I just got a problem I haven't seen before, the yaw damper light won't come off although I have switched the yaw damper ON and I also got a FLT CONT warning on the RECALL panel. I have no failures enabled.What am I missing here...?

I know it will switch back off if the IRS's aren't aligned and the position entered into the FMC, are yours?

The FLT CONTROL warning refers to the yaw damper so that one is correct.I have to admit that I'm having some trouble with the yaw damper too time from time. What helped me was to turn the yaw damper off, then switch the FLT CONTROL B to OFF and than back to ON. After that the yaw damper will come on again. I think it is some kind of a little bug.Best regards

In my case the IRS has to be aligned before switching the yaw damper on. Not sure if this is the "right" way to do it but it works for me every time. and just an FYI, I didn't have to do this with the first few releases. Hope this helps.

IRS must be active for yaw damper to stay on.

In my case the IRS has to be aligned before switching the yaw damper on.

The IRS doesn't need to be aligned, it just need to be in alignment. If you try to switch the yaw damper on with the IRS off, the YD will turn back to off. Once the white ALIGN annunciator light illiminate below the IRS switches (which indicates they are aligning), you'll be able to turn the YD on, even if you didn't entered your current position in the CDU. The YAW DAMPER annunciator light will remain illuminated until normal hydraulic pressure is established in the system. I think that's the way it should work, and works for me.

Thanks for your input guys!In my case both IRSes are aligned and I have normal hydraulic pressure but still the yaw damper light is illuminated and the switch remains in the ON position...strange...?Well, since this is only a simulation I decided to t/o despite this problem and so far so good, about 30 min out from my TOD and hope the landing will be good too without yaw damper...don't tell my PAX :(

For the case you've got the service based failures on, check if the Yaw Damper has failed.I once had that problem.

Thanks for your input guys!In my case both IRSes are aligned and I have normal hydraulic pressure but still the yaw damper light is illuminated and the switch remains in the ON position...strange...?Well, since this is only a simulation I decided to t/o despite this problem and so far so good, about 30 min out from my TOD and hope the landing will be good too without yaw damper...don't tell my PAX

That happened to me once. I did exactly the same as you. Just took off and made my flight. Everything went fine and I landed the plane. I checked the failures, but nothing was active, and also searced the QRH for a solution, but nothing worked. Anyway, when I flew again the next day, the issue wasn't there and never happended again.

I've got the same problem. My solution is: first enter your position in the CDU before switching on the yaw damper. If you switch on the yaw damper before entering the position in the CDU the warning light will remain on. I guess this is a little bug.

Now that you mention it I remember during this preflight I did switch on the yaw damper after I switched the IRS selectors to NAV but before I entered the position in the FMC where I normally doesn't switch the yaw damper on until after I entered the position so if that is not required in the real a/c maybe this is a little bug then as you suggest.Will make sure to enter the position in the FMC before I switch on the yaw damper on my next flight and see if the problem is gone by doing so...probably it will be. As for failures I have none enabled so that can't be the culprit in this case.

yaw damper needs to be put on, after engine start

yaw damper needs to be put on, after engine start

No, the yaw damper can be turned on before engine start :)

Normally I think it would be turned on as soon the APU are on, just before pushbackand start of the engines.I usually do it in that order anyway./ Leffe

Get the same problem... and turn it on when the operations manual tells me to... Try to use the manuals to get the procedures right, but I guess that it's one of those things called 'a funny'...