Apart from that, 15 fps is way too low - it would make sense to aim for at least 30 fps, and Erik came up with an interesting idea a few weeks ago, i.e. introducing "vendor/GPU profiles" with pre-selected default settings for certain graphics card - which could be based on community feedback - analogous to the existing support for joystick profiles:
Review of FG on reddit: xpost
erik wrote:The only thing I want to do is detect the video card and based on the GL renderer name turn on ALS (or not), turn on water shader (or not), turn on the 3d city shader (or not), etc.
The default would not be touched but based on the detected video card certain options would get enabled, making the first impression much more pleasant (for first time users).
Erik
http://wiki.flightgear.org/Graphics_Card_Profiles