Airbus ATHR button

[WindSheer]

I am not a pilot but quite clued up on airbus systems and logic. However, when carrying out a jump seat ride some years ago i asked the captain to provide an example of when the ATHR button would be used.
'Good question' was his answer and after a brief discussion i was left slightly confused as to its purpose.

Anyone wish to fill me in.......

[NigelOnDraft]

Re-engaging the ATHR... You will tend to turn ATHR off via other means.

[pilot-737]

Re engage the autothrust as Nigel said ... And maybe to provide redundancy if you have one of the instinctive disconnect p/b out of service ;) check MEL 22-30-02 ;)

[WindSheer]

I was under the assumption that to disconnect autothrust you simply moved the levers out of the climb detent?

[Microburst2002]

The A/THR disconnect button is in the levers, actually there is one in each lever. You also disconnect it by retarding the levers to idle.

The push button in the panel is used only in abnormal situations. We never turn the A/THR ON in normal ops. It is automatically armed when we start the take off and it will automatically activate at thrust reduction after take off.

It may be necessary to use it, for instance, if you lose one A/THR channel, after switching to the other AP.

[WhyByFlier]

The ATHR is disconnected by moving the levers so that the thrust lever angle is at current commanded thrust and then pressing both disconnect buttons on the outside of the thrust levers. If you didn't move them to current commanded position they'd spool up to climb thrust when disconnected.

As for the purpose of the ATHR pb on the FCU (AP control panel) - its purpose is to either manually arm or disarm the ATHR, reset the ATHR in case of the known glitch on some A319s with CFM engines and also potentially after a windshear - once recovered the speed can go berserk - pushing the ATHR off and on gets the thrust off whilst leaving control with the system - it's a nicer way than closing the thrust levers.

[CONF iture]

The push button in the panel is used only in abnormal situations. We never turn the A/THR ON in normal ops.
We use it every time we want to arm or activate again the A/THR following a voluntary disconnection. No ABNORMAL situation involved.

[Chris Scott]

Quotes from WhyByFlier:
"The ATHR is disconnected by moving the levers so that the thrust lever angle is at current commanded thrust and then pressing both disconnect buttons on the outside of the thrust levers..."

Agreed. :ok:

Quote:
"...If you didn't move them to current commanded position they'd spool up to climb thrust when disconnected."

In my day, the A/THR would go into THR LOCK mode if you did that. The thrust (N1 on the CFM-56 engine, or EPR on the V2500) would remain where it was. Has something changed?

Quote:
"and also potentially after a windshear - once recovered the speed can go berserk - pushing the ATHR off and on gets the thrust off whilst leaving control with the system - it's a nicer way than closing the thrust levers."

What does it recommend in your FCOM? After a windshear event, if the speed is "going berserk", due to the A/THR being too slow to reduce thrust after you've brought the throttle levers back to the CLB gate, you might be better doing what you would always do if the automatics are not coping: SWITCH THEM OFF.

As you know, closing the throttles does precisely that, and also reduces the thrust as quicklly as possible. Mind you, you must be prepared to push them forward again almost immediately. Do you ever fly in manual thrust? Have you ever flown in real turbulence? Fiddling with PB switches in even moderate turbulence can be a tricky business.

Where your airline permits, I recommend that all you young Airbus FBW pilots practise disengaging A/THR - perhaps in the cruise at FL350, workload permitting, and with the approval of your colleague - and fly in manual thrust for a while; with or without the AP. Then you can use an A/THR button to re-engage it, and reselect the throttle levers to the CLB gate. Then repeat, time permitting. You might even consider doing a step-climb or an approach in MAN thrust... :E PPPPP (practice prevents p**s-poor prformance). ;)

If you're a real pilot, get to know your aircraft!

[WhyByFlier]

In my day, the A/THR would go into THR LOCK mode if you did that. The thrust (N1 on the CFM-56 engine, or EPR on the V2500) would remain where it was. Has something changed?

FCTM OP-030 – AP / FD / ATHR:



1) USE OF INSTINCTIVE DISCONNECT (I/D) PUSHBUTTON If the I/D pushbutton is pressed when the thrust levers are in CL detent, thrust will increase to MAX CL. This will cause an unwanted thrust increase and may destabilize the approach.

Therefore, the recommended technique for setting A/THR to off is: - Return the thrust levers to approximately the current thrust setting, by observing the TLA symbol on the thrust gauge - Press the I/D pushbutton

This technique minimizes thrust discontinuity, when setting A/THR to off.

I guess it must have changed as that's how it's always been in my time (just under 3.5 years)

I do try to fly manual thrust once a week and have flown aircraft dispatched with ATHR U/S and thus flown man thr through the whole profile. You make a good input though and I too would recommend it. I'm fortunate to be in a comany where its no problem to do so.

What does it recommend in your FCOM? After a windshear event, if the speed is "going berserk", due to the A/THR being too slow to reduce thrust after you've brought the throttle levers back to the CLB gate, you might be better doing what you would always do if the automatics are not coping: SWITCH THEM OFF.

There is no recommendation other than to 'keep the automatics'. It was a 'tip' from a TRE in an LOE and it worked very well. By moving back to climb thrust and resetting ATHR using the FCU pb it all settles down ...... At least it did in the sim.:}

If you're a real pilot, get to know your aircraft!

There are those who don't know and those who don't know they don't know! I learn something new on this plane every week.

[Chris Scott]

Hi WhyByFlyer,

Thanks for your kind reply, and for not taking offence at my somewhat robust remarks, which I hope you realise were not directed at you personally! I'm glad to hear that you fly regularly in manual thrust (and that your airline permits it).

Looks like the engagement criteria for Thrust Lock must have changed in the way you describe. A frustrating trawl through the 'net revealed only the logic I described in my post, and my manuals are at least 12 years out of date...

Re the aftermath of a windsheer event, with the speed going "berserk", you say:
"There is no recommendation other than to 'keep the automatics'. It was a 'tip' from a TRE in an LOE and it worked very well. By moving back to climb thrust and resetting ATHR using the FCU pb it all settles down ...... At least it did in the sim."

This coulld make for an interesting discussion. I'm inclined to stick to my general advice that, if the automatics are compromising the flight path or flight envelope, disengage them and do it yourself. TREs are very keen on demonstrating neat tricks on the simulator, because they are constantly repeating pre-programmed exercises with a series of candidates. And simulator motion systems are incapable of simulating severe turbulence realistically. I agree with the spirit of your last sentence above.

[WhyByFlier]

No problem Chris - you made valid, worthwhile points and nothing is personal on here!

For your information, from FCOM DSC-22_30-90 P 6/12:

The Thrust Lock function is activated when the thrust levers are in the CL detent (or the MCT detent with one engine out), and:

‐ The flight crew pushes the A/THR pb on the FCU, or
‐ The A/THR disconnects due to a failure.

The thrust is locked at its level prior to disconnection. Moving the thrust levers out of CL or MCT suppresses the thrust lock and gives the flight crew manual control with the thrust levers.

When the Thrust Lock function is active: ‐ “THR LK” flashes amber on the FMA ‐ ECAM “ENG THRUST LOCKED” flashes every 5 s ‐ ECAM displays “THR LEVERS......MOVE” ‐ A single chime sounds and the Master Caution light flashes every 5 s. All warnings cease when the flight crew moves the thrust levers out of the detent.

Is it possible people were previously using the FCU pb rather than the instinctive disconnect?

[vilas]

I would like to add two things.
1. Only moving THR levers out off CLB does not disconnect ATHR it restricts the max thrust to the TLA. To disconnect you need to move them to idle.
2. To disconnect ATHR you do not have to press both I/Ds any one will do as well.

[Chris Scott]

WhyByFlyer,

Thanks for the FCOM extract. BTW, which Airbus type is it for? It may make no difference, but I should have stated that I was talking about the A320 family.

Quote:
"Is it possible people were previously using the FCU pb rather than the instinctive disconnect?"

No: we always used one of the throttle lever-mounted "instinctive" disconnect buttons, after we had retarded the levers to line up what I call the "doughnuts" with the current thrust. So, assuming my memory is correct, THR LK would only be triggered if we inadvertently pressed the button first.

As it happens, the only documentation I can find on the 'net that covers this aspect of the A320 family is posted by Moscow-based Nordwind, which seems to be in the process of obtaining a small fleet of A321s:

Airbus A320 Family Autoflight :: Flight Guidance - Autothrust (http://www.inral.com/Atto/auto_flight/fg_autothrust.htm)
(Then scroll down to A/THR DISCONNECT and THRUST LOCK FUNCTION.)

The section on Thrust Lock states, inter alia, that it is activated when the thrust levers are in the CLB detent (or the MCT detent with one engine out) AND the pilot presses the instinctive pushbutton on a thrust lever.
The section on A/Thr disconnect, however, confirms your information with what appears to be a recent amendment.

As for the A330, an old Airbus FCOM for training purposes only is available here (http://www.google.co.uk/url?sa=t&rct=j&q=a330%20autothrust%20modes&source=web&cd=9&sqi=2&ved=0CHAQFjAI&url=http%3A%2F%2Fwww.smartcockpit.com%2Fdownload.php%3Fpath% 3Ddocs%2F%26file%3DA330-Auto_Flight.pdf&ei=3Ic7Ua_CAeeR0QXYuoGgDQ&usg=AFQjCNEV_DE2CU4o2VtCSbzDNpI9FLGptg). 1.22.30 P59 covers A/THR disconnect, and clearly states:
"... the pilot pushes the instinctive disconnect pushbutton on the thrust levers (which immediately sets the thrust corresponding to the lever positions)..."

The Thrust Lock section on Page 60 is identical to what you have posted. I infer that the A320 may have been brought into line with the A330/340 at some stage, or perhaps all types have been modified.

Hi vilas,
Re your post:
"1. Only moving THR levers out off CLB does not disconnect ATHR it restricts the max thrust to the TLA. To disconnect you need to move them to idle.
2. To disconnect ATHR you do not have to press both I/Ds any one will do as well."

(1) That is all correct, and is not in disagreement with WhyByFlyer's posts.
(2) Good point.

[WhyByFlier]

I am indeed referring to A320 series aircraft - I'm with easyJet.

As for the stuff online - I tend to read it with caution and use the company provided manuals as my reference. Something like that could have been written by someone who has misinterpreted it or has not updated it.

Vilas your first point is correct and is a way of disconnecting autothrust but is not the Airbus recommended way in FCOM/FCTM. They recommend moving the donuts to the TLA and pushing an I/D pb.

[vilas]

I was replying to windsheer's following wrong assumption.
"I was under the assumption that to disconnect autothrust you simply moved the levers out of the climb detent?"
It is one of the ways ATHR gets disconnected. Obviously you can't keep closing thrust levers to disconnect ATHR.
Anyway I appreciate the amount of interest he is showing in details about A320 as a nonpilot.

[Chris Scott]

Quote from WhyByFlyer:
"As for the stuff online - I tend to read it with caution and use the company provided manuals as my reference. Something like that could have been written by someone who has misinterpreted it or has not updated it."

Very true, and one must include this forum in that caveat; including the statements and opinions of old farts like me.

Trouble is, posters so often have the experience and intellect to make valuable contributions to a discussion, but are hampered by a lack of current, type-specific information - including FCOMs. As I write, the threads on the B787 battery problems are a good example of this problem.

[Microburst2002]

Quote:
Originally Posted by M2002
The push button in the panel is used only in abnormal situations. We never turn the A/THR ON in normal ops.



We use it every time we want to arm or activate again the A/THR following a voluntary disconnection. No ABNORMAL situation involved.

absolutely true.

But they get so scared everytime I even suggest disconnecting that now it seems abnormal...