Gold Coast needs an ILS
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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.
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.
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You get 26 ends with the GBAS system.
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.
Last edited by roulette; 27th Feb 2014 at 07:47. Reason: minor refinement
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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.
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.
Last edited by underfire; 27th Feb 2014 at 21:41.
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@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.
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.
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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?
You said:
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.
As for your
"limited applicability of GBAS as far as users (operators) go"
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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.
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.
