I was on a flight in the 747, ATC gave me FL440, started to climb from FL300, at FL380 it was impossible to climb or descend anymore, the plane just kept floating up and down from FL280 to FL 380, tried to disable AP and fly manually, same thing, floating up and down. 
I think the physics bugged themselves pretty badly, had to quit the flight.
Did anybody else had this issue?

If you took off without adjusting the weights, a fully loaded 747 with full fuel and pax isn't gonna climb any higher than FL350. Gravity takes over 😉 That is why you see these giant beasts use step climbs. They start maybe at fl280, and then by the end, halfway around the world, they are up at fl380. Come to think of it, FL440 is WAY higher than any normal operation of the 748 that I know of. 

Edited September 6, 20205 yr by Andreas Stangenes

13 minutes ago, Andreas Stangenes said:

If you took off without adjusting the weights, a fully loaded 747 with full fuel and pax isn't gonna climb any higher than FL350. Gravity takes over 😉 That is why you see these giant beasts use step climbs. They start maybe at fl280, and then by the end, halfway around the world, they are up at fl380. Come to think of it, FL440 is WAY higher than any normal operation of the 748 that I know of. 

But that's where ATC wanted me to be, also it didn't even want to descend, like it was caught in some bubble or some alien pulling ray...wait a minute!👽

ATC clears you to the altitude you specified in the flight plan (the navlog before the flight). The 747-8 shoudn't be able to reach FL440. Besides that, you didn't specify what your payload was and how much fuel you had loaded

5 minutes ago, EmaRacing said:

But that's where ATC wanted me to be, also it didn't even want to descend, like it was caught in some bubble or some alien pulling ray...wait a minute!👽

Well, that is either a user error or a bug with atc. Now, the 748 is a pretty messed up airplane, I'll give you that, but faulting it for not reaching FL440 is not actually a bug 🙂 

3 minutes ago, Pastaiolo said:

ATC clears you to the altitude you specified in the flight plan (the navlog before the flight). The 747-8 shoudn't be able to reach FL440. Besides that, you didn't specify what your payload was and how much fuel you had loaded

Lots of passengers and fuel for a 2k miles flight on FSE.
But still, what goes up should at least be able to come down with engines at idle and pitching down.

8 minutes ago, EmaRacing said:

Lots of passengers and fuel for a 2k miles flight on FSE.
But still, what goes up should at least be able to come down with engines at idle and pitching down.

That is true. Are you telling us that you put the engines to idle, and then .. what..? The speed doesnt go down, and the airplane isn't descending?

14 minutes ago, Andreas Stangenes said:

That is true. Are you telling us that you put the engines to idle, and then .. what..? The speed doesnt go down, and the airplane isn't descending?

exactly, and the AP was disconnected, checked many times.

It's like I hit some ceiling and then started YO-YOing there +-10000ft

I’ve not really looked at the 747 yet, and don’t intend to until it’s been either modded to within an inch of its life of completely replaced by PMDG.

However just having a quick look now , a take off weight of 315 tonnes and its giving a cruise height of F420 in the FMC, completely unrealistic I’m afraid.

1 hour ago, EmaRacing said:

I was on a flight in the 747, ATC gave me FL440, started to climb from FL300, at FL380 it was impossible to climb or descend anymore, the plane just kept floating up and down from FL280 to FL 380, tried to disable AP and fly manually, same thing, floating up and down. 
I think the physics bugged themselves pretty badly, had to quit the flight.
Did anybody else had this issue?

Don’t you wish that everyone responding had understood the issue you experienced?  I found your OP very clear. 

So!  I have not flown the 747 as I am 100% into GA.  But I can report some strange anomalies with some flights.  Anomalies that do not recur (not yet anyway) in subsequent flights in the same aircraft.  And everyone please read this next comment carefully: And those subsequent flights taken with no changes made.  None. 

In my first flight in the 172 G1000 model, on takeoff rotate the aircraft stayed in an exaggerated nose up attitude.  It took considerable yoke pressure to level off and trimming did not resolve the issue.  I looked down and could see the trim wheel rotating as I applied trim with my yoke, and the trim wheel did not return as I let off the yoke switch.  I ended the flight. Restarted the sim, and have not had that issue recur.  Again, in all of the flights, first flight and subsequent flights, loading was default and I made zero changes to the setup or calibration of my controls.

On another flight in the 172 G1000 yesterday, none of the AP buttons functioned.  I could change target altitude and heading settings, but the AP would not turn on so I could not use the settings.  I could see AP button depress when I clicked on it.  And the keyboard mapped AP functions also did not perform.  I flew a nice VFR loop over the Drzewiecki Designs Washington DC Landmarks scenery totally VFR and by hand.  Later in the day I restarted the flight and flew it again, and that time the AP functions worked normally.  Go figure.

Diamond DA62.  I have flown eight times in it.  On one flight only,  the DA62 was nearly uncontrollable in lateral handling.  I set the AP on and HDG mode and it was fine.  But when I took it out of AP I was not able to keep the wings level.  That has not happened in any of the other seven flights in the model.  I still have made zero changes to my flight controls settings.

I hope like in my cases, that your experience does not recur.

1 hour ago, EmaRacing said:

exactly, and the AP was disconnected, checked many times.

This wasn't Flight 33 was it?

Wonky Ap, i can understand. The first flight i did on MSFS was with the 747 and in the climb it coudn't keep a normal climb speed, pitching too much then overcorrecting and so on. It appears that some planes are more far ahead in being developed than others (take the A320 for example)