A320 ATHR active on ground with engines off

[IFLY_INDIGO]

FCOM says that ATHR can be armed on ground when engines are not running by pressing the FCU ATHR pb and ATHR in blue would be displayed in the 5th column of FMA.

But when we tried the same thing yesterday, instead of arming, ATHR was active and FMA was in white instead of blue..

Any thoughts?

[gAMbl3]

Note: When the flight crew sets both thrust levers to IDLE position, the A/THR disconnects but, if the flight crew pushes the A/THR pb of the FCU, they will simultaneously arm and activate the autothrust.

Ref : FCOM DSC-22_30-90 A/THR Activation

[Sue Ridgepipe]

Note: Do not engage the autothrust on ground, as it may generate the AUTO FLT A/THR OFF warning at engine start.
PRO-NOR-SOP-06 P 15/20

[mikedreamer787]

ATHR was active and FMA was in white instead of blue..

Have a look at FCOM for arming/active requirements and everything becomes clear.

Switch it off BEFORE engine start as per Ms Ridgepipe's post above.

[Amadis of Gaul]

Just out of curiosity, why would you mess with the AT with the engines off, unless you're a mechanic performing some kind of a test?

[IFLY_INDIGO]

I read it many times.

FCOM 22 30 90

The flight crew arms ATHR:
-On ground


By pushing the ATHR pb on the FCU when the engines are not running, or



ATHR is active when it controls thrust or speed......The ATHR being disconnected, is activated when the flight crew pushes the ATHR pb on the FCU while the thrust levers are within the active range, including IDLE position. Note: When the flight crew sets both thrust levers to IDLE position, the A/THR disconnects but, if the flight crew pushes the A/THR pb of the FCU, they will simultaneously arm and activate the autothrust.

[TyroPicard]

Your last post contains all the information. Badly written FCOM... It is not SOP to push the A/THR pb on the ground... the flight crew actually arm A/THR by selecting FLX or TOGA for T/O.

[IFLY_INDIGO]

You are right, it is not SOP to press ATHR pb on ground.

So also it is logical for ATHR to NOT get active on ground when engines are off.

Active means it is in control of the thrust or speed.

Arming means it is ready to control the thrust or speed.

On ground with engines off, ATHR is getting active if you insert V2 without even preparing other pages!

[TyroPicard]

Pilots are not the only pb pushers.... maybe it IS logical for the engineers to be able to test the A/THR on the ground....

[IFLY_INDIGO]

My intention to start this post is to find out if the discrepancy in the FCOM and actual system. so that I can write to airbus through my airline and report it.

Who knows such stupid behaviour of the autothrust could lead to some emergency/disaster?

Engineers have defined ways to carry out system tests. I have never seen someone testing autothrust like that..

[TyroPicard]

Only trying to generate options instead of being totally dogmatic and then finding out that I am wrong....

[DesiPilot]

Have you tried to the A/P on the ground, you can engage that on the ground as well. Of course A/P is not controlling anything. There are a few functions that are meant for Engineers, for ground testing or other functionality checks. It is mentioned in the FCOM so that you as pilot are not caught off guard if you press that button on the ground.

The logic behind your logic is bit flawed.

[IFLY_INDIGO]

But what is written in FCOM is wrong [since it is not the case in reality]

FCOM should contain the actual cases... If what is happening in reality [autothrust getting active on ground with engines off for entire TLA range] is acceptable, same should be explicitly mentioned in the the FCOMs..

[TyroPicard]

IF_I
In the ?1980's a DC10 crew were idly speculating in the cruise on where the N1 gauges obtained their signal..... They pulled a CB marked N1 for No.3 engine (on the right wing) in spite of the fact that this was prohibited unless called for by a checklist.
The engine accelerated immediately, overspeeded (oversped?), and (among other things) a fan blade broke off. This came through into the cabin, killing a passenger who was innocently enjoying the view from his window seat.

I am not for a moment suggesting that the same thing will happen if you push the A/THR pb on the ground.

What I am suggesting is .... If FCOM recommends that you do not do something, don't do it! Spend your time before departure making sure that your captain has got everything right, then I might one day choose to fly Indigo.

[vilas]

Tyro
I agree with your comments. Cockpit is not a place to be creative especially so when it is FBW. If you want to know more write to Airbus. Experiments can prove very costly.