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Posted
June 1, 1999

Airline Updates
 
 

Presentation Abstracts

An Expert System for Operations Control Solving
Constanza Butragueno IBERIA

We present a short description and structure of the system designed for decision support in operations control, in order to solve any incident that may arise during the daily execution of the flight programme at IBERIA.  We outline the steps of the process and some graphical representations.

Crew Recovery System Using Optimisation
Francois Soumis GERAD/Ecole Polytechnique de Montreal

We mathematically formulated the problem as an integer nonlinear multi-commodity network flow model with (or without) time windows and supplementary constraints and solved it using column generation combined with a branch-and-bound method.The optimizer is embeded in a system including interactive graphic user interface,data-base and a crew schedule legality checking server. Results will be presented for long or short haul operations, one or several crew members per flight and fixed or flexible flight schedule.

Environmental Benefits of Improved Surface Departure Operations
John-Paul Clarke MIT International Center for Air Transportation

Emissions are an increasingly important factor in aircraft operations. The increased number of cases of respiratory ailments, to which the elderly and children are particularly vulnerable, in areas where there are high levels of ozone has resulted in a negative response from community groups to any activity that increases the concentration of ozone in the lower atmosphere.  Although the aviation industry is estimated to contribute only 1 to 2% of U.S. emissions, airports represent zones of concentrated ozone creating emissions.  Thus, the impact of ground and terminal area operations on local air quality is greater than indicated by national and global impact estimates.

Recent work has shown that most taxi-out delays occur when aircraft are waiting in queues or at taxiway intersections for arriving aircraft or other departing aircraft.  Observations from this study also show that during times of low or moderate traffic, experienced controllers are able to modify taxi sequences and schedules to reduce delay.  During times of high traffic and controller workload such as hub complexes, however, the ability of ground controllers to sequence and schedule aircraft to minimize taxi delay and thus emissions is reduced. Introduction of an automation aid that assists ground controllers in maintaining an emission friendly sequence during periods of high traffic is critical to minimizing ozone creating emissions generated during surface operations.  Similar automation for terminal area operations may also provide emissions reductions. A study has been conducted of the potential environmental benefits that may be obtained by limiting the number of aircraft (at any given instant in time) that are allowed to pushback from the gate and subsequently enter the taxiway system at the major U.S. airports. The results of this study suggest that thaere are siginificant environmental benefits to be achieved without loss in airport capacity.

Flight Sequencing under the FAA's Simplified Substitution Rules
Debra Hoitomt, David Kraay, Baoxing Tang United Airlines

A ground delay program (GDP) is utilized in the United States as a mechanism for slowing the rate of arrivals into a weather-impacted airport.  A GDP can wreak havoc on crews and passengers who fly through the airport to other destinations.  This presentation will describe an algorithm to sequence flights under the new simplified substitution rules (SSR) promulgated by the FAA. The algorithm uses a 2-opt interchange procedure with multiple disjoint improving steps.  The objective considers passenger, crew and aircraft
delays and misconnects, and also provides special handling for multiple flights from the same market (e.g., hourly).

Ground Resources Roster Planning
Broggio Giancarlo, Paoletti Beniamino Alitalia
Gentile Claudio, Felici Giovanni  CNR IASI

We discuss solution algorithms for Ground Resources Roster Planning. The problem has several constraints related with the work agreement; the objective is to maximize personnel satisfaction. Using a Branch & Cut approach, we built an algorithm that exploits the combinatorial structure of the problem using several classes of strong valid inequalities. This algorithm is capable of quickly finding optimal or quality guaranteed solutions for problems with approximately one hundred of personnel units. Besides, another solution model is proposed, that is based on  problem decomposition. This second approach, even if it does not find the optimal solution, finds good solutions and guarantees known solution time.  This model is more flexible and can be efficiently used as a quick solution tool - a backup model - when the problem changes due to work agreement or preferences redefinition. Both models have been implemented using the C language and CPLEX 6.0, while they have been prototyped with AMPL plus.

Ground Resources Weekly Maintenance
Broggio Giancarlo, Falcomatà Simona, Paoletti Beniamino Alitalia

We discuss a solution algorithm for weekly maintenance. The problem is solved with a network flow model that finds the best substitutions - the best roster changes - to cover the operative requirements, taking into account absent people and other modifications. The network is composed by three sub nets: one for simple substitutions, one for rest shift changes and the last to find an extra work solution.  The model has been implemented using the C language and CPLEX 6.0, while it has been prototyped with AMPL plus.

Ground Staff Scheduling at Goteborg-Landvetter Airport
Erik Hasselberg, Carmen Consulting AB

The operations at a large airport are usually exposed to peaks that occur at different times in different units. This indicates an opportunity to improve productivity if staff members could walk between units and work with various tasks at different peaks.  This idea calls for a scheduling system that schedules all operations globally and handles staff members with many different qualifications and varying work agreements. We describe a solution that is being evaluated by the ground staff operator at Goteborg-Landvetter airport. The approach is based on two steps, where the first step generates a set of working blocks based on the workload for each unit. The second step, which is based on Carmen System's crew assignment system, assigns working blocks to staff members and optimizes the individual rosters while considering qualifications and work time regulations.

Journey Management - Passenger Reaccommodation in the age of Global Airline Alliances
Michael Clarke, Ladislav Lettovsky, Abdoul Sylla, Alan Walker The Sabre Group

The main objective of Journey Management is to assist airline controllers in the reaccommodation of disrupted passengers in the aftermath of an irregular airline operation.  Currently, the process of passenger reaccommodation is typically done manually, with airport agents responsible for finding alternative itineraries.  As the size of the disruption increases, the reaccommodation problem dimensions expand exponentially, and often the situation becomes intractable.  In order to effectively deal with this problem, up-to-date flight schedule information is necessary, as well as, detailed passenger itinerary data which are typically stored in passenger name records (PNR’s).  Our proposed solution methodology is developed around an itinerary generation engine, which is capable of finding alternative paths through an airline’s network, and potentially across other airlines.  The recent development of global airline alliances has only added to the complexity of the problem, as in many cases, partner carriers use different CRS systems, that are unable to seamlessly share PNR information.

New Horizon For Airlines: Paperless Maintenance
Ender GEREDE Anatolia University Civil Aviation School

 In the airline industry there is a an excessive competition. Purchasing and operating costs are very high, however, profit margins are rather low. Furthermore, today, airline revenues are decreasing while airline costs are increasing. In this case, it is essential for airlines to control their costs and to increase utilization times of their aircraft. Reducing aircraft maintenance costs is very important for airlines to increase their profits since maintenance expenses are unique items in DOC, which are able to be controlled by airlines.  The objective of aircraft maintenance activities is to provide flight safety, reliability and availability at minimum cost. The systems which can improve safety and reliability, while reducing costs at the same time, will always provide a competitive advantage for airlines. “Paperless Maintenance” which has been used in recent years provides this advantage and increases operational efficiency. It also makes it possible to optimize the whole maintenance system. In addition, by connecting the maintenance, commercial and ground operations departments between them via computerized systems, it will be possible to increase the utilization. The technological developments allow this integration. This article describes the “Paperless Maintenance” concept and its features. It points out the disadvantages of traditional documentation and the advantages of paperless maintenance. Also it recommends doing further research to be able to integrate maintenance, ground operations and scheduling systems.

Optimizing Fuel, Cargo, and Passenger Payload on Long Haul Flights
Michael E. Irrgang, Lan Chile Airlines

 In Operations Control, it is always necessary to ensure the most rapid dispatch possible of flights with safe and cost-effective flight plans.  However, in our operation at Lan Chile, our most important long haul flights all operate effectively as "combi aircraft" with the amount of cargo that we carry, even though the aricraft themselves are normal passenger B-767-300-ER.  This presentation discusses the unique way in which we have structured our operational control environment to ensure maximim cargo with full passenger load and minimum safe fuel in minimum turnaround time.

Real Time Recovery: Aircraft, Crew & Passengers
Ladislav Lettovsk, Michael D. D. Clarke, Barry C. Smith The Sabre Group
Ellis L. Johnson The Logistics Institute, Georgia Tech

Operations research techniques, including mathematical programming, have proven to be very beneficial when applied in airline scheduling. Unfortunately, the benefits often are not realized due to deviations from the planned schedule caused by disruptions. This work addresses airline rescheduling for irregular operations. We first present a modeling approach that is a radical departure from the previous attempts to solving airline recovery. We formulate the Airline Integrated Recovery (AIR) problem as a linear mixed-integer mathematical program that maximizes total profit to the airline while considering availability of all three resources: aircraft, crew and available seats. Our computational results show that solving the airline recovery problem in real-time is indeed possible. We exploit the fact that the planned schedule is optimal and try not to disturb it more than necessary. Future aircraft routings and crew assignments are protected whenever possible. Although the solution is not guaranteed to be optimal as only a subset of the schedule is considered for rescheduling, its quality should be superior to manual ad hoc solutions that locally evaluate only a limited number of options. We believe that our solution approach can generate tremendous cost savings to the airline industry.

Robust Crew Pairing
Ellis Johnson, George Nemhauser, Andrew Schaefer  Georgia Institute of Technology

The objective is to come up with crew pairings that not only have low pay-and-credit, but in actual operations are more likely to incur less additional cost due to disruptions. A simulation, SimAIR, is used to evaluate alternative plans.

Role of Accessibility on Passenger Demand for Airline Alliances
Pablo Fernandez-Torre, John-Paul Clarke MIT International Center for Air Transportation

A study of alliances in currently underway to determine the factors affecting an alliance's success in gaining market share in specific OD markets. The objective of the study is to identify the major drivers of demand, and then analyze how such drivers influence the way in which alliances can operate their joint networks.  Traditionally, the airline industry has used ASMs and departure frequency as main supply variables. However, preliminary results suggest that in the context of airline alliances operating in a hub-to-hub mode, other variables that characterize the supply of air service have become important. A new measure, Accessibility, is being developed to capture the main characteristics affecting the passenger demand for itineraries traversing the hub-to-hub link. The concept of accessibility as used here captures those network operational variables that determine the level of service provided by the alliance through the hub-to-hub structure. In particular, it focuses on frequency, capacity, and connecting convenience as its main elements.

The Departure Planner
John-Paul Clarke, Husni Idris, Ioannis Anagnostakis MIT International Center for Air Transportation

The Departure Planner is intended to assist the short term planning operations at major commercial airports.  Its emphasis will be on supporting Air Traffic Management in the next 30 to 45 minutes from the current time, but it also has a component that does advance planning with a time-horizon of a few hours.  It consists of a set of functional components, some of which could potentially become automation tools used by the controllers to manage the various physical queues existing in the flow of departing aircraft, without increasing workload levels.

The airside operations at an airport can be modeled as a complex interactive queuing system in which departures and arrivals are highly coupled.  Initial studies of the airport system have identified the follwing airport components as the main flow constraints which introduce delays and inefficiencies: (a) the runway system, (b) the gates complex, (c) the taxiway system and (d) the ramp area (where it exists). The development of (possibly automated) decision support tools for air traffic controllers calls for a thorough understanding of links, dependencies and interactions in ATM operations and requires constant evaluation and assessment.  For system identification purposes, a first set of field observations was conducted at Boston Logan International Airport.  Results of the operational analysis at Logan Airport will be presented along with the initial concept for the departure planner.

Total Airspace and Airport Modeller - TAAM'
John G Lord, Alan Miller  The Preston Group

The Preston Group has developed and markets worldwide a powerful fast-time simulation tool called the Total Airspace and Airport Modeller ("TAAM"). TAAM is used by airlines, civil aviation authorities, air service providers and airports to model current operations and perform realistic, high fidelity "what-if" simulations.  These simulations are used for capacity planning, performance analysis, procedure changes, capital investment analysis, new terminal, airspace and runway configuration analysis/procedures, and airline/airport schedule analysis.  The Preston Group's TAAM demonstration will focus on the uses and benefits of TAAM for our airline customers.

Presentations
 

Panel Discussions

Impact of Alliances on Operations Control Centers

The rapid expansion of global airline alliances has been driven by the potential strategic gain envisioned by airline executives, with little if any thought to the operational issues related to the proposed endeavour.  Airlines strive to achieve a comprehensive network in which each airline’s passenger is treated the same, regardless of which ticket stock he/she is holding. However, there exists a need for airline alliances to look beyond the marketing benefits such as frequent flyer programs, and club lounges; and to address tactical operational issues that can significantly impact the passengers.  In this panel, we plan to discuss some of the experiences of major alliance carriers, and highlight some of the problems, and potential solutions.

Ground Staff Scheduling, Optimality versus Robustness

In this "Pentium" age, IT/OR personnel are often caught up in producing "optimal" solutions to airline problems.  In reality, the uncertainty that exists in daily airline operations often calls for schedule robustness over optimality.  In this panel discussion, we will explore some of the issues that "front-line" users face, which are often ignored during the development of computer system for staff scheduling. We hope to identify design requirements which could help improve next generation ground staff scheduling systems.
 

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June 1999, Michael Clarke/Ladislav Lettovsky