PDF Version HERE : RTWR General Rules FAQ_2015_v1.00.pdf
The RTW Race Rules are complicated - not because we want them to be, but rather to cover the wide array of situations and contingencies that result from running an air race around the entire world. In order to help race pilots and spectators understand the intention of some of the particularly nuanced sections of rules, we've created this FAQ.
A. The winds and weather play a crucial role in a round the world race. (If you do not declare before the race, you may fly the MSFS default weather engine.) In any case, you must stick with your choice throughout the race. It is important pilots not be able to "choose their own weather" by choosing the most favorable weather engine for each leg.
Teams publicly post the members' weather choices so that all competitors know what is happening.
A. Whatever weather engine you use, you must use realistic "live" weather. Your engine should be able produce a realism at least as rigorous as the default engine. That is, you should enable 15-minute updates, winds aloft, and turbulence. You may not use a fixed weather setting (that stops weather changes). Nor may you use a wind smoothing algorithm that keeps winds aloft constant. Nor may you fix the weather at your destination airport. Nor may you eliminate haze or wind on the ground. Surprise changes constitute part of the test of your flying skills.
Realism is the standard. Note that you may use the FSUIPC function that slows but does not eliminate the sudden wind shifts. You may, but need not, use your addon weather engine's advanced weather features such as enhanced thermals, invisibility in cloud, wake turbulence, and so forth.
The emphasis here is on live real world weather that is close to the actual experience. Most important, it must be unpredictable in the sense that if the real world weather changes as you fly, so should your simulated weather.