Sharing static and pitot line

On 7 Mar 2005 00:08:47 -0800, Istvan Csonka wrote:

Dear All,
I have seen several posts about how to share the TE line between
e-vario and mechanical one. Maybe I am wrong but I can not see any
post about sharing the pitot pressure (dynamic) between ASI, e-vario
(computer) and and the only one static port between e-vario, altimeter
and mechanical vario.
Any good advice or this is not a problem at all ?

The altimeter doesn't need to be connected to a static port unless you
plan on pressurising your glider ;-)
The most important instrument on the static port is the ASI, as this
measures very small changes in pressure, and the fluctuations in
cockpit pressure will make the ASI reading almost useless.
A vario on the static port will give you a completely uncompensated
vario. This is sometimes done for motorgliders to provide a VSI for
climbing under power, but would be unusual these days in a pure
glider. A vario using a capacity on the static line could give
transient errors on the ASI due to resistance in the tubing. If you
really want to do this, separate the tubes for ASI and vario as close
to the static port as possible to reduce common impedance.
Sharing the pitot line seems to be less of a problem, particularly if
the "e-vario" is a pressure one rather than a capacity type. However
if the e-vario is a flow-meter type with a typical 1 pint capacity, it
would be a good idea to separate the tubes as close to the pitot tube
as possible, for the same reason as separating the tubes to different
instruments from the static port or TE probe.
Cheers, John G.