Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. The Relationship between Air Traffic Contro 1 Ratings and Essential Job Ability Requirements Thesis presented in partial fulfillment of the requirements for the Master of Aviation degree at School of Aviation, Massey University New Zealand ShungManLO 2007 Table of Contents Acknowledgements ............................................. ... ...... ..... ... .... ... ..... ...................... ....... .. iii Abstract .. ................................................................... .. .... ... ... ....... .. .. ..... .. ................ ... ...... iv List of Tables ....... ............ ....... .... ... .. ...... ... ... ............. ... ...... .... .. ................... .... .. ..... ..... ....... v List of Figures .................... ... .......... .... ... .. .... ...... ...... .. .. .......... ....................... ... ..... ... .... .... vi List of Abbreviations ..... .... .. .. .... .. ... ... .... ... ... ...... ...................................... .... .... ....... ...... ... vii Chapter 1 .... .. .... ...... .... .. ..... ...... ... .......................................................... ... .... ...................... 1 Introduction .............................................. ...... .... ......... .... ..... ....... .... .............................. 1 Air Traffic Control (ATC) in Hong Kong .. .... ..... ...... .. .... ......... ............................... .. 1 Operational Characteristics of ATC ....................... .. ......... .. ... ....... ........................... .4 Rules and Procedures for ATC in Hong Kong ....... ... ... ... .. ... ... ............................... ... 5 HKIA and Airspace Structure .................................................... .... ...... ..................... 6 Variety and Magnitude of Air Traffic ... .. ... ... .. ... .. .... .. ...... .... ... ... ............................. ... 7 ATC job ability requirements ... ....................... .... ............ ..... ... .. ..... ...... ..................... 9 Chapter 2 .... ... ...... ...... .... ......... .. ... ....... ..... ....... .... .... .... .... .. ...... .... ........ ... .......................... 13 Method ........... ................... ................ .. ...... .... ............. .. ... ... ...... ..... ......... ..................... 13 Participants ...... ..... .... .. ... ....... ... ....... ....... .... ... ............ .. ..... ....... .... ... ... ....................... 13 Materials .. ....... .. ..... .. ..... .. .. ... ..... .. .. .... ... ........... ........ ....... .... ....... .... .... ..... ................. 14 Design and Procedure .... ........ .. .. ... .. ... .......... ................... ... ..... ... ............................. 20 Analysis ...................................................... .................. ...... ................................. .... 22 Chapter 3 ..... .................. .......................................... ...................................................... .. 23 Results ......................................................................................................................... 23 Analysis on ATC Abilities ................................. ......... ........... .................................. 24 MANOVA Tests for Significance .. .... ........... .. .. .... ... ....... ..... .... ... ............................. 28 Opinion of Participating Air Traffic Controllers in this study .... .... ... ....... ........ ...... 3 2 Chapter 4 .............. ... .... ... .................. ... ........ ..... ........ ............................... ................. ....... 33 Discussion ............... ......... .............................................................................. ............. 3 3 Nine Essential ATC Job Abilities ................... ................ ........ ... .... .......................... 33 Mental and Work Process of ATC Os in Hong Kong ....... ... ........ ..... ..... .... ... ..... ....... 34 Categorization of ATC abilities ............ ..................................................... .............. 51 Selection and Training of Student ATCO (SATCO) in Hong Kong ....................... 51 ATC Abilities with Significant Variance as perceived by participating controllers 54 II Suggestions for Further Study ............ ......... ........ .. ... .. .. .. .. ..... .. .... ..... .. .... ................. 59 Limitations of the Study .. ..... .... .. .... ..... .. .. .... .... .. ...... ................... ......... ..... ............... 60 Chapter 5 ............................................. .. ...... ....... .. ... .. .... ...... .... .. ..... .... ......... ...... .... ........ .. 63 Conclusion ........ .... ........................ .............................................................................. 63 Operational Implications ........... ... ... ... ...... ..... .. .. ..... .. .... ..... ...... ..... .... .... .. .... ... ..... .... . 63 List of Appendices ...... ....... ......... ....... .. ......... .. .. ... .... ..... .... .. .... .. ... ...... ...... .. ...... ... .. .... ...... 66 References .. ... ...... ... ........... .. ........ ....... ....... .. ......................................................... ........... 81 iii Acknowledgements I have had the benefit of the advice, guidance, cooperation and support of many friends, colleagues and advisors on conducting the research and writing up this thesis. It is with great pleasure that I acknowledge this privilege. I would like to thank Professor Graham Hunt and Dr Andrew Gilbey, my study and thesis advisors for providing me with invaluable comments and support throughout this study. My gratitude also goes to Professor Tang Fuk Hay and Mr Ng Kei Shing for their suggestions and assistance on statistical analysis of the result of my research. I would like to express my sincere appreciation to my colleagues in the Air Traffic Management Division of Hong Kong Civil Aviation Department for their active participation of the survey. Last but not least, my special thanks to Mr Andrew Leung and Ms Cecilia Chan for their assistance on managing the survey and collection of data; and Mrs Barbara Lo for her understanding and full support throughout my study. IV Abstract The mam objective of Air Traffic Control (ATC) is to prevent collisions between aircraft flying in the air or moving on the ground. Pilots must obtain ATC clearance from ATC officers (ATCO) in order to navigate their aircraft safely. There are two categories of rated ATC controllers (i.e., the radar controllers and aerodrome controllers) operating in different environments and using different equipment for ATC. They are required to apply different sets of separation criteria and rules for aircraft separation. Previous research has identified a number of abilities needed for successful on-the-job performance in air traffic controllers. These included memorization and retention of new information, spatial orientation/visualization, the ability to work well in stressful environments, the ability to shift between two or more sources of information, and the ability to combine and organize information. In recent years, one research studied the job ability requirements between Area, Approach and Tower control positions. However, there was no study investigating the relationship between Radar and Aerodrome (i.e., non-radar) ratings and their respective key performance attributes specific to a busy hub airport. This research tests whether there was a difference in key performance attributes of radar and aerodrome controllers working at the Hong Kong International Airport (HKIA). Nine ATC attributes were perceived by Hong Kong controllers as being essential, with situation awareness ranked as the most important ability. A multivariate test using the dependent variables provided no evidence that these nine essential abilities differed between radar and aerodrome controllers. However, this study indicated that there might be differences in sensory abilities between radar and aerodrome controllers in respect of visual colour discrimination and night vision requirements. Operating conditions that could have led to such differences on ability requirements are also discussed. The study revealed the need to improve ATC operating environment, traffic display tools and the desirability of reviewing recruitment criteria and controller training plans in Hong Kong. Further studies may be able to quantify how the implementation of more appropriate selection policies can reduce the cost of training and more appropriately match the expertise of ATC controllers to the tasks they are required to be engaged in. Table 3.1 3.2 3.3 3.4 V List of Tables Ability items with responses in either box 4 ( quite important) or box 5 (most important) that were above 90th percentile Mean scores and Standard Deviation (SD) for the nine essential ATC abilities of the three controller groups Multivariate test statistics of the seven ATC ability groups Mean scores and Standard Deviation (SD) of visual colour discrimination and night vision abilities YI List of Figures Figure 3.1 Percentage distribution of participating controllers' opinion on the statement "Radar (Area and/or Approach) and Aerodrome control positions require different job attributes/abilities" 4.1 Four mental processing steps for Air Traffic Control 4.2 A simple model of Information Processing 4.3 Important variables which contribute to controller's situation awareness ACARS ALAPS AMC AN[HK]O ATC ATCC ATCO ATMD ATS ATZ CAD CLK CPDLC CRT DLR DME EATMP FAA FIR GFS HKAIP HKCAD HKIA ICAO IFR ILS LCD MAP MATC OPQ PDC PRD SATCO SD SITA SMGCS vii List of Abbreviations Aircraft Communications Addressing and Reporting System Armstrong Laboratory Aviation Personality Survey Air Movement Control Air Navigation [Hong Kong] Order Air Traffic Control Air Traffic Control Center Air Traffic Control Officer ( or Air Traffic Controller) Air Traffic Management Division Air Traffic Services Aerodrome Traffic Zone Civil Aviation Department Chak Lap Kok Controller-Pilot Data Link Communications Cathode Ray Tube German Aerospace Center Distance Measuring Equipment European Air Traffic Management Programme Federal Aviation Administration Flight Information Region Government Flying Service Hong Kong Aeronautical Information Publication Hong Kong Civil Aviation Department Hong Kong International Airport International Civil Aviation Organization Instrument Flight Rules Instrument Landing System Liquid Crystal Display Missed Approach Procedure Manual of Air Traffic Control Occupational Personality Questionnaire Pre-departure Clearance Pearl River Delta Student Air Traffic Controller Officer Standard Deviation Societe' International de Telecommunications Aeronautiques Surface Movements Guidance Control System SSR TRM TU us USAF VFR VHF 2-D 3-D VIII Secondary Surveillance Radar Team Resources Management Training Unit United States United States Air Force Visual Flight Rules Very High Frequency Two Dimensional Three Dimensional Chapter 1 Introduction Air Traffic Control (ATC) in Hong Kong The Hong Kong Civil Aviation Department (HKCAD) is charged with the responsibility of managing the air traffic within the Hong Kong Flight Information Region (FIR). The Air Traffic Management Division (ATMD) of HKCAD is the sole Air Traffic Control (ATC) service provider in Hong Kong. There are altogether about 180 ATC staff working 24 hours in shifts providing aircraft with Air Traffic Services (ATS). The airspace system is a complex system which consists of a web of airways within the designated FIR. There is one international airport in Hong Kong, the Hong Kong International Airport (HKIA) serving both air passengers and air cargo flights in and out of Hong Kong. According to the statistics provided by the Air Services Division of HKCAD, more than 85 airlines operate to and from HKIA everyday and some 90 airlines operate through the Hong Kong FIR to other airports in the region. All the flight paths of these aircraft are controlled and handled by Hong Kong ATC. The Flight Movement Record (2006) of ATMD indicates that the total average flight movements are more than 1200 flights per day. All these flights coming into and going out of Hong Kong FIR are required to establish radio communication and to establish radar contact with Hong Kong ATC for flight clearance and aircraft separation purposes. An Air Traffic Control Officer (ATCO) is a specially trained professional responsible for providing ATC clearance to pilots and to ensure separation between aircraft. Radio communication equipment and radar equipment are the most important tools used by controllers for discharging their duties. In accordance with Annex 1 to the Convention on International Civil Aviation on Personnel Licensing, all controller trainees must receive knowledge and practical training on the principles and use of radio and radar equipment (ICAO Annex 1, 2006). However, aerodrome controllers who work in the control tower cab normally separate aircraft through judgement by direct 2 visual sighting, by the use of binoculars, surveillance cameras and surface movement surveillance systems. In contrast, radar controllers who work in the control center rely mainly on radar position information to separate aircraft within a three dimensional airspace block. The working conditions of radar and aerodrome controllers are significantly different. Both aerodrome and radar control are part of the ATC services provided to aircraft flying within the Hong Kong FIR. The Air Navigation [Hong Kong] Order (1995), (AN[HK]O, 1995) requires both groups of controllers (i.e., aerodrome and radar) to hold valid ATC ratings to provide air traffic control services to the limits that these ratings specified. The fundamental difference between the two groups of controllers is that aerodrome controllers are not allowed to use any radar equipment for which a radar rating is required for aircraft separation. With the aid of aircraft position and flight plan information display tools, aerodrome and radar controllers are required to follow established procedures and to apply applicable rules to manage air traffic safely and timely. They have to constantly translate their mental processes in responding to the changing traffic pictures and to decide on the appropriate ATC clearance to separate aircraft. However, the working environment and conditions of the aerodrome controller and radar controller are totally different. Aerodrome controllers perform their duties in a control tower cab with glass panels providing direct visual sighting of aircraft and the outside surroundings. Aerodrome traffic normally follows standard procedures for arrival and departure under the Instrument Flight Rules (IFR). Flight paths of these aircraft are precisely defined by electronic navigational signals called the Instrument Landing System (ILS). The Hong Kong Aeronautical Information Publication (2006) provides information on operating procedures for general aviation in the vicinity of HKIA. Light planes and helicopter traffic which operate under the Visual Flight Rules (VFR) do not need to comply with IFR arrival or departure rules, but to follow specific routes for entry into and exit from the aerodrome traffic zone of the HK.IA. The flight pattern for aerodrome traffic is well defined and structured. Aerodrome controllers are required to rely on visual separation or geographic separation in order to provide safe distance between aerodrome traffic. They also need to ensure that the runway and manoeuvring areas in the airport are cleared of obstructions and vehicles which may 3 present hazards for aircraft movements. Aerodrome controllers do not normally need to provide instructions on aircraft headings or clearances for altitude separations. In the event of bad visibility conditions or at night time when separation assurance could not be confirmed visually, geographic separations would be applied between aircraft through surface movement surveillance system, distance and position reporting from pilots of aerodrome traffic. In Hong Kong, control of aerodrome traffic is generally less time critical and less complicated than control of traffic under radar. When an aircraft operating under IFR is outside the visual range of the aerodrome controller, it is under the surveillance of a radar controller. The range (horizontal distance measured in nautical mile) and the bearing (provided by an angle reference to North of the radar site) of the aircraft is determined and its position is shown on radar display screen. With the aid of a Secondary Surveillance Radar (SSR) and an onboard aircraft transponder, the altitude of an aircraft can also be displayed amongst other useful information in the aircraft label on the radar screen. Thus, the three-dimensional (3-D) information of the aircraft is displayed almost instantly on a two-dimensional (2-D) radar screen display. Appendix A shows the 2-D radar screen display of aircraft labels. Each aircraft label contains flight information such as flight number, flight level (altitude), aircraft type, speed and track of the aircraft in flight. The radar controller who works in the control center is expected to translate the 2-D display back into a 3-D traffic mental image and to appropriately separate the aircraft either vertically, horizontally or both. The Manual of Air Traffic Control (2007) which is the policy document governing ATC procedures and standards specifies the required separation between aircraft. Aircraft are normally separated at a minimum of one thousand feet vertically or at a pre-defined distance apart horizontally (usually 3 nm and 5 nm depending on the distance of the aircraft from the radar site) under radar control. If aircraft are flying near to each other under radar control, one dimension of separation must exist between the two aircraft before the other dimension of separation is allowed to reduce below its minimum. Therefore, as aircraft from all directions are converging to the same area prior to final approach for landing, radar controllers need to provide continuous radar vectoring and to assign different altitudes to aircraft concerned for sequencing and separation purposes. In general, radar control is more dynamic and more complex than 4 aerodrome control in Hong Kong. The complexity of an ATC airspace sector depends on factors such as density of traffic, applicable ATC procedures, aircraft mix and other airspace and airport constraints. The dynamic nature of the ATC job requires specially trained people with high levels of cognitive capacity and the ability to work well under pressure (Carretta & Siem, 1999). Operational Characteristics of ATC Air traffic situation is normally quite complex especially for the airspace within 200 km range from an airport in which aircraft are crisscrossing with each other in climbing or descending maneouvers under ATC instructions. Laudeman, Sheldon, Branstrom and Brasil (1999) proposed a metric of dynamic density as the measure of ATC complexity. The factors identified by Laudeman et al were grouped into three categories: density factors, transition factors, and conflict factors. Dynamic Density has also been introduced to describe the collective effect of all factors that contribute to ATC complexity (Kopardekar & Magyarits, 2002). The set of metrics that affects the dynamic density could therefore vary from one ATC facility to another and from one controller position to other controller positions. Edmonds (1999, as cited in Xing & Manning, 2005), also defined complexity by a combination of three elements namely numerical size, variety and rules. Mogford, Guttman, Morrow and Kopardekar (1995) also proposed that air traffic control complexity should be defined as a combination of both sector and traffic complexity that affects controller workload through other factors such as system and equipment quality, cognitive strategies of controller and individual differences. Edmonds further suggested that complexity could only make sense when considered relative to a given observer. In Hong Kong, radar and aerodrome control procedures and controller operating skills are significantly different. It is therefore important to assess the complexity of the Hong Kong ATC system with respect to radar and aerodrome controller positions separately. Before the discussions on the relationship between ATC ratings and the job ability requirements, it is necessary to have an understanding of the complexity of the radar and aerodrome environment in Hong Kong. The complexity elements on rules and procedures, physical characteristics of the HKIA and its airspace structure; and variety and magnitude of air traffic for radar and aerodrome control are reviewed by this study. 5 Rules and Procedures for ATC in Hong Kong Both radar and aerodrome controllers in Hong Kong manage a complex flow of aircraft through their airspace by applying different separation standards and procedures. Radar controllers are most of the time providing tactical vectoring (not for aerodrome controllers) and both control positions need to exercise strategic planning on sequencing of aircraft at the same time (e.g., sequencing of arrivals/departures and taxiing aircraft). The objective is to provide a safe, orderly and expeditious flow of air traffic. The sequencing of traffic in a safe manner is a result of a complex cognitive decision by the controller that involves the consideration of many interacting factors such as relative aircraft position/speed, types, altitude, routing, destinations, weather conditions, runway in use and applicable rules such as separation standards. The main objective for ATC is to prevent collision between aircraft or between aircraft and other objects. The ICAO Document on Procedure for Air Navigation Services, Air Traffic Management, (ICAO, Doc 4444) stipulates the detailed functions and duties between radar and aerodrome control services. The following are the more important duties of radar and aerodrome controllers. Radar Control Radar controllers process information presented on a radar display to provide radar vectoring services as necessary to improve airspace utilization, reduce delays, provide for direct routings and optimum flight profiles to arriving and to departing aircraft. Radar control also provides radar vectoring to assist pilots in their navigation and for avoidance of adverse weather. Aerodrome Control Aerodrome controllers issue essential information and clearances to aircraft under their control to achieve a safe, orderly and expeditious flow of air traffic on and in the vicinity of an airport. The aim is to prevent collisions between aircraft flying in the aerodrome traffic zone, aircraft landing and taking off; and on the manoeuvring area. They have to also provide clearance to aircraft to prevent collisions between other vehicles operating on the manoeuvring areas and obstructions in that area. 6 Aerodrome controllers must maintain a continuous visual watch on all flights and vehicles on and in the vicinity of an airport. In low visibility or at nighttime, traffic positions should be tracked by surveillance tools when available. However, aerodrome controllers should not rely on radar position information for providing aircraft separation. In Hong Kong, aerodrome controllers perform their control duties in the ATC tower located on the top of a column structure whilst radar controllers work in an enclosed ATC center (ATCC) within a building complex next to the tower column. Both facilities are located at the center of the HKIA. HKIA and Airspace Structure The HKIA has a parallel runway configuration which is 3,800 min length and 60 m in width for both runways (Runway 25/07 with one located to the north and one to the south on Chak Lap Kok (CLK) island). The airport has obtained an aerodrome licence from CAD which is up to the standard that could accommodate the safe operations of the Airbus A380 aircraft. Although the runways are separated by 1540m which is more than the separation standards for independent mode of operation, traffic mode remains mainly segregated due to the use of the same airspace for approach and departure for the two runways. The south runway is normally used for departures while the north runway is normally used for landing. The reason for this arrangement is mainly because of terrain clearance requirements and the non-availability of the airspace immediately to the north of the airport. Appendix B shows the physical characteristics of HKIA and the co-located ATC tower and ATC center. Departures from both runways and traffic on approach or missed approach are required to share the same airspace and to follow precisely the published procedures for ATC and terrain clearance. Appendix C shows the airspace and terrain restrictions in the vicinity of the HK.IA and its complicated departure and arrival flight paths. Because of the airspace restriction, aircraft movements on the two runways are operated in dependent mode in poor visibility conditions. With the ATCC at the airport, radar controllers normally control aircraft within an airspace block up to about 50,000 feet within a radius of about 450 km which is beyond the visual range of human eyes. Their knowledge on aircrafts' precise positions is 7 based mainly on surveillance tools provided such as radar display. Aerodrome controller is more focused with the traffic within an airspace layer from surface up to about 2,000 feet within a radius of about 20 km from the airport. They have to provide their services close to HK.IA with an outside environment that alternate between day and night. Visibility from the aerodrome tower is also a natural environmental variable. Appendix D shows the picture of the ATC tower and the adjacent ATC complex (i.e. , ATCC) in HKIA. Variety and Magnitude of Air Traffic According to the Flight Movement Record (2006) provided by the ATMD, Hong Kong ATC handled more than 280,400 flight movements at HK.IA in 2006. In the same year, there were also 139,700 aircraft which over fly Hong Kong without ever landing that are also handled by Hong Kong ATC. The average annual air traffic growth rate is 6.5% since 1998 and the growth is estimated to continue at the same rate for the next few years. HKIA is ranked the 5th in terms of international passenger throughput and the 1st in the world for international air cargo throughput. More than 85 airlines operate schedule flight services to and from HK.IA. Most of these airlines operate wide-body aircraft such as the B747, B777, A330, A340, A300 and MD 11. Smaller jet aircraft operating to HKIA include Gulf-stream 200, 0550, A320 and B737. More than 99 .5% of the flight movements are classified as international of which about 88% are flights served by jet aircraft with a passenger carrying capacity of more than 150 seats. Nearly all flight movements at HKIA are operated under the IFR conditions. The Government Flying Service (GFS) which is a government department of the Hong Kong Special Administrative Region based at HK.IA operates seven medium to large size helicopters and two Jet-stream 41 turbo-prop aircraft. Flight movements by these GFS aircraft represent the major variations to the main stream of international flight movements at HK.IA. There is no recreational flying or training circuits established. Therefore, aerodrome traffic at HK.IA is less complex than other major overseas international airports in terms of aircraft mix. In addition to Hong Kong bound traffic, radar control in Hong Kong also provides daily services to about 200 through-area flights including those flights that land or depart from airports in Macau, Shenzhen and Guangzhou within the Pearl River Delta 8 (PRD) area. Appendix E shows the positions of nearby airports relative to HKIA. The close proximity of Macau and Shenzhen airports within a radius of 38 km from HK.IA made it very difficult for flight procedure design. It is also the responsibility of the radar controller who should provide sequencing and adequate separation between IFR aircraft on the ILS prior to releasing the aircraft to the aerodrome controller. The additional control requirements and complicated flight procedures for aircraft within the PRD airspace had made HKIA the airport with the most complex approach/departures arrangements in the world (Parker, 2006). The workload and pressure are therefore quite different in volume and in nature between Radar and Aerodrome positions. ATC controllers need to process information from multiple sources in order to decide on the clearance for the aircraft to proceed in relation to sequencing and separation purpose. Radar controllers make use of position surveillance tools such as radar and flight progress strips to display the aircraft's position, the direction of its movement and its relation to other moving traffic in the same airspace. In addition to these tools aerodrome controllers also make use of direct visual sighting of aircraft for separation purpose when the aircraft is within visual range in good outside lighting conditions. They can also make use of video monitoring systems and binoculars to extend the range of their vision although at night, this may not be possible. All these modem tools are able to present colour images and other flight data information for the controller to have a good understand and tracking of the aircraft. , In summary, radar control in Hong Kong provides ATC service to aircraft within a larger airspace block. As traffic density increases and arriving aircraft from different directions are converging to the final approach area, they conflict with other outbound departing traffic from HKIA. Radar controtlers therefore, rely on radar for aircraft position information and apply appropriate separation standards between aircraft by tactical vectoring. Frequent application of ATC clearance is thus required from the radar controller for sequencing of aircraft to suit his own overall traffic plan. Aerodrome control provides visual separations between aircraft normally on ILS or on departure tracks following published procedures. As there is no recreational flying or training circuit established at HKIA, aerodrome control at HKIA is less complicated and work pressure is less demanding than other major overseas airports. 9 Comparatively, aerodrome traffic is less dynamic and less complex than traffic under radar control in Hong Kong. An appreciation of the Hong Kong ATC environment and the complex airspace arrangements between radar and aerodrome control would ease the understanding on the relationship between essential job abilities and the ATC ratings to be discussed. A summary of the differences in operations complexity and dynamic density between radar and aerodrome control is tabled in Appendix F. ATC job ability requirements European Organization for the Safety of Air Navigation published the European Air Traffic Management Programme (EATMP) which included guidelines for selection procedures and tests for ab initio trainee controllers (EATMP-HRS/MSP-002-GUI-01, 2001). These included selection tests that cover a wide range of abilities such as memory functions, attention, logical reasoning, spatial comprehension and multiple task abilities. Personality factors such as decision making behaviour, stress coping, motivation and achievement should also be assessed where possible. However, these studies and guidelines only identified the more important abilities for the controller profession in general but did not address the question on whether different control positions (i.e. , radar and aerodrome) require the same or different job abilities. The selection tests recommended were not specific to Radar or Aerodrome ratings. There was no differentiation on ability requirements between Radar and Aerodrome trainee controllers in the selection methodology. The Federal Aviation Administration (FAA) has also initiated some studies on the validation of the FAA's air traffic control specialist pre-training screen (Broach & Brecht-Clark, 1994). The validated tests for student controllers were than compared with other jobs in the United States (US) such that the test constructs could be compared independently with the more general job cognitive attribute requirements. In the analysis, it was found that perceptual speed, closure, simple reaction time, and short-term memory were more relevant to the controller job than many other jobs in the US economy. Numerical computation, arithmetic reasoning, convergent and divergent thinking also appeared to be more relevant to the controller's job. However, contrary 10 to expectation, time-sharing, spatial visualization, and spatial orientation were not more relevant to ATC than to other US occupations. Finally, in the analysis of the study, with the exception of spatial abilities, other cognitive abilities requirements appeared to be reasonably homogeneous across ATC facilities types and levels. The study on the determinants of enlisted air traffic controller success by the USAF Research Laboratory had also identified several abilities requisite for successful on-the-job performance (Carretta, 1999). These abilities were memorization and retention of new information, visualization, ability to work well in stressful environments, ability to shift between two or more sources of information, and the ability to combine and organize information. The Royal Air Force conducted similar studies (Bailey, 1997 as cited in Carretta, 1999) on ATC job analysis and concluded similar results. The Civil Aerospace Medical Institute of FAA has also conducted some studies on the use of personality assessment measures in the selection of air traffic controllers (King, Retzlaff, Detwiler, Schroeder & Broach, 2003). One of the study examined the personality dimensions of the Armstrong Laboratory Aviation Personality Survey (ALAPS) against the FAA air traffic selection and training battery sores. Scores on the ALAPS 'Depression' scale were negatively correlated with selection and training battery scores. Scores on ALAPS 'Organization' scale were however, positively correlated with battery scores, suggesting that personality dimensions might also be the determinants for air traffic controllers ' success. Clarke and Robertson (2005) also conducted a meta-analytic review of the Big-5 personality factors (i.e., extraversion, neuroticism, conscientiousness, agreeableness, and openness to experience) and accident involvement in occupational and non-occupational settings. Low conscientiousness and low agreeableness were found to be positively correlated with accident involvement. Although the study was not specific to ATC professionals, it did provide evidence for the need to include personality factors such as the Big-5 factors in the study of ATC ability requirements. Air traffic control is a safety critical process with significant Human Factors involvement. Therefore, personality factors could well be the determinants for controllers' success. 11 A recent study on pilot readback errors and communications problems by the FAA suggested that language proficiency and controller communication skills had a relationship with the error rate (Prinzo, 2006). The study however, was focused on controller-pilot communications in the terminal radar approach and departure sectors. The study did not investigate the possible difference in language and communication ability requirements between Radar and Aerodrome controllers. Some of the above studies were completed quite some years ago and most of the previous studies were focused on the ATC job in general without distinction between Radar and Aerodrome control. In recent years, technological advancement in ATC has significantly changed the job nature of radar and aerodrome control hence the abilities required to adequately perform these jobs may also have changed. In a busy international hub airport such as the HKIA, the unique operating environment between radar and aerodrome control could have influenced the required ATC job abilities. A more recent study on the ability requirements for ATC controllers at DFS Deutsche Flugsicherung GmbH analysed the difference in the ability requirements between area, approach and tower positions (Eibfeldt, Heil & Broach, 2002). The overall result indicated a higher requirement on cognitive, sensory and interactive/social abilities. Only one striking difference between control positions could be identified. The sensory ability requirement in the tower exceeded the values for approach and area control. Interestingly, for most of the ability items in the German study identified, the rating for aerodrome control exceeded the amount of being required for the other two control positions. The ATC operating environment and conditions of the German study could be different from that of the ATC facility in Hong Kong which is more specific to international hub traffic at HKIA. In Hong Kong, aerodrome controllers provide ATC clearance to aircraft taxiing within HKIA as well as aircraft landing and taking off. They also provide clearance for VFR traffic (e.g., helicopters and light planes) operating in the vicinity of the ATZ from surface level to 2000 feet along predefined routes and procedures. This 2-D traffic scenario is less complex in nature and less in magnitude than radar control positions as no tactical vectoring is required. On the other hand, Hong Kong radar 12 controllers manage aircraft within a 3-D airspace block by giving tactical vectoring, altitude clearance and speed control in order to provide adequate separation between aircraft. They also need to provide a proper sequencing of aircraft where clearance precision and timing of control are more critical. These two groups of controllers have to work under different working environment and apply different procedures and separation standards. They need to process multiple sources of information and consider different constraints for deciding on the most appropriate ATC clearance. Their job ability requirements, personality and medical requirements could also be different due to differences on control tools being used in their unique working environment. In Hong Kong, many of the working controllers are streamed either to be specialized on radar or aerodrome control. However, many of the practicing aerodrome controllers who although once qualified on radar control, have since permanently given up their radar rating. Due to unique operational environment in the tower, the determinants for a successful aerodrome controller may be different from that of the radar controller. Similarly, determinants for a successful radar controller in Hong Kong could be quite different from that of the aerodrome controller due to higher level of complexity and dynamic density of air traffic. The present study is to investigate whether there is a relationship between Radar and Aerodrome rating with unique working environment and their key performance attributes as perceived by those doing the ATC jobs in a busy hub airport of Hong Kong. The result of the study may initiate the need to review the recruitment methodology, medical requirements and ATC training plans for student controllers. Successful candidates passing out from a revised selection process and/or training plan as a result of this study may stand a higher chance of succeeding in their ATC career than might otherwise have been the case. Such an outcome would produce savings in the cost of training; and a reduction in the training and medical failure rate due to inappropriate selection policies. The study may also identify the need to review ergonomics and system requirements for the radar and aerodrome control positions. 13 Chapter 2 Method Participants This study was confined to the ATC facilities in Hong Kong. Due to possible power relationship between the researcher and the more senior directorate grade controllers, only non-directorate grade controllers at the ranks of ATCO I, II and III (total: 182) as of 27 November 2006 were included for this research project in order to disconnect the perceived power relationship. In the invitation letter for voluntary participation of the survey, a statement had been included advising potential participants that their job status, conditions of employment and career development would not be affected in any way by their decision in order to eliminate any residue pressure on them for being forced to participate. For the study to be meaningful, participating controllers ought to have acquired either radar or aerodrome or have acquired both control ratings experience. Based on the collected survey forms, participants could be classified into three groups as follows : (a) Radar: Controllers who were practising radar control but might also possess an expired aerodrome rating. Response to the questionnaire would presumably be based on their recent experience on radar control in Hong Kong. (b) Aerodrome : Controllers who were practising aerodrome control but might also possess an expired radar rating. Response to the questionnaire would presumably be based on their recent experience on aerodrome control m Hong Kong. ( c) Both : Controllers who were practising both radar and aerodrome control or who had acquired previous experience on both control positions but no longer in current practice. Response to the questionnaire would 14 presumably be based on their recent experience on either one or both of the control positions or could have relied on memory of past experience. The following exclusion criteria were applied as concluded at the ATC expert group meeting : (a) No response for more than half of the 74 ability items in the survey form. (b) The consent form was not signed or had been signed without the name printed on it. (c) No response on the question on ATC rating experience which rendered it impossible to assign the participant to the appropriate group (i.e., Radar, Aerodrome or Both). ( d) ATCO I who was acting up as a directorate grade controller with a view for promotion. Materials Based on the format of previous research studies (Eibfeldt, 2002), a draft survey form had been compiled for a pilot test and was given to seven experienced controllers to complete and for comments. The seven completed draft survey forms were then submitted to a Hong Kong ATC expert group consisted of three senior controllers who were experienced in management, training and examination standards for their final assessment and validation of the form. The draft survey form had been thoroughly discussed at the expert group meeting and additional questions were added. After discussions with the expert group, six questions have been included in the finalized survey form which was reproduced as follows: Survey Form Please tick as appropriate (There are 6 questions in total.) Ql. I am D male. D female. Q2. I Dam D was D amnot a qualified pilot. Q3. I am rated on D Radar (Area and/ or Approach) but D expired. D Aerodrome but D expired. Q4. Since my first ATC rating (HK or overseas), I have acquired D less than 8 years experience. D 8 to 20 years experience. D more than 20 years experience. 15 16 Q5. Please rank the importance of the ATC abilities/ job attributes below by putting a tick in the appropriate box between 1 (least important) and 5 (most important). Note - You should rank the importance of the abilities based on your own experience and knowledge of the ATC profession. The survey is to determine the more important abilities / job attribute required for a successful ATC job position. Your ranking is not a reflection of your own abilities. - It 1s not necessary to discuss the ability ranking with other participants. - An explanatory note is provided for some ability terms but if you cannot determine the relevancy or correlate a particular ability with the ATC profession, please leave the box empty. ATC Abilities Score 1 2 3 4 5 Least Not So Important Important Average Quite Most Important Important Cognitive Abilities 1. Oral Comprehension • • • • • 2. Written Comprehension • • • • • 3. Oral Expression • • • • • 4. Written Expression • • • • • 5. Fluency ofldeas • • • • • 6. Originality • • • • • 7. Memorization • • • • • 8. Problem Sensitivity • • • • • 9. Mathematical Reasoning • • • • • 10. Number Facility • • • • • 11. Deductive Reasoning • • • • • 12. Inductive Reasoning • • • • • 13. Information Ordering • • • • • 14. Category Flexibility • • • • • 15. Speed of Closure • • • • • 16. Flexibility of Closure • • • • • 17. Spatial Orientation • • • • • 18. Visualization • • • • • 19. Perceptual Speed • • • • • 20. Selective Attention • • • • • 21. Time Sharing • • • • • Psychomotor Abilities 22. Control Precision • • • • • 23. Multilimb Coordination • • • • • 17 24. Response Orientation • • • • • 25. Rate Control • • • • • 26. Reaction Time • • • • • 27. Arm-Hand Steadiness • • • • • 28. Manual Dexterity • • • • • 29. Finger Dexterity • • • • • 30. Wrist-Finger Speed • • • • • 31. Speed of Limb Movement • • • • • Sensory Abilities 32. Near Vision • • • • • 33. Far Vision • • • • • 34. Visual Color Discrimination • • • • • 35. Night Vision • • • • • 36. Peripheral Vision • • • • • 37. Depth Perception • • • • • 38. Glare Sensitivity • • • • • 39. Hearing Sensitivity • • • • • 40. Auditory Attention • • • • • 41. Sound Localization • • • • • 42. Speech Recognition • • • • • 43. Speech Clarity • • • • • Interactive / Social Scales 44. Persuasion • • • • • 45. Social Sensitivity • • • • • 46. Oral Fact Finding • • • • • 47. Oral Defense • • • • • 48. Resistance to Premature Judgment • • • • • 49. Persistence • • • • • 50. Resilience • • • • • 51. Behavior Flexibility • • • • • 52. Sales Interest • • • • • Knowledges / Skills Scales 53. Electrical Knowledge • • • • • 54. Mechanical Knowledge • • • • • 55. Knowledge of Tools & Uses • • • • • 56. Map Reading • • • • • 57. Drafting • • • • • 58. Reading Plans • • • • • 59. Spelling • • • • • Team Resources Management Related Interactive / Social Scales 60. Co-operation • • • • • 61. Communication • • • • • 62. Leadership • • • • • 18 63. Motivation • • • • • 64. Assertiveness • • • • • 65. Self Awareness • • • • • 66. Stress Resistance • • • • • 67. Situational Awareness • • • • • 68. Decision Making • • • • • Personality Scales 69. Neuroticism • • • • • 70. Extraversion • • • • • 71. Openness to Experience • • • • • 72. Agreeableness • • • • • 73. Conscientiousness • • • • • 74. Calm Temperament • • • • • Q6. What is your opinion on the following statement : "Radar (Area and/or Approach) and Aerodrome control positions reqmre different job attributes/abilities". • • • • • strongly disagree neutral agree strongly disagree agree As could be seen from the survey form, demographic and ATC experience questions were presented first in the survey form (i.e., QI to Q4). All ATC abilities ranking questions were grouped under Q5 of the form. To follow the same categorization as in previous studies, ATC abilities were categorized into seven groups namely: - Cognitive Abilities; Psychomotor Abilities; Sensory Abilities; Interactive/Social Scales; Knowledges/Skills Scales; Team Resources Management (TRM) Related Interactive/Social Scales; and Personality Scales. 19 The ATC abilities 1 to 59 in Q5 were taken from the original F-JAS scales (Fleishman, 1992 as cited in Eibfeldt, 2002). Abilities 60 to 68 were Team Resources Management scales developed by the German Aerospace Center (DLR). Abilities 69 to 73 were the Big-5 personality dimensions (Barrick & Mount, 1991). This Big-5 model consisted of neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness. King et al (2003) studied the correlation between personality and FAA air traffic selection and training battery scores. The results suggested that there might be personality dimensions that were related to the overall skills and abilities required for individuals to achieve success as air traffic controllers. Inclusion of the Big-5 personality factors would further enhance the comprehensiveness of the list of ATC abilities for the survey. One additional item 74 (i.e. , calm temperament) was also included in the list of ATC abilities as requested by the Hong Kong ATC expert group. Due to multiple sources of input, the ability list in Q5 was more comprehensive than previous studies. Finally, in the last question (i.e., Q6) of the survey form, participating controllers were asked to give their general opinion as to whether they agree or disagree with the statement that " radar and aerodrome control positions require different job attributes/abilities". The expert group also recommended the provision of an explanatory note on some of the ability items to participants which was included in the invitation letter (Appendix G). A 5-point Likert scale was used for ranking the importance of the ATC abilities. Score 1 corresponds to "Least Important"; Score 2 corresponds to "Not So Important" ; Score 3 corresponds to "Average"; Score 4 corresponds to "Quite Important"; and Score 5 corresponds to "Most Important". Responses from participants were in the form of a tick-in-the-box without answering to open-end questions to avoid the need for subjective interpretation during statistical analysis. Although the scale of measurement was ordinal, for the purpose of this research, it was considered acceptable to apply statistical procedures that were developed for equal-interval to ordinal data (Bakeman & Robinson, 2005). 20 Design and Procedure This research would examine the relationship of the variables as defined below: (a) Radar controllers group (Radar) who have recent expenence on radar control positions in Hong Kong. Radar control positions include area, approach and departure radar controllers who rely on the use of radar equipment for traffic control and separation. (b) Aerodrome controllers group (Aerodrome) who have recent experience on aerodrome control positions in Hong Kong. Aerodrome control positions include air movement, ground movement, clearance delivery and zone controllers who do not rely on the use of radar equipment for traffic control and separation. (c) Ranking of importance of the 74 ATC job abilities of the two groups above. The 74 ATC job attributes/abilities list is compiled by integrating abilities and key factors thought to underlie the performance of the ATC controller groups above. It is based on previous studies in similar subject and expert views from experienced ATC controllers in Hong Kong. As this was a non-experimental research where no special equipment or tools were applied to participants, the main sources of error lie with the administration of the research and the design of the survey form. Precautions were taken to minimize the effects of confounding factors in order to ensure a high degree of reliability and validity. A total of 1 72 rated controllers were invited for the study. The seven controllers who were previously involved in the pilot test and the three experienced controllers in the expert group were not invited for the survey so as to avoid possible biased data returns due to prior discussions and knowledge of the study. The Guidelines for Constructing a Survey (Passmore, Dobbie, Parchman & Tysinger, 2002) was observed as far as applicable. The name list of all ATCO I, II and III controllers was obtained from ATMD. The survey forms were dispatched in 21 envelops to individual controllers by names through their personal locker in the ATCC. The survey form was attached with a covering invitation letter (Appendix G), the letter of consent (Appendix H) and some explanatory notes. Respondents were requested to return the completed survey form and the signed letter of consent in the original envelope, sealed it and dropped it back personally to a designated locker in the ATCC. A voluntary research helper from ATMD was requested to manage all the survey forms. No others except the helper could gain access to the designated locker with the appropriate key. The requirement to return the form personally by the participant was to ensure that participation was voluntary without any peer group influence. Moreover, the contents of the form could not be tampered in the process. A period of two weeks was originally reserved for the return of survey forms. Upon request by some participating controllers, the period was extended to three weeks as most controllers were required to work on shift patterns and some were having leaves outside Hong Kong. All survey forms collected by five separate occasions were individually numbered and photocopied by the ATMD helper prior to delivery to the researcher without the letters of consent. As the letters of consent were removed and were safely kept by the helper prior to delivery of the un-named survey forms to the researcher, all the collected data remained anonymous to the researcher. This study focused on the comparison of ranking of importance on ATC ability items between the Radar and the Aerodrome controller groups. This was to ensure that the ranking of importance were based on controllers' recent experience of a valid ATC rating either on radar or aerodrome control that they currently hold. In addition to the radar and aerodrome groups, the responses from the third controller group (i.e., Both : controllers who hold current radar and aerodrome ratings at the same time or who had once held both ratings before but were no longer current) would also be examined for establishing the baseline of essential and most important ATC abilities. Their views were important as they were also qualified controllers with mixed experience in both radar and aerodrome control. Participating controllers were asked to rank the ATC abilities in Q5 using the 5-point Likert scale on the survey form. They were asked to respond to questions based on their own experience and knowledge of the ATC profession. They should not 22 rank the abilities as a reflection of their own performance of the job. If they were not able to correlate a particular ability with the ATC profession, they were requested to leave the box empty in order to obtain the most reliable data for analysis. Participants were reminded not to discuss with others as they were all working close to each other in the same ATC environment in order to minimize effect of peer group influence. The whole survey form was designed in such a way that only simple and quick responses were required from the participants in order to encourage a higher response rate. Analysis Although descriptive words were assigned under the score scale in the survey form, the ranking was still representing a verbal statement of opinion in words. That said, the score scale did represent an ascending order of importance from score 1 to 5 (i.e., 1 = least important, 2 = not so important, 3 = average, 4 = quite important and 5 = most important). The use of Likert scale in this study provides measurement on the degree of importance of the ATC abilities and therefore falls within the ordinal level of measurement. Ordinal data can be regarded as quantitative in a relatively loose sense (Bakeman, 2005). There would be some merit in applying parametric tests if the distribution was normal and the sample size was sufficient (Jamieson, 2004). A test on the normality of distribution of collected data was applied to ensure the appropriateness of the application of parametric tests in this study. Similar study on determinants of US Air Force enlisted air traffic controller success (Carretta, 1999) had made use of Likert Scales and parametric tests for interpretation of results. The size of the radar controller group and that of the aerodrome controller group were both considered adequate for parametric . tests be applied. The normality test indicated that the data were normally distributed. Therefore, for the purpose of this research, the ranking of importance of the ATC abilities using the Likert scales would be treated as interval scale. Statistical analysis would be described using means and standard deviations, and multivariate analysis of variance would be applied to ATC abilities under different categories between the Radar and the Aerodrome groups. 23 Chapter 3 Results In total, 114 questionnaires were received back from a total of 172 survey forms distributed, which represented a return rate of 66.2%. All the 114 survey forms returned were de-identified and individually numbered prior to data entry for statistical analysis. A 10% random sampling check for accuracy against the data in the original survey forms was conducted after the whole data entry process had been completed. No apparent error was detected by the sampling check on forms numbered 7, 15, 22, 29, 31, 33, 45, 62, 70, 92, 98 and 108. With the survey precautions and accuracy checks taken prior to data analysis, it was considered that the data for this research had been acquired as accurate and as reliable as possible. There were 83 male and 31 female controllers who have participated the research. They represented 72.8% and 72.2% of the total number of male and female controllers in Hong Kong respectively. Years of ATC experience ranged from 42 participants (36.8%) with less than 8 years, and 72 (63.2%) with 8 years of experience or more. Any participants with less than 8 years of experience had acquired ATC experience solely :from the existing ATC facility at HKIA which was commissioned just over eight years ago. Participants with more than 8 years of ATC experience had worked as a controller in an ATC facility other than HKIA which could also be outside Hong Kong. In addition to ATC expenence, 64 (56.6%) participants have received flying training up to at least Private Pilot Licence standard. Only one return was excluded :from further statistical analysis as the participant was not able to provide rating information either on radar or on aerodrome control in Q3. His/her ranking on ATC abilities might not be reliable due to missing of important data and was therefore excluded to avoid contamination of data during statistical analysis. Out of the 113 qualified controllers participating the research, 43 (38.1 %) were classified as the Radar group, 38 (33.6%) as the Aerodrome group and 32 (28.3%) as 24 the Both group. This controller sample participating the research was considered representative to all controllers working at the ATC facility in Hong Kong. Analysis on ATC Abilities A Kolmogorov-Smirnov test for normal distribution of all the controller responses in Q5 was applied and the results indicated that all the responses on ATC abilities were normally distributed. As sufficient data were acquired for all groups of controllers, descriptive statistics were applied in respect of the objectives of establishing the baseline data of the essential job abilities and to determine the most important job attributes as perceived by the ATC professionals in Hong Kong. As a result of the discussions at the Hong Kong ATC expert group meeting and for the purpose of statistical analysis, this study adopted the terms "essential ATC abilities" and "most important ATC abilities" with the following meanings: (a) "essential ATC abilities" means the top 10% of the 74 ATC ability items (i.e., 8 items) with the highest number of controller responses either in box 4 (quite important) or box 5 (most important). Note : The expert group considered that for those ATC abilities that were ranked either box 4 or 5 on the Likert scale by controllers, these abilities were perceived as required ATC abilities. The top 10% of 74 ATC abilities with the highest number of scores with either a 4 or 5 rating were defined as essential. 25 (b) "most important ATC abilities" means the mean score for a particular essential ATC ability item of the three controller groups (i.e., Radar, Aerodrome and Both) were all ~ 4.5. Naturally, the most important ATC abilities were all from the "essential ATC abilities" list. Note : The expert group considered that all three controller groups (i.e., Radar, Aerodrome and Both) ought to acquire a mean score of~ 4.5 for a particular ATC ability to be classified as most important. With a mean score of ~ 4.5, the mode and median of the controllers' scores in their responses to that particular ability would fall into box 5 (most important). Essential ATC Abilities In order to establish the baseline for the essential ATC abilities for controllers in Hong Kong, a percentile of 90% was applied to the total number of valid controller responses ranked either 4 (Quite Important) or 5 (Most Important) on the 5-point Likert scale of each individual ATC ability. The result (in descending order of importance as perceived by participating controllers) indicated that situation awareness, decision making, speech clarify, oral expression, oral comprehension, stress resistance, communication and visualization were the eight essential ATC abilities (i.e., the highest 10% of the 74 ability items). However, the 6t\ 7th and 8th highest percentile were of the same value of 96.46% and the 9th highest ability item on problem sensitivity was at a value of 96.36% which was quite close to the next higher up (i.e., top 61 \ 7th and 8th ability items). Having discussed the result with the expert group, it was considered prudent to also include problem sensitivity for further examination and discussion as if it was classified as one of the essential ATC abilities. Therefore, for the purpose of this study, nine ATC abilities were classified as 'essential ATC abilities' (Table 3 .1 ). Table 3.1 Ability items with responses in either box 4 (quite important) or box 5 (most important) that were above 901 h percentile number of controller responses in either 26 ATC ability items in box 4 (quite important) or 5 (most important) in percentage survey form Radar Aerodrome Both AW 67 Situational Awareness 100% 100% 100% 100% 68 Decision Making 100% 100% 96.88% 99.12% 43 Speech Clarity 97.67% 97.37% 96.88% 97.35% 3 Oral Expression 100% 94.74% 96.88% 97.35% Oral Comprehension 97.67% 97.37% 96.88% 97.35% 66 Stress Resistance 100% 97.37% 90.63% 96.46% 61 Communication 95.35% 97.37% 96.88% 96.46% 18 Visualization 95.35% 97.37% 96.88% 96.46% 8 Problem Sensitivity 97.62% 92.11% 100% 96.36% 17 Spatial Orientation 90.7% 94.74% 93.75% 92.92% 26 Reaction Time 95.35% 91 .89% 90.63% 92.86% Note. a The nine essential abilities were in bold font and the percentage values under "All" were responses in either box 4 (quite important) or 5 (most important) from all three groups of controllers (i.e., Radar, Aerodrome and Both). Abilities on "Spatial Orientation" and "Reaction Time" were not perceived as essential ATC abilities as determined by the ATC expert group in Hong Kong. 27 Most Important ATC Abilities The mean score and Standard Deviation (SD) of each of the above nine essential ATC abilities for each of the groups (i .e., Radar, Aerodrome and Both) were determined. The ATC abilities with individual mean scores of 4.5 or more for all the three groups were identified. It was considered reasonable to assume that these abilities were considered by all three groups of controllers to be most important as the median and mode of these abilities for the three controller groups were both located in box 5 (Most Important) of the Likert scale. The result (Table 3.2) indicated that situational awareness, decision making, oral expression, oral comprehension and communication were perceived as the five most important ATC abilities for the ATC professionals in Hong Kong. Table 3.2 Mean scores and Standard Deviation (SD) of the nine essential ATC abilities for the three controller groups Essential ATC ability items (as numbered in the survey form) 67 Situational Awareness • 68 Decision Making • 43 Speech Clarity 3 Oral Expression • Oral Comprehension • 66 61 18 8 Stress Resistance Communication • Visualization Problem Sensitivity Radar mean (SD) 4.81 (0.39) 4.84 (0.37) 4.58 (0.54) 4.65 (0.48) 4.70 (0.51) 4.58 (0.50) 4.63 (0.66) 4.44 b (0.59) 4.45 b (0.55) Controller groups Aerodrome Both mean (SD) mean (SD) 4.76 (0.43) 4.78 (0.42) 4.74 (0.45) 4.66 (0.55) 4.4 7 b (0.56) 4.50 (0.57) 4.63 (0.67) 4.50 (0.57) 4.66 (0.53) 4.63 (0.55) 4.42 b (0.55) 4.53 (0.67) 4.61 (0.55) 4.53 (0.67) 4.53 (0.56) 4.44 b (0.56) 4.37b(0.71) 4.53 (0.51) Note. a The five most important abilities with mean scores ~ 4.5 for all three groups of controllers were underlined. b Mean scores below 4.5 for a particular controller group as such these abilities were classified only as essential but not the most important ATC abilities as perceived by the ATC expert group in Hong Kong. 28 On comparison with the mean scores of the essential ATC abilities identified between Radar and Aerodrome groups above (Table 3.2), it was interesting to note that the mean scores of the Radar group exceeded that of the Aerodrome group by a small margin for all the essential ATC abilities except for the ability on visualization. All mean scores of the five most important ATC abilities of the Radar group exceeded that of the Aerodrome group. Important ATC ability by category as perceived by participating controllers By categorizing ATC abilities on the basis of the previous study by DFS Deutsche Flugsicherung GmbH, four of the nine essential ATC abilities were cognitive in nature namely; oral comprehension, oral expression, problem sensitivity and visualization. Equally, four items (situation awareness, decision making, stress resistance and communication) were related to interactive and social abilities under team resources management category. The last one on speech clarity was under the sensory ability category but it was also related to performance of verbal communication. Least important ATC abilities as perceived by participating controllers The least important ATC job abilities were speed of limb movement, sales interest, electrical knowledge, mechanical knowledge and drafting which were mostly related to knowledge and skills requirements. They represented the least important abilities for the ATC professionals in Hong Kong as perceived by participating controllers. The scatterplots of the mean scores of all the 74 ability items can be inspected in Appendix I. MANO VA Tests for Significance (a) Multivariate test on the nine essential ATC ability items To test whether there was any significant variance on ATC job abilities between Radar and Aerodrome controller groups, inferential statistics were 29 applied usmg parametric test. MANOVA test was applied to the nine essential ATC abilities to explore whether there were differences between the Radar and the Aerodrome groups. The criterion level for significance was set at 0.05 (i.e., p < .05). Comparing 43 Radar group participants with 38 Aerodrome group participants, using the set of nine abilities that have been perceived by participating controllers as essential ATC abilities, the multivariate test provided no evidence of a group difference; Wilks' A= .925; F(70, 70) = .633;p = .765. The multivariate assumption of homogeneity of covariance was satisfied, and the numbers of Radar and Aerodrome participants were approximately equal, 43 vs. 38. Therefore, Wilk's Lambda was an appropriate test to be used. (b) Multivariate tests on the seven groups o{ATC abilities Further MANO VA tests were applied to each of the seven groups of the ATC abilities for determination of significant variance between Radar and Aerodrome controllers by ability groups. Due to increased chance of Type I error, the criterion level for significance was set at a more stringent level of 0.01. Comparing 43 radar group participants with 38 Aerodrome group participants, using the set of ATC abilities within the same group namely; Cognitive Abilities, . Psychomotor Abilities, Sensory Abilities, Interactive/Social Scales, Knowledges/Skills Scales, Team Resources Management Related Interactive/Social Scales and Personality Scales, multivariate tests provided no evidence of a group difference between ·Radar and Aerodrome except for the Sensory Abilities; Wilks' A = .636; F(12, 62) = 2.962; p = .003 as shown in Table 3.3 below. 30 Table 3.3 Multivariate test statistics of the seven ATC ability groups ATC Ability Groups Wilk's A F p Cognitive Abilities .764 F(21,39) 0.574 .912 Psychomotor Abilities .893 F(l0,63) 0.755 .671 Sensory Abilities .636 F(12,62) = 2.962 .003 Interactive/Social Scales .802 F(9,57) = 1.564 .148 Knowledges/Skills Scales .921 F(7,70) = 0.862 .541 TRM Related Interactive/Social Scales .901 F(9,70) = 0.857 .567 Personality Scales .893 F(6,72) = 1.434 .214 Follow up univariate statistics showed that two abilities within the Sensory Abilities group on Visual Colour Discrimination, F (l, 73) = .967; p = 0.006 and Night Vision, F (l , 73) = .130; p = 0.009 were significantly different between Radar and Aerodrome controllers. 31 In order to assess whether these two ATC abilities were considered by all group controllers as more than average importance on the Likert scale, the mean scores and standard deviation (SD) for these two ATC abilities for all the three groups of controller were examined. The result statistics showed that both visual colour discrimination and night vision were perceived as quite important ATC abilities (i.e., close to box 4) as indicated by Table 3 .4 below. Table 3.4 Mean scores and Standard Deviation (SD) of Visual Colour Discrimination and Night Vision abilities ATC ability items as numbered Controllers groups Radar Aerodrome Both in the survey form mean (SD) mean (SD) mean (SD) 34 Visual Colour 4.17 (0.82) 3.65 (0.89) 3.84 (0.88) Discrimination 35 Night Vision 3.40 (1.00) 3.95 (0.97) 3.88 (0.91) Note :- mean score of 3 corresponds to "average"; mean score of 4 corresponds to "quite important"; and mean score of 5 corresponds to "most important". As a very low alpha level was applied and that the result of statistical analysis could have safety and operational implications on ATC operation, the two ATC abilities on visual colour discrimination and night vision were included for further examination and discussion. It was interesting to note that the two abilities which indicated possible variance between Radar and Aerodrome groups were both vision ability related. While radar controllers perceived a higher requirement on visual colour discrimination ability (mean= 4.17) than aerodrome controllers (mean= 3.65), it was the other way round for night vision ability requirement. Aerodrome controllers perceived a higher requirement on night vision ability with a mean score'of 3.95 than radar controllers with a lower mean score of 3.4. 32 Opinion of Participating Air Traffic Controllers in this study The last question (i.e. , Q6) requested all participating controllers to provide their opinion as to whether they agree or disagree with the statement "radar and aerodrome control positions require different job attributes / abilities". The result showed that most of the participating controllers agreed to the above statement (mean = 3.65; SD= 0.99) as indicated by Figure 3.1 below. 60 50 40 ~ 30 20 10 0 Opinion on "Radar (Area and/or Approach) and Aerodrome control positions require different job attributes/abi li ties" strongly disagree disagree neutral agree strongly agree Figure 3.1 Percentage distribution of participating controllers'opinion on the statement "radar (area and/or approach) and aerodrome control positions require different job attributes/abilities" The result of Peason Chj-square test; x2 (3, N = 68) = 2.510, p = 0.473, indicated no evidence of a difference between participating Radar and Aerodrome controllers in their agreement to the statement "radar and aerodrome control positions require different job attributes/abilities". 33 Chapter 4 Discussion According to participating controllers ' responses, this study suggests nine essential ATC abilities, which is shown in Table 3.1. A multivariate test using the nine essential ATC abilities (dependent variables) provided no evidence that Radar controllers differed from Aerodrome controller. There was no evidence to suggest a relationship between specific ATC rating and its essential job ability requirements. This study also suggests that radar control positions in Hong Kong were more demanding than aerodrome control positions as perceived by participating controllers. This finding was reflected by the higher mean scores of the Radar group for the five most important abilities, which is shown in Table 3.2. The higher ability requirements for Radar controllers in Hong Kong is not consistent with the finding of the German study which suggested that Aerodrome control is more demanding and requires higher ability requirements. This study also provided evidence on two possible variance on visual colour discrimination and night vision requirements between Radar and Aerodrome groups, which is shown in the MANOVA tests for significance in Chapter 3. Nine Essential ATC Job Abilities Air Traffic Control is a service provided by an ATC unit for the purpose of preventing collisions between aircraft or between aircraft and obstructions on the maneouvenng area. [t also includes an objective of expediting and maintaining an orderly flow of air traffic. A number of studies on ATC job attributes and abilities had been administered in the past. Previous studies established the important role of cognitive and interpersonal abilities for the work as an ATCO. This research also identified similar ability requirements for both Radar and Aerodrome controllers in Hong Kong. Taking the ability items with the highest number of responses that score 4 (Quite Important) or 5 (Most Important) on the Likert scale, the current study suggested nine essential ability requirements for the radar and aerodrome controllers in Hong Kong 34 which were quite consistent with the required ATC abilities identified by other previous studies. Five of these abilities with mean scores .?. 4.5 rated by all controller groups were perceived by the Hong Kong ATC expert group as the most important ATC abilities. An examination of these nine essential abilities revealed that they were highly related to the cognitive and interpersonal abilities; and the mental and work processes of the controller's job. Therefore, before explaining why there was no variance suggested by this study on essential ability requirements between radar and aerodrome controllers, it would be prudent to have an understanding of the mental and work process of radar and aerodrome controllers in Hong Kong. Mental and Work Process of ATCOs in Hong Kong The typical mental and work process of radar and aerodrome controllers at HKIA were discussed with three senior controllers who were experienced in training, examining and on incident investigation in order to gain a full understanding of the nature of the work of ATC at HKIA. They had all given similar comments regarding the mental and work process of aerodrome and radar controllers. They opined that there should not be any significant differences between the mental processes and work procedures between the two controller groups. A comprehensive review of the ATC Approved Examiner Handbook (2003) revealed that the performance of a qualified air traffic controller would be assessed based on his/her performance in responding to a given air traffic situation by using the appropriate tools such as radar and strip display, applying proper rules and procedures; and aligning his/her control technique with the desired objective of providing a safe, efficient and expeditious flow of air traffic. There was no distinction on general assessment technique between Radar and Aerodrome control. To describe the ATC work process in its simplest term as revealed at the meeting with the expert group, the position of aircraft needs to be detected visually, processed mentally to identify all the tasks involved and a correct decision needs to be made by the controller. The controller then needs to issue an ATC clearance and communicate effectively to the pilot for execution. This can be represented by the diagram in Figure 4.1 below. Visual sighting, hearing, Radar, Flight progress strips Sensory detection a (Traffic Identification) Mental Processing Task b evaluation + i Decision c making 35 Voice, Textual Communication d with Pilot ::::: Progress of movement of •:::::--------~'' aircraft Figure 4.1 Four mental processing steps for Air Traffic Control (Opinion of the Hong Kong ATC expert group) Note. a. b. C. d. Sensory detection Task evaluation Decision making Communication The Four Processing Sleps for Air Traffic Control in sequence The following is a summary of the discussions with the three senior controllers on a typical controller's mental and work process: (a) Identification of traffic involved by sensory detection The identification of traffic under control could be achieved by radar identification, Distance Measuring Equipment (DME) / geographical fix 36 reporting with the aid of flight progress strips, or visual sighting of aerodrome traffic. All these means of identifications and detections of aircraft would require visual sighting of the aircraft or through aircraft position information display. The process of identification is confirmed by verbal or textual/signal communications between pilots and controllers, or a controller to another controller in the case of a radar handover. Traffic identification requires detection by sensory abilities such as vision and hearing. (b) Task evaluation Having identified all the traffic under control, it is necessary to process and organize all available visual information into a meaningful traffic picture. This is a more complex process that involves the mental appreciation of the constraints and influential factors that constitute the traffic problem such as aircraft types involved, airspace restrictions, separation requirements, speed of closure and weather considerations to say the least. For radar and aerodrome control , the ability to project and to anticipate situational changes after an ATC clearance has been issued to an aircraft is of paramount importance. In ATC training terms, a good controller must be able to "lead" the traffic situation to fit into his/her own plan. This task evaluation process is highly related to the performance of an ATC controller especially in an emergency situation. ( c) Dec is ion-making After evaluation of the tasks, the controller needs to assess all options available prior to making a decision. The expert controllers at the meeting all mentioned the need to apply the correct procedures, rules and separations between the aircraft concerned. The effectiveness of an ATC clearance depends heavily on controller's previous experience and knowledge and his/her ability to evaluate options available in a particular traffic situation. He/She may also need to sort out ATC clearance in its priority order. This is particularly true in a radar environment as there are many solutions to a 37 traffic problem by providing heading, altitude and speed changes. The controller will need to make the best possible decision and convey the clearance to the pilot in order to 'pave the way' to create the desire traffic picture that suit his/her own control plan. (d) Communication with pilots to complete the task Once a decision has been made, it would be delivered in the form of an ATC clearance using standard phraseology to the pilot for execution. The communication of clearance could be verbal, in textual format or in visual signal as for the case of having an aircraft experiencing radio failure. Most of the communications between controller and pilot in high density airspace today are performed through verbal means using radio communication equipment. In Hong Kong, all ATC clearance communications between controllers and pilots are verbal transmission through Very High Frequency (VHF) radio equipment except for passing Pre-Departure Clearance (PDC) to a departure aircraft in parking bay. For PDC, clearance has to be typed in via keyboard input and then transmitted through SITA digital communication network in a textual format to Aircraft Communications Addressing and Reporting System (ACARS) equipped aircraft. Actions taken by the pilot which affects the movement of the aircraft would then feed back to the controller verbally through clearance read back and visually through aircraft position display tools. This mental process of a controller repeats again as traffic continues to develop. Niessen, Kyferth and Bierwagen (1999) proposed a model for the cognitive processes of experienced air traffic controllers. The model has been developed on the basis of experimental research with air traffic controllers. The main components of the model consisted of five modules namely data selection, anticipation, conflict resolution, update and control with several procedures and information processing cycles connecting these modules together. The module on data selection is related to sensory detection with an added element of distinguishing focal and extrafocal objects. The anticipation and conflict resolution modules are related to task evaluation. In these 38 modules, focal objects are being monitored more frequently for safe operation and conflict detection. The update module initiates steps to prevent any impending conflicts and to make assessment on traffic priority. The process eventually leads to making a decision. The result of making a decision leads to execution of control by controller-pilot communication. This ATC cognitive processing model proposed by Niessen et al is consistent with the four mental processing steps suggested by the Hong Kong ATC expert group. The four mental and work processing steps by both radar and aerodrome controllers as described above are highly relevant to the nine essential job abilities perceived by participating controllers in this study. It is very similar to the information processing model in ATC as proposed by Isaac and Ruitenburg (1999) "The essence of the information processing model have at least four major mechanisms that mediate information in the environment and from movement. These are the sensory mechanism, the perceptual mechanism, the decision mechanism and finally the effector or response mechanism" (p. 40). Figure 4.2 below shows the four major mechanisms of the information processing model. Peripheral Sense _.. Organs _.. _.. _.. _.. Perceptual Mechanism Central Processes Memory Decision Mechanism Feedback Effector Mechanism Peripheral Muscular System Figure 4.2 A simple model of information processing (Extracted from Air Traffic Control, Human Performance Factors, Issac, A.R., Ruitenberg, B. (1999)) 39 Introduction This study suggested nine essential ATC abilities as perceived by participating controllers. Although controllers were working in different environment, applying different rules and procedures with different complexity, this study provided evidence that they all required the same essential abilities to perform their ATC job effectively and successfully. To explain this result, the radar and aerodrome job functions would be evaluated against the identified essential ATC job abilities using the information processing model as proposed by Isaac and Ruitenberg (1999) which is similar to what had been described by the Hong Kong expert group controllers at the meeting. The evaluation and discussions would take the order of sensing mechanism, perceptual mechanism, decision mechanism and effector mechanism. Traffic detection and identification by sense organs The information processing loop of a controller is being initiated by the time when an aircraft has been visually detected by the controller. Before a traffic problem could come up from an ATC standpoint, at least one aircraft 's position must be detected visually in the block of airspace under his/her control and ATC/pilot communication established by the controller. Both radar and aerodrome controllers, rely on hearing and vision as their primary sensing mechanisms for traffic detection. In accordance with ICAO Annex 1 requirements, controllers are all required to pass the same medical standards for hearing ability and vision tests irrespective of the type of ATC ratings (ICAO Annex 1, 2006). In the case of Hong Kong, the medical certificate form part of the ATC licence without which controllers are not allowed to exercise the privileges of their ATC ratings (AN[HK]O, 1995). Both radar and aerodrome controllers need to have high requirement standards on hearing and vision abilities. Some of these medical tests are repeated at regular time intervals. The length of time between medical tests is depending on the age of the licence holder. Although medical fitness requirements for radar and aerodrome controllers are the same, this study has provided evidence on possible variance between the ability requirements on visual colour discrimination and night vision between Radar and Aerodrome controllers in Hong Kong (Table 3.3). This will further be discussed below. 40 Sensing mechanism in relation to problem sensitivity (i.e. , the 9th highest score amongst the nine essential ATC abilities, Table 3.1) Problem sensitivity (9th highest score) After traffic detection, the controller must be sensitive to changes and problems generated by the interactions between all identified traffic and applicable control procedures. The Radar group had a mean value of 4.45 , SD 0.55 and Aerodrome group with a mean value of 4.37 , SD 0.71 which were quite consistent with each other in terms of ability requirement on problem sensitivity. Sensitivity to problem involves more than just detection of aircraft positions through body sensory organs as described above. The scope and magnitude of ATC problems are positively correlated to the complexity of traffic. Therefore, the controller must be able to appreciate and correlate interactions between all the aircraft under his/her control and the interplays of other ATC positions, application of the appropriate rules and procedures in order to achieve a traffic flow plan. The interaction between conflicting aircraft and the need to apply rules and separations between aircraft would present traffic problems for the controller to resolve in real time. Airspace and traffic complexity creates problems to controllers. Although radar and aerodrome controllers work under different environment, they both need to have the ability to apply appropriate rules and procedures. They also need to apply their skills and experience to separate conflicting aircraft within their respective airspace while at the same time achieving an orderly flow of air traffic. A radar controller normally applies heading, speed and altitude adjustments for aircraft separation (i.e ., tactical vectoring). Conflicting traffic could be a combination of departures, arrivals or both. Similarly, an aerodrome controller has to face conflicting traffic in the vicinity of the airport or on the manoeuvring area albeit with lower level of complexity. Separations between aircraft and/or obstructions in its flight path are provided through the issuance of correct clearance to the pilot to take certain actions in a timely manner such as clear to land, clear for takeoff, instruction to carry out missed approach procedure or taxy instruction to a bay for parking. Again, 41 safety and order of sequence of aircraft are the most important elements that both radar and aerodrome controllers need to consider. Although the nature of the traffic problem and the solution to it could be different, the ability to detect and be sensitive to the traffic problem under controllers' jurisdiction is essential for a successful radar or aerodrome controller. In an ATC environment quite naturally, problems are mostly related to air traffic interactions, but problems are not just related to traffic conflictions in a complex system. It could be a problem in ATC hardware, organization; a problem on coordination with other controllers or even a physical or physiological problem inherited with the controller. This is consistent with the SHEL model as developed by Edwards (1972, as cited in ICAO Human Factors Digest, No. 1, 1989) which relates Human Factors with liveware, hardware, software and the environment. Despite the nature of the problem, the ability requirement to be sensitive to problems is therefore applicable for both radar and aerodrome controllers who are the human components of an ATC system. In the course of their control duties, they are provided with various means to identify emerging problems such as radar and flight progress strips for aircraft position display, warning signals and alarms to keep track of traffic development and equipment serviceability. They must also be sensitive to their own physical conditions and mental stress symptoms. Sensitivity to problem could be enhanced through better understanding of Human Factors and the knowledge and skills required for the work. Problem identification and traffic situation analysis have long been introduced in various ATC training exercise for both radar and aerodrome control. Prior to obtaining the ATC rating, student ATCOs are required to gain their experience through interaction with other liveware, hardware and traffic situation in an appropriate simulator. Both radar and aerodrome controllers must therefore be sensitive to problem and its effect on the overall management of the air traffic situation. This study suggested the need on such job ability for both radar and aerodrome controllers in Hong Kong. 42 Perceptual mechanism in relation to visualization (81 h highest), situation awareness (No. I highest), and stress resistance (6'h highest) amongst the nine essential ATC abilities Visualization (8'" highest score) The Radar group has a mean value of 4.44, SD 0.59 and Aerodrome group with a mean value of 4.53 , SD 0.56 which are quite consistent in terms of the ability requirement on visualization. The most important piece of infom1ation available to both radar and aerodrome controllers is the visual image of traffic such as a target on a radar screen or sighting of an aircraft in flight or on the maneuovering area. It provides a precise position of the aircraft in relation to other traffic or obstruction and terrain. These visual images coupled with other supporting information from various communication channels such as radio position reports, produce a 3-0 traffic picture that is meaningful to the controller concerned. This visual picture is vital for problem identification, application of rules and procedures. The visualization and forward projection of visual images of traffic help better planning and decision-making by the controller in ATC sense. This is particularly relevant to radar control environment which is normally rather complex and fast changing. Other supporting information about the flight is printed on flight progress strips in textual form and is being put in front of the controllers for reference. The strips are also colour coded to represent the nature of the flight e.g. departures in yellow, arrivals in blue and marked with estimated time to reporting points. Such information can provide the controller with a less precise traffic picture. In a procedural non-radar environment, controllers may have to rely solely on flight progress strips for separation between aircraft. Nowadays, it is rather uncommon to have an ATC service that provides just procedural control due to high traffic density. However, if the controller are not able to maintain the visual image of the aircraft through direct sighting or surveillance of a radar due to equipment failure or 43 obscured visibility, the controller will still be required to provide adequate separation for the traffic concerned by visualizing the traffic picture in the 3 dimensional sense using the flight progress strips, time information and other available cues. Aerodrome controllers rely primarily on strip display information for separation and sequencing of aerodrome traffic. Therefore the power of imaging and the ability for visualization are essential determinants for both radar and aerodrome controller's success. Power of imaging and visualization should be trained and enhanced throughout controller's training syllabus as the ability for visualization is severely impaired if controllers are required to follow a moving target with their eyes, hand or arms at the same time. The ability to retain visual patterns is also disrupted if the visual images comprise material that is visually similar or confusable (Isaac, 1999). In recent years, especially in high traffic density airspace, callsign confusion has been identified as a major contributory factor on ATC incidents. Aircraft labels and display strips with similar callsigns can easily confuse a controller when the work pressure is high. Therefore, it is essential for both Radar and Aerodrome controllers to have high level of ability for generating, retaining visual images; and visualizing the 3-D traffic picture in real time. Enhancing visualization could be developed through traffic simulation. Both radar and aerodrome controllers in Hong Kong are provided with simulator training that represents the local traffic environment in order to strengthen their power of visualization in correlation with the local environment. Both groups of controllers require such ATC ability for their job. Situation awareness (No. 1 highest score) Situation awareness is defined as the capability of one to stay always alert within a dynamically changing environment. It involves awareness on changes and the anticipation of trend development based on the knowledge of both the past and the present (Eibfeldt, 2002). All the 113 subject responded with either a 4 (quite important) or 5 (most important) rating for situation awareness. It is the most important ATC job ability perceived by the controllers participating this research. The Radar group's response provided a mean score of 4.81, SD 0.39 and Aerodrome group with a mean of 4.76, and 44 a SD 0.43. Situation awareness was therefore also perceived as the most important ATC ability by both Radar and Aerodrome controllers. As all radar and aerodrome traffic are moving targets, the traffic picture 1s changing all the time with new traffic coming into view that requires identification and communication to be established by the controller. Both radar and aerodrome controllers will need to have high perception power to appreciate the dynamically changing traffic. They also need to develop a good anticipation of situational development in order to evaluate the possible strategies to handle the changing traffic situation. As traffic complexity increases, more selective attention to a specific traffic problem and priority management will be required. More information will need to be integrated for decision making such as aircraft performance, weather, terrain and aerodrome conditions which demand much on their working memory. According to Endsley (as cited in Francis, 2002) suggested that attention and working memory are limiting factors in situation awareness. With experience these limitations can be overcome through the development of long-term memory and automaticity. She also suggested that stress, automation, and work overload and under load are threats to situation awareness. From an operational viewpoint, design of ATC system and work stations should have given due considerations to these important human cognitive limitations. More traffic planning tools and conflict alert systems should be made available to controllers for enhancing situation awareness. The more important variables other than the radar and strip information display which contribute to controllers ' situation awareness could be summarized in Fig 4.3. (Isaac 1999). These important cognitive variables are common to radar and aerodrome controllers although the applicable knowledge and information could be different. Both control positions are required to use specific tools and equipment for management of air traffic, interact with other ATC related work positions and to consider the operational impact on aircraft in respect of prevailing weather conditions. Sit