Carl,
Many aircraft have a substantially different cockpit static vs the factory
external static position.
Open cockpits with large windscreens tend to be low (altimeter reads high)
Closed cockpits are a bit of a mix. Generally cockpit static is fairly goo
d.
The underwing static position of the XS Europa factory static tube is quite
accurate.
Alternate pitot tubes with static ports are generally good provided the sta
tic port is well below the wing surface toward the trailing edge. At least
4-5 inches separation of the static tube from the wing surface is generall
y good enough for good static readings. Side of fuselage static ports are
again hit or miss and manufacturers spend considerable time getting it righ
t...
In 12AY, which is a trigear with enclosed center tunnel, rear vented D pane
l, and full door seal enclosure, the difference between cockpit static and
underwing is 2 knots and 20 ish feet. I use a simple cockpit air switch fo
r IFR equipped Europa=92s for an alternate static source and then fly and t
est and calibrate it. My choice for a small inexpensive valve is made by
Pneumadyne. I use the latching toggle for two or three way normally open
with 10-32 fitting with 1/8 barb. In my panels, I have found the 1/8 inch
tubing to be an outstanding full proof pitot static tubing. I also use a n
umber of the CPC products quick disconnects for IFR quick disconnects when
doing the biannual pitot static checks to isolate the altimeter and encoder
from A/S etc. where leaks are possible. Saves time and sometimes money on
pitot/static testing.
Flight test of a cockpit static is easy with a couple of CPC connectors to
make a quick cockpit change of static source to experiment with. I use the
same cockpit seal technique from plane to plane, so I just install the val
ve and then flight test.
Testing has to be at all altitudes, airspeeds and configurations. I tested
in increments from max cruise to stall clean and dirty from 1000 to 10,000
feet cruise and 1000 to 5000 for approach configuration. Cockpit air vent
s open and closed with door seals installed but vents in the rear bulkhead
to allow cockpit venting must be checked also.
Each airplane is different. The air rush through the tunnel into the cockp
it or door seal options change things for each aircraft as venting of the c
ockpit is non standard and builder dependent. If you seal up the cockpit a
nd wing seals things are fine with trigears, mono=92s could be slightly dif
ferent as I have never personally done an IFR mono.
Regards,
Bud Yerly
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________________________________
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matr
onics.com> on behalf of carlp101 <cparkinson@cisc-uk.com>
Sent: Friday, March 2, 2018 7:19:04 AM
Subject: Europa-List: Re: Alternate static port & Switch
Being an aircraft that does not have the ability to be configured with a pr
essurised cockpit, I've often wondered why people route static ports to the
outside world instead of just leaving the static port unconnected behind t
he panel? I discussed this recently with the LAA and they didn't see and is
sue with leaving them unconnected in non-pressurised aircraft.
Thoughts?
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