Sofia Altitude Cap?

First off this isn’t a support request, just an observation at this time. Right now in the Chicago region on expert server, the Sofia 747 won’t exceed FL360. Engine RPM was at an unrealistic 118% N1 and still couldn’t climb. Weight is light, 207,581kg and pressure is 1,013hPa (760mmHg). Can anyone weigh in as to why Sofia couldn’t climb higher? I used to take this one above FL400. Thanks in advance for any information.


Maybe Chicago doesn’t allow aircraft to go higher than FL360? (I have no idea)

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I’m going to see what happens if I try now, I’ll let you know how I go

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Please do, I landed at KORD with no issues other than unobtainable altitude.

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What was your VS?
What speed where you trying to maintain?
Did you keep trim consistent?

Trim was set to 0, in other words not adjusted. VS was set to 800+ and speed was roughly 15kts below overspeed at every given interval.

Try a lower VS.

I’d advise picking up speed at lower altitude and staying at M.86 the whole way up. Don’t neglect your trim.

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Copy that. To clarify that was 800.00 VS and not 8,000. May be common sense but just to be clear. I’ll manipulate the trim next time to see if I can improve the result.

Perhaps climb real slow like 250

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800 may just be too much for it in that regime.

Go as slow as 100 VS and see if it moves at all.

FL360 still have a VS of 3900
FL380 small trouble, but lower VS allowed for climb
FL400 reached without trouble

Not sure why you couldn’t get higher, maybe you made a move to abruptly?

I concur with that thought. @zbelle I will invest more time in the climb. Theoretically, at what altitude should I lower the VS after leaving the airfield?

Could be glitch.

Heck, the 772 sometimes feels like it’s gasping for air as low as FL340.


It was all controlled by AP after FL020. I set the VS and altitude target, otherwise I only adjusted the bearing and maintained speed 15 below overspeed.

This was my original thought but I hesitate to discount physics when I can’t claim to be a pro just yet.

It is weird because I could maintain 4000VS up to FL380 then I reduced to about 3000VS and I got to FL400 without a problem? Maybe it is because I flew solo rather than online?

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Solo rather than online is a pretty substantial variable given that solo does not offer live weather. Part of that is why I included the pressure reading, my thinking is that pressure is what deterred me from lifting that big girl higher without enough molecules beneath my wings.


True, but I haven’t had issues in the past getting to FL400 on Live? Maybe it was a once off and you just got unlucky?

I also believe this to be the case. I’m not discounting your experiment in the slightest, thank you for taking the time to see the results for yourself. Regarding Sofia, I would routinely make FL400 before the dev’s put the telescope door on the actions command, before it was commanded by reaching FL400 if my memory serves correctly.

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It was controlled on your FL previously and you did have to reach FL400 for it to open, I had lot’s of fun doing that with my friends.

Don’t mention it, you wanted help, you got it! We’re a community and we are here for each other, even for the small things :)

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