Genghis
Thanks for your detailed reply, but to go back to a few points that need clarifying.
1. I think you would be shocked to learn just how accurate and reliable the equipment is that I am using, my avionics LAME commented during calibration tests and bench tests he never gets these results on the Boeing & DHC stuff he works on, so lets just say for the purposes of the exercise, they are near enough.
2. I agree with you on the theory of IAS/CAS etc and that your head / X-wind components should make ZERO difference. Thats why I am asking the question to see what sensible reasons for the observations are.
3. The observations regardless of what equipment and its accuracy shows a relative trend.....and that is really all that matters here.
4. Some have commented on a change in winds and windshear etc, and yes a slight and temporary increase or decrease due to the lag in instruments and inertia or whatever, but this would stabilise in seconds. What I have seen many times is a change that stays.
Yes turbulence and changing pitch and roll will have your speed going up and down all the time, but in reasonably smooth air in the same location doing a 5 minute leg Square Hold, it would seem that the results vary.
I will in future make closer observations, but its not me dreaming this up.....I hope.
Thanks again!
J
PS
But there is no relationship between TAS and head/tailwind component for a constant CAS value in perfectly level flight - just not possible.
Just a thought. Is there a difference in efficiency of the prop, airframe or something that changes with a different angle relative to track due to the X-W component? Does the pitot tube suffer from any effects of the same?