GLS approaches - why G16A 21146

[Capt Groper]

Why are the GLS approaches identified by code unfriendly to pilots.

Example is YSSY
Why 16A when the approach is to RW 16R could the codeing be changed to GLS 16R (A is OK for a deck base appoach designer but L, R, & C have more significant meanings.)

Also what does 21146 channel mean to a pilot.
If we comfirm the ident to be GLS16R do we need to know it's channel 21146?

[Microburst2002]

It depends

How many 16R runways are there in the world with a GLS?
probably very few, today, but many in the future. Each GLS has to be unique, I supose

[Denti]

No clue why it's named 16A, can't see a real reason for it. I guess FlightpathOBN should know more.

The channel number is for a GLS approach the same as the frequency for an ILS. It selects which approach datalink to receive, especially which approach geometry as there might be several different ones for each runway or quite a lot different runways served by one installation.

[aterpster]

Cat Groper:

Why are the GLS approaches identified by code unfriendly to pilots.

Example is YSSY
Why 16A when the approach is to RW 16R could the codeing be changed to GLS 16R (A is OK for a deck base appoach designer but L, R, & C have more significant meanings.)

Also what does 21146 channel mean to a pilot.
If we comfirm the ident to be GLS16R do we need to know it's channel 21146?

I don't find a GLS IAP at YSSY, so it must be a special issuance procedure. As to the channel number, that is common protocol with local or wide area differential procedures because there are some avionics (very few) that require manual selection of the differential channel.

[Denti]

Yup, for example the 737 Multi Mode Receiver.

[Microburst2002]

guys

have you flown GLS yet?

How's it like?

[Spitoon]

Not my area but is it possibly to allow for a variety of intermediate approach paths?

[turnandburn]

About to find out shortly just doing my 747-8 conversion

[Denti]

@Microburst, in general it flies exactly the same as an ILS approach. However it feels more smooth and stable, especially if you have a preceding aircraft as there is no beam distortion at all, no real protected areas etc. Very very nice to fly actually.

[FlightPathOBN]

Capt, all...

So far, that is a custom procedure. In AUS, the customs have anything but the standard ICAO designation. Note the GNSS RW16 Z approach, which matches ICAO standard. Currently, as there is no designation from ICAO on GBAS system nomenclature, so the common custom designation is RW XX (channel)
ICAO designated "Z" for the lowest min, "Y", "X" etc...to designate which procedure has the lowest min...this is quite a problem, when you design a procedure, and the min is lower, all of the others must be changed...

AUS has a legacy for naming customs, (much as the interesting waypoint naming..BEERN, CHIPS, etc) the person who started it all went with "M" for approach from the mountains, "P" approach from the plains, and "U", approach from the Ocean, (underwater maybe??) but all of the transitions range from "S", "T", "Q", you name it, as long as it wasnt in accordance with ICAO std., so if you were to see a database of custom procedures, you would note many letters outside of the ICAO standard.

The procedure designation is irrespective of the common RW16R for good reason, another issue is the ARINC 424 coding accepts only RWXXX, so the procedure is named RW16Z, but in the coding it is RW16R

[FlightPathOBN]

However it feels more smooth and stable, especially if you have a preceding aircraft as there is no beam distortion at all, no real protected areas etc. Very very nice to fly actually.

Good to hear!...
From what I have noticed, it is far more accurate (2cm) and reliable as weather will not affect transmission of the beam.

As Denti stated, there is no disruption or distortion from other aircraft operations, as its not a beam, its a signal.

When coupled with RNP transitions, the baro-vnav transition to GBAS is seamless, not having a beam to intercept, the regain.

There is currently a curved path GBAS signal in certification process. Other projects include horizontal and vertical offsets for wake turbulence separation.

I am not really sure why GBAS hasnt become extremely popular, one system could replace 23 VOR's, (yearly maintenance and cert on 3 VOR's pays for the system) CAT I to CAT III autoland, all weather operations, and the avionics package is already on all new aircraft...

[Pavan_218]

Can some one help me how a channel number is derived for a GLS approach?

[underfire]

It is a specific designator 5 digit designator, just like a waypoint.

GLS channel number is required for the particular approach. The pilot tunes the MMR to the specific channel, or the channel is selected when the approach is selected in the FMC.

The channel number is encoded with the frequency to be used for the VDB data link receiver and with an identifier for the particular approach and missed approach path.

That is why there can be many channels for the same approach, the different channels can have a different GPA, displaced threshold, or TCH, for the same runway end.

[alphacentauri]

At the moment GLS at YSSY is on operation trial only with QANTAS the only approved user. Trial has been ongoing for about 8 yrs now. Commissioning is expected sometime early this year.

FPOBN, whaddya mean we don't follow the ICAO standard? (joke) I agree and it's very frustrating working with a 'we know better' attitude all the time. Changes are being made.....slowly

[underfire]

I gave up trying to figure out what the procedure designatorwould be, so would just toss it back and let ASA call it...

Rumour I heard that the GBAS will be moved to YMML...

Makes more sense there, YSSY has far too many constraints to get benefit from GBAS.

For the question on channels, here is a sample of GBAS coding: Note G26 A, G26B, etc. (different GPA)

"RX_WEEK";"RX_TOM";"GBAS_ID";"FAS_VAL";"FAS_LAL";"OPTYP";"SBAS_ID";"AIRPORT_ID";"RW_NO";"RW
_LTR";"APP_DESIG";"ROUTE_IND";"RPDS";"RPID";"LTP_LAT";"LTP_LON";"LTP_H";"DFPAP_LAT";"DFPAP
_LON";"TCH";"GPA";"C_WIDTH";"RW_LEN_OFFSET";"CRC_OK"
1634;303799.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"Z";21;"G26A";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;3.000000;80.000000;0;1
1634;303800.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"Y";22;"G26B";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;3.200000;80.000000;0;1
1634;303800.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"X";23;"G26D";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;3.500000;80.000000;0;1
1634;303801.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"W";24;"G26E";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;4.000000;80.000000;0;1
1634;303801.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"V";25;"G26F";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;4.500000;80.000000;0;1
1634;303802.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"U";26;"G26G";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;5.000000;80.000000;0;1
1634;303802.437500;"TATM";10.000000;40.000000;0;0;"EDVE";26;0;1;"T";27;"G26H";52.31964167;
10.56400556;131.300000;-0.00098056;-0.01751667;15.240000;5.500000;80.000000;0;1
1634;303803.437500;"TATM";10.000000;40.000000;0;0;"EDVE";08;0;1;"Z";28;"G08A";52.31866111;
10.54648889;125.900000;0.00098056;0.01751667;15.240000;3.200 000;80.000000;0;1