In theory, both the butterfly and the CN have enough innards to really advance variometry, because they have the potential to measure the vertical speed of air around the glider.

If you fly in to a thermal, the g meter increases. If you pull back on the stick the g meter increases. But the gyros can tell that the glider nosed up in the latter case. So, the vario can measure "netto g" if you will, the acceleration of the glider caused by changes in the surrounding air.

This is much faster than a vario. For a vario to work, you have to fly into the rising air, g increases, F = MA does its work, the glider starts rising vertically, then the vario can start to measure it. The system based on g and heading does it instantly, at least giving a second or two earlier lift detection.

Looking at sideways g, correcting for yaw, also can tell the vario if there is a sideways gust. Looking at fore and aft g can tell the vario if the glider has entered a wind shear on the nose rather than vertical thermal.

Eventually, by comparing the GPS track through space with the relative wind, these various could also measure outside air motion directly.

I don't know how much of this is currently programmed in to either one, but the potential seems intriguing.

John Cochrane