The facts rather than the NAStrowaffle – Part 1
ICAO Annex 11 – Air Traffic Services
2.2 Objectives of the air traffic services
The objectives of the air traffic services shall be to:
a) prevent collisions between aircraft;
b) prevent collisions between aircraft on the manoeuvring area and obstructions on that area;
c) expedite and maintain an orderly flow of air traffic;
d) provide advice and information useful for the safe and efficient conduct of flights;
e) notify appropriate organizations regarding aircraft in need of search and rescue aid, and assist such organizations as required.
2.3 Divisions of the air traffic services
The air traffic services shall comprise three services identified as follows.
2.3.1 The air traffic control service, to accomplish objectives a), b) and c) of 2.2, this service being divided in three parts as follows:
a) Area control service: the provision of air traffic control service for controlled flights, except for those parts of such flights described in 2.3.1 b) and c), in order to accomplish objectives a) and c) of 2.2;
b) Approach control service: the provision of air traffic control service for those parts of controlled flights associated with arrival or departure, in order to accomplish objectives a) and c) of 2.2;
c) Aerodrome control service: the provision of air traffic control service for aerodrome traffic, except for those parts of flights described in 2.3.1 b), in order to accomplish objectives a), b) and c) of 2.2.
2.3.2 The flight information service, to accomplish objective d) of 2.2.
2.3.3 The alerting service, to accomplish objective e) of 2.2.
2.4 Determination of the need for air traffic services
2.4.1 The need for the provision of air traffic services shall be determined by consideration of the following:
a) the types of air traffic involved;
b) the density of air traffic;
c) the meteorological conditions;
d) such other factors as may be relevant.
Note.— Due to the number of elements involved, it has not been possible to develop specific data to determine the need for air traffic services in a given area or at a given location. For example:
a) a mixture of different types of air traffic with aircraft of varying speeds (conventional jet, etc.) might necessitate the provision of air traffic services, whereas a relatively greater density of traffic where only one type of operation is involved would not;
b) meteorological conditions might have considerable effect in areas where there is a constant flow of air traffic (e.g.scheduled traffic), whereas similar or worse meteorological conditions might be relatively unimportant in an area where air traffic would be discontinued in such conditions (e.g. local VFR flights);
c) open stretches of water, mountainous, uninhabited or desert areas might necessitate the provision of air traffic services even though the frequency of operations is extremely low.
2.4.2 The carriage of airborne collision avoidance systems (ACAS) by aircraft in a given area shall not be a factor in determining the need for air traffic services in that area.
2.5 Designation of the portions of the airspace and controlled aerodromes where air traffic services will be provided
2.5.1 When it has been determined that air traffic services will be provided in particular portions of the airspace or at particular aerodromes, then those portions of the airspace or those aerodromes shall be designated in relation to the air traffic services that are to be provided.
2.5.2 The designation of the particular portions of the airspace or the particular aerodromes shall be as follows:
2.5.2.1 Flight information regions. Those portions of the airspace where it is determined that flight information service and alerting service will be provided shall be designated as flight information regions.
2.5.2.2 Control areas and control zones
2.5.2.2.1 Those portions of the airspace where it is determined that air traffic control service will be provided to IFR flights shall be designated as control areas or control zones.
Note.— The distinction between control areas and control zones is made in 2.10.
2.5.2.2.1.1 Those portions of controlled airspace wherein it is determined that air traffic control service will also be provided to VFR flights shall be designated as Classes B, C, or D airspace.
2.5.2.2.2 Where designated within a flight information region, control areas and control zones shall form part of that flight information region.
2.5.2.3 Controlled aerodromes. Those aerodromes where it is determined that air traffic control service will be provided to aerodrome traffic shall be designated as controlled aerodromes.
2.6 Classification of airspaces
2.6.1 ATS airspaces shall be classified and designated in accordance with the following:
Class A. IFR flights only are permitted, all flights are provided with air traffic control service and are separated from each other.
Class B. IFR and VFR flights are permitted, all flights are provided with air traffic control service and are separated from each other.
Class C. IFR and VFR flights are permitted, all flights are provided with air traffic control service and IFR flights are separated from other IFR flights and from VFR flights. VFR flights are separated from IFR flights and receive traffic information in respect of other VFR flights.
Class D. IFR and VFR flights are permitted and all flights are provided with air traffic control service, IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights, VFR flights receive traffic information in respect of all other flights.
Class E. IFR and VFR flights are permitted, IFR flights are provided with air traffic control service and are separated from other IFR flights. All flights receive traffic information as far as is practical. Class E shall not be used for control zones.
Class F. IFR and VFR flights are permitted, all participating IFR flights receive an air traffic advisory service and all flights receive flight information service if requested.
Note.— Where air traffic advisory service is implemented, this is considered normally as a temporary measure only until such time as it can be replaced by air traffic control. (See also PANS-ATM, Chapter 9.)
Class G. IFR and VFR flights are permitted and receive flight information service if requested.
2.6.2 States shall select those airspace classes appropriate to their needs.
2.6.3 The requirements for flights within each class of airspace shall be as shown in the table in Appendix 4.
Note.— Where the ATS airspaces adjoin vertically, i.e. one above the other, flights at a common level would comply with requirements of, and be given services applicable to, the less restrictive class of airspace. In applying these criteria, Class B airspace is therefore considered less restrictive than Class A airspace; Class C airspace less restrictive than Class B airspace, etc.
ICAO Doc 4444 – Air Traffic Management
2.7 SAFETY-ENHANCING MEASURES
2.7.1 Any actual or potential hazard related to the provision of ATS within an airspace or at an aerodrome, whether identified through an ATS safety management activity or by any other means, shall be assessed and classified by the appropriate ATS authority for its risk acceptability.
2.7.2 Except when the risk can be classified as acceptable, the ATS authority concerned shall, as a matter of priority and as far as practicable, implement appropriate measures to eliminate the risk or reduce the risk to a level that is acceptable.
2.7.3 If it becomes apparent that the level of safety applicable to an airspace or an aerodrome is not, or may not be achieved, the appropriate ATS authority shall, as a matter of priority and as far as practicable, implement appropriate remedial measures.
2.7.4 Implementation of any remedial measure shall be followed by an evaluation of the effectiveness of the measure in eliminating or mitigating a risk.
4.5.1.4 ATC units shall issue such ATC clearances as are necessary to prevent collisions and to expedite and maintain an orderly flow of air traffic.
4.5.1.5 ATC clearances must be issued early enough to ensure that they are transmitted to the aircraft in sufficient time for it to comply with them.
6.2 ESSENTIAL LOCAL TRAFFIC
6.2.1 Information on essential local traffic known to the controller shall be transmitted without delay to departing and arriving aircraft concerned.
[I]Note 1.— Essential local traffic in this context consists of any aircraft, vehicle or personnel on or near the runway to be used, or traffic in the take-off and climb-out area or the final approach area, which may constitute a collision hazard to a departing or arriving aircraft.
If there is ANY risk of not getting the ‘essential information’ to aircraft immediately. How is that resolved tactically early? = Separate
7.6 CONTROL OF AERODROME TRAFFIC
7.6.1 General
As the view from the flight deck of an aircraft is normally restricted, the controller shall ensure that instructions and information which require the flight crew to employ visual detection, recognition and observation are phrased in a clear, concise and complete manner.
If there is any doubt = separate
ICAO Doc 9426 - ATS Planning Manual
2.5 APPROACH CONTROL SERVICE
2.5.1 Whenever it has been decided that there is a justified requirement for the provision of approach control (APP) at a specific aerodrome, or for more than one aerodrome if these aerodromes are located in close proximity to each other and it is therefore more effective to provide this service from a single APP, the following aspects, further to the relevant provisions in Annex 11, need to be taken into account in the planning and operation of such a unit:
a) the co-operative arrangements between APP and the associated aerodrome control tower or aerodrome control towers;
b) the internal arrangements between controllers for the task of providing APP service;
c) measures required to ensure that a possible mix of instrument flight rules (IFR) and visual flight rules (VFR) operations at and around the aerodrome(s) in question do not impair the safety of flight operations.
2.5.2 One way to achieve flexibility is to provide both APP and the aerodrome control tower(s) with means permitting them to be aware of the traffic situation at each location and assist with appropriate action when the need arises and without the need for lengthy and time-consuming verbal coordination.
2.5.5 Since approach control is primarily concerned with controlled IFR flights operating at or in the vicinity of aerodromes, it will be faced with the problem of avoiding dangerous situations which could be created by the simultaneous presence of controlled IFR flights and VFR flights in the same airspace. While methods to overcome, or at least reduce, this problem to an acceptable level are at present under study, it appears desirable to mention some basic considerations which are already relevant to this subject.
2.5.5.1 One point which needs to be made first, from an ATS point of view, is that the prohibition of VFR flights at aerodromes where IFR flights are conducted is certainly not the preferred solution to the problem of mixed IFR/VFR flights in the same airspace. Such a course of action will deprive certain users of airspace and facilities which should normally be available to everybody on an equal basis. However, it is also evident that, if there is a likelihood of collision risks, a reasonable degree of interference with the freedom of operation of VFR flights must be accepted, be it that pilots of such flights may be required
to have skills not normally required for the conduct of a VFR flight (radio communication and/or certain navigation capabilities) and that aircraft must be equipped with certain radio communication and/or navigation equipment, or that VFR flights are restricted to certain areas and/or routes and required to comply with procedures additional to those normally required when operating at or around an aerodrome.
Vertical Splits
3.2.9 The reasons for the vertical division of airspace as described above can be two-fold:
a) either to split the workload of ATS so that the workload imposed on one ATS unit remains within manageable proportions, both as to its area of responsibility and the amount of traffic it is required to handle; or
b) to apply to air traffic operating in the upper airspace, operating conditions which are different from those applied in the lower airspace and which are motivated by operating parameters which are peculiar to traffic operating in that airspace (e.g. prohibition to operate in accordance with visual flight rules (VFR), use of the area-type control versus the airway type, etc.); or
c) a combination of a) and b) above.
In any case, if such a vertical split is made, it should be ensured that the plane of division, chosen for the reasons under a) above, is not different from that chosen for the reasons given in b) above because it will complicate procedures for pilots as well as for controllers.
Appendix C - Techniques for ATC Sector/Position Capacity Estimation
1. INTRODUCTION
1. Knowledge of the capacity of air traffic control sectors or ATC operating positions is necessary for two reasons. Firstly, for long-term planning, adequate warning is required of any future shortfall in capacity, as indicated by traffic forecasts. Secondly, if there is already a shortage of capacity requiring the application of flow control, it is necessary to know what the capacity is, in order to limit air traffic to a level which does not overload the system or penalize the operators excessively.
1.2 A considerable amount of work has been devoted in recent years to methods of estimating capacity. Of particular interest has been the work proposed by the United Kingdom, Directorate of Operation Research and Analysis (DORATASK Methodology for the assessment ofATC en-route sectors capacity - DORA Interim Report 8818; the application of this technique to current London Terminal Area Sectors - DORA Interim Report 8916; and calibration of the DORATASK Simulation Model on two en-route sectors at the London Air Traffic Control Centre - DORA Report, 8927) and the work by Messerschmidt, BGlkow and Blohm (MBB) of Germany resulting in the development of a procedure to quantify the control capacity of ATC working positions, known as the “MBB Method”.
The essence of both methods was to measure the necessary time for all control working actions and to relate this time to the total time available.
Note.- The most appropriate measure of capacity was likely to be the sustainable hourly traffic flow, rather than daily or annual flows. Such hourly capacities could be converted into daily or annual values.
2. SUMMARY OF THE “DORATASK”* APPROACH
2.1 The proposed DORATASK work centred on the assessment of the workload carried by the radar controller, summing the time spent on routine and conflict resolution (observable) tasks on the one hand, and planning (nonobservable) tasks on the other. In addition to these two interrelated elements of the controller’s tasks, there was a third element - a “recuperation” time. This was a minimum proportion of time not allocated to specified tasks (observable or non-observable) but considered essential for the safe operation of the sector. The controller’s time, therefore, is divided between observable tasks, nonobservable tasks and periods of recuperation. Although the workload was determined by the sum of the time spent in observable tasks and non-observable tasks, the capacity is considered as the level of workload which leaves the controller a safe margin for recuperation.
2.2 Observable tasks are those which can readily be recorded and timed by an outside observer; examples include radiotelephony (RTF) and telephone communication, strip marking and direct-voice-liaison coordination. Routine tasks, for a particular aircraft, are those which must be carried out even if there are no other aircraft in the vicinity. In order to get from “A” to “B”, all aircraft need to contact ATC to be given certain headings and flight level clearances and be handed off to the next sector. The sequence of instructions routinely given to an aircraft will be virtually fixed by the route it takes through the sector and by its origin and destination. The routine workload was, therefore, assessed by assigning aircraft to one of a set of standard flight profiles through the sector; associated with them were fixed sequences of tasks and, hence, a task execution time.
2.3 A simulation model was introduced to utilize the traffic sample to assess the number of occasions on which the controller would consider taking additional action because of the presence of another aircraft, including those not on the controller’s frequency. The total observable workload was the sum of time spent on routine tasks and on conflict resolution.
2.4 The routine workload during (say) an hour’s observation was dependent solely on the number of aircraft in each flight profile that enter the sector. The conflict resolution workload, however, would increase during a peak flow of traffic, as opposed to regular flow.
2.5 Non-observable tasks are those which are carried out almost continuously by the busy controller in parallel with the observable tasks, and which cannot generally be directly recorded or timed by the observer. These tasks, which include monitoring the radar screen and planning future actions, are, however, critical to the business of the sector controller. The non-observable workload was determined by calculating, for each aircraft within the sector area, how many strips it produces and how many other strips already present on the boards must be checked against it when it is first given to the radar controller. This number of checks was then multiplied by a “time per strip check” to give the total non-observable workload. The time for a strip check was not considered as a duration time for a physical task but as a factor calculated when the model was calibrated to reflect the time taken by the whole
planning task. The latter was the main aspect of DORATASK which required more detailed research. This kind of workload would be increased significantly during a peak flow of traffic.
2.6 The workload measure for a given sector and traffic sample was the sum of the observable and non-observable workload times. To arrive at capacity it was necessary to determine a minimum proportion of time that the controller must have for recuperation if the sector was to continue to be operated safely. This proportion was likely to increase with the length of time that a “capacity” flow rate was expected to continue. Initially it was assumed that the sector would operate at capacity for no more than one hour without either the controller changing or the traffic declining. The amount by which the traffic flow was to be set at a lower rate in order for safe operation to continue was studied further. While it was assumed that the time spent per strip check, which determined the weight given to the planning workload, was two seconds, the following conclusions were derived:
“THE AVERAGE WORKLOAD AT CAPACITY MUST BE LESS THAN 80 PER CENT AND WORKLOADS OF 90 PER CENT MUST NOT BE EXCEEDED MORE THAN 2.5 PER CENT OF THE TIME.”
2.7 The calibration of the DORATASK model was carried out in two parts. Firstly, the workload predicted by the model was compared with the observed workload during the study period and the model parameters were adjusted to align the two. Secondly, the workload was plotted against flow for a number of hours for two sectors whose capacity was agreed upon beforehand by other means; the criterion for setting the capacity as outlined in 2.6 above was derived from the results.
2.8 The principles of the DORATASK methodology of airspace sector capacity estimation remain fundamentally the same whether they are applied to the en-route sectorization or to the terminal control area (TMA) sectors. Three notable changes are, however, required in the implementation of the method in TMA sectors. Account must be taken of the workload involved in the control of stacks. The conditions used for identifying potential conflicts must be altered to allow for the additional complexity of a specific TMA route structure. Finally, the method for modelling the planning workload must be altered to reflect the fact that the controller relies principally on the radar screen for conflict detection, rather than on the stripboard.
Mixed IFR/VFR Operations
2.3.8 An experiment with a new type of airspace, which is between controlled airspace (visual exempted) and controlled airspace (instrument/visual), and associated provisions regarding service to aircraft in this airspace, is being conducted at Lyon (France). The Federal Republic of Germany provides an “improved” flight information service to VFR aircraft in controlled airspace below FL 100 and outside those portions of the airspace wherein VFR flights must be conducted as controlled VFR flights.
Mr
Griffo will be interested in that last one
ATC’s and ANSP’s have forgotten more about ATM and related than the NAStronauts collectively
think they know. Don’t be fooled by their ill-informed pontificating!
More to come!