PPRuNe Forums - View Single Post - The NAS, facts and fantasies
View Single Post
Old 16th Oct 2003, 03:52
  #167 (permalink)  
on your FM dial
Join Date: May 2000
Location: Bindook
Posts: 114

Once all the aircraft know where everyone else is and they can separate themselves, and reading between the lines, when you see no need for ATC (or “ground based radio operators” as you call us), who decides who changes level, who diverts off their track to let the other guy stay at his preferred level, who volunteers to hold while he waits for the other guys who got there at the same time to make an approach.
The pilots decide - just as they’ve been doing in Australia’s class G airspace (and “OCTA” before that) for decades.

Even with ATC when you tell two company aircraft that one of them has to change level and ask them to decide who it will be, a lot of the time it ends up neither want to change cos they both have good reasons to stay at their preferred level. That is one of many of the reasons why you do need a third party even in Enroute Airspace.
I suspect that it’s more likely that both crews are aware of the other aircraft but do not consider that there is a collision risk. In many cases ATC separation minima are unnecessarily conservative. Air traffic controllers are obliged to apply minimum separation criteria – pilots are not.

I do not agree with your suggestion that we need a third party ground based radio operator in enroute airspace.

Here’s an old article that may be of interest.

From Flight International 04-March-2003 :

Pilots ‘will control future airspace’
Dutch study suggests cockpit crew could take responsibility for airborne separation even in dense traffic, using ADS-B

Pilots could easily take over the task of airborne separation from air traffic controllers, even in high-density airspace, according to research from the Dutch aerospace research laboratory (NLR).

Speaking at the Jane's ATC Maastricht Conference in the Netherlands last month, NLR air traffic management department chief Jan Terlouw said that “sooner or later the responsibility for separation assurance should be transferred from controllers to pilots”.

The conclusion comes from a “pilot in the loop” study into future air traffic management (ATM) in a “free-flight” environment using automatic dependent surveillance-broadcast (ADS-B). The experiment involved 24 graduate and near-graduate pilots from the KLM Flight Academy using simulators, and followed six years of research into free-flight concepts involving tactical airborne separation assurance in busy airspace by pilots rather than air traffic controllers. “Pilots could easily fly their preferred routes,” he says. “The number of conflicts was low because the pilots used the conflict prevention support. Sometimes there were slight deviations to avoid conflicts - but otherwise the pilots [were able to keep to their course].”

The pilots were provided with horizontal and vertical displays of traffic information, including resolution advisory tools, that would depend on all aircraft using ADS-B. They “flew” in airspace traffic densities up to three times those typically found in Europe, including complex airspace geometries, but Terlouw says they had no difficulty.

The inevitability of this change, Terlouw insists, results from the need for greater airspace capacity and thus more efficient use of airspace, at the same time as maintaining or improving safety. Ground-based tactical separation on the present model depends to a large extent on a route network, he says, which means that much of the sky is not used. In future, he says, the air traffic service providers' role “will shift from separation assurance to strategic resource management” - in other words, overall traffic flow-rate management.

Terlouw says he does not consider the sample study to be proof, but that it indicates self-separation is feasible.

[ends] (emphasis added)



Any chance you could post something that doesn't take an hour to read?????
If it takes you an hour to read my previous post then your reading speed must be a bit on the slow side. Is it that you find yourself having to sound-out each word syllable by syllable? Or is it that you find the concepts a bit tricky to digest?

Whatever your particular handicap, perhaps you might find things to be less mentally taxing if you just look at the pictures, rather than trying to comprehend the text. With you in mind, I have included a pretty picture later in this post.

In any case, I very much doubt that anyone is holding a gun to your head and forcing you to read these posts, are they?

G’day again snarek,

Cost savings to who?? Government, RPT yes, most likely. But to achieve those ‘savings’ you have to do a cost shift, i.e. mandate equipment.

So, VFR must subsidise RPT/Govt to achieve ‘cost savings’. I can feel a howl of protest starting now....
The Australian tax payer is never going to pay to fit ADSB to private aircraft (as you have advocated). And nor should they.

At this moment in time hardly any Australian aircraft are fitted with ADSB.

Most Australian aircraft that have an electrical generating system are already fitted with an altitude encoding transponder.

Pilots of those aircraft should ensure that they switch the transponder on to ALT whenever they go flying – irrespective of whether they are anywhere near air traffic control radar coverage or not.

Owners of aircraft that have an electrical generating system, but which do not have an altitude encoding transponder, should be encouraged to get one.

Which cost would aircraft owners rather incur – the cost of installing an altitude encoding transponder in a relatively small number of aircraft, or the cost of an ADSB installation for virtually all aircraft?

But why not use it to expand ‘radar’ coverage??? I can't see the harm in that unless you have something personal against ATC....
What I have against the current ground-based air traffic control system is that it is outdated, expensive, inefficient, and causes unnecessary delays. All that would have to be acceptable if there were no better way. But there is a better way – provide traffic data directly to pilots and cut out the expensive middle-man.

Surely more coverage is a good thing??? Surely more coverage will result in cost savings via routing savings....
More coverage = more unnecessary infrastructure expense. Once you put a radar-like screen in an air traffic control centre you then have to pay for someone to sit there all day and watch it. Who’s going to pay for that?

And you are assuming a need for controlled airspace.

I’m assuming non-controlled airspace.

If you take-off and at 500 feet turn towards a 5 mile final at your destination (see UPT article further on), then how can any sort of air traffic control infrastructure (no matter how expensive) offer any kind of “routing savings” compared with that? The only thing that they are able to do is delay you.

If the technology exists to provide reliable real-time traffic data directly to pilots (and I have no doubt that it does) then why do we need the additional expense of a ground-based third-party radio operator to relay that very same information? I suggest that we don’t.

I guess, in a way, that it’s kind of like the reason why we no longer have the delay and expense of manual telephone exchanges – technology has moved on and there is simply no need.

....when fully paid for by those who will benefit from it, full ADSB will improve Australian airspace.
I hate to be the bearer of bad news, but if you think the Australian tax-payers are going to fork-out for ADSB in private aircraft then you might be in for a surprise.

As a very wise Australian once said :

Tell him he’s dreamin’ son....

Now that that’s out of the way, thanks for the info on ADSB. I found this article earlier today and thought it might be of interest.

From Flight International 04-March-2003 :

FAA approves display combining air traffic with collision avoidance

An integrated anti-collision cockpit display system developed by UPS Aviation Technologies (UPS AT) has been certificated by the US Federal Aviation Administration. The system fuses automatic dependent surveillance-broadcast (ADS-B) data with traffic alert and collision avoidance system (TCAS) information and presents it on single 150 x 125mm (6 x 5in) display.

UPS AT calls the screen the cockpit display of traffic information (CDTI). “All the TCAS information is there, but aircraft transmitting ADS-B also appear,” says UPS. The TCAS provides traffic advisories (TA) as it normally would, and resolution advisories (RA) on the vertical speed indicator, but the pilots benefit from the additional “rich detail” supplied by ADS-B traffic.

ADS-B provides flight identification, speed, heading and future position of equipped traffic within about 220-370km (125-200nm). The CDTI can call up several displays, including a terrain awareness moving map, weather, and visual flight rules and instrument flight rules airspace charts. Future display enhancements will enable pilots to view a highly accurate moving map of the airport surface and even other traffic moving on the ground.

The CDTI can also provide terrain awareness warning system information. Certification will allow cargo aircraft already outfitted with the CDTI AT2000 display to add TCAS capability, thus meeting the FAA notice of proposed rulemaking (NPRM) which requires the previously exempted all-cargo aircraft to carry collision avoidance systems by 31 October this year. The NPRM definition of a collision avoidance system excluded any solution other than TCAS, which the Cargo Airline Association has disputed. Initially, UPS will install the display on its103 Boeing 757-200 and 767-300 freighters.


G’day Keg,

Unhealthy over reliance on TCAS going on here (similar to the unhealthy over reliance on see and avoid!).
I’ve never been a big advocate of “see and avoid”.

TCAS will NOT display ALL of the traffic around you. It selectively picks up and drops off various paints in busy traffic environments.
I agree. TCAS automatically de-clutters the traffic display. TCAS will always show the most relevant intruders – ie those with the least time to closest point of approach. As the relative trajectories of nearby aircraft are constantly changing so too is their rank order of priority.

Refer : Honeywell TCAS II Users Manual
(see PDF page 11 of 83 - which is the same as original document page 8)

“TCAS II can track as many as 45 aircraft, display up to 30 of them and can coordinate a resolution advisory for up to three intruders at once.”

On the 744 into LAX years ago I remember getting a TA on traffic that just ‘appeared’ as a TA – ie, we couldn't develop the picture before hand because it wasn't being fed to us.
You mention that it was “years ago”. In that case I would imagine that you would have been using TCAS v6.04? Most aircraft now have v7.0.

I am delighted to learn that even with a now superseded version of TCAS you were still able to avoid a collision in the busiest airspace on the planet. Great stuff!

....we couldn't develop the picture before hand because it wasn't being fed to us.
Of course it is also quite possible that you were a bit tired after a long flight....

Aviation safety should be about layered defences.
I fully concur.

TCAS is an error management strategy, not a threat management strategy at the first level. It is the LAST line of defence. Heaven help us when it is the first also!
TCAS will never be the first line of defence – the Big Sky Theory will always be the first line of defence. Even if you funnel all the traffic into the same few flight levels and down the same few airway routes there is still an extremely high probability that there will not be a collision. If you allow aircraft to fly their preferred “freeflight” trajectories then the chance of a mid-air collision is reduced even further.

TCAS has been mandated (for many aircraft) because the air traffic control system was not, on its own, able to keep the planes apart with sufficient reliability.

I believe that the day is coming when aircraft will fly direct tracks and a TCAS-like airborne separation device will be used to augment the Big Sky Theory. Whether we will need the existing ground based air traffic control infrastructure as a back up remains to be seen.

It’s not just because I say so - there is currently a project underway in Australia along those very lines. Don’t expect the results to be up and running anytime soon though - the government bureaucrats plan to take the next 15 years to milk the project for all it’s worth.

FMC equipped aircraft have been able to navigate their way from anywhere to anywhere with great accuracy since about 1983 (ie 20 years ago). Additionally, FMC equipped aircraft have been able automatically calculate their optimum flight level in real time and with great accuracy and reliability.

Alas, all this airborne capability has been more or less useless because aircraft have had to follow circuitous routings at non-optimum flight levels for reasons of ATC convenience.

If this project (below) takes another 15 years to come to fruition then it will have taken the air traffic control infrastructure 35 years to catch up to where the aircraft capability was in 1983. Better late than never, I suppose.

From Flight International 30-Sep-2003 :

Australia to launch Tasman UPR plan
Routes would mean quicker flights and less work for pilots

In a project intended to lead to gate-to-gate user preferred trajectories (UPTs) on Australian domestic and international services within 15 years, Australia is to introduce user preferred routes (UPRs) in en route airspace across the Tasman Sea in the next year. The project is part of Australia's revised air traffic management (ATM) strategic plan announced by transport minister John Anderson at the Canberra-based Safe-skies conference in late September.

The plan has been developed by the Australian Strategic ATM Group (ASTRA) which comprises ATM stakeholders and government agencies. It lays out a broad ATM strategy - at the heart of which is the replacement of fixed air routes with UPTs. The strategies are designed to develop and implement numerous changes, including: a concept for conflict management to support UPTs, which would replace rigid separation standards; flexible use airspace; national demand/capacity balancing to optimise traffic flow; an integrated decision support information network to provide high-quality operational data to users; an ATM performance measurement and reporting system; and a security definition and assurance model.

A five-stage implementation plan is proposed, starting with UPRs in the Tasman Sea en route airspace for aircraft with satellite navigation and datalink. This will be followed by the creation of international flex tracks across Australian airspace and UPRs for international operations to and from Australia. Stage four will see the introduction of UPRs in Australian flight information regions (FIR), followed by the final stage of UPTs in the Australian FIR.

ASTRA says UPTs will reduce environmental impact, flight times, and controller and pilot workload. It will also improve airspace utilisation and airport capacity, enhance safety, and provide operational flexibility.



If this is what the rabid NAS stalwarts want, I'm glad I'm not flying away from the big cities.
One of the highest traffic densities in Australia is in the class G airspace just west of Bankstown. You don’t have to leave the big smoke to find lots of aircraft flying in class G.

....you don't want service do you? G = Good???

BTW....I see on a daily basis the fact that see and avoid doesn't work..

Scores of the near misses were spotted....
I’ve never been a big advocate of “see and avoid”.

And there are no war zones in Australia.

But in any case, in relation to the war-zone you refer to, how many collisions have there been? How can you be certain that the aircraft that did not collide would have collided if air traffic control had not taken the action that they did?

....the big sky theory worked in the old days, not with the new squizzy nav kit that will put you both nose cone to nose cone tracking direct from A to B and B to A.
I have been suggesting for some time that GPS/FMC users should use a random right offset.


Transponders, ELB, ADSB. CDTI and any other “safety” items should be fully tax deductible, purchase, installation and maintenance.
For the vast majority of aircraft owners they already are.

Here to Help,

I don’t really care whether they put “frequency boundaries” on maps or not.

What I am interested in is the misguided perception that VFR aircraft in enroute class G airspace have to talk on the radio as much as possible and maintain a careful listening watch on a specific radio frequency in order to avoid a mid-air collision. Such notions are demonstrably untrue.

As has been posted elsewhere, these ideas are a throw back to the days of VFR full reporting.

VFR aircraft wants to listen out for VFR and IFR broadcasts in his area - what frequency does he listen to?
If the VFR aircraft is near an airport then they should be using that airport’s CTAF frequency.

If the VFR aircraft is not near an airport then what broadcasts are you talking about? Who is making these broadcasts and why do they need to make them? More to the point, why does the VFR aircraft need to listen to them?

If pilots just want to have a chat then the civil air-to-air frequency in Australian FIRs is 123.45 MHz.

Refer : ERSA / Navigation and Communications / 3. Air to Air Communications – Civil

VFR aircraft requires assistance from ATS for an in-flight emergency - what frequency does he transmit on?
I’d use 121.5 MHz or any nearby air traffic control frequency.

VFR wants information (nav, met, PRD) from ATS for whatever reason - what frequency does he transmit on?
They should have got all that stuff off the internet before they left home.

Actual met conditions are available from :
  • AWIB/AWIS (either VHF or on the telephone)
  • ATIS

ATS wants to broadcast to a radar observed VFR about to enter a restricted area or CTA - what frequency does she hope the VFR is on?
If it’s controlled airspace then the air traffic controller should be transmitting on the air traffic control frequency.

ATS observes 2 aircraft about to come together in Class G with no avoiding action apparent and broadcasts a traffic alert - what frequency does she hope the VFR is on?
Air traffic control is not required to provide a separation service to VFR aircraft in class G airspace. You should leave ’em alone.

If they are near an airport then they will be on the CTAF frequency.

If they are not near an airport then they will probably be on 104.9 MHz.

Actually – the two aircraft you describe are probably my hooligan mates and I doing some formation aerobatics. You can rest assured that we’ll be talking to each other – but we won’t be on any frequency that you can transmit on.

ATS broadcasts a hazard alert for an aerodrome in her airspace, what frequency should a nearby VFR be on to hear it?
If it’s an “an aerodrome in her airspace” then it must be a controlled aerodrome. Broadcast the hazard alert on the air traffic control frequency and/or ATIS / AERIS / VOLMET.

VFR PJE aircraft wants to conduct a drop in Class G, what frequency does he broadcast on?
Most drop zones are on or near an airport. He should be on the airport’s CTAF frequency.

ATS broadcasts an LJR - what frequency does she hope the VFR is on?
Permanent military low jet routes are notified in ERSA. Temporary military low jet routes are notified via NOTAM. The VFR pilot should obtain NOTAM information off the internet before leaving home.


“AOPA will be telling NASIG that VFR and IFR aircraft in the same airspace must be on the same frequency.
If it’s controlled airspace (A thru E inclusive) then everyone should be on the air traffic control frequency.

If it’s class G airspace then the civil air-to-air frequency in Australia is 123.45 MHz.

ICAO Class G = no service, no delay, no charge.

We do not agree with any proposal to counsel VFR pilots who talk to IFR aircraft (or any aircraft) about a possible conflict on the area/centre frequency.”
Neither VFR aircraft nor IFR aircraft should be making broadcasts or making pilot-to-pilot transmissions on an air traffic control frequency.

If it’s class G airspace then the civil air-to-air frequency in Australia is 123.45 MHz.

G’day NOtimTAMs,

Mate, they do that now and have done for years - whether it's Dubbo, Ballina, Charleville or Roma!! Where's the midairs? Won't make much of a difference to these guys at all, actually.

And since most of these guys have been flying VFR for the last five or six years (ever since enroute charges were introduced) they have been doing just fine without directed traffic information.

DTI seems like an expensive waste of time.


I asked earlier :

....what can ADSB do for me that TCAS doesn’t already do? Is it that ADSB offers greater functionality, or is it that an ADSB cockpit traffic display is less expensive than a TCAS cockpit traffic display?

In earlier posts you suggested that airborne ADSB traffic displays would be much cheaper if they were not certified. In what circumstances is it permissible to fit non-certified avionics to a flying machine?
Any suggestions?
BIK_116.80 is offline