Addressing the Pushback Time Allocation Problem at Heathrow Airport

Abstract

T his paper considers the problem of allocating pushback times to departing aircraft, specifying the time at which they will be given permission to push back from their allocated stand, start their engines, and commence their taxi to the runway. The aim of this research is to first predict the delay (defined as the waiting time at the stand or runway) for each departure, then to use this to calculate a pushback time such that an appropriate amount of the delay is absorbed at the stand, prior to starting the engines. A two-stage approach is used, where the feasibility of the second stage (pushback time allocation) has to be considered within the first stage (takeoff sequencing). The characteristics of this real-world problem and the differences between it and similar problems are thoroughly discussed, along with a consideration of the important effects of these differences. Differences include a nonlinear objective function with a nonconvex component; the integration of two sequence dependent separation problems; separations that can vary over time; and time-slot extensions. Each of these factors has contributed to the design of the solution algorithm. Results predict significant fuelburn benefits from absorbing some of the delay as stand hold, as well as delay benefits from indirectly aiding the runway controllers by reducing runway queue sizes. A system for pushback time allocation at London Heathrow has been developed by NATS (formerly National Air Traffic Services) based upon the algorithm described in this paper.

Pruning Rules for Optimal Runway Sequencing

“…The importance of this work is also illustrated by the fact that we are currently building upon it in our work on multi-runway sequencing with en-route dependencies (considering the interactions between multiple departure and/or arrival routes) and our work in integrated airport operations (in particular the integration of ground movement and runway sequencing). Within this context we would like to refer to our recent work on Target Start-At Time allocation (TSAT) at London Heathrow Atkin et al (2012). The TSAT generator is used to allocate pushback times to aircraft and to negotiate optimal calculated times of take-off (CTOTs or slots).…”

“…For the purpose of illustrating their efficacy, these rules were implemented within a dynamic programming algorithm and this is explained in Section 3.7. The results of applying this algorithm to the take-off sequencing datasets for Heathrow (from Atkin et al (2012)) are then given in Section 4, where the problems which would occur if a constrained position shift approach was used are also shown. Finally, some conclusions are drawn and the wider implications of this work are discussed in Section 5.…”

Coordination of scheduling decisions in the management of airport airspace and taxiway operations

“…In the latter context, Balakrishnan andChandran (2010), andSölveling et al (2010) focus on the runway scheduling, Artiouchine et al (2008), Hu and Chen (2005), and Di Paolo (2008,2009) focus on the landing scheduling from airspace resources to runways, while other authors deal with the coordination of the TCA airspace and the runways (landing and take-off scheduling), e.g., D'Ariano et al (2012D'Ariano et al ( , 2015, Lieder and Stolletz (2016), Murça and Müller (2015), Samà et al (2013Samà et al ( , 2014Samà et al ( , 2015. Other papers focus on ground control (including taxiway resources and runways), e.g., Atkin et al (2008Atkin et al ( , 2013, Clare andRichards (2011), Marin (2006), Ravizza et al (2013). Overall, most of the optimization models proposed in the literature for a single control area suffer from a lack of coordination between air and ground operations, so that the solutions produced are not always feasible when implemented in practice.…”

Aircraft taxi time prediction: Comparisons and insights

“…Especially since airport ground movement operations link runway sequencing and gate assignment problems and accurate taxi time predictions support various different stakeholders at airports. For example, the benefits for take-off sequence of having accurate taxi times was shown in [3] and recent developments for Heathrow [4] require accurate taxi times both for take-off sequencing and for allocating pushback times to aircraft, at which they should leave the stands. A significant proportion of the actual travel time can be spent on airport's surfaces especially with short-haul flights.…”