NAS rears its head again

[Josh Cox]

So:

Peuce is of the opinion that C and E cost the same to operate and C is safer.

Capt Bloggs is of the opinion that C is a problem as it will cost more than E, i.e. will cost more than E where there are great numbers of VFR movements, due to an increased workload for they controller, requiring more controllers and C is safer.

So the problem really lies in the actual facts regarding actual operating costs between C and E in a high volume VFR area/aerodrome ( which Broome for example is ), would C and E still cost about the same to operate when there is a great amount of VFR traffic ?.

I am not a controller, and am speaking from relative ignorance, I can not imagine C in a high VFR movement area costing the same to operate as E in a high VFR movement area.

[Jabawocky]

As to you staement that the cost of E and C being the same, well I disagree:

E = clearance/traffic for IFR, any VFR info available, so clearance for say 100 movements per months ?.

C = clearance and separation for eveybody, so all of a sudden the +2,000 (guestimated figure) odd VFR movments plus the 100 IFR = 2,100 per month would require clearance and separation, a hugely larger number.

As a pilot...not an ATC, but have a few mates that are....when you consider the RPTs are in pre planned bursts of activity, they are well planned and managed. The other 2000 VFR's spread over the rest of the month would equate to about 5.55 per hour, just enough to stop them going mad or to sleep.

The system works well and the very reason why Rockhampton's recent survey said to keep C over D backs that up. And I wonder how much VFR they have compared to Broome?

Capt Bloggs is of the opinion that C is a problem as it will cost more than E, i.e. will cost more than E where there are great numbers of VFR movements, due to an increased workload for they controller, requiring more controllers and C is safer.

Bloggs has never said anything like that You may have just made some typo there I think?

[Capn Bloggs]

Josh,

would C and E still cost about the same to operate when there is a great amount of VFR traffic ?.

I've answered your question in my previous post. With lots of VFR, C will be more expensive. Do not forget, though, that C is still required, because of the increased traffic, to protect against Midairs. I will hit a VFR just as hard as an IFR. Metal on metal doesn't differentiate between flight categories, as would occur in E.

In E with lots of VFR, I will probably hit one without knowing it and there are no defences against a midair apart from eyeballs out.

However, at Broome and Karratha, the VFR levels are low enough to allow C instead of E. If they get too high, then E is not the answer; a C with a radar (or ADS-B) is the answer.

The irony: with low numbers of VFR, E is not necessary. With high numbers of VFR, E is not safe (Ledsled if you don't get the context of what I mean by "not safe", too bad). Therefore, what's the point? The point is that E allows Dick and Ledsled to career through the airspace doing their own thing. That's all.

[Jabawocky]

Frank

As a spectator for most of the time on this thread, all I can say is I now understand why some in the animal kingdom eat their young.

And now I understand that some escape!

J

[peuce]

Josh,

Rule No 1: The NASdebate does not always make sense
Rule No 2: The NASdebate is full of statistics, models and analyses (many hidden from prying eyes)
Rule No 3: Statistics, models and analyses don't necessarily make sense

But to put another slant on your confusion ...

Given the traffic figures we have available for Broome, many Controllers ( as well as their Union) believe that C can be performed for basically the same cost as E.

Yes, if you significantly increase the VFR traffic levels, then either more Controller positions or installation of surveillance equipment would be required ... which is an extra cost.

But, as Capn Bloggs points out, if it got to those levels ... E could not possibly be an option ... without significantly increasing the risk to IFR aircraft .

And remember, we are discussing a specific volume of airspace here. Bring another area into the equation and we might have a totally different point of view.... taking into account traffic, facilities, geography, weather, airline movements etc

[Frank Arouet]

Bloggs;

With lots of VFR,

Quantify that please.

EDIT to add for the Jabawocky post.

Yes the strongest!

[Capn Bloggs]

[Capn Bloggs]

Frank,

Quantify that please.

Ledsled will be able to help you there. He's the expert on risk analysis and allocation of alphabet airspace.

The value doesn't actually interest me, because whatever the VFR traffic level, E is either not required or too dangerous. There is no in-between.

[Jabawocky]

EDIT to add for the Jabawocky post.

Yes the strongest!

No that is not what I was suggesting but you knew that, along with a few others.

[mjbow2]

Howabout

as regards your comment:

Quote:
You controllers have two irreconcilable positions on Class E. That is, we should use enroute Class C, because we can but only until traffic levels reach that of the United States, then we should downgrade it to Class E so we don't run into grid lock. Extraordinary!

Who actually said that? In context and with references please.

This is what Peuce said to Howabout in this thread about NAS.

Howabout,

As all the others have said, the issue in Class E is vectoring IFRs, whilst VFRs track as desired. With surveillance, there's some mitigation, without surveillance, it's Russian roulette.

As Dick will quite rightly say ... "they do it all day, every day in the States"

Yes, they do ... because they have to. There's no other way to process that amount of traffic. Imagine if it was all Class C.

My bolding

Again I ask. Are you controllers all in agreement in your objections to NAS or is your intent to say anything at all, regardless of how ridiculous and contradictory, in your attempts to discredit NAS?

Do you controllers really believe it costs the same to provide Class C as Class E? This is an ill conceived con by Civil Air to resist NAS and it looks like some controllers are finally admitting the truth about the real cost of Class C.


ozineurope

mj - do you have any idea of what you speak? If an IFR aircraft is collected/collects another aircraft in G airspace the controller could find themselves in front of the coroner for failing to pass a traffic alert and suggested avoiding action to the IFR.

For you to say that G absolves the controller shows that you have no idea of the rules that ATC operate under in Australia.

This is an extraordinary statement.

The Baron and the Saab were both IFR operating in IMC, in radar covered class G airspace on the CTAF frequency.

If what you are saying is true, that you do have a responsibility, then how could you possibly not want Class E so you can guarantee separating them, thereby keeping your job safe. Think about what you are saying ozineurope!

The Chaser

You know full well that the statement in the Orange report about airspace at Orange being NAS compliant is false. Completely false!

Go and read the NAS document again. The interim design was to make Class E corridors into selected airports.The end state design of NAS was to have all radar covered airspace a minimum classification of Class E. On both counts this included Orange as the radar coverage is close to the ground.

The Chaser. It is a fact that if Orange had Class E this near collision in IMC would not have happened.

Owen Stanley

I know you blokes are keeping it civil but I'm a kinda 'call a spade a feckin' shovel' type of guy.

What a complete w@nka, don't think I'd come across a bigger tossa if I had two life times.

A self professed expert suffering relevance deprivation syndrome (as well as dementia)

What a w@nka

I would rather be called a NAStronaut please. :-)


OZBUSDRIVER

mjbow2...you ARE Dick Smith's pilot!

It is true that I have been seen in a certain Citation, I will admit that. However it was registered in the United States where I was paid to fly it, but not by Dick Smith.

Surely you know that conspiracy theories are looked upon with skepticism and lack any real evidence.

[LeadSled]

Josh,
I will try it one more time ---- G through A are not ascending levels of safety.

Do a bit of basic study on the subject, don't take anything here as gospel, satisfy yourself. Eurocontrol ( for those who are so anti-US that they will not even consider what happens in the US) publish some quite good background material, they also publish their design risk levels in various airspace, and follow up by publishing assessed achieved levels v. the design levels.

With the appropriate addition of services as traffic/traffic mix increases, the intent of ICAO airspace classifications is that any category of airspace, correctly serviced, is equally safe.

As I have said, time and again, the separation assurance standard is the same in each classification, and it is so high that adding additional resources does not "increase safety". The risk level remains the same, just the system costs increase --- classical economic waste.

One of the major problems in Australia, when we moved to "alphabet soup airspace", was that there was no genuine attempt at real reform to take advantage of the new design principles. We just gave our existing "controlled/uncontrolled" airspace names that were close to the new classifications. In short, the miss-allocation of resources continued. Only now are we going to adopt real Class D for non-radar towers, instead of the "D that wasn't D" we have operated for years.

I just love the claim about "the paradox of E" ---- claims made by (I very strongly suspect) alleged pilots or ATC who have little, if any, experience outside of Australia. All they know is what they don't know they don't like.

Only in Australia (and then only in the minds of a few people) is E a "paradox", or regarded as in any way controversial. For any body who has done any serious international aviating, E is extremely difficult, if not impossible, to avoid. Outside of Australian, nobody gives a toss about E, they just get on with the job.

But, the "little Australians" know it doesn't/won't work.

The real issue is the resistance to any change in the aviation scene in Australia, at a great cost to the Australian industry as a whole. In many ways it is part of the legacy of the "two airline" era, where "cost plus" ruled, and silly pilot demands (like E/Os on B767) were just lumped on the ticket costs. I don't find it at all surprising that both the airline of the "two airline policy" era, no longer exist.

From memory, there have been about five investigations into Australian airspace management over the last twenty years or so, conducted by highly qualified and respected bodies, such as UK NATS, Roake Manor Research (Siemans), and of course the FAA, there are more, but each one has made essentially the same recommendations, that we should adopt the intent of the "new" ( but its been around for years, now) ICAO approach to CNS/ATM, to ensure that assets are properly allocated, not something we do now.

Given the proven traffic handling capacity of the US system, and also given that it produces the best air safety outcomes, is it surprising that US NAS is the basic starting point for Australia?? ----- but not if the recalcitrants, the little Australian, get their way.

Tootle pip!!

[squawk6969]

mjbow2

You know full well that the statement in the Orange report about airspace at Orange being NAS compliant is false. Completely false!

Go and read the NAS document again. The interim design was to make Class E corridors into selected airports.The end state design of NAS was to have all radar covered airspace a minimum classification of Class E. On both counts this included Orange as the radar coverage is close to the ground.

The Chaser. It is a fact that if Orange had Class E this near collision in IMC would not have happened.

If you would like to turn the vast chunks of RADAR covered G into E, that would be a great idea for those days when its IMC in the backblocks, however I think if you remember this is about much busier terminal areas with high capacity RPT Jets and NO RADAR.

SQ

[peuce]

Let's take a breath!

To The Nastronauts,

Lots of he said and I said and why don't you both say here. Everyone is entitled to their individual opinions ... even Controllers. It's still a democracy and the fact that 100% of Controllers might not agree on a specific issue ... does not the issue prove , or disprove. Everyone has their own knowledge and experience... and thus opinions are formed from those. The challenge for the reader is to sort through all the offerings and form their opinion.

So that we don't continue to go round and round in circles forever, I would like to attempt to encapsulate the two basic opinions here. So, let me know if I've got it worng. Here goes ...

The Nastronaut Argument

• Someone, somewhere, has done the maths and come up with the probability of a MAC over Broome and Karattha, if Class E Airspace was mandated, as x.
• x is considered to be in the "Safe" zone.
• If Class C Airspace was mandated, then the probability would come out at y
• Y is also in the "Safe" zone
• Therefore, as "Safe" has been achieved in Class E, there is no need to move to a higher, more expensive Class of Airspace ... as minus 60 degrees is just as cold as minus 50 degress

The Fundamentalist Argument

• Y will be achieved with absolute certainty ... as positive separation is provided for all
• x will be achieved IF the data used to do the sums was correct, if the sums are correct and if "murphy"doesn't poke his nose in it
• As Class C costs are similar to Class E costs, why take the chance on x being correct, when y is a certainty?
• If we have it wrong and Class C costs more than Class E, why sweat the small difference, if an absolute safety factor can be assurred?

Let me know if I have mis-represented anyone's position.

[peuce]

Nastronaut Inconsistency

It is difficult to warm to your ideas when you publish inconsistencies.
Here is a statement from mjbow2

...The end state design of NAS was to have all radar covered airspace a minimum classification of Class E

Followed by Leadsled's creed:

As I have said, time and again, the separation assurance standard is the same in each classification, and it is so high that adding additional resources does not "increase safety".

On the one hand you appear to be demanding a blanket Class E ... beacause you can. On the other, you say that once safety is assurred ( as in current Class F) it is rediculous to upgrade the classification.

You can't have it both ways ....

[mjbow2]

peuce you clearly do not understand. There is no inconsistency at all.

The concepts expressed by Leadsled as I understand it is that an IFR aircraft flying from an uncontrolled airfield to a major airport should be exposed to the same minimum level of risk from the point of departure to the destination.

Surely you can see that this means than a ground controller is not required at Ballina but is required in Sydney. And that different Classes of airspace are required. As the actual risk increases the level of risk mitigating also increases so the resultant risk is at the same acceptably small level regardless of where the IFR aircraft is.

peuce. We do not have Class F in Australia. There is no IFR to IFR separation even 'as far practicable', we get traffic information.

No one is demanding blanket Class E. I want to see allocation of airspace classifications based on scientifically supported risk assessments. Not based someones Alice in Wonderland type 'belief' that enroute and link airspace are as risky as Sydney airport or in the case of regional airports, more risky than the towered Class D airspace.

[peuce]

mjbow2,

..Surely you can see that this means than a ground controller is not required at Ballina but is required in Sydney. And that different Classes of airspace are required. As the actual risk increases the level of risk mitigating also increases so the resultant risk is at the same acceptably small level regardless of where the IFR aircraft is.

Doh! ...

No one is demanding blanket Class E

Really? Do you not want Class E wherever there is radar coverage?


From "The Australian Airspace Policy Statement 2010":

Class F: IFR and VFR flights are permitted, all participating IFR flights receive an air traffic advisory service and all flights receive a flight information service if requested. This class is not used at present in Australian-administered airspace.

If it looks like F and it smells like F ... it probably is F.
Class G in Australia is the figment of someone's imagination.

[Dick Smith]

I find it fascinating that there are two or three Controllers and two or three Pilots who post on this site who are totally opposed to Class E.

Once again, I post the comments by the “Voices of Reason”.

Class E Airspace and United States Practice

We have watched with incredulity at the dangerously naive statements being made on threads in the Australian PPRuNe sites, concerning the operation of Class E airspace. Class E airspace is NOT an unsafe categorization of airspace, and is in fact used safely and effectively in substantial portions of the globe.

EACH AND EVERY transport and passenger carrying aircraft operating in the United States is required to operate for some portion of their flight in designated Class E airspace – effectively between 18,000 feet and the upper limit of Class B, C or D airspace – or the surface for non controlled aerodromes. This equates to over 10,000 passenger-carrying flights per day, every day of the year. The Class E airspace within which they operate is in the so-called most dangerous phase of flight – climb or descent. Your national carrier is no exception.

There are in excess of 150,000 general aviation aircraft operating in the United States, to either the visual or instrument flight rules – many many thousands per day.

There are CONSTANT interactions between IFR passenger carrying aircraft and VFR aircraft on a daily basis – with no hint that this practice is unsafe.

There are countless examples where aircraft provided with routine terminal area instructions whilst still in Class E airspace are routinely provided sequencing descending turn instructions by controllers in one breath, and VFR traffic information in the other.

We agree that Class E airspace is mostly within radar cover in the United States – probably the greater part of 95%. In that airspace, air traffic controllers positively separate IFR flights from other IFR flights – and where they can, provide traffic information on VFR flights.

Radar coverage is NOT a prerequisite for Class E airspace, and in fact in several cases the Class E airspace linking certain aerodromes to upper airspace is not covered by radar. In that airspace, air traffic controllers positively separate IFR flights from other IFR flights – and as they cannot observe VFR, do not pass traffic unless they know by some other means. That positive IFR-to-IFR separation may, in many cases, be applied on a “one in at a time” basis. The airlines accept that mode of operation.

NOT ONE SINGLE AIRLINE in the United States is lobbying for a higher level of service in current Class E areas.

Our observation in relation to the Australian experience has been one of giving proper effect not just to training and education, but also to the cultural change requirements. Pilots need to understand that operating in Class E airspace IS FUNDAMENTALLY DIFFERENT to the service that they have received in the past – but need to accept that this is a normal way of doing business.

Australian controllers need to STOP being negative, embrace the concept of Class E airspace and to be blunt, get on with it. Controllers in the United States provide services in Class E, without questioning its “safety”, day in and day out, and have done so [either as Class E, or its predecessor], for over 50 years.

NOT ONE SINGLE CONTROLLER in the United States is lobbying for a higher level of service in current Class E areas.

We are concerned that this constant questioning and second-guessing by your pilot and controller fraternity will in fact generate a safety deficiency larger that the problem you are trying to solve. By our estimation, there is NO JUSTIFICATION for the large amount of Class C airspace presently designated in Australia, and subject to the appropriate change management processes we have previously described, you should introduce Class E airspace wherever possible

I dare the Class E doubters to answer this particular post in an objective way.

[peuce]

Dick,

That old quote was a waste of a lot of forum space.

I think I can say with confidence that no one on this foruim is against Class E Airspace per se.

I can also confidently say that most on here:

1. Do NOT support Class E airspace ... without surveillance
2. DO support the appropriate installation of Class E Airspace
3. Do NOT believe that Class E above Broome or Karattha is an appropriate option

Brow beating, name calling and condesension isn't going to change my opinion. And, from what I read, I don't think you will change your opinion either.

So, it's up to them in high places to make the decision ... and we will all have to live with that decision ... no matter our personal opinions.

[Dick Smith]

Then I trust they will take notice of VOR.

Could it be true that he now works at ????.

[ARFOR]

Stand easy - Smoke em' if ya gotem

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!