07.06.2011, 10:10
Hi, and welcome to the community 
Few visible objects and sparse terrain features nearby might not have anything to do with it. This is because System Ram is effected by things which are not visible on the screen. Data packages and the acknowledgements for each one can be delayed in different possible ways.
Visible things on the screen are handled by Video RAM and System RAM only handles very rudimentary data on the things that are shown on screen. Image data is ignored by System RAM and is sent to Video RAM, for the most part.
We want the action on the screen to be in real time but the computer system can struggle to keep smooth operation of the program when System RAM becomes full.
Let me explain.
Since your system has only 4GB of RAM ( I consider it to be about the minimum required in today's modded IL-2 ), it is possible that your RAM is getting full after a while. This can happen while using the same gigantic map with or without many objects and so forth. It usually takes a little time for it to get full.
Reasonably sized maps and ones with a fair amount of objects do not have this problem. On the other hand, some maps are so large that there are freezes very early when there is small RAM capacity, sometimes freezing during the loading.
FPS can get low in other circumstances when your System RAM gets full and the system begins to send data to Page File Size ( size can be determined by you ). Low FPS and stuttering can occur at this time. Page File Size as far as IL-2 is concerned only stops a crash from occurring. A crash would happen if System RAM was full but with no more overflow ability to Page File Size, such as when both become full. Using Page File Size stops a crash, but does not make IL-2 run better. In this case, low FPS and/or stuttering is caused by the shuttling of data to RAM card -THEN... RAM is full so it next goes to Page File, digital acknowledgements must occur between all components, and the following packet of data is delayed in being handled - causing lower FPS in some cases but definately increased stuttering.
Low FPS is always caused by some kind of delay in the processing of each packet of image data. It's a delay in the processing of one frame of image. This general statement has many possible causes, but I will give you the most likely by the information that you gave us.
Though you are flying in an area with few map features and objects, you could have full RAM, because the System RAM usage has to do with the whole map and all invisible objects, vehicles, events, server/ client communications, and other data, visible or not. Video RAM only comes into usage when you actually see something on the screen. System RAM is used for the other things not visible. These things are generally true with a few minor exceptions that I will not cover here.
Since you write that there isn't much in the way of features or objects on the screen when FPS drops, then Video RAM is not the issue.
System RAM becoming full is a possiblity. Let me know about the size of the map and amount of planes and objects in the mission.
Malware or hacking can cause your system to be bogged.
Another possiblity which does not seem to apply here is that the InterNet connection is not fast enough or the data stream not broad enough. Today's modded IL-2 really needs true broad band InterNet for online play.
Another remote possibility that your branch of the InterNet system is reaching system capacity.
Check to make sure that your system is not overheating.
If you do not have this problem on other maps - especially from the same server, then that would eliminate many things and shed light on that map as being the focus of trouble.
I hope that this helps.
Fireskull
Few visible objects and sparse terrain features nearby might not have anything to do with it. This is because System Ram is effected by things which are not visible on the screen. Data packages and the acknowledgements for each one can be delayed in different possible ways.
Visible things on the screen are handled by Video RAM and System RAM only handles very rudimentary data on the things that are shown on screen. Image data is ignored by System RAM and is sent to Video RAM, for the most part.
We want the action on the screen to be in real time but the computer system can struggle to keep smooth operation of the program when System RAM becomes full.
Let me explain.
Since your system has only 4GB of RAM ( I consider it to be about the minimum required in today's modded IL-2 ), it is possible that your RAM is getting full after a while. This can happen while using the same gigantic map with or without many objects and so forth. It usually takes a little time for it to get full.
Reasonably sized maps and ones with a fair amount of objects do not have this problem. On the other hand, some maps are so large that there are freezes very early when there is small RAM capacity, sometimes freezing during the loading.
FPS can get low in other circumstances when your System RAM gets full and the system begins to send data to Page File Size ( size can be determined by you ). Low FPS and stuttering can occur at this time. Page File Size as far as IL-2 is concerned only stops a crash from occurring. A crash would happen if System RAM was full but with no more overflow ability to Page File Size, such as when both become full. Using Page File Size stops a crash, but does not make IL-2 run better. In this case, low FPS and/or stuttering is caused by the shuttling of data to RAM card -THEN... RAM is full so it next goes to Page File, digital acknowledgements must occur between all components, and the following packet of data is delayed in being handled - causing lower FPS in some cases but definately increased stuttering.
Low FPS is always caused by some kind of delay in the processing of each packet of image data. It's a delay in the processing of one frame of image. This general statement has many possible causes, but I will give you the most likely by the information that you gave us.
Though you are flying in an area with few map features and objects, you could have full RAM, because the System RAM usage has to do with the whole map and all invisible objects, vehicles, events, server/ client communications, and other data, visible or not. Video RAM only comes into usage when you actually see something on the screen. System RAM is used for the other things not visible. These things are generally true with a few minor exceptions that I will not cover here.
Since you write that there isn't much in the way of features or objects on the screen when FPS drops, then Video RAM is not the issue.
System RAM becoming full is a possiblity. Let me know about the size of the map and amount of planes and objects in the mission.
Malware or hacking can cause your system to be bogged.
Another possiblity which does not seem to apply here is that the InterNet connection is not fast enough or the data stream not broad enough. Today's modded IL-2 really needs true broad band InterNet for online play.
Another remote possibility that your branch of the InterNet system is reaching system capacity.
Check to make sure that your system is not overheating.
If you do not have this problem on other maps - especially from the same server, then that would eliminate many things and shed light on that map as being the focus of trouble.
I hope that this helps.
Fireskull