XPLM_API void XPLMReinitUsersPlane(void);
This function recomputes the derived flight model data from the aircraft structure in memory. If you have used the data access layer to modify the aircraft structure, use this routine to resynchronize x-plane; since X-plane works at least partly from derived values, the sim will not behave properly until this is called.
WARNING: this routine does not necessarily place the airplane at the airport; use XPLMSetUsersAircraft to be compatible. This routine is provided to do special experimentation with flight models without resetting flight.