ComputerDoc wrote:
glide circle a REALLY nice feature as it would dynamically change
with actual glide performance (that is the GPS should be able to essentially "know" windspeed and direction and be showing a distorted circle with a longer glide in the downwind direction visually right there on screen.... as well as shrinking the circle as altitude is lost.)
I am pretty certain that after a few mintues of flight with modest change of course taking place there is sufficent information in the GPS to calculate the windspeed and direction analytically. I can almost do it by eyeballing change in groundspeed as I turn, say, 10 degress left of course and swing back 10 degrees right.
Far better than counting on unreliable Wx wind reports which vary much.
A glide perimeter is low priority only until you need to glide to an emergency off field landing . ;-)
Alex
You are able to do it because you can look at your compass and/or heading indicator and compare that to the groundtrack you see on your GPS moving map. You understand whether your engine settings are changing or your airspeed is varying due to a climb or descent. Your GPS doesn't know which way the nose of your aircraft is pointing. It also doesn't know if speed changes are due to winds or other flight dynamics.
So your GPS isn't as smart as you think it is. It lacks critical information to determine windspeed automatically. To fill in those blanks, either AP needs to code in assumptions, which may or may not be accurate, or the user needs to input the necessary information (pressure altitude, outside air temp, calibrated airspeed, heading), they way a panel-mounted GNS 430 or 530 handles it...and update those data as they change during the course of a flight.