A320 Auto Flt A/thr off

[bond2002]

AUTO FLT A/THR OFF
Can anyone explane the note in the AUTO FLT A/THR OFF discription in the FCOM abnormals.
Note If the A/THR is recovered with AP 2, A/THR will be lost again at AP 2 disengagement.

[Jonty]

The AP1 auto thrust channel is the master channel. So when you switch off AP2 the auto thrust will try to revert to AP1. And if the AP1 channel is unavailable, you wont get auto thrust.

[bond2002]

will it be the same if AP 2 was engaged or AP1 A/T Chanel is the master come what may.

[Jonty]

If AP2 is in use then the auto thrust will use the AP2 channel. However, when there is no AP engaged then the Auto Thrust will always try and use the AP 1 channel.

Also, when both auto pilots are engaged, the auto thrust will revert back to the AP1 channel, no matter which AP was engaged first.

[bond2002]

Thanks a lot sir.

[FlightDetent]

A small note on the above. A/THR channel (1 or 2) is chosen on whichever FMGS is the master one. Sure, selecting AP2 the FMGS 2 takes the role and in consequence A/THR channel 2 is active.

2 examples, both assuming A/THR channel 1 is faulty:
. flying on AP2 everything works. As you engage the APPR mode AP1+2 A/THR disconnects. This is because with AP 1+2 FMGC1 becomes the master one and A/THR channel 1 (faulty) gets activated.
. flying on AP2 everything works. As you disengage it A/THR disconnects. This is because with no AP FMGC1 becomes the master one and A/THR channel 1 (faulty) gets activated.

[nopoal]

Hi,

Do you know how long after retarding the a/thr to the idle position, the auto flt a/thr off memo takes to appear in the Ecam memo?

Why this memo appears on some long flares?

Airbus references?

Thanks.

[Fursty Ferret]

Hmm...


Last week we experienced a problem with the autothrust dropping out in the cruise. Switching to AP2 recovered it. Disconnecting the AP for approach should have resulted in loss of A/THR, but it remained in.


Confused now. Admittedly it was close to the ground (~200ft RA) but above alert height.

[vilas]

bond2002


DSC-22_10-30 P 2/6
MASTER FMGC LOGIC

‐ If one autopilot (AP) is engaged, the related FMGC is master:


•It uses the onside FD for guidance


•It controls the A/THR


•It controls the FMA 1 and 2.


‐ If two APs are engaged, FMGC1 is master.


‐ If no AP is engaged, and

•The FD1 pb is on, then FMGC1 is master


•The FD1 pb is off, and FD2 pb on then FMGC2 is master.


‐ If no AP/FD is engaged, A/THR is controlled by FMGC1.


So what ever causes FMGC 1 to take over ATHR will be lost. For instance If you select AP1 or switch off both APs then FD1 is on so FMGC1 will be master and also with APP mode engaged when you put second AP on FMGC1 will be master and ATHR will be lost.