Thank you Jenny, I do understand all of your points, been flying for few years. My problem is that the plane, and it's happening to all of my models at least once in a while, is that during level flight without any elevator input, the model start pitching up and down. The oscillations are very fast and violent and usually end up in a crash. Two of my models ended up in tall grass with no damage and checks did not show any problems at all. The problem is that it happened at least once to all of my different models during last few years. I had suggestions from our club members ranging from my fingers twitching on the sticks to CG being out, but no one can point it out. The only common thing if i really think about it would be that it would happen during gusty wind condition but that would only be flying during sea breeze which is about 15 - 18km/h which is still nice flying weather, best Jan