and 9-5 show typical diversity in airport configurations. The air traffic control procedures developed for the variety of airport configurations must include safety margins that can limit operations when necessary, particularly in the case of bad weather Such safety margins are required because pilots and controllers still rely in part on their ability to see approaching traffic. Thus,

OCR for page 222
AIR TRAFFIC CONGESTION 227 for example, at Chicago's O'Hare Airport and at Dallas-Ft. Worth, triple arrival streams to a set of parallel runways and one intersecting runway are used only in daylight with a ceiling of at least 1,000 feet (ft) and 3 miles' visibility and, in Chicago, when runways are dry. Several procedures tailored to runway spacings have been developed for use in any weather conditions at busy airports. Such procedures include parallel approaches to runways separated by at least 2,500 ft. using reduced spacings (2 NM) between arrivals on the adjacent instrument landing system (ILS) localizer courses; and simultaneous ILS approaches to par- allel runways separated by at least 4,300 ft. At Newark International Airport, tests are being conducted to reduce the in-trial spacing between successive arrivals to that required to accom- modate minimum runway occupancy time (ROT). The tests are based on the concept that when the average ROT is 50 seconds (s) or less, a separation of 2.5 NM is adequate unless wake turbulence rules apply. The 20 15 a) u) o In o o of - a) 1 0 Ct - ._ E 3 ._ X 5 o Short Range Medium Range Long Range / oooX In 7571200 / 737-300~67-200 / / 707-300 / ~ 3OO~ 0 100 200 300 400 500 Seats FIGURE 9-3 Impact of wake turbulence rules on seat throughput. Increasing airplane size to increase seat throughput can produce a reduction in throughput if airplane gross weight exceeds 300,000 pounds.

OCR for page 222
228 9,000 ~ . ~u o,coo ~ OR .- _ .. ~ 26L I c.:: ~ 1 1,889 ft 9,000 ~ THOMAS CRAIG N FIGURE 9-4 Runway operation patterns at Atlanta's Hartsfield International Air- port. West flow operated 60 percent of the time; reverse or east flow operated 40 percent of the time. procedure cannot be used at all airports, however, because the SO-s average is not attainable at some locations. Airport capacity can also be affected by congestion on the ground. The O'Hare Airport runways and air traffic control system currently can process more traffic per hour than the gates will accommodate. Many ground delays are caused by this situation. iIsplaced Threshold oVertU ~ ~ N T ax 11 27 ~ ?< FIGURE 9-5 Runway operation patterns at Boston's Logan International Airport: four configurations with the west flow configuration operated 42 percent of the time.

OCR for page 222
AIR TRAFFIC CONGESTION TABLE 9-3 U.s. Air Traffic Forecasts 229 Traffic Volume (billions of RPMa) Size of U.S. Jet Fleet (number of units) Year Boeing FAA Beginning Domestic Int'l. Domestic Int'l. Boeing FAA . 1986 293 77 279 68 3,248 3,031 1990 351 88 341 82 3,446 3,412 1997 480 119 479 119 3,821 3,976 aRPM = revenue passenger miles. Environmental concerns and local noise abatement rules influence the capacity of many, if not all, major airports. If noise problems limit the airport to a single initial departure track when actually multiple runways are available, the airport's departure capacity can be reduced by two-thirds or more. Arrival track location requirements can also limit capacity. The Charlotte-Douglas Airport offers a classic example of this situation: only one of the three runways may be used during church hours, and only two may be used during the school year. Some airports experience particularly serious congestion or delay when weather conditions do not permit visual approaches. Denver, San Fran- cisco, St. Louis, and Minneapolis all fall into this category. Arrival ca- pacity can be reduced by 50 percent or more when visual separation procedures cannot be used.* PROSPECTS FOR IMPROVEMENT FAA forecasts offer no prospect of relief from airport congestion and delay, at least as far as scheduled air carrier operations are concerned. Tables 9-3 through 9-6 show both FAA and Boeing projections for certain classes of commercial air traffic. Table 9-3 shows, for instance, that both the FAA and Boeing forecast continued growth in the volume of air traffic and modest increases in the size of the U.S. jet fleet. Both sets of pro- jections convey the same message: air taxi/commuter operations are mak- ing, and will continue to make, heavy demands on airport and airway facilities without moving a commensurate share of the traffic. Defining this situation is not meant as an indictment of the air taxi/ commuter airlines. They are, in fact, doing precisely what the architects *The author is indebted to Boeing Air Traffic Control Systems Analysis for this discussion of conditions contributing to airport congestion.

OCR for page 222
230 THOMAS CRAIG TABLE 9-4 Boeing and FAA Projections of Commercial Air Carrier Operations Including Air Taxi/Commuter Operations (in millions of tower operations) Air Taxi/Commuter Air Carrier Operations Operations Year Boeing FAA Boeinga FAA 1986 1 1.8 1 1.9 7.3 1990 13.1 13.4 - 8.7 1997 14.2 15.2 1 1.2 aBoeing has no forecast of air taxi/commuter operations. Of deregulation envisioned providing service to smaller communities that want the speed and convenience of air travel. Nevertheless, the impact on major facilities is unacceptable. The system cannot afford to have 42 percent of commercial air carrier movements account for less than 8 percent of the passenger enplanements.* One proposed way of easing the growing congestion at major hubs is to bypass, or overfly, these cities. Unfortunately, most air travelers in the United States either come from a large hub or want to get to one. In fact, about 92 percent of all passengers begin and end their journeys at a large hub, regardless of the route flown in between. This limits the amount of relief that might be achieved by overflying. In short, airport congestion will continue to be a major air travel problem throughout this century. Solutions require cooperation among the many interests involved, each of whom approaches the problem from a slightly different point of view. The FAA must be involved, along with the local airport authority; the community; special interest groups that represent environmental concerns, the airlines, and the airframe and engine man- ufacturers; Congress; the financial community, which must float bonds; and finally, the passenger, who pays the penalty for delay in lost time and frazzled nerves. The chances of an agreement among these various entities on a set of actions designed to relieve airport congestion seem remote. The FAA now has in place a plan to meet its responsibilities for relieving airside congestion. First released in December 1981 the plan includes four main air traffic control programs. The cornerstone of the plan is a new *Each time a passenger actually boards an airplane is a passenger enplanement. For example, one person traveling from Carmel, California, to Buffalo, New York, would represent four enplanements if routed over San Francisco, Chicago, and New York City on four different carriers.

OCR for page 222
AIR TRAFFIC CONGESTION: TABLE 9-5 Projected Commuter Air Traffic in Relation to Total Passenger Enplanements (in millions) Scheduled Passenger Enplanements 231 Year Total Commuter Percentage 1986 413.1 25.9 6.3 1990 5003 35.0 7.0 1997 693.1 54.5 7.9 SOURCE: Federal Aviation Administration. February 1986. FAA Aviation Forecasts, Fiscal Years 1986-1997. Washington, D.C.: U.S. Department of Transportation. state-of-the-art computer system, which provides the increased capacity needed to handle growth in traffic. The new system will also integrate and automate control services both in the terminal and en route. The first installation was completed in Seattle in late 1986; the system is expected to go on-line in June 1988. Initially, the computers will use the existing air traffic control computer program. All computers are expected to be in operation 6 months after delivery. An advanced automation system is the second component of the plan. The advanced system uses minicomputers to improve controllers' pro- ductivity through modernized software and controller hardware. Third, the voice-switching and control system will automatically switch any in- trafacility voice communication between controller positions. Fourth, the consolidation of 200 terminals and en route radar facilities into 23 area control facilities will bring significant savings in manpower and costs. When the fully modernized system is in place by the late 1990s, it will be able to handle 25 percent more operations than was possible in 1980, with a controller work force of fewer than 10,000. The plan to modernize the nation's air traffic control system is now being put into operation, but budgetary problems are jeopardizing its timely completion. Congress must reauthorize the funding for the plan each year. TABLE 9-6 Projected Commuter Operations as a Share of Total Air Carrier Operations (in millions of tower operations) Total (including Commuter Share Year Air Carrier commuters) (percentage) 1986 1 1.9 19.2 38.0 1990 13.4 22.1 39.4 1997 15.2 26.4 42.4 SOURCE: Federal Aviation Administration. February 1986. FAA Aviation Forecasts, Fiscal Years 1986-1997. Washington, D.C.: U.S. Department of Transportation.