The current rules allow for one turn to final under APCH...so it doesnt have to be the AR cost to the airline.
Or, pretty simple, put in the 'T', let the ac make the turn. No harm , no foul

ICAO missed kills ya though

However I don't think you can do that at 3-4 miles from the threshold at a few hundred feet which is what is required here.

But the minima would be nowhere near an -AR or ILS, would it?

You would have to look at the approach/missed to see where the obstacles are. Public RNP AR/APCH is 0.3 RNP. RNP 0.1 do pretty well, but that is more expensive for the airline.

Couple of key factors for the turn location:
1. FROP at 500 feet
2. 30 seconds of stabilized flight before minima
3. Min 250 HAT for minima.

Theoretically, you can have a 2nm short final. (Ask WJ in Canada!) That close in, with FAS, the turns can be pretty tight, 2nm radius for 737. Perhaps only a quarter delta turn could get you in there nicely. That may get you around that tower(s) on final to RW14, not sure about RW34.

With the public RNP, you could have a 15 degree angle point at 2 miles. Up to 15 degrees is not considered a turn. I see they have a 12 degree angle, so its a tight one. That may also get you past those towers. or, move the towers!

I beleive the cost for an ILS is about $2Million per runway end.

If the locals dont want an airport, why not just close it, flog the vacant real estate to the chinese, hell they would probably buy the lot when property prices collapse and unemployment goes through the roof.

Just some info, to add depth to the discussion.

1. Gold Coast are not putting in hial for 14 approaches. They don't have the real estate for it. Unfortunately, this doesn't help. As has been stated the problem at Goldy is vis more than cloud base.

2. The current Naverus rnp approaches for Qantas have a roll out point at 2 mm from threshold, with rd turn before it. The icao ones coming later in the yr will be same.

3. There have been rwy aligned rnavs already designed for 14. Final at 5nm with 10-15° turn. The designs have been floating around for 3yrs, but can't be implemented due noise issues. If ils gets approved, then new rnavs will come.

4. Thankfully the terrain environment to the south will not have a bad impact on rnp-at missed approach.

5. Generally rnp minima is about 100-150ft higher than ils, and about 100ft lower than rnav. The difference at Goldy will be Currumbin hill and how accurate survey data we can get.

6. I didn't say it wasn't going to happen. But there is a long journey still to go, as technology develops there might not be a need for one. Gbas is about to go live at yssy. Gbas would allow us to solve a lot of problems at the Gold Coast.


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Excuse my typing, I'm on an iPhone and autocorrect doesnt come with an aviation acronym dictionary


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It spelt "Android" correctly! :D :}

Do you mean RF turn? I'm havung trouble keeping up with the designer language you and underfire are using.

Yes that is what he means, an RF turn to a short final.
If I remember the design correctly, the Naverus criteria goes down to 0.10/0.15 RNP AR. The FAF is at the beginning of the turn, not the end.
Not sure how ICAO would look at that, but an exemption is always possible for the National Carriers, difficult for international carriers.

FROP-final rollout point, end of the turn, tangent to final.

RNP APCH the 'T' configs you see. (now one coded turn allowed)

ILS min 200' HAT (height above threshold)

RNP min 250' HAT

That will always be the sticking point. Air Asia doing RNP-ARs? Since the national carrier is about to become extinct :}, I think the overseas market/carriers will be the driver for what goes in...

Well, thats not exactly the point. It is somewhat convoluted.

Exemptions to the standards are easy for CASA to grant within their area of pervue. ASA and CASA have control over the National Carriers.
When International Carriers get involved, per the Chicago Convention, the airport and procedures must meet ICAO standards. Exemptions to these standards are not as easy, as the ICAO stds are, well, lets say, crazy talk anways!

AUS tried to argue the RNP missed to stay the same RNP level as the approach, ie 0.3 RNP approach = 0.3 RNP missed containment areas. (ie ICAO containment assumes the world falls apart when you go missed, and the RNP containment goes from 2x 0.3 RNP or 0.6nm, to 2RNP or 2nm wide.)
Probably still hear the screams....(poor Dirk)

Surely there is enough room there to put some sort of lighting in. You have the runway and some open space there at the end. Without that it makes the whole thing a bit pointless as the you will be in the situation where the DA is low enough but the rain puts the viz is below the minima.

I suggested earlier on in this thread as to why they can't do a RNAV STAR that leads you right into an abbreviated ILS at 5 miles?

That will get you away from the houses and the hills and will be available for all.

They need 450m at least for hial, this will help vis minima. Max benefit is obtained by putting in standard 900m. As I said, gold coast doesn't have the room. There are no plans for it's installation.

We looked at an rnav star to late ils option. It isn't ideal for 2 main reasons. a) I need to provide at least 2nm on loc before gp intercept. This pushes intercept out to 7nm. For a 5nm join, you wouldn't intercept gp until 3nm. Initial airline feedback was that it would be too close. b) There needs to be a nav mode change from rnav to loc at only 5nm out. Again this was argued to be too close. I think it would work, but it would involve an amount of training and trial.....with gbas though....it's a lot more possible


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Yes, 5nm is too close. Only a minor hiccup capturing the LLZ will prevent GS capture and the whole approach rapidly turns to worms. Besides, you can't descend below the local MSA (at least 1500ft? coming in over the water towards terrain) until you've captured the LLZ; you'd be above the GS by then.

GBAS could be more feasible. The cost to put in GBAS is about equal to an ILS for each runway end, so cost would be a wash.

I would like to see the GBAS approach procedures (and departures) re-thought in the criteria.

First off, there is no reason it should not be CAT III at this point in the game.

CAT I, and 250 HAT, following ILS criteria is not where GBAS should be at this point in time.

RNP transition from the STAR to GBAS 0.1 CAT III final is where this should be at. ASA as 50% owner of SmartPath should have the system at every airport in AUS, and should be dictating the criteria to ICAO.

That's strange... I've been told GBAS is orders of magnitude cheaper than ILS.

GBAS system costs about the same as 2 ILS runway ends.

You get 26 ends with the GBAS system.

With each ILS, its about $50K/year for maintenence. GBAS is little to nothing per year.

There must be room for HIALS on 32. The displaced threshold is about 600m!

Do you need an ILS on 32?

Well it sounds like there aren't many options available. :(

Airservicess' website says that the GBAS is the ILS replacement, yet it doesn't seem to be catching on anywhere. People are building replacement ILS's not GBAS systems.

After reading this it sounds like yet another aviation infrastructure project that will meander on forever with no decisions being made because it's all to hard.

Guess the RNP is the best of a bad choice.

Careful on this one. The FAF is at the beginning of the turn, not the end. There are many combinations of ac/fms types that will not allow a turn inside the FAF.

Bringing in the FAF close has its own issues as well. While some FMS models will taper the ROC, others will hard lock the 500' ROC at the FAF.
This is why on some approaches with the A320, the HW ac does fine, (HW uses 400' ROC at the FAF), the Thales box will prox warn....

Lots of flight vals with different equippage must be done for the ICAO procedures.

IF you've got 26 runway ends within the coverage area, no?

Exactly! GBAS coverage is defined by area, not the number of RWY ends.
Essentially each installation will have defined coverage and maximum use areas, some of which may be dependent on the installation itself, what's contracted for by the purchaser, terrain, non-resolvable multipath/interference issues, etc.

But it's not the ultimate solution yet - mainly because of the limited number of aircraft/FMSs that can fly GBAS and the limited number of certified systems (and hence supplier & cost options).

A useful summary can be found on GNSS Frequently Asked Questions - GBAS
OK, it's the FAA, but it gives a reasonable overview of what's relevant globally and thereby what's available to Oz.

I reckon it's definitely the way of the future - but there's a ways to go yet before it will outdo other solutions (mainly due to cost and breadth of usability) - even given that the annual maintenance costs are completely negligible compared with ILS.

Eventually I suspect you'll find that RNPx (AR or not) APCHs and DEPs will interface with GLS in the final stages of APCH and early stages of DEP. Even now, in some places, there are RNPx (sometimes AR) APCHs being joined to ILS Cat X finals to achieve lower minima than might be otherwise available if using only RNP AR. Not yet documented by ICAO, but it's being done.

It is defined by the number of channels.

It is a VHF transmission, so there are no multi-path issues. That is how you can have APP and DEP on the same runway end.

Remember, GBAS system broadcasts a correction factor for the onboard system, that augments GPS. The signal also includes the information on the procedure for the aircraft to follow.

It is not a beam, just a signal.

If there is a terrain interference issue, another broadcast ant can be set up.

Yes there are already RNP to GBAS final approach procedures which are seemless to the ac. APCH to ILS is not seemless to the ac or the operator, and are very difficult to control.

All aircraft from Airbus and Boeing have had GBAS as a standard, at no cost option for the last 4 years. You just have to ask.

There are a few places that are currently using CAT III GBAS procedures with no issues.

@Underfire, regardless of number of channels and number of approaches &/or departures supported, each GBAS system is still limited by the physical area of coverage and maximum use areas for the installed system. So if you have aerodromes sufficiently close and dependent on runway alignment, one GBAS system could in fact support multiple aerodromes.

The multipath I was talking about may or may not influence how the GBAS system is set up (on the ground) and ultimately the maximum areas of use. Ditto for terrain. This has nothing to do with the VHF transmission of the procedures to the aircraft.

Acknowledge your comment re difficulties in transitioning GNSS to ILS - mainly because the boxes weren't originally set up to handle the transitioning from one nav system to another in that fashion (different integrities, different ways of handling the nav tolerances and so forth, transitioning of CDI, etc.

Re aircraft options, obviously bigjet world is centred on Airbus and Boeing, but there are a lot of RPT aircraft that come from other manufacturers (not to mention legacy systems :}) - hence the comment about current limited applicability of GBAS as far as users (operators) go.

multipath problems etc
 

Roulette,

You said:
What "multipath" problems are you referring to?

As for your how is that different from RNP for legacy aircraft? Surely we have to start somewhere and these systems will exist in parallel for a long time until one or the other gains the ascendancy in operator choice?

Rou,

Yes, I am curious what multi-path issues you are thinking about.

In regards to one system serving mutliple aerodromes, I would have to ponder that.
Currently, the system needs at least 3 ant, and 4 is optimal, placed as far apart as possible, but still within a certain zone. These feed the unit, which is balancing all of the GPS signals, but several other factors in the accuracy. Atmospheric conditions are considered, # of sats, etc, nothing new there.

The information from the ant is fed to a single ground unit, which then balances the data based on the location of the ground unit. The correction factor is based on this location, and the advertised accuracy of the GBAS system is based on this location.

That being said, the system accuracy is tested for the aerodrome and associated runway ends. I am not aware of any locations where the accuracy of the broadcast has been tested for points on aerodromes nearby. It was never meant to be wide area augmentation.

Internally, I am not sure of the grid size or what method the GBAS system uses in its determination relative to the geiod. That would be the issue with trying to expand the system to other aerodromes.

This not only relates to the GBAS system, but has a correlation to the particular avionics as well. If you get too far outside the grid or lookup function of the onboard GPS, accuracy will degrade or potentially disco.

Hope that helps.

EDIT: Just noting that aviation needs to get out of the 'lowest common denominator' factor when providing systems at an aerodrome. There have always been casualties of evolution.