On 16 Apr 2004 03:27:43 -0700, (Robert) wrote:

Hello! Can someone tell me which compensated varios do not need a
total energy probe? (no electronic compensation) Thanks a lot! Robert

While some people report good results with pitot/static TE your
results may differ. I wonder if thy've tested two identical varios
capable of being on pitot/static or TE side by side on the same
sources then on the different sources side by side. I've done this
with TE probes mounted in different places on the ship and got
interesting results.The gear doors are a good location for a TE probe.

Generally pitot and static probes/ports are much more sensitive to
sideslip than are good TE probes.(Good TE probe = Irving type two hole
probe )

You may have timing issues due to the distributed flow resistance and
capacitance of the sailplane plumbing.

Remember for pitot/static TE you are measuring two large signals and
subtracting them. Minor timing differences in the signals and small
non linearities in the measurement show up as large unwanted
transients on your vario.

These problems are mitigated somewhat by making the vario response
rather slow.(not what you really want)

I flew an ASW20 at Minden once which had a Schuemann box on a Sage
vario. The TE was OK but the thing was terribly slow compared to a
thermistor electronic vario with TE probe that was also fitted.

The problems of pitot static TE are solvable at some trouble in
installation and tuning but you are still left with the sideslip and
pitch sensitivity of the ports or probes. These can be solved also but
you end up with things like Kiel tubes for pitot and fancy static
probes which you then have to ask - what have you achieved?

The sensitivity of both TE systems to gusts is the same.

Mike Borgelt

Borgelt Instruments