i belive that is a known issue as of now... an easy temp solution, use launch stablizers along wing edges or under wings, then upon sim start, hit the (g) key and let the wheels drop, cycle your stating so that you release the supports and off you go.. the only major downfall is your weight distrobution has to be nearly perfect, thankfully .17 has some new features in the assembly buildings to help with center of mass and such.