A320 2D/NPA FINAL mode

[gbotley]

Hi guys,

First things first.. go easy on me as I'm currently mid type-rating on the 320. Secondly, I have already consulted the manuals but haven't found a concrete answer.

Can anyone provide comment on what triggers/events must have occurred for FINAL mode to engage in a fully managed NDB/2D approach with vertical guidance. When running these through in VFDs the aircraft will simply overfly the FDP and not descend, despite FINAL being armed in blue.

In addition to this if this approach was an NDB approach which had a hold as part of it - such as EGNX - and the outbound leg requires you to fly around that hold once more, at what point would you tell the aircraft to exit the hold?

Thanks all.

[sierra_mike]

have a look at DSC-22-30-80-30 Non Precision Approach in your FCOM for info about flight guidance in non precision approaches. the answer to your „FINAL“ question specifically is in the subchapter Engagement Conditions

[Roj approved]

G'day gbotley,

Welcome to the wonderful world of Airbus. Check out:

Auto Flight - Flight Guidance

AP/FD Common Modes - APPROACH

DSC-22_30-80-30-20 p3/10 (in my FCOM, but may be slightly different in yours)

For all non- ILS app

ARMING CONDITIONS

A/C above 400ft AGL
Flight plan is valid (Lat and Vert)
Active FLT PLAN has non ILS approach selected
GA mode not engaged

then a little further on

ENGAGEMENT Conditions

FINAL APP will engages when:
NAV or APP NAV is engaged
FINAL is armed
Predictions in FMGS
APPROACH Phase active

*the a/c is in the capture zone
LAT - +/- 1.5nm from FDP
VERT - +150ft abc FDP
*A/C intercepts a descending leg of the Vert flt path (this is a big one, we can't press the APP button now until the active WPT is the one with a coded vertical path, otherwise it does some funky stuff)

A BLUE arrow is displayed on the ND to show where the FINAL APP conditions are met and where final descent will begin
If a WHITE arrow is displayed, at least one engagement condition isn't met, FINAL APP won't engage and the a/c will not descend automatically.

So while you have FINAL APP in Blue on the FMA, if you don't have the blue arrow, then it won't descend. On the line we tend to activate the APP PHASE a little early, this gives the a/c time to slow down and you can get configured, plus it gives you time to check for the blue Arrow.

So, if you are in a HOLD, once turning inbound, IMM EXIT, then if the next WPT is the FDP you can press APP.

I hope that helps.

[gbotley]

Thanks for the responses so far guys. I'll have to dig in the FCOM a little deeper then. There's only so much reading you can do of that incredibly narrow typeface before your head hurts!

@Roj approved

*A/C intercepts a descending leg of the Vert flt path (this is a big one, we can't press the APP button now until the active WPT is the one with a coded vertical path, otherwise it does some funky stuff)

By that do you mean you can't arm it until the vert flight path in question is the final descent.. or simply you have to be descending AND intercepting the inbound radial for this to work? I have to say that at this point, with developing knowledge of the A320, it seems to overcomplicate NPA approaches slightly.

A BLUE arrow is displayed on the ND to show where the FINAL APP conditions are met and where final descent will begin If a WHITE arrow is displayed, at least one engagement condition isn't met, FINAL APP won't engage and the a/c will not descend automatically.

When we tried this in the sim/VFD we didn't get any blue/white arrows despite the approach being programmed correctly. Is there anything which could cause that to happen in your experience?

So, if you are in a HOLD, once turning inbound, IMM EXIT, then if the next WPT is the FDP you can press APP.

That's as I thought then. So we just need to make sure the NEXT waypoint is the FDP for the approach, which in this case it wasn't.

Thanks again. It's a great aircraft, but certainly complex haha.

[Roj approved]

Hi gbotley,

Yes, it’s a new change for arming approach for 2D and LNAV/VNAV approaches, you must be tracking to the wpt that is on the coded approach and has the Vert slope. This is usually the IF.

If you didn’t get the any arrows, blue or white, then maybe you didn’t have all the required parameters. Best check with the Instructor. (Is it an older SIM/VFD?)

Yep, make sure the FDP is the next WPT, and it should do as advertised. ( but it’s an Airbus, so sometimes it’ll do something else😂😂)

There is lots of this sort of thing in this funny little aeroplane, but once you get a handle on it, you can sit back and watch the magic happen

[FlightDetent]

If the approach and programming look normal, there should be no surprises. Does the lateral mode change from NAV to APP NAV when on the intermediate segment?

If the WPT and top ND corner is correct, approach phase activated, my next guess would be misconfigured training device (FM DB/ FMS sw).

[gbotley]

Hi guys,

We gave this another shot this afternoon on a different training device - albeit programmed to exit the hold at the correct time this time - and thankfully the approach was flown successfully.

I will of course follow this up for further explanation with our instructor later this week. Thanks for your input! :-)

George.