More than observation, but a thorough test program to make all the performance graphs, V speeds, range, etc. A lot more than what is required for the Phase 1 test hours. I had more than 40 hrs in the test period in the little simple SSSC. Everyone who has flown it, said it was one of the best little airplanes they have flown. A lot of tweeking. Its all about the details.When I read this, Emperical comes to mind.