747 Yaw dampers

[cowpatz 243]

Just wondering if these are correctly modelled. The yaw damper EWICAS message should disappear as soon as the first IRS alligns. This does not seem to be the case.CheersSteve

[Guest s_L_Y_F_a]

I guess pushing yaw damper switch UPR and LWR would help too.

[cowpatz 243]

These are already in the on position and should not need to be cycled. As the first IRS alligns both yaw damper messages should disappear from the EICAS sreen. Next time, however, I will recycle them to see what happens. It appears at the moment that they disappear when the hydraulics are pressurised.CheersSteve

[Qavion 19]

Not sure what happened here. The EICAS msgs and INOP lights may have been operating properly at one time.... The beta team knew that the messages should disappear with the IRU's aligned (no hydraulics required.. at least this is the case _on the ground_). Perhaps the air/ground logic got lost somewhere in the betas?During the development of the sim, I recall that we were not sure how intelligent the YD computers were, to recognize hydraulic failures in the air:Here's what we knew/didn't know:Hydraulic Systems 3 & 2 are used (respectively) for the Upper & Lower Yaw Damper actuators.Signals from the respective HYDIM's are sent to the YD computers (but what these signals are for, I don't know).There are position feedback sensors in the Yaw Damper actuators, so I guessed that if the Yaw Damper computers gave a command for the YD actuators to move and hydraulics were not available, then a fail signal would probably be generated. However, since the YD system is not active on the ground, then a failure signal probably wouldn't be generated.We were also not sure if the YD computers were smart enough to know if the rudder surface itself was not moving due to other hydraulic system or rudder power actuator failures.There were several complex, unresolved issues like this, but, as you can imagine, at some point, you have to release a sim anyway ;) (EDIT: Note: There were no volunteer test pilots available to switch off the hydraulics in the air on the real aircraft)This has been added to the list of things to do (should the 744 be updated)Cheers.Q>

[Guest snyperAL]

I do not know what Yaw dampers are.Alan

[cowpatz 243]

I dont have a great deal of info on them but what I do have says that if you get a fault light it means one of the following:Module fault, actuator fault, IRU's off or in align, switch off or module power off. It doesn't mention hyd power.I think the snag sheet is large enough now for PMDG to look at a pax patch. If the goal is to simulate the real McCoy as close as possible then lets also look at the maintenance aspect. If a RW aircraft has a faulty system then it is repaired. One would hope PMDG sees this in the same way. I know there is a lot on the go at PMDG at the moment but I for one will be observing how well the Queen is "maintained" and before looking at future purchases.CheersSteve

[markadeane 272]

From the manual (jolly good read it is too!)"The rudder function is supplemented by twofully independent yaw damper systemsdesigned to improve aircraft directionalstability, and to improve aircraft roll rate andturn performance during turns.The yaw dampers receive hydraulic controlfrom hydraulic systems 2 and 3. Yawdamper deflections are applied directly tothe rudder control surfaces in proportion toany turn or yaw tendencies detected by theIRS yaw sensors located in the nose and tailof the aircraft.Yaw damper rudder input cannot be sensedby the crew via the rudder pedals, and willnot interfere with crew rudder input."

[markadeane 272]

My suspicion is that the current 747 PAX will under go a functional overhaul for FSX, and if we're lucky, those changes will filter back to the FS9 744Pax user community in the form of a patch.

[Qavion 19]

Perhaps the input to the YD Module from the HYDIM is simply for fault discrimination. That is, the INOP lights do not go on if there is no hydraulics, even though the actuators fail to move (with the absence of hydraulics). On the other hand.... wouldn't you want to know your YD system was inop, irrespective."If the goal is to simulate the real McCoy as close as possible then lets also look at the maintenance aspect."The goal is more likely to be "as close as practicable". We all know the limitations of MSFS and the limitations of a $50 flight sim.Anyway, I hope you've been keeping a list of the snags... I haven't :(Cheers.Q>

[Guest snyperAL]

I'm on chapter two at the mintue...AL

[cowpatz 243]

Q the list isn't long and as has been suggested with FX coming along this would present a great opportunity to sort some of these issues out. The yaw dampers issue is not huge.....first IRS alligns the inop lights go out! If it is a FS9 limitation then lets have someone from PMDG come out and say that. If it is not going to be practical to model it then let's hear it.Steve

[Guest airspace]

Nice to see the 'flying jumbo' jet again, Steve. Off-topic question here that i'm sure you can tell me and that is:- what is the flying distance from LHR to AKL via HKG . i've looked at some timetables and believe that it is a slightly longer flight time than going in a west direction via LAX. Darren:-)

[Qavion 19]

"The yaw dampers issue is not huge....."Having been involved in the beta testing of 3 Boeings and countless updates you get to understand that things are not always as simple as they seem.In the following pic, both YD switches have been selected, but the hydraulics AND IRS's are off. Why isn't the Upper YD INOP Light illuminated? Both YD Modules have electrical power. http://forums.avsim.net/user_files/154026.jpgBug? Cheers.Q>

[markadeane 272]

I don't think Steve is referring to the complexity of the fix as being 'not huge' but that the anomaly is not a showstopper, in other words we can live with it.I think even the casual PMDG customer with zero beta test experience would appreciate that a great degree of complexity is inherent in every feature!