Airbus - Autothrust question

[TotalBeginner]

Why is the area between IDLE and the CL gate on the airbus thrust levers labelled A/THR? Is this not the range where thrust is controlled manually?

[TotalBeginner]

Any ideas?

[TopBunk]

But it's also the range of thrust settings available to the aircraft with autothrust engaged and in the CLB detent.

[TotalBeginner]

But it's also the range of thrust settings available to the aircraft with autothrust engaged and in the CLB detent.

I don't understand

[Clandestino]

With autothrust off, thrust levers on A320 (and I suspect on the other FBW airbi too) work as normal trust levers. However, autothrust operation is much different compared to Boieng's autothrottle. Airbus thrust levers don't move with power changes and while A/THR is working, their position sets limit to maximum N1 the A/THR can command. Normally they're set to CLB detent or MCT in one engine operation. N1 equivalent to current thrust levers position is displayed as small circles on N1 ECAM EWD display (upper center one).

So on airbus after you set the thrust levers to clb position, the autohrust is active and its control range is between climb power and idle. I don't claim this to be the answer to the original question, but it's the best that I can think of.

[hotmetal]

pulling the levers out of the CL detent when autothrust is engaged does not disengage the autothrust. You could have the levers half way between idle and Cl [can't think why you'd want to] and autothust will still work but max thrust will be limited to the position of the levers.

[TotalBeginner]

Now it's crystal clear! Just out of interest, what would happen if you set the thrust levers to a limit that meant the A/THR could not maintain the speed. For example, the aircraft is descending in "open decent" and the THR levers are at IDLE. When the aircraft levels, would the speed decay, until some sort of flight envelope protection takes over, or would the A/THR exceed the commanded limit in order to preserve the speed?

[DBate]

would the speed decay, until some sort of flight envelope protection takes over

Yes, correct - with the conditions you mentioned (Thrust Levers at idle, OP DES).

[Clandestino]

Pulling the thrust levers all the way to idle is one of the ways to disconnect the autothrust. But even with autothrust off, when certain (quite high) value of AoA is reached, autothrust will command TOGA power regardless of the position of the thrust levers. Airbus calls it alpha floor.

[lostcomm]

ATHR

but this is not so if the aircraft is below 100 ft. Then no TOGA. Remember AirFrance crash.
LC

[TotalBeginner]

but this is not so if the aircraft is below 100 ft. Then no TOGA. Remember AirFrance crash.

I guess to prevent TOGA during a normal landing?

[lostcomm]

Silberfuchs,

that is what I ment. The alfa floor function is inhibited. In manual thrust all setings are available all the time. This is kindda logical dont you think. As I remember Clandestino was talking about the autothrust function and alfa floor. MAybe you shoud read better the next time.