Sharing static and pitot line

While on the matter of line sharing, the following is relevant to sharing
the Total Energy line between a number of flow variometers, mechanical
(Winter, PZL, etc.) and / or electrical (Cambridge CAV II etc.)

Each of the variometers fed by the one TE source have flow through the
instrument to their own flask.

All flasks running off one TE source must be the same physically and
thermodynamically. If you mix flasks with different characteristics then
you will get cross flow between the instruments. You can try this test on
the bench provided you do it carefully. Get two identical pneumatic varios
(with hopefully little inherent instrument error) and two diferent flasks,
say one vacuum flask with heat sink material inserted and the other a same
type vacuum flask without heat sink material inside. Apply a signal via a
Tee junction to the two variometers. Note the variometer readings of the
two variometers at different flow rates, ie calibrate one vario relative to
the other. They won't read the same! Then swap the flasks between the
variometers and repeat the calibration. The relative calibration will swap
over between the varios showing that the flasks are influencing things
strongly due to their different characteristics. Install identical flasks
and the varios will resume responding together.

So use identical flasks to avoid cross flow when using a common TE source.

Roger Druce

"Istvan Csonka" wrote in message
om...
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 ?