Research Project: Developing a Framework to analyse the Impacts of ADS-B Implementation on Aviation Safety

Background

For effective air traffic control (ATC), it is essential to know accurately the position of an aircraft on a continuous basis and be able to estimate its future position. Surveillance systems provide the air traffic controller with the information necessary to ensure the specified separation between aircraft, to manage the airspace efficiently and to assist the pilot in the navigation of their flight. However, the current surveillance systems in ATC suffer from deficiencies, e.g. an inability to support surveillance in oceanic airspace and in remote areas. In addition, airport surface movement surveillance is ineffective during bad weather with current surveillance systems.

A major breakthrough in surveillance is the Automatic Dependent Surveillance Broadcast (ADS-B) System. ADS-B automatically transmits aircraft position and other relevant data contained in the flight management system, such as speed, via a communication link to ground-based computers at an air traffic control centre as well as between appropriately equipped aircraft in airspace. ADS-B is effective in remote areas or in mountainous terrain where there is no radar coverage. It also works at low altitudes and on the ground and can be used to monitor the traffic on the taxiways and runways of an airport. It is proposed that ADS-B will be fully implemented worldwide by 2025. However, prior to its implementation concerns remain regarding its safety for operations.

Methodology

The focus of this PhD research project is to develop a framework to analyse the impact of ADS-B implementation on the aviation safety as a whole. The objectives of this research include:

1. Identify and measure the deficiencies in the current surveillance systems to meet the future demand based on specified parameters
2. Identify and measure the capabilities of ADS-B to close the gaps identified in the current system based on similar parameters
3. Assess and quantify the safety level of ADS-B in the following operational scenarios:
   a. ADS-B operating alone
   b. ADS-B combined with radar system
   c. Both radar system and ADS-B system operating independently
4. Develop a framework to analyse ADS-B impacts to safety
5. Model the new ATM operational loop with the implementation of the new technology

In addition, this research also investigates the change in operational concepts for air traffic controllers and pilots and their subsequent impacts.

Collaborations

This PhD is sponsored by the Malaysia-Imperial Doctoral Program (MIDP) of the Malaysian Ministry of Higher Education, and the research is conducted in cooperation with EUROCONTROL, NATS and British Airways.

Publications

Ali, B. S., Majumdar, A., and Ochieng, W.Y. (2011) Technological Evolution - A Paradigm Shift in Future ATC based on ADS-B, 1st International Conference on Application and Theory of Automation in Command and Control Systems (ATACCS). Barcelona, Spain, May 26-27 2011.

TESA: Trajectory prediction and conflict resolution for enroute-to-enroute seamless air traffic management

Background

Currently aircraft operate essentially on 3-Dimensional flight plans (in the air) and 2D plans (on the ground), with limited advance planning, aircraft being given priority on a first-come first-served basis. This leads to aircraft out-of-slot being served before that in-slot if the out-of-slot aircraft arrives first. The lack of highly accurate and reliable planning capability has resulted in a lack of efficient and reliable standard optimized arrival- or departure sequencing tools.

On the ground, the lack of advance planning leads to poor predictability of the taxi process, and the non-integration of the turn-around process leads to non-optimal overall planning, as well as insufficient runway incursion prevention measures. Furthermore, poor departure and arrival sequencing tools and the non-integration of these tools with surface movement tools lead to incorrect assumptions in the planned runway capacity and unnecessary high separations between aircraft (i.e. inefficiencies in runway usage). This leads to domino effects in delays of other aircraft, increasing airborne and ground holdings. These primary shortcomings lead to secondary shortcomings, such as non-optimal flight paths (i.e. horizontal and vertical flight inefficiencies), resulting in delays, increases in fuel consumption, and increased impacts on the environment. Overall, the current ATM system is thus far from optimal, unable to perform advance planning to maximise airport and Terminal Manoeuvre Area (TMA) capacity. With the tools and procedures in use today the increase of capacity will therefore, be fundamentally limited and is already reaching its limits. Moreover, the limit imposed on airports by inadequate infrastructure, and environmental and political considerations, is a key driver of overall airspace capacity. This adds to a number of operational shortcomings that contribute to the creation of capacity bottlenecks in the terminal areas and at airports. Further limitations identified in SESAR of the present system are the fixed volume and route structures, which are fragmented, preventing aircraft from flying their optimal trajectory and creating unnecessary additional workload for controllers.

Project Objectives and expected Results

The aim of this project is to address current capacity shortages of air travel in European airspace by increasing the overall level of automation of ATM, whilst maintaining or enhancing safety and minimising the impacts of aviation on the environment. In this respect, this project will contribute to the development of the elements of an ATM system that is increasingly strategic and where the role of the human operator will increasingly shift towards the employment of automated decision support tools. Therefore, the first concrete objective is to develop a trajectory prediction (TP) tool with the necessary integrity to provide the necessary confidence to controllers and pilots for their use in a real environment. The proposed development will focus on understanding and modeling TP uncertainties. This in turn will provide the basis for the development of a conflict detection and resolution (CDR) decision logic which simultaneously optimises safety and efficiency. Currently, CDR tools are limited in performance. This is because a significantly large safety margin needs to be allocated to any resolution maneuver in order to compensate for the lack of knowledge of the TP uncertainties. By better understanding these uncertainties, the conflict resolution decision logic can be rendered more efficient, the second key objective of this project.

Approach / Methodology

To achieve this vision, the TESA project aims to address issues that currently limit the use of trajectory prediction and conflict detection and resolution in improving air travel safety and capacity. The following approach will be used:

• Develop advanced realistic trajectory prediction algorithms under nominal operations, addressing the key limitations of current models of aircraft dynamics and the Flight Management System (FMS).
• Develop TP uncertainty models, placing special emphasis on developing a reliable estimation methodology of TP integrity.
• Develop novel advanced conflict detection models, based on the developed TP uncertainty models.
• Develop novel advanced conflict resolution tools, optimising safety, efficiency and capacity, based on the developed conflict detection and TP tools.
• Validate the above tools by means of advanced simulations as well as extensive real aircraft flight and taxiing data.

Research Project: A Framework to assess the Ability of Automation to deliver Capacity Targets in European Airspace

Background

SESAR envisages a 73% growth in capacity in 2020 compared to 2005 in the European transport network, and EUROCONTROL forecasts a 41% increase in capacity between 2007 and 2030. Currently, the primary constraint in Europe at the busiest airports, e.g. Heathrow, is a lack of runway capacity and whilst this will remain for some airports, others have developed plans to increase capacity in a major way. There are airports that are not currently runway limited and for these, en-route airspace is in theory, the major constraint to capacity. En-route airspace capacity depends not only on spatial- geometrical separation criteria, but also on air traffic controller (ATCo) workload and other factors.

SESAR, with its promise of progressive automation to assist pilots and air traffic controllers, e.g. with the introduction of advanced decision support tools based upon accurate aircraft derived data, as well as dynamic airspace planning in a more intertwined ATM system than at present, will have a profound effect upon the tasks of ATCo, their workload and hence has the potential to ensure the target of airspace capacity is achieved whilst also ensuring safety, environment and cost targets are met. Constraints though will still remain, e.g. implementation timescales for, and ability to invest in, ground-based and on-board system and capacity enhancements and maintaining stable and efficient operations in an air traffic network where spare capacity is increasingly scarce. Much is therefore, required to ensure that this promise can actually achieve the SESAR capacity target and beyond, in a systematic manner.

Methodology

This PhD will develop a robust integrated gate-to-gate framework for the quantification of the contribution of automation to capacity in Europe, with the expectation that the ensuing model framework will be transferable to other regions of the world. Its novelty is to model and estimate gate-to-gate (or enroute-to-enroute) capacity within a specified airspace treating it as a network of air routes and airports together with the associated management infrastructure, operations, human factors, procedures and other contextual factors.

This research seeks to analyse the factors that directly affect capacity and develop a methodology to quantify the impact of progressive levels of automation on operational capacity of a gate-to-gate network. It attempts to answer the following questions:

1. What factors affect airspace capacity in a gate-to-gate network?
2. Is there a functional relationship between these factors and airspace capacity?
3. Can these factors and the functional model cater for new technology, with its varying levels of automation, and procedures planned the SESAR timeframe and beyond?
4. How can other aspects of the performance-based targets, to be introduced by SESAR under the SES package, including safety and the impact on the environment be modelled in such a framework?

The research will undertake the following:

• An extensive literature review, surveys and discussions with ATM experts and SESAR partners to provide a full list of factors that affect airspace capacity.
• Literature review, questionnaires and discussions with ATM experts and SESAR partners to derive a number of operational scenarios of the future post-SESAR ATM
• Categorisation of the list of factors to establish their relationship to operations, procedures, controller working and other factors.
• A high level mapping of these factors to the ATM system.
• Analysis to determine factors impacted by new technology and extent of their impact.
• Development of a functional relationship between these factors and capacity.
• Comparison of this functional relationship with the traditional approaches to operational airspace capacity, where special emphasis is placed on controller workload measurements and its simulation modelling.
• Model the effect of local action and aspect (demand and performances of each element of the air transportation system) into the whole scenario (network effect) and investigate trade-off between various management criteria.
• Develop the appropriate mathematical optimisation techniques.

Collaborations

This PhD project is part sponsored by the HALA! SESAR Work Package E Thematic Network “Towards greater automation in ATM”.

Publications

1. Tobaruela G, Majumdar A, Ochieng W.Y. (2012) Identifying Airspace Capacity Factors in the Air Traffic Management System, 2nd International Conference on Application and Theory of Automation in Command and Control Systems, Imperial College London, May 29-31 2012.
2. Tobaruela G, Majumdar A, Ochieng W, Capacity Estimation for the Single European Sky, Proceedings of the 5th International Conference on Research in Air Transportation - ICRAT 2012. University of Berkeley, California, USA, May 22-25 2012.
3. Tobaruela G, A Framework to Assess the Ability of Automation to Deliver Capacity Targets in European Airspace, 1st International Conference on Application and Theory of Automation in Command and Control Systems (ATACCS). Barcelona, Spain, May 26-27, 2011.

Research Project: A framework to assess the safety of the future Air Traffic Management (ATM) system in the European Airspace

Background

Statistics show that air transport today is the safest mode of transport. For example, research shows that walking or riding a motorcycle involves a fatality risk more than 100 times higher than travelling by air (Elvik and Bjornskau, 2005). On average, an aircraft occupant could expect to travel on a passenger flight every day for over 6,400 years before being killed in a fatal accident (CAA, 2008). Over the years, safety has been influenced by two main factors: (i) increasing traffic as a result of rising demand for air travel, and (ii) technological and operational advances. Despite the increased levels of traffic, up until the end of the 20th century the technological and operational advances contributed to a reduction in the number of incidents/accidents.

In the past decade, however, safety performance measured by accident rate has remained constant. It is widely accepted that this is because the current technological and operational instruments are unable to cope, particularly given that air traffic is forecast to increase at a rate of 2.8% per year, doubling the number of flights in Europe by 2030 (EUROCONTROL, 2011). This has the potential consequence that incidents and accidents will increase, unless urgent action is taken. Therefore, faced with the need to satisfy the increasing demand for air travel without jeopardising safety, the aviation communities in Europe and the United States have initiated programmes the SESAR (Single European Sky ATM Research) and NextGen (Next Generation Air Transportation System) respectively, to develop advanced technologies together with associated operational procedures and processes with the goal of increasing capacity while improving safety and efficiency, and reducing environmental impact and costs.

In Europe (the focus of this research), the structure of the future Air Traffic Management (ATM) system envisaged within SESAR is highly complex, comprising a “system of systems”. Therefore, the conventional piecemeal approach to safety management with individual fail-safe components and sub-systems is no longer sufficient. 

Objectives

A new holistic approach is needed that considers the planned and unplanned interactions between the sub-systems which might have an impact on safety, and has added benefit of cost-effectiveness.

Even though the idea of SESAR is very promising, before it materialises there are many barriers to be overcome particularly in the safety domain. This research aims to address the safety element of SESAR through a detailed failure modes and effects analysis. The specific objectives are:

1. Detailed review of the SESAR Concepts of Operation (ConOps) and specification of the functional and physical architecture of SESAR, taking into account the timeline of implementation
2. Creation of a Failure Mode Register with the goal of identifying safety critical area(s)
3. Development of a detailed safety model for the critical area(s) identified (2)
4. Validation of the model and detailing of implementation and operational procedures.

Research Project: Safety Case for the European Rail Traffic Management System (ERTMS)

Background

History has shown that high profile safety failures such as Harrow and Wealdstone in 1952 and more recently the Ladbroke Grove crash in 1999 lead to numerous injuries and fatalities. Events such as these have heightened public concern towards safety measures in place to reduce risk.

Subsequently, advancements in railway system design have accelerated the progression towards the application of automated technology. Examples of such implementation are shown through computerised train control and operational methods. An example of such railway system development is shown in the European railways through the implementation of the European Railway Traffic Management System (ERTMS). This move to increased automation has had a number of key drivers, namely, failures in railway safety experienced on conventionally signalled railways, progression of interoperability, standardisation and capacity.

Approach

Initial analysis focusing on the railway system structure from physical architecture to its corresponding functional interfaces highlights the complexities and sophisticated nature of the railway. Railway systems have a number of safety integration issues which need to be analysed in the move to railway development. The integrity of the railway is heavily influenced by the safety culture exhibited by an organisation, its employees and users in addition to the more recognisable safety of technical systems.

This research focuses on the safety issues encountered in introducing a new rail system into an existing system. A case study of ERTMS is analysed as it is a complex technology of which some aspects are still in the deployment phase. The move to ERTMS will additionally change the human machine interface, a key influencing factor for safety.

Incorporating a new system into an existing system will have considerable impact on safety and is in the interest of railway users and the railway industry.

Publications

Smith, P., Majumdar, A. and W.Y. Ochieng (2012) Recent Developments in the European Railway Networks and their Impact on Safety, Transportation Research Board – 91st Annual Meeting. Washington, D.C. USA, Jan 22-26 2012.

Research Project: Integrity Monitoring of a GNSS-based Navigation System to support safety-critical Railway Applications

Background

Trains are currently located using blocks, i.e. sections of the railway where no train is allowed to enter until the previous one has left. Whilst this system ensures a safe distance between trains, it is not optimal as the spacing can be more than the minimum required stopping distance.The use of a Global Navigation Satellite System (GNSS) on-board allows a train to have a continuous and more precise knowledge of its position. Therefore, trains can run closer, enabling capacity of a railway to be increased. Another application of GNSS will be to replace lineside signalling infrastructure by signals displayed to the driver in the cabine, thus reducing maintenance costs.

However, to guarantee the safety of operations, the performances of a GNSS-based navigation system need to be assessed and compared with the requirements of a railway. An important feature is integrity risk, which quantifies the trust that can be placed in the correctness of the position measured. This value needs to be continuously monitored in order to detect any substantial failures that might to lead to an incident or an accident. To avoid these, the driver should be warned within a specified time when the system must not be used.

Research Objectives

The railway community has shown a growing interest in satellite navigation, for example to support the development of a European Train Control System (ETCS).

This research aims to define the requirements for a railway, in terms of navigation, for safety-critical applications as signalling. A GNSS-based navigation solution able to meet such requirements will then be developed and tested.

Research Project: Intelligent Urban Positioning

Background

The potential of GPS has been demonstrated worldwide in terms of the vast applications that it is able to support. However, in urban areas, buildings block, attenuate, reflect and diffract radio signals. This has conventionally been a major hindrance to positioning with errors of tens of metres common and often no position solution is available at all. This presents significant challenges to the provision of positioning and navigation services with the required levels of accuracy, integrity and continuity, to support the two main areas of significant economic impact (location based services and land transport). These services are vital both for the economy and societal problems both of which urban areas contribute to in significant proportions.

Approach

The goal of this project is to improve the accuracy, integrity and continuity of mobile positioning in urban areas using a combination of Global Navigation Satellite Systems (GNSS), signals of opportunity (SOOP), 3D city models and context-adaptive positioning algorithms. This is to improve the reliability of many current Intelligent Transport Systems (ITS) applications and unlock new ones that are currently held by the limitations of the underlying positioning technology. The project aims to achieve positioning accuracy at the metre level. This is in order to address the requirements for a number of applications including:

• Improved emergency caller location accuracy will enable emergency service vehicles and personnel to be guided directly to a caller rather than just the general vicinity, significantly improve response times.
• Better performing location and route guidance for city guidance will improve the user experience, increasing take-up of such services and making them more attractive to advertisers.
• Advanced intelligent transport systems will enable more efficient use of road space, reducing lost time due to travel congestion. It also provides a method of aiding priority routing for emergency vehicles.
• Advanced rail signalling systems, using precise train locations, will enable separation between trains to be safely reduced, increasing the capacity of the rail network without having to build extra track.

An important aspect within this project is to address the Integrity requirements for a number of safety critical applications within urban environments. This is to improve the safety for road transport users. Examples of such applications include:

• Intelligent speed assistance: this is to warn drivers if they exceed the speed limit.
• Lane departure warning: this application is associated with lateral control.
• Collision avoidance: this is associated with longitudinal control systems.
• Automatic safety control: an example of this application is the release of air bags when the positioning/navigation system detects that an accident is about to occur.
• Blind crossing and cooperative intersection: this application facilitates the safe crossing by road vehicles of intersections without traffic signals by automatically exchanging positioning information between vehicles.