A320 A/Thrust Failure

[Easy226]

A/Thrust fails in flight with AP1 engaged so to recover autothrust you can engage AP2 so that it runs on the FMGC 2 channel. With the APP p/b pressed on the FCU for an ILS approach, you go to press AP1 again. After looking through the FCOMS and other notes I reckon you will only get CAT3 single as AP1 will not engage.

My reasoning behind this is that AP1 is the master when you have AP2 engaged also (CAT 3 Dual) and therefore runs off FMGC 1 however the Autothrust cannot run off FMGC 1 due to the earlier failure of the A/Thrust. I have gathered an understanding of what is going on here but cannot find a definitive answer after sifting through the books.

[rudderrudderrat]

Hi Easy226,

You have 2 options:
1) Leave only AP2 engaged and do CAT3 Single.
2) Engage both APs - but Autothrust will fail because FMGC1 is the master - thus CAT2 only.

Edit Σεβασμός aristoclis.

[aristoclis]

Hi there,

Option 1: You do not select AP1 after APP is armed. You have AP2 and A/Thr operating, you are CATIII single.

Option 2. You want for whatever reasons 2 APs. So you engage AP1 after APP is armed (I understand in your case A/thr Ch1 was the problem and not AP1). FMGC1 becomes master, A/thr fails again (if not transient failure). So you have 2APs but no Autothrust. You are CATII.

Regards.

Edit: Respect Rudderrudderrat ;)

[Easy226]

Thanks for the replies - I was on the right lines then! I couldnt find a direct explaination in the notes, but has been cleared up now.

Cheers