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Re: REFLECTOR: Pitot / static accuracy




On Mon, 28 Sep 1998 09:44:46 -0400 "Andrew L. Judge"
<AJudge1@compuserve.com> writes:
>I've seen the factory put a piece of adhesive tape in front of the 
>static source on the elite and I've seen another elite do the same with
a 
>fixed bump.  I assumed it was for icing.
>
>Andy Judge
>N55AJ  FGE
>
Andy,

The bump has nothing to do with icing. Since most static ports on the
Velocity are forward of the door, it is on a facing angle of the fuselage
to the relative wind. This causes a slight pressurization of the static
port. This results in artificially low altitude readings and slow
airspeed indications. The bump, known as a trip strip, is located close
enough to the port to allow the airflow to be disrupted. Properly
located, this neutralizes any pressurization effects to the static
system.  

Improperly located, this trip strip will either have no effect or can
actually cause an artificially high altitude and high airspeed
indication. By using your GPS and making opposite direction, same
indicated airspeed passes you should be able to correct  your airspeed
readings by placing the trip strip accordingly. 

Yes, gusty winds, crosswinds, etc. can render this testing procedure
useless...soooo,
fly on a nice calm day if possible.

Unfortunately, there are no two Velocity's exactly alike, so there is not
a given trip strip size, thickness, shape, or position. Your popsicle
stick thickness is a good place to start. Just move it closer or away
from the port as necessary.

Safe and Speedy Resolutions!

Martin



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