"Dick" wrote in message
...
Can a GPS with compass, heading & groundspeed capability be used legally
in
lieu of a separate compass and airspeed instruments on an experimental
homebuilt airplane? Or at least in lieu of the separate compass?
Thanks



Short answer, no.

The GPS is showing ground track, not heading, even though this information
is displayed on the GPS as if it were a compass. That said, once I knew
where I was going, which way I was pointing lost a lot of significance. The
GPS "compass' shows where you are actually going.

For the most part, ATC personnel are used to fast jets where the heading and
track are essentially the same. Give them a Cub and a strong 90 degree
crosswind and it gets interesting. They will say, "turn left, heading 270"
clearly expecting the blip on their radar will move westward even though the
Cub is fighting a stiff North wind while heading West and tracking
Southwest.

I fly gliders cross country and sometimes it is very important to track
precisely toward a known safe landing spot. I use the GPS "compass" for
this since it will steer me exactly over the intended point without any wind
calculations at all. Compared to GPS, a magnetic compass is nearly useless.

Bill Daniels