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Date: Wed, 03 Oct 2012 14:04:57 -0400
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From: Dave Saylor <dave.saylor.aircrafters@gmail.com>
Subject: Alternate Static Requirement
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FAR 23.1325   Static pressure system.

(b)(3) If a static pressure system is provided for any instrument, device,
or system required by the operating rules of this chapter, each static
pressure port must be designed or located in such a manner that the
correlation between air pressure in the static pressure system and true
ambient atmospheric static pressure is not altered when the airplane
encounters icing conditions. An antiicing means or an alternate source of
static pressure may be used in showing compliance with this requirement. If
the reading of the altimeter, when on the alternate static pressure system
differs from the reading of the altimeter when on the primary static system
by more than 50 feet, a correction card must be provided for the alternate
static system.

******************************************************

The way I read this is that if you don't have a heated static port, and
there's any chance that ice will block your static port, you need an
alternate static, VFR or IFR.  I know this seems to apply to "normal,
utility, etc., and not experimentals, but your op limits will say you need
a static check per part 43 appendix E, which then refers back to part 23.

We had an a customer's plane go all goofy when water in the static line
would freeze at altitude.  Utterly VFR but an alternate static source still
would have come in handy.

McMaster-Carr makes an nice little valve (P/N 6791T21) that looks like a
toggle switch that fits the bill nicely.  It's about $15.

Dave Saylor
831-750-0284 CL

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<h5>FAR 23.1325=C2=A0=C2=A0=C2=A0Static pressure system.</h5><p>  (b)(3) If=
 a static pressure system is
 provided for any instrument, device, or system required by the=20
operating rules of this chapter, each static pressure port must be=20
designed or located in such a manner that the correlation between air=20
pressure in the static pressure system and true ambient atmospheric=20
static pressure is not altered when the airplane encounters icing=20
conditions. An antiicing means or an alternate source of static pressure
 may be used in showing compliance with this requirement. If the reading
 of the altimeter, when on the alternate static pressure system differs=20
from the reading of the altimeter when on the primary static system by=20
more than 50 feet, a correction card must be provided for the alternate=20
static system.</p><p>******************************************************=
</p><p>The way I read this is that if you don&#39;t have a heated static po=
rt, and there&#39;s any chance that ice will block your static port, you ne=
ed an alternate static, VFR or IFR.=C2=A0 I know this seems to apply to &qu=
ot;normal, utility, etc., and not experimentals, but your op limits will sa=
y you need a static check per part 43 appendix E, which then refers back to=
 part 23.</p>

<p>We had an a customer&#39;s plane go all goofy when water in the static l=
ine would freeze at altitude.=C2=A0 Utterly VFR but an alternate static sou=
rce still would have come in handy.<br></p><p>McMaster-Carr makes an nice l=
ittle valve (P/N 6791T21) that looks like a
 toggle switch that fits the bill nicely.=C2=A0 It&#39;s about $15.</p><p>D=
ave Saylor<br></p>831-750-0284 CL<br>

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