HelloCan someone explain why the IRS must be aligned before the Yaw Damper light will go out?I looked in FCOM 2 and could not find the information.ThanksDon

The yaw damper functions using information from the ADIRUs.

To elaborate on what Darrol said......the Yaw Damper System utilises information from the aircraft Air Data Inertial Reference Units (ADIRU's), so that the Yaw Damper System can: (i) detect yaw motion, then, (ii) calculate a command to move the rudder in the opposite direction to decrease unwanted yaw motion... thereby reducing the effects of Dutch Roll and or Turbulence.That is the simple explanation and I hope it helps.Ash Frew.

To elaborate on what Darrol said......the Yaw Damper System utilises information from the aircraft Air Data Inertial Reference Units (ADIRU's), so that the Yaw Damper System can: (i) detect yaw motion, then, (ii) calculate a command to move the rudder in the opposite direction to decrease unwanted yaw motion... thereby reducing the effects of Dutch Roll and or Turbulence.That is the simple explanation and I hope it helps.Ash Frew.

What you're saying is that the ADIRU's actually drive the Yaw Dampers. It's in fact not necessary for a yaw damper to have to have movement info from an inertial system. What if there is an inertial system failure? You certainly don't want Dutch roll to develop then!!vololiberista

Refer to FCOMv2, Page 9.20.13:"[...] yaw dampers are controlled through Stall Management/Yaw Damper (SMYD) computers. The SMYD computers receive inputs from both ADIRUs [...]"Oliver BranaschkySent from my iPhone using Tapatalk

In old aircrafts the yaw dampers use their own sensors to detect yaw movements, this is a waste of weight and a more complex system, and requires more maintenance (one more piece that can break or can introduce errors).As the ADIRUs are installed, and they have all required accelerometers and gyros for yaw detections, so it is not needed another device to do that.The yaw damper will need this information to work correctly, and the switch can be armed only if the SMYD find an IRS turned on.The yaw damper will fully work if IRS is aligned (OFF light will extinguish) or can be armed during IRS alignment, in this case the ALIGN lights must be ON.The Y/D Off light in this case will be on for the entire IRS alignment procedure, but will extinguish after alignment.In case the IRS will stop working or is not in align mode, the Y/D will trip to the OFF position.

vololiberistaNo. That is not what I said. To quote myself... "the Yaw Damper System utilises information from the aircraft Air Data Inertial Reference Units (ADIRU's)".Utilise - as defined by the Australian Oxford dictionary - "Verb - makes practical use of; turn to account; use effectively".Furthermore, and I will quote myself yet again... "so that the Yaw Damper System can: (i) detect yaw motion, then, (ii) calculate a command to move the rudder in the opposite direction to decrease unwanted yaw motion".From my quote, it can be detracted that I implied that the Yaw Damper System (a system which is categorized in ATA Chapter 22) is the system that controls the Yaw Damper System functions, and not the ADIRU's, which is categorized in the Air Data Inertial Reference System in ATA Chapter 34.Lastly, Oliver is quite right, and has explained a fact, and appropriately referenced (good on ya mate!) what I refrained from explaining, to give, and I will quote myself again... <a>"simple explanation".I will leave you with this question, to which I require no answer, and a statement - if there are any ADIRU failures, don't you think you have bigger problems to solve other than the problems concerning the Yaw Damper System? Which, in all honesty, isn't really required as the aircraft can still be operated without the system being serviceable.Ashley Frew.

Edited January 25, 201214 yr by Avroboeing

Just to complete the requirements of the 737 NG yaw damper:From ADIRU:AirspeedImpact pressure.Lateral accelerationRoll angleRoll rateYaw rate.From FMC: (avaiable also the manual input from the main panel knob)Gross weightFrom sensors:AOAFlap limit switch (yaw damper limits 2 / 3°)MCP (autopilot engagement)rudder sensors (for rudder position)

Andrea and Vololiberista - look up the word "sciolist". I mean really! Sometimes I don't know why I participate in this forum; or rather, why sciolistic people like yourselves blurt tactless scribbles on this forum.I bid you two, farewell and I hope the rivet counting doesn't take too long to accomplish.Ashley Frew.PS. Andrea - Since you've gone through all that trouble, you might as well post the part number of the Stall Management Yaw Damper computers... you know, just to exercise just that extra bit of knowledge base you've got going there.

Edited January 25, 201214 yr by Avroboeing

Just curious: what's wrong in sharing what someon e knows?It is better than noone will share things? So, PMDG could do the same with its product, maybe it is sufficient to have a fsx default plane, as the other things are "too much" for you. Or, Why do you not ask pmdg to remove the FCOM wich contains instructions for not simulated items as it is for real planes.You are free to read or not, write or not, there is nothing "dangerous" in posting informations, and it could be interesting for others. I don't see how these words can hurt people.These continous attacks by people like you are a non sense... Or at least I cannot understand.So, if there is a reason why you and others are so reluctant to read some informations on the real plane, please explain, and we continue to speak if wheater radar will be implemented or not, if the activation code is working or not, dangerous approaches in FS, and oter simulator related things.Just wondering why then real pilots are taken in a different attitude and never attacked...

There is nothing wrong with sharing information in a manner that is constructive to the subject being discussed. However, there exists a distinct difference between imparting with knowledge that is helpful, and imparting with knowledge that can be perceived as being "over the top". I scrutinized you, and not attacked you, because I considered what you wrote to be over the top; a pointless display of knowledge - sciolistic. Do not fear though, as you are not the only one, and, admittedly, I have been sciolistic myself once or twice.Moving on - Pilots simply don't attract the same level of scrutiny because they never allow people the opportunity to - generally because their subject matter is concise.Ashley Frew.

Yes, well! On my panel updates for the VC10 I had to simulate three yaw dampers! Not just switches mind. Actual gauges showing deflection of each.One standby and two active. Think about how you might simulate two active gauges when the sim only has a single yaw damper either on or off!vololiberista

There is nothing wrong with sharing information in a manner that is constructive to the subject being discussed.However, there exists a distinct difference between imparting with knowledge that is helpful, and imparting with knowledge that can be perceived as being "over the top". I scrutinized you, and not attacked you, because I considered what you wrote to be over the top; a pointless display of knowledge - sciolistic. Do not fear though, as you are not the only one, and, admittedly, I have been sciolistic myself once or twice.Moving on - Pilots simply don't attract the same level of scrutiny because they never allow people the opportunity to - generally because their subject matter is concise.Ashley Frew.

Ok, then:

HelloCan someone explain why the IRS must be aligned before the Yaw Damper light will go out?I looked in FCOM 2 and could not find the information.ThanksDon

The answer, without going Off Topic, is:IRS give necessary information to the YD.It is a good answer? It is not OT, it gives the requested answer without going out of the discussion...Another answer could be: "it is required in accordance with FCOM vol 2 page 429.Another one "read the manual"Both without going OT and answering to the question...Is what you want? Is the best thing for training?I don't think...

I am done bickering. I have aircraft to arrive and depart.Ash Frew.

Just to clarify: my post on this topic was solely related to vololiberista's question regarding the yaw damper being dependant on the ADIRUs. No offense meant towards Andrea. In fact, Andrea, I honestly appreciate your contribution to this forum. Keep sharing your knowledge with us, please!Regards,OliOliver BranaschkySent from my iPhone using Tapatalk