Wind and Groundspeed
I can't get an answer to the question below which came about when I was practising for the diversion part of my skills test.
As a rule of thumb, if the wind is 90 degrees to your heading you make no adjustment to your groundspeed.
Having played with my new toy (CX2 flight computer - why do the FAA allow it for exams and the CAA don't??) I find that this is not the case. The higher the wind speed the more the groundspeed changes. Why ??
Anyone know the definitive answer ?
P.S. Passed my skills test last month, so this is just to satisfy my curiosity.