[ventus45]

The ATSB tells us that the "calibration" of the BTO's at Gate C-1 is "good", ie, we can take the calculated "bias" as given, and go from there with the handshakes (pings).

They then tell us that the "match" between the R and T channels is "good" when another "constant" of 5,000 microseconds is applied to "align" the R and T channel bursts in any given handshake sequence.

Up until now, it seems that everyone has accepted that logic.

Close inspection of the chart below makes me wonder about that.

If we look at the last two bursts in the chart (surrounded in green) comprising the climb and flight up until and including the last ACARS prior to Igari, it is evident that the "range rate" between the R and T channels is "different", as evidenced by the "different slopes" as plotted.

Now the first thing to say is that the scales are "off-set" by that 5,000 microseconds, so the origins are not the same, so the slopes are not compareable. That is obviously true, but, if the "off-set" was simply that, the actual "slope" of both channel's bursts over time "should be the same", since they are occuring together, in any given "hanshake sequence".

Therefore, "why" is there an "apparent" difference in the "slope" of the R and T channel bursts ?  Logic suggests there should be no difference. If this effect is evident so early in the "flight", what influence does it have on the analysis of all the later pings ?