Basic relationships for LTA technical analysis

An introduction to airship performance is presented. Static lift equations are shown which, when combined with power requirements for conventional airships, allow parametric studies of range, payload, speed and airship size. It is shown that very large airships are required to attain reasonable speeds at transoceanic ranges

Impacts of technology on the capacity needs of the U.S. national airspace system

December 1991Includes bibliographical references (leaf 57)Introduction: Air passenger traffic in the United States showed remarkable growth during the economic expansion of the 1980's. Each day a million and a quarter passengers board commercial flights. The boom coincided with the advent of airline deregulation in 1978. This drastic change in the industry has inspired professional and newspaper articles, graduate student theses, and books which have discussed the causes, effects, costs, and benefits of deregulation with predictably mixed conclusions. Economists, who like to predict the future by exercising econometric models, are finding that conditions in air transportation have become too dynamic (chaotic?) for their models to cope. Certainly the future of the air transportation industry is unclear. There has been, however, an unmistakable trend toward oligopoly, or, as industry spokesmen describe it, "hardball competition among the major airlines." This trend has been accompanied by formations of hub fortresses owned by these survivors. Air traffic has always been concentrated in a few large cities; airplanes will go where there is a demand for them. But airline (rather than traffic) hubs have created artificial demand. Up to seventy percent of travellers boarding airplanes in the hub cities do not live anywhere near these cities - in fact, they may have no idea at which airport they are changing planes. Most passengers do not care, while travel cognoscenti soon learn to avoid certain airports (and airlines which frequent these airports). A hub airport is a frenzy of activity for short periods of time during the day, as complexes of airplanes descend, park and interchange passengers, and take off. Then the airport lies quietly. If observers were to arrive at a major hub between times of complexes, they would be perplexed to hear that "this is one of the most congested airports in the world." Thus congestion and its evil twin, delay, are not constants in the system. Rather, they appear only if a number of conditions conspire to manifest themselves simultaneously, or nearly so. First, the weather must deteriorate from visual flight conditions to instrument flight conditions. Then, this must occur near peak demand conditions at the airport. Of course, some airports in the Unites States are always near peak conditions, among them the so-called slot constrained airports: New York's La Guardia and Kennedy, Washington's National, and Chicago's O'Hare. When weather goes bad at these airports or other major hubs during complexes, ripple effects start nearly all over the country, because some airlines have now designed schedules to maximize utilization of their airplanes. Very little slack time is built into the schedules to account for potential delays, although "block-time creep" exists: the phenomenon that travellers discover when they arrive at their destinations ahead of schedule (if they happen to leave on time). This "creep" protects the airlines from being branded as laggards by the DOT's Consumer On-Time Performance Data hit list. Thus a combination of management practices by airlines (which place great demand on terminal airspace over a concentrated period of time) and mother nature (which provides currently unpredictable behavior of weather near the airport) conspire to limit the capabilities to handle arrivals and departures at various airports below the numbers that had been scheduled. Travellers complain that the schedules aren't being met, and if enough people complain to Congress, or if the travellers themselves happen to be members of Congress, a national problem appears. How much of a problem is this? In 1988 there were 21 airports, according to the FAA, which exceeded 20,000 hours of annual aircraft delay, perhaps 50,000 hours per year, or 140 hours per day. (One, Chicago's O'Hare, exceeded 100,000 hours.) These airports, in turn, averaged 1,000 operations (arrivals and departures) per day, so that each operation would have averaged about 8 minutes of delay. At O'Hare, for example, 6% of all operations experienced in excess of 15 minutes of delay. (In excess means just that - there is no knowledge of how much "in excess" is.) Conversely, this means that at that most congested airport in the United States, 94% of all airplanes arrive or depart with less than 15 minutes of delay. However, airline delay statistics may be similar to the apocryphal story of the Boy Scout troop which drowned wading across a creek which averaged two feet in depth. There are estimates that on a dollar basis, delay accounts for a $3 billion cost to airlines, or a net societal cost of$5 billion if travellers' wasted time is included. Since in their best years U.S. airlines make about $3 billion in profit, reducing delay is a sure-fire way for airlines to climb out of their all too frequent financial morasses, as well as diminishing their passenger frustrations. Even though all of the numbers mentioned in the paragraphs above are subject to substantial caveats, it is indisputable that on certain days during the year the air transportation system seems to come to a crawl, if not a halt. Travellers either find themselves sitting at airport lounges observing cancellation and delay notices appearing on the departure and arrival screens, or sitting in airplanes (on runways or at gates) being told that there is an "air traffic delay." Old-timers grumble that the only difference twenty years of technology improvements has made to the U.S. airspace system is that the wait is now on the ground instead of circling in the air near their destinations. To the casual observer, it would appear that a number of solutions exist to solve this problem. The most obvious is to pour more concrete: more airports, more and longer runways, more taxiways, more gates and terminals. This is analogous to widening highways and building more interstates for ground transportation congestion. The concrete solution, alas, runs into both financial and citizen roadblocks. It is very expensive - the latest airport coming off the drawing boards (Denver International) carries a tag of some$2 billion, with about $400 million of that in bonds being backed by a new funding creature, the Passenger Facility Charge (a head tax of up to 3 dollars assessed to every passenger enplaning at an airport - voluntary or not). The citizen roadblock is community objections to airport noisiness. The bill creating the PFC in 1990 also carried with it a mandate for the FAA to create a national noise policy so that individual airports would not wreak havoc with the whole system by creating their own local operational rules, such as curfews. The bill also attempted to pacify airport neighborhoods by setting a deadline for all U.S. aircraft to be quiet(er) - complying with Stage 3 regulations by the year 2000. More damaging than financial difficulties are the anti-noise sentiments, and the concomitant not-in-my-backyard syndrome, that are at the forefronts of protests of either an alert citizenry, or New Age Luddites, when any expansion plans are made public. Whatever one's view, it is a crowd vocal and seemingly powerful enough in local political circles to stop any large- scale progress to ground solutions of the congestion problem. That, then, leaves the air. It is intuitive that if airplanes were closer spaced than they are now, much more traffic would move through a given area in the same amount of time, and consequently airplanes would land (and take off) quicker, reducing any waiting (queue) time. This obviously increases airport noise levels. There are two problems with this approach. The first trick is to accomplish this safely. Safety has at least two dimensions: there is the physical, i.e., airplanes should not run into each other (or the ground, as a result of weather disturbances and wake vortices); and pilots (and controllers) should feel they are still in control of the situation, even after separation standards are reduced. The first aspect is mostly a matter of technology, the second mostly a matter of human factors. But if traffic moved quicker and noise of the aircraft is not reduced, the same citizens who had vehemently opposed the construction of additional ground facilities would once again rise in righteous anger and demand a stop to the more efficient techniques of flying airplanes which have caused an increase in the noise levels in their neighborhood. They, too, must be considered. This report will attempt to address some of the issues outlined above. The focus will be on technology and where it is best suited to provide an equitable and efficient expansion of capacity in the air transportation system. Ultimately, the discussion will be centered on NASA's potential contributions to solving the capacity problem

Modelling risk in ATC operations with ground intervention

Cover titleJuly 1991Includes bibliographical references (leaves 17-18)Preface: It was part of a continuing series of research work aimed at creating models for estimating Collision Risk for ATC operations which can be used by the Federal Aviation Administration and ICAO to establish safe criteria for separations between aircraft.Introduction: The purpose of this information paper is; a) to provide a document describing the problems of analyzing risk for ATC systems which have surveillance over air traffic and which allow ground controllers to intervene to avoid unsafe encounters; b) to propose a framework for future studies which attempt to solve these problems. The need for such methods of analyzing risk arises in justifying reduced ATC separation criteria which ensure safety for newer forms of ATC operations. The benefits of these new systems strongly depend on achieving a reduction in current ATC separations, and as a result, an increase in capacity and efficiency for aircraft operations. These benefits must be weighed against the costs of developing and operating the new ATC systems.Supported by the Volpe National Transportation Systems Center of the US Department of Transportatio

Aircraft requirements for low/medium density markets

A study was conducted to determine the demand for and the economic factors involved in air transportation in a low and medium density market. The subjects investigated are as follows: (1) industry and market structure, (2) aircraft analysis, (3) economic analysis, (4) field surveys, and (5) computer network analysis. Graphs are included to show the economic requirements and the aircraft performance characteristics

A fault-tolerant multiprocessor architecture for aircraft, volume 1

A fault-tolerant multiprocessor architecture is reported. This architecture, together with a comprehensive information system architecture, has important potential for future aircraft applications. A preliminary definition and assessment of a suitable multiprocessor architecture for such applications is developed

Extended-range operations by transport aircraft, A review of

April 1987Includes bibliographical referencesIntroduction: The safety of enroute operations of aircraft engaged in public transport has been a continuous concern since the early days of air transportation. There are a variety of inflight emergency situations which can create a need to land the aircraft as soon as safely possible: fire in cargo compartments or toilet areas, incapacitated crew members or a medical problem with a passenger, insufficient fuel or oil, failure of one or more engines, or failure of other major aircraft systems such as electrical or cabin pressurization systems. All of these occur frequently enough in public air transport to cause airline operators and airworthiness authorities to consider the time to reach airports suitable for enroute diversion as a factor in planning and approving the operation of any aircraft along its intended route. One of the inflight emergencies which does occur commonly in air transport is the failure or inflight shutdown (IFSD) of an engine. The shutdown of a single engine creates a situation where aircraft are exposed to the risk of an independent failure of a second engine, during the period of the flight to a diversion airport. For a twin-engine transport aircraft, this "double independent failure" case leaves the aircraft with no means of propulsion, and may be considered a catastrophic event since the probability of fatalities in the ensuing forced landing away from an airport is very high. The past five years have seen the introduction of operations by modern twin-engine turbofan transport aircraft on long-haul oceanic routes. These have been dubbed ETOPS (Extended-Range Twin-Engine Operations). This caused a review of the safety of enroute operations by twin-engine aircraft with an emphasis on the situation where there might be an inflight shutdown of one engine. Various airworthiness authorities around the world have established safety regulations to approve ETOPS operations by a specific operator and aircraft-engine combination on "extended range" (ER) routes. In 1986, ICAO amended Annex 6 of its International Standards and Recommended Practices to provide guidance on "extended range operations by aeroplanes with two power-units (ETOPS)" to its contracting states. In June 1985, the FAA issued its Advisory Circular AC 120-42 which "states an acceptable means, but not the only means for obtaining approval under FAR 121.161 for two-engine airplanes to operate over a route that contains a point farther than one hour flying time at the normal one-engine inoperative cruise speed (in still air) from an adequate airport." By the end of 1986, there had been a few years of experience with ETOPS activity by several US and foreign carriers on the North Atlantic routes and in other areas of the world. This study is a review of the current ETOPS situation, carried out for the Transportation Systems Center and the Office of Aviation Safety, FAA, at the request of the FAA Administrator. While the activity of the past five years has focused on extended-range operations of twin-engine transport aircraft, there now seems to be general agreement that some of the regulatory actions should be extended to cover ER operations by all transport aircraft

Aircraft requirements for medium density markets

Statement of responsibility on title-page reads: R. Ausrotas, S. Dodge, H. Faulkner, I. Glendinning, A. Hays, R. Simpson, W. Swan, N. Taneja and J. VittekSeptember 1973Includes bibliographical references (p. [197]-[199])Introduction: In 1971, the joint Department of Transportation, National Aeronautics and Space Administrations, Civil Aviation Research and Development Policy Study (CARD) Report, identified the problems of providing air service to low density, short haul markets, as the third most pressing difficulty facing the United States' aviation industry. In the words of the report, "Low-Density Short Haul: While lower in priority than noise and congestion, solutions to the problems of low-density, short-haul service will be important to the future of civil aviation and to its ability to contribute to the goals of the Nation. This service of civil aviation can be a positive force in future regional development. In order to obtain a better definition of the problems and potential of low-density, short-haul service, a program should be established to determine accurately market sensitivities to changes in service, fare, frequency, and equipment. A government-sponsored market demonstration is required for this purpose. Concurrent and integrated with this demonstration, the Government should fund studies for the conceptual design and analysis of economical vehicles for the low-density, short-haul market." (Emphasis Added, p. 2-6) In response to this policy statement, NASA has undertaken a number of technical and systems studies as outlined by Mr. George Cherry, Deputy Associate Administrator for Aeronautics and Space Technology (Programs) in his 1972 testimony before the U.S. House of Representatives' Subcommittee on Aeronautics and Space Technology of the Committee on Science and Astronautics. "1 In FY 73, NASA programs relating specifically to low-density, short-haul will fall into three main categories: a. Continuing an effort begun in FY 72 which is identifying technology problems associated with providing economical air service to sparsely settled regions. b. Continuing an effort begun in FY 72 which will investigate and develop very-low-frequency navigation techniques for en route and terminal area navigation for civil aviation, especially low-density, short-haul service. c. Increasing knowledge of economic and operational factors which bear upon technology and aircraft requirements. Studies will be undertaken to fit existing and hypothetical aircraft into realistic low-density, short-haul arenas and to identify where and why economic short-comings appear. Those that can be improved by technology will be identified. In addition, programs will be undertaken to investigate: ride-quality improvement as it influences aircraft design and passenger acceptance, crosswind landing characteristics, and operational techniques." This study attempts to answer some of the questions in Item C