From: Sky2high@aol.com
Message-ID: <67.a841a92.2710739c@aol.com>
Date: Sat, 7 Oct 2000 08:39:56 EDT
Subject: Static Ports
To: lancair.list@olsusa.com
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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Rob, et al,

Static port position error is determined by testing a proposed site against a 
site yielding true pressure.  Lacking any test equipment with true static 
pressure available, such as CAFE uses, we try other techniques.  As you 
pointed out, airspeed is only useful to determine that there is error in the 
pitot/static system, not where it lies.  Flying formation with a buddy in a 
certified plane helps check the static data (within FAA required sloppiness). 
 It turns out that the Piper-style blade had position error for both ram and 
static readings, but the readings were steady.  The giant chrome pitot/static 
had static ports in the top and bottom of the tube.  It was very sensitive to 
attitude and must have been operating in a slightly turbulent area beneath 
the wing, leading to a very twitchy altimeter needle.  Those static ports 
were definitely in the wrong place.  Lancair's recommended location, 
utilizing both sides of the airplane, yielded no static "position" error.  
Then the pitot location was determined to be accurate at the speeds tested by 
comparing true airspeed against the average GPS groundspeed resulting from 
flying the legs of a triangle (120 deg turns, constant altitude).

Ask me what time it is and I will tell you how an hourglass works.

Scott Krueger
N92EX
  
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