LOC only app in the FMGC

[PilotJames]

Guys, what is the advantage of having a LOC only approach in the FMGC rather than just the ils for that runway.
If you fly the loc only you can only fly this with loc/fpa. I can't see any advantage to having a loc only approach rather than just selecting the ILS approach and then if needs be selecting loc only and fpa modes if you need to fly a LOC only approach.
A some airports there is both a LOC approach and an ILS that can be selected in the FMGC for the same runway.

[Uplinker]

Not all LOC only procedures are identical to the ILS procedures for the same runway.

There might be different platform altitudes, a different descent angle, different MAPs, different minima or maybe different go-arounds, so that information is needed if programming the approach into the FMGC.

[lambourne]

Guys, what is the advantage of having a LOC only approach in the FMGC rather than just the ils for that runway.
If you fly the loc only you can only fly this with loc/fpa. I can't see any advantage to having a loc only approach rather than just selecting the ILS approach and then if needs be selecting loc only and fpa modes if you need to fly a LOC only approach.
A some airports there is both a LOC approach and an ILS that can be selected in the FMGC for the same runway.

A LOC approach may also have an intermediate step down fix between the FAF and the runway that the ILS may not contain. I want to say SFO has one of these but don't have the motivation to look right now but it was a foot stomper in recurrent on why to selec the LOC if doing a LOC versus just the ILS.

[PilotJames]

Cheers guys,
I can see that the go around if different is useful so we can fly it in managed nav. The predictions for descent arrows and the like would also be incorrect if the box didn't have the correct vertical profile inserted. It might also start at a different platform altitude.
Not sure why the intermediate fix matters too much as you would be flying in FPA?

[lambourne]

Cheers guys,
I can see that the go around if different is useful so we can fly it in managed nav. The predictions for descent arrows and the like would also be incorrect if the box didn't have the correct vertical profile inserted. It might also start at a different platform altitude.
Not sure why the intermediate fix matters too much as you would be flying in FPA?

Looked at the Jepp chart. ILS/LOC 28L SFO has a fixed that between the FAF and the Runway that is Noted as to only apply to the LOC. If you line selected the ILS you will not have that fix. I don't speak Airbus so I don't know about your FPA being sufficient to disregard fixes on charted approaches.

[good egg]

LOC only is certainly useful if the glidepath signal is out of service for some reason (e.g. maintenance).

[PilotJames]

Looked at the Jepp chart. ILS/LOC 28L SFO has a fixed that between the FAF and the Runway that is Noted as to only apply to the LOC. If you line selected the ILS you will not have that fix. I don't speak Airbus so I don't know about your FPA being sufficient to disregard fixes on charted approaches.

Yeh, in an Airbus if you fly in Flight Path Angle mode then it will disregard any altitude restrictions in the FMGC :)

[Metro man]

Some airports have a LOC approach with no GP, such as Macau VMMC runway 16. I went to a Chinese airport the other day which had 4 ILS approach charts per runway. Procedures may vary with radio aids U/S, non radar, climb performance required, RNAV or non RNAV, missed approach procedure ATC require etc.

Fly the correct chart for the approach ATC have cleared you for.