Airbus Thrust Levers

[rich49]

I have always been curious as to the thrust lever movment on the Airbus.
I know that they are not backdriven and that they have 'gates' for the different autothrust settings. When you move the levers to the FLX gate for example, do they 'click' in? Then when you move them back to the CLB gate do you have to use pressure to get them out of the gate and then they pop back into the CLB gates, sort of like moving a flap lever? If so, when moving the levers without the automatics engaged (ie you want to move the levers like in a regular airplane) whats stopping the levers from going into ther gates? Can anyone tell me how the autothrust and thrust levers work on the airbus?
Thanks

[DBate]

Hi rich49!

To answer your questions:
1. Yes, the levers do 'click in' when you reach a detent and
2. yes, you have to use pressure to get them out of the FLX detent.

But when you move them towards the next detent, the levers do not move automatically to it. That way you can move the levers like in a conventional airplane.

Generally:
The thrust levers can only be moved manually. They move over a sector that is divided into four operating segments and has five positions divided by detents or stops. The thrust lever position is transmitted to the FADEC, which computes and displays the thrust rating limit and the N1 for that Thrust lever angle.

In autothrust mode the levers are set in the CL detent. They do not move even with a power change by the A/THS. The max. range for the A/THS is from idle to max. climb power (both engines). But the max N1 rating is limited by the thrust lever angle. I.e. if you set the levers somewhere between idle and CL, the max. N1 that canbe set by the autothrust system will be the one corresponding to that thrust lever angle you set.

Hope this helps a bit.

[rich49]

Ok thanks. I have read the 'fly by wire at a glance' on the tech log links thread too btw.

So, from the idle position up to the CL gate the levers move conventionaly, does that mean that when the TLA is set just before the CL detent that max N1 thrust is commanded,or is max thrust reached in the TOGA detent? What happens if you are in the CL gate and pull the thrust levers bellow it but not to idle, does the autothrust dissenage?
Cheers

[330 heavy]

Think of the levers themselves as limiting switches. From above idle detent to clb detent all you are doing is setting the max limit of the auto-thrust. FLX and TOGA are not used in the auto-thrust system. To disconnect you can pull the levers to idle, use the instinctive disconnect switches( 1st match the thrust lever to the current amount of thrust indicated by the TLAs-Thrust Lever Angle indicators on the EPR guage), or push the auto-thrust button on the FMA. Or, if you are really brave, you can set power yourself just like a conventional airplane.
330

[rich49]

Ah, Ok thanks for your answers.
So autothrust does NOT dissengage when you pull the levers out of the CL gate, only when they are put into the idle gate (or you push one of the disconect buttons) this just limits the amount of thrust the A/THS system gives you.

ONE last question then if you don't mind. If you want to set the thrust manualy without autothrust engaged, and you want almost full thrust, you would have to move the levers almost to the top of the quadrant, if autothrust is NOT engaged and you move the levers past the CL detent because you want almost full thrust the levers will not go into the CL detent will they? I ask this because would it not get annoying if you want to control the thrust manualy but everytime you move the levers past the CL gate for the higher thrust ratings they move into the detents?
Thanks.

[330 heavy]

There is a bit if room between the CLB detent, the FLX detent, and the TOGA detent. The levers will remain where ever they are placed. They do not just drop into the detent. Just to clarify, the thrust levers are just switches. FADEC controls thrust based on the TLA ( among other factors) regardless of autothrust engagement.
330:D