ATC loses my IFR plans on long distance flights...

Is it possible that you missed some transmissions and your IFR plan was terminated by ATC?

As for the second, no idea. Winds perhaps? On 16x (or higher?) it might be noticeable and A/P can't keep up?

Um...when you set the simulation rate to 16x, you can't just leave the plane sitting there. ATC has frequency changes and such that you need to comply with. And if you don't do it, and they try and contact you for too long, they'll just dump your flight plan.

Simple fix

Leave it on 16x, but STAY AT THE COMPUTER

if the simulation rate was at 16x you definately will have missed the atc (without ever hearing it) as for the bouncing, again this is because the simulation rate is so high. little variations in pressure will mean that normally the A/P will slowly follow the altimeter in it's small variations. At 16x this will be amplified.

Hmm... I thought I stayed at the computer for most of the flight... although I went to the bathroom once, so maybe that was it...

And as for the altitude problem, it was happening at normal speed, not 16x speed.

Spuddi: How do I complete an 8 hour flight if I can't use 16x speed? That's crazy.

I'm sure you did stay at the computer for most of the flight, but like someone mentioned, at 16x you won't even be able to hear ATC give you frequency changes, let alone comply. If you want to keep your flight plan open on long hauls like that when you get your first frequency change, say the whole "thanks, going over to blah blah blah," but don't contact the next center. Then, when you pull out of "warp speed", you can simply contact the center you're in and they'll assume nothing ever happened. It's a handy little trick for long hauls.

The way you complete 8 hour flights without speeding up the simulator is to let the auto-pilot (or FMC in payware aircraft) fly the plane for you while you go and get some lunch 😉 . I've sat in the PMDG 747 cockpit for a 6 hour stretch, but that one was rough! Most people try and make Flight Simming as real as possible, so that's why you dont' hear too much about the 16x speeds =). Glad to hear you're flying the long hauls though!

there is a trick to fool the ATC: once you settle down at your cruising alt, wait for the ATC to hand you off to the next control, then reply like you normally do, switch to the new frequency, just stop there! stay at that frequency and don't contact the controller. In this way, nobody will bother you while you are away or at 16x speed. You are able to keep the flight plan and actually as you move along, the frequency changes itself. so when you wake up next morning or after a snack at 16x, you will resume the normal control by contacting the local ATC. The ACT just assumes that you are under their control all the time, they won't blame you for your delinquency... 😀

Actually, guys, you're mistaken. You WILL hear ATC. It just goes so fast that if you're not at the PC, you will quite possibly miss the calls. And if you're serious and not actually hearing the ATC, you've either got Sound Card issues or Ear issues.

I had the same problem. Turns out that I missed ATC transmissions, so my flight plan was cancelled.

On long haul night flights just go to bed.
In the morning with probably an hour or so flight time left this works......
Change from NAV/GPS to HDG hold, setting HDG to the current GPS course in the flight plan.
Press ATC button if not already displaying window and select load or create flight plan.
Find the flight load it, without having the sim move your current position.
In ATC window, simply request IFR Clearance when shortly you will receive your usual
approach instructions.