Air traffic management

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.

Modelling safe Descent Profiles for Approaches under low visual cueing Conditions for Helicopters operating Offshore

Background

In offshore energy exploration and production activities, helicopters play a vital role in the movement of people to installations in the sea. However, this particular activity is also prone to accidents, especially in conditions where visibility is poor, e.g. the night-time. Given that some of the World’s major energy production facilities are in the seas of countries where the climatic conditions require night-time flights, e.g. Norway, UK, USA, and Canada, then such operations pose concerns to both regulators and operators. There is therefore a need to understand the factors that underlie such accidents with a view to their future avoidance. Furthermore, with major energy reserves discovered offshore in emerging nations, especially Brazil and Russia, together with attendant pressure to exploit such reserves with night-time flights for example; this need will become greater in future.

Human factors have already been highlighted as the main driver to safety on such operations. Less attention, however, has been paid to understanding such factors under a systemic approach which accounts for all their drivers. To date, a number of issues relevant to safety during offshore flights in degraded visual environments (DVE), especially at night, have been identified and remain unaddressed. Gaps exist, for example, in the absence of an integral approach to crew training, interaction between crew members, crew readiness, human-aircraft interface characteristics, offshore installation characteristics, environmental conditions, operating procedures, organisational support and safety oversight. As a consequence, helicopter crews consistently make wrong decisions and high accident rates result.

Methodology

In order to support the decision-making process of regulatory bodies, oil & gas companies, helicopter service providers and pilots in relation to accepting or rejecting offshore missions in DVE, this thesis aims to develop a framework for the analysis of helicopter crews’ ability to fly in such conditions. Six research objectives have been formulated to achieve this aim:

1. Develop a systemic approach for offshore helicopter operations, identifying the actors, the interactions and the contextual factors affecting safety in such an activity;
2. Critically investigate the variability in such relationships resulting from the presence of DVE, using a mixture of accident and incident analysis and expert consultation (interviews and questionnaires);
3. Assess criteria for the evaluation of crews’ ability to fly in realistic operational scenarios;
4. Model and validate the relationships between contextual factors and crews’ ability to fly;
5. Recommend criteria for risk acceptance or aversion in offshore operations in DVE;
6. Recommend strategies for enhancing crews’ ability to fly safely offshore in DVE.

Collaborations

This research is conducted in conjunction with offshore helicopter operators, regulatory authorities and the EASA.

Publications

1. Nascimento, F.A.C., Majumdar, A. and S. Jarvis (2012) Night-time approaches to offshore installations in Brazil: Safety shortcomings experienced by helicopter pilots, Accident Analysis & Prevention, Volume 47, July 2012, Pages 64-74.
2. Nascimento, F.A.C., Jarvis, S and A. Majumdar (2011) Factors Affecting Safety During Night Visual Approach Segments for Offshore Helicopters, The Aeronautical Journal of the Royal Aeronautical Society.
3. Nascimento, F.A.C., Majumdar, A., Ochieng W.Y. (2012) Night-time offshore helicopter operations – identification of contextual factors relevant to pilot performance, Proceedings of the Applied Human Factors and Ergonomics International 2012 Conference. San Francisco, USA, July 21-25 2012.
4. Nascimento, F.A.C., Majumdar, A., Ochieng W.Y. and S. Jarvis (2012) Assessing the hazards of night-time offshore helicopter operations, Transportation Research Board – 91st Annual Meeting. Washington, D.C. USA, Jan 22-26 2012.
5. Nascimento, F.A.C., Majumdar, A., Ochieng W.Y. and S. Jarvis (2011) Safety hazards in night-time offshore helicopter operations, Proceedings of the 37st European Rotorcraft Forum. MAGA Valente, Italy, Sep 13-15, 2011.

The anticipated level of future air traffic requires airspace strategic optimisation if capacity demands are to be met without jeopardising safety. This project builds upon the “High-Performance Robust Aircraft Trajectory Prediction” project to develop a real-time strategic advanced capacity optimisation algorithm. High-performance trajectory prediction enables advanced conflict detection. In this respect, a key aspect of this work will be the development of advanced strategic conflict resolution algorithms, with emphasis on maximising capacity, minimising deviations of aircraft from their nominal trajectories, as well as minimising impacts on the environment.

Sponsor: Imperial College London

Research Project: Modelling Airport Surface Safety

Background

The steady growth in air traffic has been one of the major features in transportation over the last 50 years and forecasts indicate a further growth for at least the next twenty years. In addition to problems associated with congestion and delays, this growth has considerable safety impacts. One major area highlighted by a number of aviation authorities is that of airport surface safety, in particular runway and taxiway safety.

Although previous and current initiatives increasingly emphasize this topic, the industry is characterized by a piecemeal approach and surface safety rarely considered in an integrated manner. To address this issue, this research proposes to develop a model of airport surface safety.

Methodology

As a first step, a theoretical model of normal airport surface operations is developed. Subsequently, a global study of the critical factors that underlie airport surface accidents and incidents (occurrences) is conducted, and used to develop a new holistic taxonomy of causal and contributing factors. The taxonomy incorporates the viewpoint of all relevant aviation stakeholders (regulators, Air Navigation Service Providers, airlines, airport operators,ground handling companies, Accident Investigation Boards) involved in the subject matter. Its robustness is facilitated by the application of different research methods (literature, multi-national safety data analysis, airportssurvey, interviews). In a thirst step, statistical analysis is used to identify the impact of airport characteristics (e.g. airfield geometry, level of equipment, operations) on safety occurrences. Airports can then be categorized in terms of airport surface risk.

The final model of airport surface safety assesses the functional relationship between accidents and incidents and their underlying critical factors in order to outline effective safety mitigation strategies. The model considers the viewpoints of all relevant aviation stakeholders and accounts for data quality issues (i.e. weighting of different databases). All models are validated through accident/incident data and observational data at selected representative US and European airports.

Collaborations / Project Partners

Data was provided by the UK Civil Aviation Authority (UK CAA), Federal Aviation Administration (FAA), New Zealand CAA (NZ CAA), Avinor, OSL Lufthavn, Norwegian A/S, Signature Flight Support and easyJet. The results have been validated with subject matter experts from EUROCONTROL and the FAA.

Publications

1. Wilke, S., Majumdar, A. and W.Y. Ochieng (2012) A Holistic Approach toward Airport Surface Safety, Transportation Research Record: Journal of the Transportation Research Board, Washington D.C., USA, (accepted).
2. Wilke, S. and A. Majumdar (2012) Critical factors underlying airport surface accidents and incidents: A holistic taxonomy, Journal of Airport Management, 6 (2), pp. 170-190.
3. Wilke, S., Majumdar, A., and W.Y. Ochieng (2012), Assessing the quality of aviation safety databases: An external data validation framework, 5th International Conference on Research in Air Transportation — ICRAT 2012, University of California, Berkley, 22-25 May 2012.
4. Wilke, S., Majumdar, A. and W.Y. Ochieng (2012) A holistic approach towards airport surface safety, Transportation Research Board – 91st Annual Meeting. Washington, D.C. USA, Jan 22-26 2012.
5. Wilke, S., Majumdar, A. and W.Y. Ochieng (2011) Analysis of critical factors underlying airport surface safety occurrences – A global comparison, 1st Conference of Transportation Research Group of India (CTRG). Bangalore, India, Dec 7-10 2011.
6. Wilke, S. and Majumdar, A. (2011), A multi-national causal analysis of airport surface safety occurrences, 11th AIAA Aviation, Technology, Integration, Operations (ATIO) Conference. Virginia Beach, USA, Sep 21-22, 2011.
7. Wilke, S., Majumdar, A., and W.Y. Ochieng (2011), The potential of automation to improve airport surface safety, 1st International Conference on Application and Theory of Automation in Command and Control Systems (ATACCS), Barcelona, Spain, 26-27 May 2011.

Completed projects in the period 2010-2012

1. En-Route Sector Capacity Estimation Methodologies: An International Survey

Estimation of en-route sector capacities is of essential importance, especially in high-density traffic areas where controller workload is the bottleneck, e.g. Western Europe. En-route sector capacities are usually estimated using fast-time computer simulation techniques using models of controller workload. This research analysed the methodologies employed by a number of countries to estimate the capacity of en-route airspace, primarily in Europe and North America. The necessary data for the research was captured through interview based questionnaires of ATC/ATM airspace planners and managers. The research identified the strengths and weaknesses in each approach and suggested how the strengths could be combined to create a more useful methodology. The project was funded by the UK National Air Traffic Services (NATS).

Sponsor: NATS

2. Assessment of the impact of future air traffic management technologies and procedures on airspace capacity.

With global demand for air transport doubling every 10-15 years, the total number of flights in Western Europe is forecast double between 2000 and 2010. Current air traffic management (ATM) procedures and technology cannot cope. There are increasing safety risks, with growing numbers of recorded 'near misses', and ever increasing costs of delay due to congestion. The technological challenge is to increase airspace capacity without compromising safety, environmental and economic requirements. The research made key advances in the two main areas concerned with controller tasks and the development of analytical methods for assessing the factors affecting controller workload. It showed that there is to be a significant gain in capacity as a result of proposed procedures and technologies for the future ATM. The research was carried out by Imperial College in collaboration with Qinetiq and Eurocontrol.

Sponsor: Eurocontrol; DERA (Qinetiq)

3. Aviation and climate change

Research is ongoing into the links between aviation and climate change, focussing on carbon dioxide emissions and contrail formation. Air traffic simulations have been used to explore the impact on fuel burn, journey times and air space congestion of policies adjusting aircraft cruise altitudes to reduce contrail formation. An additional project is now underway, looking at the implications of a changing climate for UK air transport operations and at the feedback mechanisms which may influence the future climate impacts of air transport.

Sponsor: EPSRC; EUROCONTROL

4. Recovery from equipment failures in Air Traffic Control (ATC)

The aim of this research is to analyze failure modes of technical systems that support air traffic controllers, controller response to such failures, and recovery processes. Its objectives are to identify hazards associated with ATC systems and to develop a predictive tool/method of system recovery and human recovery from those hazards. Appropriate attention will be given to the contextual factors surrounding occurrence of the failure and their impact as well. The developed method/tool could be used during the design process for better understanding of human reactions and performance during the low-probability equipment failures.

Sponsor: EUROCONTROL; Universities UK (UUK); Imperial College London; Various air traffic service providers and regulators from around the world

5. Incident analysis of New Zealand airspace

Research has been undertaken with the New Zealand Civil Aviation Authority (NZCAA) over the last year on the analysis of controller caused incidents in New Zealand airspace. In addition, the CTS has over the past year engaged in discussions with a number of civil aviation authorities with respect to occurrence data. As a consequence of this, the CTS has managed to acquire occurrence data from a number of countries including Australia, the UK and the USA. Current research focus on the following: (i) Assessment of the reliability of reporting in the New Zealand ASMS incident reporting database, and (ii) Development of airspace safety indicators. The two objectives will rely heavily upon incident data from New Zealand and a number of other countries using the technique of benchmarking. A major feature of this research is the use of international data to inform this process. Achievement of these objectives should assist the NZCAA in its overall safety research and analysis objectives.

Sponsor: New Zealand CAA

6. Analysis of controller overloads

The objectives of this research are to analyse the ATC complexity factors causing controller overloads, i.e. sector and air traffic factors; and to analyse the development of controller overloads over spatial and temporal dimensions. This analysis should help in identifying the conditions that occur in the ATC sector and with the air traffic pattern that cause major increases in controller workload, to the point of saturation. Requirements for this study include a number of controller overload reports for the last year and the associated: (i) radar picture and (ii) R/T telecommunications for each overload. In addition, typical traffic patterns for the sectors in which overloads occurred and the times at which they occurred will be analysed to enable the unique conditions associated with an overload to be determined. The results of this analysis can inform fast time simulation studies in providing a much more sophisticated understanding of controller tasks and consequent workload at capacity, and presenting an opportunity to derive a complexity indicator for en-route airspace capacity.

Sponsor: NATS

7. Cross-sectional time-series analysis of simulated controller workload data

En-route airspace capacity in the high density European air traffic network is determined by controller workload. Controller workload is primarily affected by the features of the air traffic and ATC sector. This research considers the air traffic and ATC sector factors that affect controller workload throughout the whole day. Simulation studies using the Re-organized ATC Mathematical Simulator (RAMS) model of air traffic controller workload are conducted for a number of Upper Area Control Centres in Europe. A cross-sectional time-series analysis of the simulation output is conducted with corrections for temporal autocorrelation in the data. The results thus far indicate that a sub-set of traffic and sector variables and their parameter estimates can be used to predict controller workload in any sector of these regions in any given hour. Current research focuses on the use of controller interviews and the use non-linear estimation methodologies to obtain a greater robustness in the analysis.

Sponsor: EUROCONTROL

8. Robust conflict detection and resolution (CDR) taking into account flight data uncertainty

This project has developed novel CDR algorithms for future autonomous aircraft operations in flexible airspace. The research was funded by the Engineering and Physical Sciences Research Council (EPSRC) and carried out in collaboration with the University of Glasgow, EUROCONTROL, ISA Software and the UK Civil Aviation Authority. The project has made advances in a number of areas. (1) Characterisation of the distributions of residual satellite based navigation system errors and application of Extreme Value Theory (EVT) to deal with the tails of the ensuing distributions. (2) Development of a novel approach for the representation of flight intent information through an ordered sequence of Trajectory Change Points (TCPs). TCPs are the points where a significant change in the aircraft state is required. (3) Development of a novel 4-D TP model with minimal assumptions on the mathematical model of aircraft motion and that uses data on Expected Time of Arrival (ETA). Current schemes for TP do not always consider ETA data. The proposed TP model incorporates two additional innovations: (a) a scheme to emulate the control system used for aircraft lateral guidance and (b) a procedure to estimate aircraft speed based on intent information. (4) Specification of a novel strategic, pair-wise, performance-based and distributed CDR scheme. (5) Development of a framework to assess the impact of delegating responsibilities from ground control to pilots.

Sponsor: EPSRC; EUROCONTROL; UK CAA; ISA Software

9. Robust statistical framework for monitoring the integrity of space-based navigation systems, and preparing the marketplace for integrity-based services

Integrity monitoring of satellite navigation systems such as the Global Positioning System (GPS) offers a level of protection against potentially hazardous failures or malfunction. Existing integrity monitoring approaches rely heavily on statistical assumptions regarding the characteristics of the residual navigation errors after various error modelling and mitigation schemes have been applied. Some studies have pointed to the fact that in practice, residual navigation errors although not very different from normal laws, may neither have normal tails nor zero mean. Furthermore, there has been insufficient data to demonstrate the nature of the distribution. The aim of this PhD research project is to test the assumption that residual navigation errors come from a normally distributed population with zero mean. Real GPS data from around the world will be used to test the statistical assumptions underpinning current methods with the objective of specifying a new and robust statistical framework that takes into account the spatio-temporal characteristics associated with the residual navigation errors. The research will follow this by studying the potential user services to be supported by systems employing the new statistical framework.

Sponsor: Imperial College, EPSRC and LogicaCMG

10. Determination of the effects of GPS performance and failures on aviation applications – Phase 3

This is a collaborative research programme between Imperial College London and the University of Leeds that is developing a comprehensive simulation process for GPS Failure Modes and Effects Analysis (FMEA). To-date, the research programme has realised a software simulation capability to assess the effects of GPS failures on the system’s capability to support non-precision approach (NPA) flight operations. The work to be carried out in phase 3 will involve consolidation, further validation and the usage of the comprehensively validated simulator to assess the performance of GPS for NPA operations at selected airports.

Sponsor: The UK Civil Aviation Authority

11. GPS Approaches to the British Virgin Islands

This project integrated a digital terrain model into the failure mode and effects analysis (FMEA) software developed for the UK Civil Aviation Authority (UK CAA) by Imperial College London and the University of Leeds. It also specified and executed an incremental validation strategy to the FMEA software. The validated FMEA software was then used to carry out simulations to support the safety case for GPS supported non-precision approaches to the British Virgin Islands.

Sponsor: Air Safety Support International (ASSI)

Completed projects in the period 2007-2009

1. Support to GNSS Flight Trials (Survey Analysis)

This work is contributing to the assessment of a number of issues of relevance to the safe use of GPS for non-precision approach (NPA) at selected CAA airports. An important element of the trials will be the capture of ‘pilot experience’ through the completion of an on-line questionnaire (augmented with information from air traffic control). The responses generated will be subsequently analysed and a report generated presenting the findings of the study.

Sponsor: The UK Civil Aviation Authority

2. Cooperative Approach to Air Traffic Services (CAATS-II)

The European Commission is calling for a paradigm shift in the provision of air traffic services to reflect the changing pressures on the air transport system. The objective of CAATS-II is to improve coordination between strands of research to allow consolidated progress towards this goal. The project will develop best practice manuals for assessing new air traffic management concepts, focusing on safety, human factors, business and environment and validation. This European project has 11 partner organisations in 7 countries and includes universities, service providers and engineering consultancies. The Centre for Transport Studies will focus on determining best practice approaches for mitigating environmental effects of aviation, specifically noise, local air quality, and climate impacts.

Sponsor: European Commission, NATS

3. Complexity Analysis

This research has a long term goal of studying the relationship between airspace capacity modelling and safety assessment. An interesting approach is to merge airspace complexity modelling into capacity modelling approaches, defining safety "thresholds". This phase of the project defined an exhaustive list of complexity shaping factors, and then determined those to be considered for merging with capacity modelling approaches.

Sponsor: Eurocontrol

4. A framework for the analysis of factors underlying the workload of training captains: a case study for a short-haul low cost airline

Training captains play a vital role in any airline as they are responsible for pilot training and the maintenance of performance standards. The role of the training captain is inherently variable as training takes place ‘on the line’, in the simulator and in the classroom. Pilots with various qualifications must be trained at different tasks and training captains complete desk-based work and ‘fly the line’ themselves. For short-haul low cost airlines it is essential that the work of training captains, like that of all crew, is rostered in an efficient manner. Considering the variability in the training captain role it has been suggested that workload associated with their different tasks should also be considered. Crews involved in short-haul operations face particular problems associated with high-levels of workload, multiple sectors with short turn-around times, as well as early starts and overnight duties. There has been little previous research on the factors that impact on fatigue and the workload of short-haul pilots, there has been no research to consider the fatigue and workload of training captains, especially on short-haul low cost airlines. In conjunction with Clockwork Consultants, and a low-cost short-haul airline, the CTS is conducting research into the factors underlying the workload of training captains working for a short-haul, low-cost airline operating in Europe. All the training captains at this short-haul airline completed workbooks for a three-week period in which they assessed every duty. In addition to personal details, further questions assessed items such as duty hours, sleeping patterns and the commute to work. The training pilots were also required to fill in details of the sectors flown and the conditions encountered and trainee student criteria. Training captains self-assessed their workload using the NASA-TLX method. Statistical analysis of this data is being conducted to develop a model of the factors underlying the training captains’ workload. Such a model can be used for predicting their workload and potentially inform the allocation of design of better work allocation and roster design.

Sponsor: Clockwork Consultants

5. Causal factors analysis of helicopter accidents and incidents in New Zealand and the United Kingdom: 1986-2005

Helicopter accidents result in many fatalities worldwide and their avoidance is a major area of work for Civil Aviation Authorities (CAAs) around the World. Two major causes of such accidents and incidents are human error and the failure of technical systems of the helicopter. This research investigates these two types of causes using helicopter accident and incident data from the CAAs of New Zealand and the United Kingdom, covering the period 1986-2005. After a prior categorisation of helicopter accidents and incidents, project develops a framework by which to analyse helicopter accidents and incidents in detail based upon the human factors and technical causes. The human factors analysis is based upon the Human Factors Analysis and Classification System (HFACS) and the technical failures are analysed using system reliability modelling. In addition to developing risk indicators for helicopter safety, this project provides recommendations to mitigate such accidents and incidents.

Sponsor: New Zealand Civil Aviation Authority and UK Civil Aviation Authority

6. Development of an enhanced air traffic controller task base for CAPAN/ RAMS fast time simulation models

The discrete-event simulation models, RAMS and CAPAN, are used by EUROCONTROL to estimate airspace capacity in the en-route sectors of Europe. In order to do this, the tasks that air traffic controllers must do to conduct aircraft safely through their airspace are modeled. The current task base in CAPAN accounts for 110 tasks, divided into five major categories. However a number of issues remain with regards to these models, e.g. inadequate modeling of the monitoring tasks, the degree of adequate cognitive modeling, with respect to the controller task base used to estimate en-route sector capacity using fast-time simulation methodology. In particular the project aims to: 1) assess the efficacy of the controller tasks currently defined in CAPAN and RAMS; 2) account for a greater level of complexity in the tasks modelled, e.g. sequence, hierarchy; 3) incorporate theories of cognition in modelling the tasks; 4) assess the workload threshold for capacity estimation in function of the nature of tasks and the airspace complexity.

Sponsor: EUROCONTROL Airspace, Flow Management and Navigation (AFN)

7. The study of airspace capacity evaluation and management in Japan and Europe: what lessons can be learnt?

This project aims to compare and analyse how Europe, primarily the UK, and Japan are impacted by high air traffic capacity problems. The project involves the study of how airspace capacity is currently estimated in both areas, including the limitations of these methods. This study is based upon study visits to the headquarters of the Japan Civil Aviation Bureau, the major air traffic control facilities and airports in Japan. Amongst the facilities visited were the main air traffic control centres in Tokyo and Fukuoka and to the terminal control centres of airports at Haneda and Narita. Observations and interviews with air traffic controllers, airspace and airport operation managers were conducted. This project. The analysis of the Japanese and European experience are compared to suggest methods to improve the current weaknesses in the airspace capacity estimation in both Europe and Japan.

Sponsor: Daiwa Anglo Japanese Foundation Small Grant Award, Japan Civil Aviation Bureau

8. Development of a Framework for defining a Tolerable Level of Safety (TLS) for air traffic service provision in Europe

Aviation regulators have a requirement to measure safety for both design and operational purposes. This is no simple matter given the complexity of the aviation system and its constituent components. In order for any such safety measure to be valid, robust and have acceptability in the aviation community, a number of questions must be raised and answered satisfactorily. However aviation is not unique in this field and valuable lessons can be learnt from other safety critical industries. Using a total aviation safety system approach this project aims to define a framework for the definition of Tolerable Level of Safety (TLS) for the air traffic service provision, in particular with respect to ATM, for use by regulatory authorities. Other safety critical industries are analysed in this project to assist in this developing the framework, e.g. the nuclear, railways and maritime industries. The framework developed attempts to be flexible and adaptable to national airspace and airports throughout the ECAC States, and can be implemented in feasible, practical manner.

Sponsor: EUROCONTROL Safety Regulation Unit

9. Characterising the distribution of safety occurrences in aviation: an approach using extreme value theory (EVT)

Safety occurrences in aviation are events during which the safety of an aircraft and its passengers and crew are compromised. Data on such occurrences provides a rich asset for safety analysis and consequent mitigation measures. However such data are small in number and this poses difficulties in robust statistical testing and inference. This project aims to analyse safety occurrence data by developing a method to characterise such data more efficiently. The method uses extreme value theory (EVT) on the limited amout of information available on occurrences and defines a distribution that can be used to make statistical inferences. EVT is a fairly new theory of rare events which is very useful when a limited amount of data is available and which allows for efficient extrapolation. Whilst widely accepted in areas such as insurance and risk analysis in defining statistically rare events, EVT has not been thoroughly studied in aviation. This project uses the safety occurrence databases from regulators and ATM providers.

Sponsor: NZ CAA, UK CAA, Airways New Zealand and EUROCONTROL

10. Estimation of the impact of new technologies and procedures on en-route airspace capacity

Air traffic in Europe has grown rapidly and capacity has lagged behind demand, leading to costly delays and other inefficiencies suffered by passengers. In the European air transport network, the primary constraint at the busiest airports, e.g. Heathrow, is the lack of runway capacity. However, for airports that are not runway limited, en-route airspace capacity is the major constraint. This en-route airspace capacity depends not only on spatial-geometrical separation criteria, but also on the workload of air traffic controllers. The current European Air Traffic Management Programme (EATMP) envisages a "gate-to-gate" concept, in which flights are treated as a continuum, from the first interaction with ATM until post-flight activities. To achieve this, a broad range of procedures and new technologies within the CNS functions (as defined by ICAO) of ATM are being considered both on the ground and in the air. The use of such new technologies and procedures will have a profound effect on tasks of controllers, their workload and hence capacity in en-route European airspace. The construct of workload however, poses difficulties in its definition and measurement, and these difficulties are further compounded when attempts are made to quantify the functional relationship between workload and capacity. Such attempts require recourse to fast-time simulation modelling along with resource expensive real-time simulation. Research, however, indicates that workload is in turn affected by numerous factors, e.g. air traffic and ATC sector features and the quality of the ATC equipment. This research will seek to build on existing research to study the factors that directly affect capacity and develop a methodology to quantify the impact of new technologies and procedures on capacity. It will attempt to answer the following questions: • What factors affect airspace capacity? • Is there a functional relationship between these factors and the capacity in en-route airspace? • Can these factors and the functional model cater for the new technology and procedures that are planned to be introduced in the next 20 years? If not, then develop the enhancements require

Sponsor: NATS

11. An investigation of the relationship between ATC complexity and airspace safety: the example of New Zealand airspace

Air Traffic Control (ATC) complexity can be thought of as the interaction between air traffic and the sector characteristics through which this air traffic flies, and research indicates that this is the prime determinant of the air traffic controller’s workload. There has been considerable literature in the past that have attempted to define and classify air traffic complexity variables, which have in turn been used in to assess the capacity of en-route airspace in Europe and North America. In addition, such variables can be used to assist in ATC sector design by highlighting those complexity factors that can lead to high workload situations as well as potentially risky scenarios for the controller. A method by which to investigate the impact of such ATC complexity variables on airspace design is by a detailed examination of the loss of safety incidents in airspace, e.g. a loss of prescribed separation between two aircraft in controlled airspace. Such an examination can reveal the extent to which ATC complexity conditions were prevalent at the time such an incident occurred and enable a functional relationship to be developed between ATC complexity factors, e.g. the phase of flight of the aircraft, geometry of the aircraft flight paths. Such an analysis requires a detailed database of incidents. Furthermore, analysis of the conflict resolution manoeuvres undertaken by controllers permits optimal resolution strategies to be estimated given a certain configuration of ATC complexity factors. Using a very detailed database from New Zealand’s air traffic control provider, Airways NZ, this project aims to extract complexity factors that occur during loss of separation incidents as well as airspace maps. The project aims to undertake statistical analysis relating these factors to the occurrence of loss of separations and develop safety indicators relating ATC complexity factors to loss of separation incidents.

Sponsor: New Zealand Airways

12. The prediction of airline pilot performance and fatigue for a short haul airline: an assessment of current methodology

This project analyses pilots’ schedules with available models for assessing performance and fatigue, with subsequent statistical analysis. The data for this study is provided by easyJet and includes objective sleep records, subjective ratings of fatigue, observed performance and work schedules. The results of this study will be used to enhance the way in which easyJet measures fatigue risk within its fatigue risk management system.

Sponsor: Clockwork Consultants, easyJet

13. Development of a Framework for Incident Precursor Analysis in Air Transport

To maintain the number of air transport accidents directly related to the provision of Air Traffic Management (ATM) as low as possible, the ATM system is developing ways of improving and monitoring its safety performance level. The search for precursors based on safety related incidents data (where no accident occurred but safety was jeopardised) is becoming more and more exploited. However several safety methodologies describing different concepts of accident mechanisms are currently in use, e.g. linear cause and effect models, accident barriers analysis or systemic accident models. Each methodology has an impact on the data collection, processing and analysis leading sometimes to potential bias. There are several drivers that distinguish methodologies between each other such as: the accident causation theory, the system complexity characterisation and associated taxonomy (human, technical or organisational), the type of probabilistic assessment and analysis, and the nature of safety recommendations that could result. In this study, incidents data from several civil aviation authorities and air navigation service providers are being processed. All databases are different and vary in terms of information quantity and quality. Once all safety methodologies have been evaluated, each database should ideally be assessed and mapped with the most appropriate methodology. This matching drives the subsequent statistical analyses and assists in identifying objectively the factors that are more frequently related to ATM incidents. Overall, this study aims to provide a consistent framework for the analysis of incident databases which take into account the quality and reliability of the databases.

Sponsor: NZ Airways, NZ CAA, UK CAA, CASA Australia, Air Services Australia, Avinor (Norway), the US Federal Aviation Authority and the LRET

Completed Projects prior to 2007

1. Development of a safety performance indicator for aviation: the case study of the Aerospace Performance Factor (APF) for a low cost airline

Historically, the aviation system has relied on numerous basic metrics such as those associated with traffic counts, delays, flight cancellations, incidents and accidents to gauge performance. These measurements never really evolved beyond simplistic ratios and have never been fully integrated into a system-wide performance measurement tool. This has led to the criticism that aviation safety places more emphasis in trying to redefine events to lessen their significance rather than analyzing the data in order to take system wide corrective actions. For any organisation to operate at its most efficient, with the lowest level of risk, accurate data reporting, using multiple sources of information is necessary. That data must reflect quantified information, allow for a repeatable and consistent assessment of the experience and judgment of subject matter experts, and it must be balanced in the way it reflects positive and negative events. This approach allows for the development of a robust indicator to assist in identification of long-term trends and better management of a system. That is the design goal of the Aerospace Performance Factor (APF) and it aims to present a graphical representation of a system’s performance over a long period of time compared to a specific baseline. By collecting and utilising all the safety data, the APF will not focus on a single aspect of a large-scale operation. By showing all data, and the relative significance, or weighting, of one data set to another, the APF aims to provide a balanced measure. This weighting is based upon the use of subject matter experts and subsequent multi-criteria decision-making techniques, such as analytical hierarchy processing (AHP). In addition, the APF is designed to operate, not as a sole indicator of a systems performance, but as part of a wider safety management systems’ (SMS), data mining and analysis, organizational goals measured as an integrated set of metrics, and cost. This is currently undergoing validation. Imperial College has developed a case study of the APF for airline flight operations using data and subject matter experts from the low cost airline, easyJet.

Sponsor: US Federal Aviation Authority, easyJet Airlines

2. A review of safety research relevant to the safety priorities of the National Air Traffic Services (UK) Ltd

NATS Ltd provides Air Traffic Control (ATC) services to aircraft flying in UK airspace, and over the eastern part of the North Atlantic. Safety is NATS' priority, as is providing an efficient and cost effective service. Key to safety at NATS is the organisation’s mature Safety Management System (SMS) that it applies to all aspects of its operational business. The key safety priorities of NATS are documented in the NATS Strategic Plan for Safety. Whilst NATS keeps at the forefront of safety priorities in the domain of air traffic control and management (ATC/ATM), there is scope for the organisation to learn from and apply the results of research in other safety critical industries. In particular, systems, tools and new technologies, analysis methodologies and human factors advancements specifically focused on delivering safety improvements industries such as nuclear, oil and gas, railways can greatly add value to NATS. This study aims to inform NATS of other such safety methodologies or tools that may be of benefit to its operation in further reducing the risk of accidents. The study undertakes both a carefully structured literature review, as well as interviews with key safety experts and organisations worldwide to enhance the results of the literature review.

Sponsor: NATS Plc

3. A review of three-dimensional collision risk modelling

Collisions are rare events and collision risk modelling (CRM), essential for safety assessments of controlled airspace, relies upon the use of proxy input data. Whilst there may be a number of ideal proxy data requirements for a robust and reliable CRM, these are not always available. However, a CRM model with appropriate input data and subsequent robust validation can be perfectly adequate for the purposes for safety assessment. EUROCONTROL has developed a 3-Dimensional Collision Risk Model (3D-CRM) with the aim of providing a standardised method of assessing the en-route safety level across the European airspace. This mathematical model computes the collision risk between aircraft as a function of time, geographical location and traffic density and is to be validated using appropriate radar data. Imperial College London is involved in researching the proposed EUROCONTROL methodology and its validation, with emphasis on: the context in which the CRM is used; the mathematical models and their underlying assumptions; and the validation methods developed. This research is carried out in conjunction with INECO of Spain.

Sponsor: EUROCONTROL

4. Future air traffic control working methods: FASTI case study

As air traffic increases, the First ATC Support Tools Implementation (FASTI) Programme aims to improve Europe’s current ATM system by highlighting the need for the co-ordinated implementation and rapid deployment of an initial set of controller support tools. One crucial aspect of FASTI is the change in the traditional methods of working. This project assesses the workload balance between controllers in an ATC team and how this is impacted by the complexity of airspace and traffic. Fast-time simulations, followed by controller interviews, are undertaken in this project.

Sponsor: EUROCONTROL

5. An analysis of the New Zealand Civil Aviation Authority’s Risk Profile Scheme

The New Zealand Civil Aviation Authority (NZ CAA) has designed a Risk Profile to highlight aspects of an aviation participant’s operation that may involve increased risks to safe operation. It requires the CAA to assess a client’s organisational culture and internal functioning in many areas and rate the performance of the organisation in those areas against a standard scale. Risk Profiles may be generated and/or changed by any CAA staff having interaction with a client during routine and non routine surveillance and certification. In addition to this direct human assessment routine automatic evaluation of client information held by the CAA is carried out and risk records updated where necessary. The Risk Profile assesses an organisation in some 30 areas. Approximately half of these areas are assessed by CAA staff during interaction with clients, and the remainder are assessed automatically by monitoring changes to client data recorded on the CAA database. These areas cover aspects of an organisation not directly covered by audit modules. An organisation is rated using a scale of 1 to 5, in each assessed area, with 1 being an exemplary score. It is a qualitative rating and relates solely to the interaction the CAA staff member is having with the client at that time, or to changes in the organisation recorded in the CAA database. Ratings of 2 to 5 will be used to record higher levels of risk. Risk items are “weighted” according to the CAA’s assessment of their likely effect on an operator’s overall risk. This project analyses the NZ CAA’s risk profile data in a number of areas, in particular to assess whether there is any relationship between an organisation’s risk profile score and its safety record in terms of the number of accidents and occurrences the organisation had. Further analysis considers the features of organisations with high and low risk scores in the 30 categories to provide guidelines to industry best practices.

Sponsor: New Zealand Civil Aviation Authority

6. High-Performance Robust Aircraft Trajectory Prediction

European airspace capacity is currently reaching its limits. The demand for air travel continues to rise with the consequence that traditional ATM methods struggle to satisfy capacity demands, resulting in delays and associated negative impacts on the economy, safety and the environment. Therefore, there is an urgent need to develop novel methods to ATM, making use of available and future technologies to increase capacity and efficiency without jeopardising safety and environmental impacts. Currently aircraft operate essentially on 3-D flight plans, described by a number of waypoints (WPs) representing the geometric path to be followed by the aircraft from its departure airport to its destination, under the supervision of Air Traffic Control (ATC). The two key functions of ATC in this respect are the provision of aircraft separation and aircraft synchronisation, both relying crucially not only upon the 3D aircraft position information, but also on the predicted arrival times of aircraft at given WPs. Such information is at present very limited and, as a result, the current approach to Air Traffic Management is essentially tactical with limited advance planning capabilities. This increases Air Traffic Controller (ATC) workload and the actual physical airspace that needs to be allocated to each aircraft, thereby significantly reducing ATM performance. To cater for the general increase in air traffic, there is thus an immediate need for a more efficient, and hence safer, approach to air navigation. As already recognised by the SESAR and NextGen initiatives, TP is expected to be at the core of future ATC decision support tools (DSTs) including conflict detection and resolution (CDR) tools, and airborne self-separation assistance systems (ASAS). This project developed a novel high-performance TP model with a performance able to meet the 4D navigation system requirements of the en-route phase of flight up to (and including) Non-Precision Approaches (NPA) and departures. The ability to predict aircraft trajectories to this high level of performance is expected to have significant benefits. Advanced decision support tools (DSTs) based upon TP will reduce controllers’ workloads, thereby enhancing airspace capacity. Moreover improved TP will allow more advanced conflict detection and improved conflict resolution for onboard aircraft safety systems, thereby contributing towards enhancing the safety and capacity of air travel.

Sponsor: Internal

7. ANALYSIS OF CREW PERFORMANCE FOR THE easyJet HUMAN FACTORS MONITORING PROGRAMME (HFMP) STUDY

One of the aims of the easyJet Human Factors Monitoring Programme (HFMP) study is to link instances of fatigue-related risk precursors in roster schedules to crew performance and recovery sleep through increasing the frequency of measures taken over a longer time period of crew schedules to overcome data limitations that are apparent in previous domain-dependent studies. The end goal of this research program is to minimise the number and complexity of these measurements by showing reliable associations among them so as to identify the simplest reliable measurement system for monitoring fatigue performance. This study assesses the statistical relationships relating to crew performance measures across the flexible rostering variation.

Sponsor: easyJet