A320 A/THR channel

[marsattacks]

Hi everbody!

How do I change the A/THR channel during low vis approach, to restore cat 3 dual?
I do actually know how it works (AP's off, and reengage in sequence AP2-AP1) but I couldn't find any explanation in FCOM 1 or 4 so far!:confused:


Thanks in advance ;)

[tom775257]

You can't get Cat3 Dual back if you are talking about Athr channel 1 fail...

You can get Cat3single ie Cat3a approach capability. With both AP 1+2, Athr channel 1 is working (it has priority). If this fails you will get thrust lock, Athr will drop out and you will just have Cat 2 capability. Simply press AP1 (which will disengage AP1) and press Athr button. You will now regain Athr through channel 2, with AP2 working giving Cat3 single.

The moment you hit AP1 again with a failed Athr channel one, you will go back to thrust lock and Athr will drop out.

[tom775257]

Ollicrj: This is something that interests me because the original poster suggests this and you said this also.

I have tried this in 2 different simulators and each time with an a/thr channel 1 fail I can't get Cat3 dual back.

For a quick reference check, my company manual says:

"When both APs engaged in APP mode, no 1 ATHR is the master and controlling channel. If ATHR subsequently fails, ATHR channel 2 may be re-engaged after disengaging AP1. This will raise the landing capability from CAT2 to CAT3 SINGLE."

Because both my company manual suggests this and the fact I have seen it with my own eyes suggests to me one of two things. Either you are both mistaken, or there is a modification to the systems available that will allow ATHR channel 2 to operate with both APs engaged depending on engagement order. I will try to have a look through FCOMs tomorrow to see if there is an answer there.

Anyone else any thoughts?

[Field In Sight]

tom775257, you are exactly right and for the reasons that you specified.