Hi guysWell I had this problem about a year ago but without me doing anything it just disappeard untill 2 days ago and I have made 4 flights and in al of them I have had this problem, Here it goes, Cruizing at Fl350, everything seems normal, suddenly A warning comes up ">Altitude Alert" and soon I get a message in FMC saying Max ALT something stupid like FL 173 or 168 (Past two Flights) and when i delete this message and check CRZ VNAV page it showed that OPT ALT was FL344 so flying at FL350 was reasonable then the worst part begines,747 starts to descent and going off course, ( looks like its going on a holding pattern, start turning left or right), AP is engaged as well as VNAV and LNAV eventually, It is the most annoying problem Ive ever had in FS since PMDG747 is my main AC.... So guys if you can think of anything please let me know. P.S I use AS6 and load the 747 using the load Manager. Thanks Navid

I have seen very strange things happen using AS6 if your not using weather smoothing in both AS6 and/or FSUIPC. If your not using it I would suggest turning it on and seeing if the problem persists. If you need help setting up there is a lot of information in the forum, try doing and advanced search.

Hi FalconIve been using pmdg 747 just after the first week it came out so as AS.Never had problem at all until about a few month ago when it started and I didn't use it for 2 weeks and after that it was fixed.it was ok for about 6 months untill last week.Weather smoothing is checked on both fsuipc and AS6.Thanks for you help.Navid

What settings are you using in FSUIPC. I use 1 knt and 1 degree changes in wind every 3 seconds. I also have barometric pressure smoothing turned on.

This only happens to me on occasion if I go into menu settings perhaps or save the situation without pausing first - whend oes it happen to you? (With me, the engines momentarily fail - hence the max alt message and the descent!)Perhaps it's not the same as you though?

Hey GuysIn fsuipc I got the wind chanes 1kt and 1 degree every 5 secs.And it just happens when i only sitting and monitoring things...Thanks

When it starts having issues, what's the TAT?

Hi thereThanks for reply, for example today it was at -17 when it happend.Thanks

>This only happens to me on occasion if I go into menu>settings perhaps or save the situation without pausing first ->whend oes it happen to you? (With me, the engines momentarily>fail - hence the max alt message and the descent!)>>Perhaps it's not the same as you though?That's exactly what I'm experiencing sometimes. Do you have any solution for this problem?CheersPaul

NavidHad this same thing myself whenever I change something in the weather.Pressing the VNAV button a second time seems to re-engage the autothrottle. (Look at the top of the PFD at the throttle mode control when it occurs. Seems the autothrottle is momentarily disengaged when going out to en external routine).Peter

Hi folks, sorry to randomly chip in but I had this exact same problem myself yesterday on the way to HK. Cruise Alt was FL350 but the FMC was saying max alt 13500, and VNAV mode was disengaged. In fact the modes were switching on and off all over the place with lights flashing on and off on the MCP. The plane seemed to completely lose it. Could you summarise how I would go about fixing this problem?Many thanks,Tim F