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Jetlinker

747-8F Electrical Issue

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Hello all,

I’ve searched the forum here but cannot seem to find any posts with this issue. This is an intermittent problem that seems to occur after doing a quick turn on the ground. Just after starting all 4 engines GEN 3 and 4 are being kicked offline, and I receive the ELEC GEN OFF 3 and 4 message. Resetting the GEN CONT switch does not reset it. The only thing that gets it working is to disconnect the drive and reconnect, and even then sometimes the issue returns. I have also tried shutting down and restarting the 3 and 4 engines to no avail.  There are no active failures shown in the PMDG menu on the FMC when this occurs.   

I fly the 747-8 in the real world. I am aware that even the real aircraft has been known to have electrical hiccups during engine starts, particularly with undesired load shedding. For this reason it is customary (at least where I work) to provide a 10 second wait between each individual engine start to prevent the generators from coming online simultaneously. Even with doing this I’m still having this issue. 

 

Any suggestions?

 

Thanks,

 

Jeffery Williams


Jeffery Williams

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I haven't seen this topic since not long after the release of the -400.  Give the N1 a slight bump with the throttle and that should solve the problem.  If you are not getting sufficient airflow through the engine and N1 lags then the generator drives will pop off.

I have not had this problem but I don't think I ever tried a quick turn and it is likely that this is a factor.  I've looked for minimum turn times in the manuals and haven't found it yet but I know that such things as brake temperatures put a limit on how short a turn can be.  Just guessing that this is a factor but I don't know what else it might be.


Dan Downs KCRP

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Thanks for the reply. I say quick turn as in I kept the sim up and running but in reality it was around 90 minutes or so. This last time around after solving the problem by disconnecting and reconnecting the drives it happened again upon advancing to 45% while beginning the takeoff roll. I pulled off and once again did a reset. Upon trying another takeoff only the #3 GEN knocked offline. I went ahead with the takeoff and it reset with the GEN CONT switch in the air, and stayed online for the entire flight. I thought perhaps the issue could have been with the SSB not being in the correct position but I did not think to note it’s position when it occurred. Still, SSB open or closed should not result in losing 2 generators that are powering that side of the system with all engines running. I’m at a loss. 


Jeffery Williams

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Have you tried using the default panel state (engines running) and saving your own panel state to load? I had several issues with the provided panel states and deleting them solved everything. Although I don‘t think the generators where involved, but not sure anymore.

Edited by Ephedrin
Typos

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18 hours ago, Jetlinker said:

Thanks for the reply. I say quick turn as in I kept the sim up and running but in reality it was around 90 minutes or so. This last time around after solving the problem by disconnecting and reconnecting the drives it happened again upon advancing to 45% while beginning the takeoff roll. I pulled off and once again did a reset. Upon trying another takeoff only the #3 GEN knocked offline. I went ahead with the takeoff and it reset with the GEN CONT switch in the air, and stayed online for the entire flight. I thought perhaps the issue could have been with the SSB not being in the correct position but I did not think to note it’s position when it occurred. Still, SSB open or closed should not result in losing 2 generators that are powering that side of the system with all engines running. I’m at a loss. 

SSB?

I'm with Marc on this one.... when weird things happen always suspect the panel files.  They are not always the source of the problem but often enough with all the changes to versions we've had there is a high probability that they can cause problems.


Dan Downs KCRP

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Forgive me for my ignorance, I’m not all that savvy on the intricacies of the simulator itself. I just recently started using it to prepare for an upcoming training cycle. I’ve never actually used the panel state option or any of the provided panel state files, instead I will either begin by loading a previously saved FS scenario in which I have left the aircraft in the same state that it would have been left by us in the real world or I will start a new scenario using the default with the engines running and set it up myself. 


Jeffery Williams

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SSB is the split system breaker. There is a guarded switch for it up in the mx panel but it’s not one that is ever used. I checked it last night and that isn’t it though, the SSB relay is doing what it should be doing.  


Jeffery Williams

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24 minutes ago, Jetlinker said:

I’ve never actually used the panel state option or any of the provided panel state files, instead I will either begin by loading a previously saved FS scenario in which I have left the aircraft in the same state that it would have been left by us in the real world or I will start a new scenario using the default with the engines running and set it up myself. 

That pretty much rules out the use of panel states from earlier versions of the PMDG QOTSII.

FYI, all PMDG aircraft have a lot of stuff that is outside of the normal stuff found in the simulator.  For example the automatic flight system is all in code outside of the simulator so when you use the SAVE feature of the simulator it only saves it's "organic" autopilot.  Therefore, PMDG uses panel state files to keep track of the hundreds of variables that are outside the box.  The files have the same filename as the saved scenario and reside in the <P3D>\PMDG\PMDG 747 QOTS II\PanelState folder.

Back to the original problem.  I think we've ruled out the normal user induced problems so would you please submit the problem description on a trouble ticket at PMDG Product Support.  The support accounts are separate from sales accounts so you will have to create a new account there before creating a ticket: http://support.precisionmanuals.com

PS:  PMDG asks that we sign our full name on all posts in their forums.

Edited by downscc

Dan Downs KCRP

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On 10/19/2018 at 6:13 PM, Jetlinker said:

Hello all,

I’ve searched the forum here but cannot seem to find any posts with this issue. This is an intermittent problem that seems to occur after doing a quick turn on the ground. Just after starting all 4 engines GEN 3 and 4 are being kicked offline, and I receive the ELEC GEN OFF 3 and 4 message. Resetting the GEN CONT switch does not reset it. The only thing that gets it working is to disconnect the drive and reconnect, and even then sometimes the issue returns. I have also tried shutting down and restarting the 3 and 4 engines to no avail.  There are no active failures shown in the PMDG menu on the FMC when this occurs.   

I fly the 747-8 in the real world. I am aware that even the real aircraft has been known to have electrical hiccups during engine starts, particularly with undesired load shedding. For this reason it is customary (at least where I work) to provide a 10 second wait between each individual engine start to prevent the generators from coming online simultaneously. Even with doing this I’m still having this issue. 

 

Any suggestions?

 

Thanks,

 

Jeffery Williams

I've seen the exact same thing with the same two, GEN 3 and 4. Like you, reset does not work either. When disconnecting the drive and reconnecting fails, reloading the aircraft is the only thing that will work. 


Eric 

 

 

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