A320 LOC Beam Capture

[tdehuya]

Hi, guys
I got confused about loc beam capture. FCOM says that we have enhanced loc beam capture function which helps aircraft turn earlier towards loc beam in pre-capture zone, but within 2.3dot ,it was loc beam which makes aircraft stay on centerline, here are my questions:

1. If gps primary lost, or let’s say enhanced capture function inoperative, if the interception angle with runway heading is 150 degree, for example final 180 degree aircraft flying 330degree, within 2.3dot beam, what will happen? Aircraft turn left overshoot the final then coming back from the other side or turning right because it stays in 90hz beam which makes it think centerline on right side?

2.Without entering ils course on radionav page, the conditions above the same, what will happen?

3.can a320 fly a exact ils course ,let’s say the real beam course is 180degree ,I put 182 on radio nav page, can the aircraft stay on 182 course?

Help me , Captains,
Many thanks:ok:

[noptawat]

https://www.pprune.org/tech-log/627597-a320-loc-beam-capture.html (http://www.pprune.org/tech-log/627597-a320-loc-beam-capture.html)

Same Thread - Duplicate

[noptawat]

can a320 fly a exact ils course ,let’s say the real beam course is 180degree ,I put 182 on radio nav page, can the aircraft stay on 182 course?

YES !

But please :) It can even fly LOC Back Course :)

[tdehuya]

:rolleyesYES !

But please :) It can even fly LOC Back Course :)


thanks for answering but the beam center line is 180 :rolleyes: can it really stay on 182 ？what will pfd show？magenta deviation stays in the middle？

[tdehuya]

THANKS for answering I never tried on real flight or on sim, but i do find the PFD deviation bar always follow beam.
so if I want to fly 183 ,use rose ILS, disregard the PFD indication ,right?
and how the aircraft maintains 2 or 3 degrees ILS lateral deviation?

[Goldenrivett]

can the aircraft stay on 182 course?
No. It will still track down the centreline of the ILS LOC beam.
The only difference you will notice is the magenta "dagger" will be 182 giving the impression of a different angle of drift.

[Fursty Ferret]

Autoland might be exciting as it tries to decrab to align with the ILS course...

[tdehuya]

thanks what about the interception with large angle？150 degree interception，which direction will ac go？

[PGA]

No. It will still track down the centreline of the ILS LOC beam.
The only difference you will notice is the magenta "dagger" will be 182 giving the impression of a different angle of drift.

That's what I always thought as well. However I tried the following in the (A380, so still Airbus) SIM recently. ILS RWY 23, with a LOC QDM of 232, hard-tuned 210 in the NAVAID page, the magenta dagger showed 210 as expected and released the SIM at 6 miles. The aircraft started to turn towards 210 degrees, and subsequently the autopilot disconnected.

It left me slightly baffled as to why it would do that, since I was under the impression the aircraft would simply track the localizer beam, which it didn't. Took a video of what happened but can't share that here. I was always under the impression the course had to be checked at 350ft to make sure the course is within 5 degrees for the de-crab, but somehow more seems to be happening.

Funnily enough, we don't get the AUTOLAND warning light if the LOC signal disappears below 15ft RA, however if you do an auto land in a 30 knot crosswind, how does the aircraft then make sure it stays on the centerline, considering the fact that it could easily drift off in those last 15ft?

Regards,

PGA

[Check Airman]

I’d guess that what happened in the 380 sim was because of the enhanced loc capture. You had a 210 inserted and the comparison between raw data and fms data bewildered the AP.