REFLECTOR: Pitot static problem

[Jim Agnew]

I have the same probe and all I did was slide an O ring about 1/8" in dia. over the probe and rolled it back and forth until I found the proper point I then cast a small ridge on the top & bottom of my probe using Aeropoxy construction adhesive and it works fine.  Does your probe have top and bottom ports? That is why I have the bump strip on the top & bottom.  After casting I sanded and filed the strips on the front side to a ramp and vertical on the backside that is almost touching the holes.
 
Jim
 
James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying 



----- Original Message ----
From: Laurence Coen <lwcoen at hotmail.com>
To: reflector at tvbf.org
Sent: Saturday, September 2, 2006 12:51:09 PM
Subject: REFLECTOR: Pitot static problem


I have a Kolsman, shark fin pitot static probe on the nose of my plane.  I have determined that the static port is not usable in this configuration.  Apparently the pressure wave extends enough ahead of the nose to cause a static error of approximately 0.25 psi at cruse. This in turn drops the airspeed indication some 30 to 40 knts and lowers the altitude by over 500 feet.  My first attempt at a fix was to install a safety wire "bump" ahead of the static port.  This reduced the altitude error to about 150 feet but created a new problem.  My IAS for went from 60 knts to 70 knts for Vso.  This means that my true speed is 10 knts slower that the IAS.  A feller could get hurt that way.  After looking at a number of pictures of installations of this type of probe it became evident that it needs to be mounted on about a 3 foot boom.  Not what I wanted to do.  I installed a static port beneath the pilot side door.  Now both air speed and altimeter are behaving as they should.
 
Larry Coen
N136LC
SE/RG Franklin/IVO
 
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