This week we had a visit from Professor Jürgen Doneit who perform GV-Test for DULV. It was really interesting to compare the theoretical calculations to the measured resonance frequencies. Even though we have taken all the possible measures to preven flutter (for ex. all control surfaces are mass balanced), we learned a few new tricks that are not written in text books. We tested 65 and 100% mass balance. By changing the mass balance, you change the resonance frequency and make sure the wing and