Controlling as an area controller
edited 250510
Objectives
Explain what an area controller does.
Explain some basic techniques about the actual working methods.
Note: This is an informative document. Basic knowledge about the use of IvAc is necessary.
Introduction
If you look at a radar blip on your radar screen, you look at a flat presentation of an image that in reality is not flat at all. In fact, on the radar screen you only see 2 elements, a bearing (direction) and a distance. But the position of the aircraft is defined in 3 dimensions. There are 3 elements: bearing, distance and height. On the radar picture this height element is missing. Therefore this altitude information is written in the so-called label that is associated to the position of the aircraft. So, with the imagination of your brains you have to make a realistic 3D picture.
You look at the aircraft's position in the horizontal plane (your screen) and you add altitude information to create the third dimension of the picture.
e.g. an aircraft is on the radial 080 of ODS, distance out is 18nm, altitude shown on the radar FL90.
Radar picture and information
The so-called label associated with the radar blip provides a lot of information about the aircraft. Some parts of that are taken as actual information directly from the radar system, other parts are taken from the flight plan. A quick interpretation of this information is a great help for the controller to speed up his work.
We see the velocity leader (speed vector), the little line in front of the aircraft position (blip). This line is selectable with choices of 0 (=none), 1, 2, 4 and 8. It indicates the predicted forward flying time per 1, 2, 4 or 8 minutes based on ground speed and the current direction (=track) of the flight.
The little dots behind the blip are the history, the previous positions of the aircraft. These are not only speed related, but also give a clear indication of the movement of that aircraft.
Comparing velocity leader (future) and dots (history) indicate the instant movement of the aircraft. In this example, the aircraft apparently started to turn to the left since the velocity leader is not in line any more with the history dots.
The Airspace
The Belgium airspace is divided into two major parts:
· from ground to FL195, called the Flight Information Region (FIR), and
· from FL195 to unlimited, called the Upper Flight Information Region (UIR).
In real life the FIR and the part of the UIR (up to FL245) are controlled by Brussels ACC (Belgocontrol); the airspace above FL245 is controlled by Maastricht UAC (Eurocontrol).
In IVAO, normally it will be worked as one combined airspace controlled by Brussels ACC (in IVAO EBBU_CTR). Only on special occasions in IVAO will it be that separate Upper Sectors will be activated.
Area Controller Tasks
In short, controlling an area consists of three main points of attention:
1. The incoming traffic.
Make sure, when it enters your area, it is properly separated from any other aircraft that is already in your area.
3. The outgoing traffic.
Make sure it is properly separated from any other traffic and ..... it is in accordance with the existing LoA (Letter of Agreement)
2. The "working" area.
In between this ‘entry’ and ‘exit’ there is the "working" area, where the traffic is guided through the area from entry to exit, regardless whether it is climbing, descending or proceeding in level flight.
Note: therefore this sequence read here 1, 3, and 2 ☺
Phase 1: Incoming traffic.
Normally, when there is a previous ATC unit active, incoming traffic from that active area will be separated in line with the standard separation minima and in line with the Letter of Agreement (LoA), unless prior coordination (that is before the handover) established a different agreement between the controllers.
On radar contact, first thing (or earlier if possible) to do is to notice the destination and with that the expected route for that incoming traffic. Read the label!
This information immediately determines what you may expect from this pilot and how you have to clear him:
· A flight inbound to a destination within your area should be given the STAR (Standard Arrival Route) with the clearance limit and the expected landing runway.
· A flight with a destination to an (close) adjacent airport (neighbouring area) should descent in due time to reach the boundary exit point at the level agreed in the LoA.
· A departure flight entering from an (close) adjacent airport (neighbouring area) shall be further climbed to its requested cruising flight level, if available.
· Overflying traffic should be given the onward clearance.
Typical EBBU example 1:
Start at the right bottom of the picture.
DEM012 makes initial contact.
Controller: (Flash, flash!) he thinks:
Inbound EBBR,
thus: “DIK, BATTY, (clearance limit =) FLO, landing RWY 25L”
Next flash: Aircraft has to descent so as to be at FL60 at FLO. Mind, realistically, first descent FL250 (handover to EBBU lower :)
Immediate next flash: Where is the other traffic that is possibly conflicting with this descending one??
In short, a series of flashes that should come automatically, by training and routine.
Note: In general the traffic situation and the airspace structure in the East sector of the Brussels FIR/UIR are very different from the West Sector. In average, in the West the streams of traffic cross each other under ‘90’ degrees angle, with roughly east-west-east and north-south-north directions. In the East the streams could be in any direction. Therefore controlling traffic in the East side is different from the West.
The feeding of traffic into the East Sector takes place from several different directions and at different levels according to the existing LoA’s. Therefore a good structured way of controlling is a must.
* Note: Since you may expect traffic from NOR at FL180 or FL160 this has been indicated in this diagram.
Simulating the real life airspace, traffic entering the Brussels FIR/UIR at high levels (above FL250) shall descent first to FL250. There they are “transferred” into the lower airspace.
Typical EBBU example 2:
Start at the right bottom of the picture.
DEMO12 makes initial contact.
Controller: (Flash, flash!) he thinks:
Inbound EHAM,
thus: “DIK, BUB, (clearance limit =) HELEN”
Next flash: Aircraft has to descent from FL340 so as to be over BUB descending to FL250 out of FL280. Mind, realistically, the division between Uppers and Lowers, but here a handover to Lower West, if active, as well.
After BUB, further descent to FL200 for EHAA, and well separated from traffic FERDI-DENUT (FL220)!!.
Next flash: Where is the other traffic that is possibly conflicting with this one?
In short, a series of flashes that should come automatically, by training and routine.
Phase 3: Exiting traffic.
Traffic that is leaving your area has to be at the correct flight level, mentioned in the Letter of Agreement (LoA). Therefore, it may have to climb or descent. Starting that climb or descent in time is important to reach this agreed flight level in time.
A situation of "leaving your area" is equally valid for inbounds to an airfield in your own airspace. This inbound traffic has to be guided towards the correct initial approach fix (IAF). In addition, it has to be sequenced properly in line with other inbound traffic. Approach Control has to be able to accept it and to continue those inbounds in a proper and safe way.
Phase 2: The working area.
Working between entry and exit means an area controller is constantly busy with many things: Climbing, descending and separating traffic. For that, he will continuously scan his screen from left to right and from top to bottom. And backwards! Even though the total airspace of Belgium is not that big by itself, in reality a lot is happening in there.
To be able to do all these tasks properly, you need to have a working plan. A constantly changing plan, because in fact the traffic situation is not fixed. It is constantly changing with the movement of all the aircraft under your control. Aircraft may descent faster than you expected or outbound traffic may climb slower than you had hoped. Therefore, your main goal has to be to observe all these movements and constantly be aware what to do next. Be prepared!
Quite often a planned or intended next step in your working plan cannot be done immediately, because another aircraft will call you or there will be a slow-speaking pilot. That will take all your attention and valuable time. Meanwhile the rest of the traffic keeps on moving, safe or not. That is why your working plan is important, because it helps you to recover from that unexpected deviation of attention.
On the other hand, as the traffic picture has changed in that time, you may have to update your plan immediately. Be prepared and constantly update your plan, while at the same time you are working on executing that plan.
Realise that you are controlling a whole area, where things happen both left and right on your screen at the same time. While concentrating on one item on the left side, don’t forget about that other item on the right side of your screen.
Get used to clearing aircraft to safe intermediate levels first before you re-clear them further. Step by step is more appropriate than a loss of separation.
The work of an area controller is very flexible and hardly steady. Every moment is different, with constant changes and constant adaptation. Situations can change into something different than what you thought it would be. But every time again, you’ll have to have a new updated plan for the next step to take.
Technical, about separation
Separation.
There are two types of separations in ATC:
1. horizontal separation (left or right, but also in front and behind), normally 5 nms.
2. vertical separation (above and below), normally 1000 ft
At least one of the two separations has to be valid at any time to be sure that separation minima are met.
Therefore, compare it with a kind of big ball. The aircraft is in the middle of the ball and all the other aircraft are around it, at all sides. Outside the ball, but to all sides with sufficient distance away.
Now, air traffic control will try to keep this distance big enough not to have collisions. Or, expressed in the more official way:
Air traffic control will provide sufficient separation, by horizontal (5nm) or vertical separation (1000ft), to prevent collisions at any given moment!
Air traffic control will provide sufficient separation, by horizontal (5nm) or vertical separation (1000ft), to prevent collisions at any given moment!
Separation standards for IVAO:
horizontal 5 nm
vertical 1000ft if below FL290; 2000ft above FL290
in RVSM area: also 1000ft between FL290 and FL410
How does separation work?
As we indicated here above, there are two types of separation: horizontal and vertical.
Horizontal separation
Horizontal separation is established by maintaining a safe distance between aircraft flying next to each other, but in front or behind one another as well. This is the distance in the horizontal plane.
To all directions in the horizontal plane a minimum safe distance of standard 5 nautical miles (about 8 kilometres, 1 nm = 1.8 km) has to be maintained.
e.g. If two aircraft are flying next to each other at the same altitude, the minimum distance between them has to be 5 miles. The same is valid for two aircraft when one flies behind the other (see further).
Vertical separation
Above and below any aircraft a safe distance or height of 1000 feet (about 300 meters; 1 foot= +/- 30 cm) is to be maintained if they are closer than 5 nm of each other.
Note: It is the one or the other:
or horizontal or vertical separation!!
Separation techniques
To maintain the different separation minima as mentioned above, there are different techniques that the air traffic (area) controller will apply.
Very important hereby is to realise that speeds of the aircraft are much higher at high altitudes and therefore aircraft behave differently than aircraft at lower altitudes, like in the approach area (TMA).
Main separation techniques available are: altitude separation, headings, and speed control.
Altitude separation
Aircraft closer than 5 nm to each other have to fly with a vertical distance of at least 1000ft. As soon as they have crossed each other with more than 5nm, they could climb/descent as convenient.
Very simple, wait until the aircraft have passed each, gained enough separation (more than 5 nm) and then climb or descend them as convenient.
However, if this waiting would be too long, it would be nicer to find another solution. Sometimes waiting is the better solution, but not the fastest. If not, apply the technique as explained in the next paragraph.
Headings
By applying different headings to aircraft one could separate aircraft by putting them next to each other or by turning them away in such a way that a proper crossing is possible.
Next to each other, parallel
One could turn two aircraft in such a way that they will continue on parallel tracks. Helpful to climb or descent the one through the level of the other. Be aware that these parallel tracks could be opposite as well!
Demo01 (left to right) will be instructed first to continue his present heading. Secondly, demo02 (right to left) will be turned left by 10 degrees and instructed to continue that heading thereafter. When there is 5nm horizontal separation, only then demo02 could be climbed. After 1000ft vertical separation has been established, both aircraft could resume their own navigation again, normally to the next available known (way) point.
In this way a horizontal separation of 5nm (next to each other) is established first and maintained until the moment the vertical separation of 1000ft (above each other) is a fact, or until they have passed each other in such a way that separation remains 5 nm or more.
Crossing traffic.
Traffic is crossing your area from all directions, sometimes even at the same level, or they may cross each other’s path while in climb or descent.
It may sound difficult, but it is not. Think about driving your bicycle. In front of you is a person crossing the street. Now, if you would not change your own course, you may hit this person. So, you decide:
You steer a bit to the right and pass in front of him, or you steer a bit to the left and you will pass behind him. That is exactly what ATC will do in the air.
Aircraft will be turned either to the right so as to pass well in front or they will be turned to the left to pass well behind of each other. Or the other way around.
See the example:
Both aircraft are on a conflicting track (orange tracks). In about 3 minutes the separation will be lost (less than 5nm at same level).
Like on a bicycle, turn both aircraft either left or right, e.g. by 10 degrees. This will increase their minimum reachable distance if their speeds are close to each other. In orange is the flight path without corrections, in green it shows the effect of a 10 degree turn to the right for both of them. In fact, after about 2 ½ minutes they have reached their minimum possible distance already, which is now more than 5 nm.
Speed control
If the aircraft in front will be faster than the one behind him, separation will increase steadily. As soon as 5nm or more is established this way and it is assured that the speed difference remains at least constant or increasing, the one could be climbed or descended through the other.
Note that at higher altitudes, normally about FL250 or higher, aircraft will be cruising at a Mach number and not at indicated airspeed (IAS).
And note that, while aircraft start to climb or descend, their forward speed may change.
Additionally, aircraft at the same level and in the same direction which have a safe distance of 5nm or more, could be instructed to maintain the same or increasing speed to allow them both to continue at the same level.
e.g. first aircraft cruises speed M 0.80, second aircraft cruises speed M 0.78. Tell the first one: Cruise M 0.79 or more, the second one: Cruise M 0.79 or less.
Climb and descent
When an aircraft is instructed to change its altitude from level A toward level B, it has to cross a number of flight levels. At each of these levels there can be other traffic that could cause a conflicting situation. Therefore, the moment you intend to instruct a level change, first scan the area to a reasonable distance in front of that aircraft for potential conflicting traffic.
It may seem a difficult mathematical calculation, but it is easier than it seems.
On the left, an aircraft at FL210 is instructed to climb to FL290. Average rate of climb will be 1000 feet per minute. Thus in 8 minutes the aircraft will be level again. With a speed of let’s say 7nm per minute this 8 minutes flying means a distance of 56 nm. As such, climbing from FL210 to FL290 means a level band of 8000’ over a distance of 56 nm.
Conclusion: If I clear this aircraft from FL210 to FL290, I have to make sure that in the next 56nm or 8 minutes forward there will be no other aircraft in the vicinity in that progressing level band between FL210 and FL290. Otherwise I could have a conflicting situation.
So, if there would be possible interfering traffic, start with an intermediate level first and watch how the situation is developing. Only when you are sure, you will clear for further climb.
Note: You could use the extended velocity leaders to see the situation in 2, 4 or 8 minutes
Let me show you a case study :)
Right top:
TRA5673, reporting and shows FL256 climbing FL290 southbound.
TRA5673, reporting and shows FL256 climbing FL290 southbound.
Notice on the left of the picture GSS3463 at FL300 and DLH236 at FL330 both eastbound. They will cross the path of TRA5673, which has to climb finally to RFL390 (RFL=Requested Flight Level).
First step action: Initially climb TRA safely to FL290. That's 1000 below GSS.
To predict what the situation will be in a few minutes, we will use the extended velocity leaders (speed-vectors). Here we selected 4 minutes.
Observe that vertical separation at the predicted crossing point looks doubtful.
Theoretically, in 4 mins TRA could be passing FL310. That is 1000 ft above the GSS. This should work.
We instruct TRA to continue climb FL320, rate of climb of climb 1000/min or more, until passing FL310. This is to make sure that pilot knows what is expected.
We instruct TRA to continue climb FL320, rate of climb of climb 1000/min or more, until passing FL310. This is to make sure that pilot knows what is expected.
We do know as well that if pilot is unable to fulfil the clearance, he has to say so ....
While TRA climbs FL320, he will remain 1000ft below DLH236, since that is the next one to be in the way. We have time now to evaluate whether TRA and DLH really will be a conflict.
On the third picture here on the right we have meanwhile selected 2 minutes velocity leaders.
Now we can see that in two minutes the distance between TRA and DLH still be more than 5nm. So while climbing TRA further to his RFL390 now, he should pass well in front of DLH without a problem.
In the picture hereunder we see the moment where the 1000ft separation will not exist any more, since TRA is leaving FL320 climbing. Still he will have more than 5 nm with DLH and it will remain more than that needed minimum of 5 nm.
Keep an eye on the situation as it evolves and see that it is working the way we had planned it. No alternative actions needed.
Finally, TRA is about to pass FL330 while he will properly pass in front of DLH, here shown still with two minutes velocity leaders.
Note at that at these altitudes these aircraft fly with a Ground Speed (GS) of more than 300kts. That is divided by 60 more than 5 nm per minute. Roughly said, one minute flying time as shown by the speed vector represent in such case more than 5 nm.
Now both problems have been solved in a standard way of doing. That is:
Step by step (climb) and calculating every time what the situation is and what it will be BEFORE the next step is made.
Letter of Agreement (LoA)
The purpose of the Letter of Agreement is to establish common working procedures and agreements between adjacent (neighbouring) sectors or FIR's. Mainly it applies at and around the common borders between those sectors.
Specific local situations may exist which make it necessary to have a local agreement between the parties concerned.
Letters of Agreement will determine matters like:
· specific airways to be used for designated destinations, arrivals or departures
· specific required flight-levels at specified points to facilitate proper climb or descent profiles in relation to departure and/or arrival airfields
· establishment of transfer of control points and transfer of communication points
· designation of transfer of responsibilities in respect of control releases after assuming control
· the use of specific transfer flight-levels
· city pair restrictions
· indication of the different sectors' responsible at different points
In short, a whole list of items specifying the details about the hand-over procedures between the different units concerned. There is a lot to learn and remember here.
Let's go through these different items step by step.
· specific airways to be used for designated destinations and arrivals
specific inbound and outbound routes make the process of separation easier. Eventually, routes for one way or only used for particular airfields or airfield groups could be designated. Designated routes for a specified purpose will make it easier to regulate that flow of mainly descending or climbing traffic at those places where there is a lot of that type of traffic.
· specific required flight-levels at specified points to facilitate proper climb or descent profiles in relation to departure and/or arrival airfields
To make sure that the particular streams of traffic can be facilitated properly, it may have been agreed upon to descent or climb traffic only to agreed flight-levels. After transfer the receiving (next) unit will take care of further changes in these flight-levels. E.g. standard levels at the Initial Approach Fix (IAF) for inbound traffic.
· establishment of transfer of control (TCT) and transfer of communication points (TOC)
At or prior to the (geographical) boundary between two sectors there will be a transfer of control point (TCT). At that point the transfer of responsibility from one control unit to the next control unit takes place.
It is obvious that, to be able to assume such control, it is necessary to have the aircraft on your frequency in time. For this reason the transfer of communications point (TOC) is, depending on the local situation, before or the latest at the relevant transfer of control point (TCT). First the aircraft has to be on your frequency before you can control it!
Important to know and realise is that the “transfer of responsibility” means that the next controller will take over and guide that pilot further. Therefore he has to be sure that the traffic, which was handed over to him, is separated from other traffic in such a way that he is able to accept this responsibility of control. He should never be presented with a conflicting traffic situation!!
As we saw before, the task of the area controller is quite specific in accepting entering traffic and in transferring exiting traffic. Realise that, at the first moment the pilot checks in on the frequency, the receiving controller needs a little time to adapt to the new traffic situation.
· the use of specific transfer flight-levels
It could be agreed upon to have all inbounds into a certain area or TMA descending to the same level, say FL250. In addition it could have been laid down in the LoA to have all outbound traffic at that same point climbing to the same level, say FL240. As a consequence of such agreement the use of those common flight-levels 240 and 250 for the purpose of overflying is thus not allowed.
By adding such an agreed procedure into the LoA, it reduces the amount of individual coordination between the units concerned, since there is a standard agreement for handover. Therefore, in these cases, after the traffic has passed the agreed transfer of control point (TCT) and has been transferred onto the next frequency before that point, control can be assumed. Thus, further climb or descent may be started, clear of known traffic. That way more traffic could be controlled more easily.
Note: The examples of FL240 and 250 is typically an agreement between a lower and an upper sector.
· city pairs level restrictions
To regulate the flows of traffic and to reduce the heavy workload nowadays, it could be agreed to establish a so-called "city pair" level restriction. This means that traffic between airfields of those cities is only allowed to fly below a maximum agreed flight level for the route connecting these cities.
e.g. from A to B maximum available flight level will be FL230 and the other way around maximum FL240. You will see such agreements typically if there is a higher sector above starting at FL245.
· indication of the different sectors responsible at different points
To indicate which sector units are responsible for which airways and transfer points, a list with this information is shown in the LoA to clarify the different situations at the borders.
Be aware that quite often it is not simply an agreement effecting only two sectors, but often even four sectors.
Suppose traffic in the high sector is descended to the lowest available level. As it has to go into the next lower sector, more than two sectors are concerned here.
Example: Traffic descending to FL250, transferred to EBBU West and not to Eurocontrol West, as you may expect.
In short, a Letter of Agreement is a very important document to allow a reduction of coordination between different control units. The lesser needs there are to coordinate traffic individually, the more time remains to concentrate on the working plan and the actual controlling tasks itself.
Mind and realise always, contrary to real life, in IVAO we sit alone on any position, where in real there are most of times two man sectors.
Enjoy J
Bob van der Flier (copy-rights)
Bob van der Flier (copy-rights)
