Swindled on my ground speed
Got a question,
My wee puddle jumper cruises at 120mph indicated at 2400rpm, today there was a very light westerly wind for my east bound journey at 1000msl. The airspeed showed 120, the VFR GPS was reading 115mph which I figured was about right given the light headwind.Turned around and started heading back west but climbed to 6000 thinking I will get my usual 120 GS plus the stronger tailwind wind at that altitude,plus a bit more speed because of the altitude when I looked the air speed it was what i expected at 120 but theGPS ground speed was 103, I thought it would be up around 130 plus.
Now why would that be? Is it be because the wind gradient at that altitude may remove the tailwind? Or is the GPS is less accurate at altitude or is it the horsepower from 2400 rpm at 6000 is less than the hp at the same rpm at lower levels or is it just the way things are and I,m thinking to much about stuff and should just look out the window and enjoy the beautiful view of the snow capped highlands and leave the answers to those ground speed anomalies to others.