Eric,

Karel's scheme on his Ventus 2cxt which I intend to
copy is:

a standard fin pitot with an Ilec extension used for
the ASI and vario which is switchable to nose pitot
when the engine is running (SH include a manual switch
for this but Karel's glider switches the pitots automatically
with little electrical driven pneuatic switches)

a fin double probe for vario TE and static only - with
the engine up the TE is pneumatically switched to fuselage
static.

(The ASI system on SH gliders is specified to use the
fuselage statics and fin/nose pitots)

The problem with using a triple probe for all the vario
inputs is that with the engine running the probe TE
and ASI fin pitot are switched leaving the probe pitot
in the propwash. A third pneumatic switch could be
added but that would add more lengths and complexity
to the pneumatic plumbing and there is no real advantage
in using a triple probe pitot over a standard fin pitot
with an extension.

A very simple and sensible plan and Erwin Salzinger
who makes the probes also recommends it for MGs when
I contacted him. He makes a special order TE/static
probe that is not pictured on his website but consists
of a two pronged TE probe with the static as a central
extension. The probe is mounted with the twin prongs
horizontal so as not to interfere with the pitot probe
underneath. He says that the probe works well horizontally
and has good pitch and yaw insensitivity.

John Galloway


At 03:36 27 June 2004, Eric Greenwell wrote:
In article , says...

BTW - if considering a triple probe for a MG get a
double TE/static probe instead. That way the varios
etc can take dynamic pressure off the fin pitot (switchable
to nose with the engine on), the TE can be switched
to static and the double probe static won't be bothered
much whether the engine is running or not. Thanks
to Karel Termaat for that scheme - as used on his Ventus
2CXT.

I didn't understand this:

-are there two identical probes, each with a TE venturi
and a static?

-a single probe with two TE venturis and one static
port?

-regardless, why won't the static on the probe(s) be
bothered by the
engine propwash?

-is there a separate pitot tube, or is that incorporated
into the
'double TE/static probe'?

--
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Eric Greenwell USA