Hello my friends, At the moment, I'm doing an estimation and analysis of flight performance for UAV (unmanned aerial vehicle). During climbing flight analysis, I have a problem regarding calculation of rate of climb (vertical velocity), my calculation value of rate of climb seem weird, the vertical velocity (RC) bigger than velocity vector. If my rate of climb is not correct, so I have faced also difficulty to find absolute and service ceiling. I hope someone can help me to solve this problem quickly, I have already calculate it many time but the result still same. I would like to attach xls file (example of analysis table), so I really want a help from all of you here. I don't know what's the problem in my analysis. Please help me ..... If all of you don't understand, ask me for explanation.