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heathbuckley
03-26-2006, 07:07 PM
I have a '58 Tripacer and believe the pitot tube angle is off. My Pitot-Static system has been checked and found accurate but I believe my indicated airspeed is off approximately 10 KTS on the low side. :confused: I think it the culprit is inaccurate angle on my pitot tube. Does anyone have a diagram with the pitot tube angle or any information that may assist me on this. Thanks in advance.

Heath Buckley
PA-22-160
N9308D

13010
03-26-2006, 09:37 PM
You won't be far off if the pitot tube is parallel with the bottom of the wing.
J.D.

Homer Landreth
03-27-2006, 12:15 AM
Hello Heath;
The Pitot tube alignment is parallel with the longitudinal axis of the plane. Get a real small spirit level and set it on the floor of the plane and note how far out the bubble is. Then take the the level out to the pitot tube and lay it along the bottom of the pitot tube. Bend the pitot tube until the spirit level bubble matches the location of the bubble when it was on the floor. Make sure the tube is also pointing forward in azimuth, this is best done by picking any wing rib and measuring the distance from the root of the pitot tube going into the wing, and measuring the distance of the tip of the pitot tube to the same rib, keeping your measuring instrument perpendicular to the rib.
That being said, unless your pitot tube is pointing off to the Jonses, it's alignment probably is not giving you 10 MPH error. Kind of a valid question is what are you using to determine that you have that error ? Airspeed indicators in old PA-22's are as old as the plane, and they don't last forever, so getting a shop to give you an accuracy check of the airspeed indicator may save you a lot of grief and effort. (Incidently, I didn't get into the check this and check that aspect of your pitot static system because you said it was OK. If it is indeed OK, then the process of elimination leaves you with a bad airspeeed indicator).