A321 Auto Throttle

[7gcbc]

Probably the wrong subject header, but I have a question on the A321 ?

Does the FMS/Autothrottle "Hunt" the heading and alt set - irrespective of the speed?

For example, you set a fairly complex departure with a climb, a level, a turn, another climb/turn and then a level and so forth, will the FMS cope with this , is it normal procedure and no great shakes ?

Just a query on a European operator I was on as pax last week, either the FMS or the FO was working bloody hard at 7-8 throttle changes up and down before cleaning up at TOC.

FYI outta LHR to DUB.

cheers

7gcbc

[swh]

7gcbc,

The autothrottle would have been doing all of that, only one change is made to the thrust levers after takeoff.

Thrust is then changed either by managed speed schedule from the FMGC or the manually selected speed/altitude/vertical speed.

:ok:

[Phoenix_X]

Most likely this was caused by short climbs, which the crew chose to fly in the standard way, ie full thrust with pitch adjusted for speed.

In this way, the thrust will go to max to start the climb, shortly after which the required level is reached, and the thrust goes back to a level flight setting. Then the next climb instruction is received, and it goes to full thrust again to climb, and so on.

This is why some pilots will choose to make short climbs with a set vertical speed, so that the thrust changes are limited.

[oldebloke]

Excellent description Pheonix of 'trying' to soften the climb steps,with Vert Spd,and avoiding the multiple engine 'failure'at noise level off alt,at the reduced airspeed!!:ok:

[catchup]

There is no "autothrottle" at all in the whole 320 family...

;)

Regards

[7gcbc]

Swh, Phoenix,

Thanks for replies, I just wanted to confirm that it was automatic inputs (or computer instructions) that were making the power changes.

catchup, agreed , I do not know the correct terminology, auto throttle was the closest I could get. :O

cheers

7gcbc

[Phoenix_X]

In case you're curious, the Airbus family has 'Autothrust,' as the throttles do not move. :ok:

[DVR6K]

Here's a question that is only slightly off-topic but nevertheless Airbus throttle-related...

As I understand it when you slide the throttles into one of the gates or detents on take-off, the autothrottle automatically kicks in and delivers TOGA/FLEX as selected and then climb once airborne and the throttles are moved back. Now when it comes to a visual approach and you want to disconnect the autothrottle, how do you select a thrust setting manually without the throttles clicking into one of the gates? Does this not just re-arm the autothrottle? I imagine the Airbus is cleverer than that and probably prevents this happening but are the gates disarmed or something when operating outside of the autothrottle?

Have had a look in the A320/330 FCOM but it doesn't seem to cover it.

PS - Having used "autothrottle" throughout the whole of my post, please take it to read "autothrust" as I cannot be arsed changing it all, ta!

[Gary Lager]

the 'gates' or 'detents' for the thrust levers are (ignoring reverse) IDLE, CLB, MCT/FLEX and TO/GA.

The thrust lever range you would use for a manual thrust approach is only likely to be between IDLE (naturally) and CLB (max climb thrust). Thus you would not move the levers as far as any of the gates.

Anyway, I think that after disconnection, A/THR is only re-engaged if the thrust levers are moved into the TO/GA gate (or the pb is pressed), so you could even use CLB or MCT thrust on your visual approach without re-engaging the A/THR.

Although if one needed MCT during a manual thrust, visual approach, I would suggest that selection of TO/GA would become a good idea in very short order...;)

[Phoenix_X]

As an addition, the autothrust does not engage when the levers are moved to FLX or TOGA; it arms. Moving the thrust levers to CLB only will do nothing with the autothrust if it is disengaged.
Once autothrust is armed, moving the thrust levers back to the CLB detend can engage it (subject to some conditions).

On a visual approach, moving the thrust levers to the CLB detend for max climb thrust, will not engage or arm the autothrust.

[Gary Lager]

Ah yes, that sounds more correct.

It's been a few years since my last A320 flight.