Jasenka Rakas

Optimal time advance in terminal area arrivals: Throughput vs. fuel savings

The current operational practice in scheduling air traffic arriving at an airport is to adjust flight schedules by delay, i.e. a postponement of an aircrafts arrival at a scheduled location, to manage safely the FAA-mandated separation constraints between aircraft. To meet the observed and forecast growth in traffic demand, however, the practice of time advance (speeding up an aircraft toward a scheduled location) is envisioned for future operations as a practice additional to delay. Time advance has two potential advantages. The first is the capability to minimize, or at least reduce, the excess separation (the distances between pairs of aircraft immediately in-trail) and thereby to increase the throughput of the arriving traffic. The second is to reduce the total traffic delay when the traffic sample is below saturation density. A cost associated with time advance is the fuel expenditure required by an aircraft to speed up. We present an optimal control model of air traffic arriving in a terminal area and solve it using the Pontryagin Maximum Principle. The admissible controls allow time advance, as well as delay, some of the way. The cost function reflects the trade-off between minimizing two competing objectives: excess separation (negatively correlated with throughput) and fuel burn. A number of instances are solved using three different methods, to demonstrate consistency of solutions.

Statistical Modeling and Analysis of Landing Time Intervals: Case Study of Los Angeles International Airport, California

Existing literature suggests that analyses of landing time intervals employ simple statistical models based on time-separation histograms, usually approximated by normal distributions. Although the literature focuses on important issues such as safety, capacity improvements, and separation rules, it does not take into account another important issue: the possible, unique behavior of airlines, pilots, and controllers. In this study such possible, unique behavior is taken into account and a statistical analysis on landing time intervals is performed to find the operational properties of Los Angeles International Airport (LAX), California. On the basis of the properties found, operations of a dominant airline at LAX are compared with those of other airlines by using the Performance Data Analysis and Reporting System (PDARS) database. The PDARS database allows the calculation of landing time intervals on a runway level. A new mathematical model is constructed to fit the probability distribution of landing time intervals, and it is found that the proposed model has the best maximum log likelihood estimations compared with those of existing models. The results also reveal that the behavior of the dominant airline differs from that of the other airlines. The proposed model better approximates the shape of the probability distribution, especially the left-hand side, which usually contains information of greater importance regarding airport operations and especially regarding safety, since all smaller landing time intervals and the landing intervals that fail the safety requirements are concentrated in this part of the probability distribution curve.

USER REQUEST EVALUATION TOOL AND CONTROLLER-PILOT DATA LINK COMMUNICATIONS: INTEGRATION BENEFITS ASSESSMENT

Explored are the benefits of integrating User Request Evaluation Tool (URET) and Controller-Pilot Data Link Communications (CPDLC). Controller-pilot voice-communication messages and aircraft traffic flows and conflicts are analyzed in great detail in one representative, URET-operating en route sector. On the basis of the mapped URET data and the real-world communication messages, a base case and two alternative scenarios were analyzed to estimate the number of clearances that are given to pilots to resolve aircraft conflicts a sufficient time before the start of the conflict, and to determine the reduction in frequency congestion possible if such messages were sent via data link. It was found that the highest frequency use, which corresponded to the first traffic peak, was reduced 27% after the second-scenario messages were removed from the base-case scenario. After removing the non-time-critical conflict-resolution messages, the total reduction was 59%. Frequency use during the highest number of aircraft conflicts was reduced 65% after all messages from the second and the third scenario were removed. Thus, the benefits of integrating CPDLC and URET are significant. If non-time-critical conflict messages were transmitted via data link in the integrated CPDLC and URET environment, they could considerably improve the frequency congestion. More important, the largest benefits would be experienced in situations involving a large number of aircraft conflicts, or during busy periods of traffic. These improvements could further help to reduce the number of communication errors (and the consequent air traffic control workload), as well as the number of operational errors.

Economic Benefits of Increased En Route Sector Capacity from Controller-Pilot Data Link Communications

The En Route Controller-Pilot Data Link Communications (CPDLC) program is designed to enable digital data communications between controllers and pilots. CPDLC Build 1A has been proposed as the first step in the nationwide rollout of this program to en route airspace by implementation in eight air route traffic control centers. Because CPDLC will automate several routine air-ground communications tasks, one potential benefit is reduced controller workload, which could lead to increased sector capacity and thus reduced flight times for flights traversing busy sectors. To quantify the workload reduction, a comparison has been made of the time currently required to perform communications tasks, as determined from recordings of actual air-ground communications, and the time required to perform the same tasks with CPDLC, as determined by a controller-in-the-loop simulation. This comparison indicated the potential for a significant reduction in the time spent on controller-pilot communications. A model was constructed to relate the reduced controller communications workload to increased sector capacity. The National Airspace System Performance Analysis Capability (NASPAC) model was used to estimate the reduction in flight times associated with the modeled sector capacity increase. NASPAC was run for both an idealized good weather day and a sample actual bad weather day. By 2017, the last year of the projected economic lifetime of CPDLC, average flight time savings from CPDLC-related capacity increases were estimated to exceed 9, 400 min/day.

Economic impact of a lightning strike-induced outage of air traffic control tower: case study of Baltimore-Washington International Airport

This research investigates how lightning strike–induced outages of airport infrastructure and facilities affect airport performance from an economic perspective, using Baltimore (Maryland)–Washington (D.C.) Thurgood Marshall International (BWI) Airport as a case study. On September 12, 2013, lightning struck within 300 m of the air traffic control (ATC) tower at BWI, causing injury and ATC tower and airport closures. The study findings reveal that the economic losses of the outage-related delays from that single event were almost five times higher than the ATC tower refurbishment that was planned, but unimplemented, in support of lightning protection, grounding, bonding, and shielding (LPGBS). The aim of this research is to support FAAs mission to better understand and quantify consequences of lightning strike–induced outages on airport performance. The research methodology and results can assist FAA in making sound decisions in support of LPGBS, and thereby help protect the National Airspace System infrastructure from lightning strikes and extreme weather and related delays.

Methodology for Environmental Sustainability Evaluation Of Airport Development Alternatives

This study develops a new approach for the evaluation of greener airport systems. The proposed concepts demonstrate how to implement greener practices from the early stages of an airport infrastructure project in an economically rational and stakeholder-focused manner. Objectives of the proposed methodology are two-fold: 1 to promote greener design practices among airport planners, designers, and managers, and 2 to institute active communication among all airport stakeholders. The study contributes to the state of the knowledge in airport environmental management by proposing the combination of five distinct considerations: 1 the evaluation of environmental sustainability with a focus on the planning and design stages of airport facilities, 2 a procedure for screening and ranking alternatives, 3 examples of applicable performance criteria, objectives and indicators with sample scoring procedures, 4 a Multi-Criteria Decision Making MCDM approach combined with cost and utility functions, and 5 a flexible implementation strategy to enable end-users to adjust the complexity of the evaluation. This study is intended to open a discussion for the development of a methodological tool that fulfills aims of promoting greener airport design, while at the same time satisfactorily addressing stakeholder concerns.

Airport Availability Modelling: A Different Perspective

This study proposes a systems-level approach to airport and runway availability assessments and prediction, and addresses the problem of the aging or continuously degrading aviation infrastructure. Although the availability block diagrams are often used in the availability assessment of aerospace and electronic systems, their application to the airport availability problem on a system level, developed in this study, is novel. The proposed methodology is intended for short-term and long-term planning of the Communication, Navigation and Surveillance (CNS) equipment acquisition, and investment and modernisation decisions. A better understanding of the effects of equipment outages on airport availability is important in determining a required level of airport equipage and equipment reliability, particularly during critical operating conditions, such as bad weather and increased traffic demand. With proposed methodology, an analyst can precisely quantify the additional level of airport availability achieved by upgrading or adding new pieces of CNS equipment.

Cost -effective Sampling to Evaluate Condition of Un -staffed Facilities in National Airspace System

This paper proposes a methodology to evaluate the condition of un -staffed facilities in the infrastructure assets of the National Airspace System (NAS). The NAS contains around 5,000 un -staffed facilities and 9,000 structural towers. NAS facilities are very diverse in terms of their type, construction, size, geographic location, environment and the traffic area they serve. Given the significant number and the diversity of these facilitie s, assessing their performance and condition at an aggregate level is a challenging proposition. Specifically, systematic assessment of each facility in order to establish a comprehensive database is extremely expensive. We review sampling techniques previ ously developed and identify the advantages and disadvantages of each. We then propose a two -stage sampling methodology, which provides an adequate representative of the whole population. The current state -of -the -art in assessing facility condition and per formance is not very advanced. For certain type of facilities, only preliminary estimates have been made. Given (i) a large number and variety of facilities, (ii) the high cost of maintaining and updating a facility wide database for inspection and mainten ance of facilities and (iii) the budget constraints for FAA, this research will provide FAA with a cost effective method to assess its various un -staffed facilities.

MODELS FOR THE NATIONAL AIRSPACE SYSTEM INFRASTRUCTURE PERFORMANCE

This paper develops a methodology for sel ecting optimal maintenance policies for the National Airspace System (NAS) infrastructure facilities . The NAS is one of the largest, the most complex, technologically advanced and integrated civil infrastructure systems, consisting of over 48,000 complex f acilities and services that are in various stages of approaching physical or technical obsolescence. The proposed constrained optimization model is based on Markov decision processes. The model solve s an optimal steady -state NAS in frastructure manageme nt problem by minimizing the expected total cost , associated with performing maintenance activities and the user costs , subject to budget constraints . Optimal maintenance policies to minimize the total costs are obta ined through linear programming , a tech nique often used to model network -level problems. Because our problem treats many different types of facilities , where each type of facility has a different failure rate, this paper focuses on the non homogeneous network -level problem. The model is appl ied to a set of runway navigational equipment based on fault trees for VFR and category I, II and III (CAT I, II and III ) precision approaches during instrument meteorological conditions to a hypothetical one -runway airport . The model produces a set of opt imal maintenance actions to achieve a desired level of equipment availability (conditions) subject to budget constraints. The proposed methodology should assist the Federal Aviation Administration to make better decisions about NAS infrastructure inspect ion, maintenance, investment, and modernization .

AIRPORT OPERATIONS: MODELING AND ANALYSIS DURING EQUIPMENT OUTAGES

This paper develops a methodology for examining the airport airside operational performance, during unscheduled equipment outages, under the assumption that air traffic control procedures are used to compensate for the lack of available navigational e quipment. Airport performance level is the result of a combination of factors. When unscheduled navigational equipment outages occur, airports often rely on backups of the same equipment or on substitute equ ipment that can provide similar operational functio ns. If backups or substitute equipment are not availabl e, unscheduled outages can contribute to cancelled and re-routed flights, runway closures, and degraded ca pacity at an airport in general. This research use s empirical data to explore the influences of unsched uled Very High Frequency Omni-directional Range (VOR) outages on daily runway operations at San Francisco International Airport (SFO).