Tim,

 

Arrrggghhh!  I forgot to mention another static issue for non-pressurized aircraft..............

 

If a good altimeter can be found, take it on a flight with it just sitting on the seat with the same baro setting and note the altitude differences at cruise speed and slow flight.  In my wee Lancair, at 185 KIAS cruise, my cabin is 300 feet higher than the panel indicated altitude and that goes to only about 50-100 feet at around 100 KIAS.  The cabin altitude is reduced slightly when air vents are opened.

 

Go ahead, give it a try - just another reason to go flying and learn more....

 

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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