HII am running 747X on Vista, and i'm in the middle of a flight from London Heathrow to Johannesburh, South Africa. The problem is firstly that my FMC says that MAX ALT is FL317... This can't be right? Secondly I can't even reach FL300 because the speed drops so much that I am afraid off stalling :S . I now cruise at FL200, (I tried to go higher but the even with a climbrate of 100 ft/min the speed would drop below the "red tagged dots") with a IAS of 270 TAS 417 and GS about the same. I am off course pretty heavy loaded since it is an 11 hour long flight. I think I started with about 90 percent fuel and 2/3 full pax load. Any one experienced something similar, or any one know what's wrong?

The beast will climb to about FL300-310 when taking off at MGTOW, and that's with care. If the winds are shifting (common in FSX) then you're not going to get that far. Your climb speed sounds way too low, off the top of my head the speeds should be about the same as your econ cruise speed (320KIAS/0.85M). The lower speed will result in the problem you experience.The climb is long at gross, it takes over 25nm just to pass 10,000.

I know the speed is way too low, but I am running my engines at nearly 100% and the speed still remains low even when I climb with 400 ft/min :SBtw, I have a tailwind of about 7 kts now

I recommend some short flights (e.g., 2 hr like KORD-KMIA an actual 744 route for Polarair). Get used to the systems, especially VNAV and A/T. Note that she accelerates to the 300+ climb speed after climbing through 10,000. Much harder to accelerate the higher you go because the thinner air (half the air density is at 14,000) restricts the amount of excess thrust.Are you using VNAV, V/S or LVL CHG?

Xmagnus, (sorry, I don't know your real name since you didn't sign your post as per forum guidelines)Are you by any chance doing these flights online with FSInn? If so then turn the FSInn weather off and use either FSX's downloaded weather or something else like Active Sky. This is a known issue with FSX/FSInn and causes the exact symptoms that you've described. I could be wrong but it sounds spookily familiar!

Ok, thanks Bill, will try that and the other tips i've got :) Yes I fly this flight online on VATSIM with FSINN.I actually have flown quite a few flights with the queen but none as far as to south africa. I used V/S on the climb of this flight and changed to VNAV when I reach my "Cruise level" off FL240 or so.Magnus EliassenENGM

Hi MagnusIn that case it is definitely the FSInn weather that is causing your problem! Of course excessive weight will also slow and limit your climb but if you're only managing FL240-FL260 then that is the boundary at which the temperature issue becomes a major problem. My solution of turning off the FSInn weather (click the cloud next to the Vatsim button to turn it off) and using something else WILL work.See you at ENGM on Vatsim sometime, I'm a regular visitor in the 747X or 737NG (and a certain 767 ;-) )