I use 8x accellerated mode while flying the 747 during long flights since I don't have the time to sit here and watch it fly. It has a problem in which the engines fluctutate up and down in N1 causing auto throttles to disengage. It will continue even with autothrottles disengaged. It won't do it in 4X mode. I realize I can't fly in any faster mode but the manual suggested at least I could do 8X. Also when It does this the FMC has a message calling out a much lower altitude. Does anyone ever seen this problem? Hopefully someone has a idea.Thanks, John

Manual notwithstanding, in my experience with the 737NG 2X mode is okay but even 4X mode will occasionally experience oscillation in one or more axis or velocity and anything higher is unusable except for short intervals. There's much to like about a short trip where the STAR begins and the end of the SID transition, and there's many of them.

Are you using real time weather? Is so you need weather smoothing turned on? Otherwise at 8x significant changes in wind/pressure/temp will unpredictably affect the model. I use FSUIPC's smoothing and have no problems at 8x.

I do use real time weather and FSUIPC. I will check the settings for weather smoothing and try again.Thanks, John

I tried using the smoothing in FSUIPC still had the problem. Seemed to improve when cruising above 35000 feet and with IAS speed hold instead of MACH speed hold. John

How did you set the smoothing? I use 1knt every three seconds and 1 degree every three seconds to ensure the changes are very gradual and the sim can respond. I haven't used 8x much with these setting but if your still having problems up the change time to something like 1knt and 1 degree every five seconds. Try different settings until you find one that works best for you.

I set the smoothing to different settings, no luck, but I did notice that when the center fuel tank goes empty the problem will clear up. These engine fluctuations are so bad the autothrottle speed modes will clear nad the aircraft will lose speed and its hard to get it back up to speed. I don't know yet if its "CG" related or its something to do with the center tank having fuel in it or not. I'll have to do some more flights and check it out.Thanks, John

I use "native" FS9 weather and get this engine problem all the time in 8X accelerated mode. Also significant airspeed losses which can't be recovered.It would be better if PMDG found a fix for this rather than accept it as an FS9 limitation. It makes long haul routes impossible for me, and doesn't affect other sophisticated add-ons I have.Kevin