Tim,

 

Yeah, get it accurate because there's even more to it than that.  Sometime before the Phase I flight testing was completed and every two years thereafter the FARs require testing of the static system, the sensitive altimeter and the pressure altitude encoder used currently for transponder Mode C replies.  However, while that ensures the integrity and accuracy against test data, there is no in-flight check on the accuracy of the static port and system for vertically locating the aircraft. 

 

Some of this will be interesting with NEXGEN (ADS-B) since the precision WAAS GPS will provide data for locating the flight on the "globe" model used by all the other aircraft in your traffic 30 NM hockey puck and as broadcast on ADS-B Out.  Of course, if flying below 10,000 you may be relying on some other guy's crummy Mode C approximation of his altitude.   True Speed will also be taken care by the GPS data for your "force" vector.  (Eerie, eh?)  Oh, that's right, the wing only cares about accurate indicated airspeed to hold everything up........

 

Uh, I'd get the static fixed so it was right.  Maybe fly level with someone's certificated craft in formation and compare (altimeter error adjusted by each guy's logbook entries).

 

Grayhawk 

 

Exactly...and so would be wind display and things that rely
on getting an accurate TAS.  That's why I actually change ports
to get the error low.  I don't know that without a lot of work
a person can guarantee static port accuracy down to the 0-1kt
range, especially when it changes with cruise speed, but I
think it's very worthwhile to try to minimize the error.  As
Grayhawk says, if it is static error, it could mean altitude
is off by a long ways too.

There are ways to do things like build up little dams in front
of or behind the static port, to test what effects you can
have and make it read accurately.  The first step though
would be a good leak test.  Once you know the system is tight,
and you make sure your OAT probe is accurate and all the puzzle
pieces have been inspected, it isn't too big of a problem to
just troubleshoot port location error. It does take a few test
flights, but this is what I see as our responsibility as homebuilt
pilots...to make sure we can match quality and standards to
certified levels.  What I find is that if you do the
diligence on your systems, it will pay in rewards of everything
working well and being accurate.

Tim


On 8/20/2012 7:07 AM, Sky2high@aol.com wrote:
> If your static port is off, so is your indicated altitude - by a
> lot.................
> Grayhawk
> In a message dated 8/19/2012 1:19:03 P.M. Central Daylight Time,
> Tim@myrv10.com writes:
>
>     Could it be static error...maybe port location, or other?  Mine was
>     off by 8 kts (reading low). A rework of the port to a domed one and
>     my error is now 2kts low.  But, depending on your particular port
>     issue if any, yours could be reading high.
>     Tim

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