"Jack Harkin" wrote in message
...
How about instrument error, position error and ram air temp rise?
For the first two, consult the Pitot/static error chart or table in your
glider's POH.
That'll give you CAS (Calibrated Air Speed).
The difference between IAS and CAS has to be less than 3% or 5kt in a
certified aircraft.
Typical installations are actually very accurate, within 1kt at typical
flying speeds.

Hence, the use of IAS for calculating TAS is prfectly acceptable, in fact
done everyday in thousands of cockpits around the world. 1 or 2kt of
accuracy is usually more than what you can actually see in the instument
face.


Ram air temp rise, and compressibility are not a factor for the speeds and
altitudes we fly.
Try a 1% error at 180Kt @ 30000ft.

But if you applied that correction to TAS, the result would be called EAS,
for Equivalent Air Speed.