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WindSheer
5th Nov 2009, 21:29
Could somebody kindly explain what this button is used for.

It is not pressed under normal conditions, so what does it do??
I am not an airbus pilot, obviously; hence my concern.

Cheers...:ok:

Dan Winterland
5th Nov 2009, 21:52
Er, it turns the autothrust on or off!

But I find I use it very little, if at all. AT goes automaticly at thrust reduction and off when either the disconnect buttons on the TLs are pressed, or if the TLs are retarded to idle in the flare.

charlie83
6th Nov 2009, 03:51
Never actaully done this myself, but have seen a few people use this button to "recylce" the system on approach when autothrust maybe slow to capture Vapp. IE Vapp (correct target approach speed) is plus 10-15kts and the thrust is still coming on, some guys press the A/T button to engage "thrust lock" ( basically locks the thrust at time of pressing this button) thus by resetting the system seems to give the autothrust a little kick into life to get the power to spool down and achieve Vapp....

Apart from that, no I've never seen it pushed for anything else under normal ops.

Hope that makes sence....

Cheers

Pro Spin
6th Nov 2009, 08:13
Expanding a bit on Charlie83's comments from my experience:

On some Airbus A320 family aircraft there is an issue with the Autothrust function if you use speedbrake when flap is deployed (usually an issue with Flap 2 and greater) whereby the Autothrust settles the speed at about VAPP + 10kts and makes no effort to reduce it back towards VAPP once fully configured.

As Charlie83 quite rightly states - turning the autothrust off (engages thrust lock momentarily) and then back on again rectifies this issue.

Other example - We used to have a rule in a previous company that we couldn't land the A321 with Autothrust disconnected (tailstrike worries). So pilots wanting to practice manual thrust approaches would press the autothrust button, then reselect the thrust levers to the CLB detent to re-engage the autothrust.

If the workload suddenly gets higher than expected on a fully manual approach this is a great way to reduce the workload again... I always brief how I will re-engage the automatics if I am going to fly fully manually...

Cheers

PS

CaptainProp
6th Nov 2009, 13:30
It's used in the NO ATHR / NO FD departure procedure for example, to actually turn ATHR back on if I remember correctly.

CP

Frankie_B
6th Nov 2009, 14:23
Yes, it is used to re-connect the A/THR: You press the A/THR button (provided thrust levers are above idle and below or at CL), and advance the throttles to CL gate. Otherwise, you'd have to kick it to TOGA and then back to CL to re-engage auto-thrust, and you don't wanna do that usually :suspect: