Turb Damping

[Creases67]

Hello All, There is a Turbulence damping push button on all busses. It is ON in normal conditions. Couldn't find a reference as to when it would need to be put OFF. My reference would be to specific failures. If there is no likely situation other than unexplained upsets, why have an extra switch to scan ? Also, I don't find the use of the same in any procedures. Any light ?

[TopBunk]

There is a Turbulence damping push button on all busses

Is there? News to me (although I haven't klown the A319/320/321 since 2005).

[Squawk-7600]

The TURB DAMP function uses additional accelerometers I believe, they may develop a fault which is undetected by the aircraft however detected by the pilots. I presume an option to override this was required during certification, as it modifies the Normal Law behaviour of the aircraft. I've never seen or heard of it being turned off.

I'm not sure what you mean by "scanning" switches or lights on. Remember Flying an Airbus is all about rumours and facts; any switch position is merely a rumour, what the aircraft tells you on the SD is the fact of what is going on.

[Creases67]

Thanks Squawk. My question is,if there is no procedure that requires switching off the damper, then how does the pilot know when to switch it off. If no such situation exists, why have it in the first place ?

[TopBunk]

Creases

Do you mean the Yaw Dampers?

[Okivan]

There was a TURB button on the FCU on Airbus300B4 .Do you mean that?
It locks the roll function to keep the wings level and gives you the manual "pitch" command. Is it what you are asking?

[Squawk-7600]

Thanks Squawk. My question is,if there is no procedure that requires switching off the damper, then how does the pilot know when to switch it off. If no such situation exists, why have it in the first place ?

Yes there is a procedure, and it should be covered in your FCOM. It is when the pilots believe the TURB DAMP function is faulty, yet the aircraft itself doesn't detect the fault. If you don't mind I won't look up the precise quote, but to paraphrase what Airbus say, it's when the pilots believe the TURB DAMP function has developed a fault such that it is ADDING TO the aircraft deviations and not damping them down. In other words if the aircraft were flying in still air, yet was deviating as if it was in turbulence then you might expect the TURB DAMP function may have developed a fault that, for whatever reason, the aircraft didn't detect. You would then turn the TURB DAMP off and see if the flight path deviations reduced to normal (which in calm conditions should obviously be zero).

Hopefully that helps.

PS And no it's not a yaw damper being discussed, nor the function on the A300.