I've been doing some homework on how to
calibrate airspeed indications and get the TAS of a plane. Given 3 GPS tracks
taken at the same airspeed you can compute a complete solution for the heading
on each track and the TAS.
Folks might be interested in my spreadsheet which contains real data from my
plane at low altitude. I will gather some more data over
time.
You can
find my spreadsheet via my Soaring and Flying page at: http://www.dragonnorth.com/soaring.html scroll
down a bit there is discussion a link to a reference document and a link to the
spreadsheet itself.
My true
airspeed as computed from my airspeed indicator is about 14 knots faster that
the measured result.