"The only thing that changes is the temperature."
Thank you GP, at last. Like pulling teeth!
So the temperature has risen and as we all know hot air rises therefore the scales will indicate less.
Got there eventually.
psst, how about this;
Does the TRT in the hover, actually EQUAL the a/c weight, or does it have to be ever so slightly greater in order to compensate for gravitational acceleration, due to momentary lapses in constant lift throughout the rotor disc area??