Hi, I'm having some trouble with my IB Extended Essay. I want to do some flight testing in a Piper PA-38-112 Tomahawk (carb. recip. single, fixed-pitch prop). The measuring equipment available to me is an airspeed indicator, altimeter (set at 1013hPa for pressure altitude), outside air temperature and tachometer. I already found a way to find RPM at a power level and pressure altitude. The thing is that I'm still unsure on what to investigate. I first thought of finding true airspeed at different altitudes and power settings, but my physics teacher says that's not scientific enough. He says I should find the coefficient of drag, but the whole induced drag thing can get quite complicated without an angle of attack indicator. Any suggestions for what I could do? Have some idea of prop efficiency at different tip speeds, but I'm still unsure.