This last week, while tracking a radial on a VOR, at low level (3000') we had a strong headwind around 20 knots, from the 10 oclock position, at a point in time we quickly entered a less headwind area, say 10 knots, the wind vectors all changed and our GS improved. The TAS improved also by several knots
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This may be a red herring, but if you are measuring tas, then you must also be measuring air temp and alt to get the right answer. If you aren't using a proper tat probe and just using a simple probe in the airstream, the temp measurement may not be accurate for all conditions of airflow. There may also an effect from the static port w/respect to small variation in measured alt value as the wind changes direction.
Do you get the same effect using a mechanical asi ?...
Chris