Pitot tube attachment

[Shipl14 19]

Anybody have good pics of a pitot tube attachment? Want something that can be attached after covering.

[wypaul 448]

I used a steel brake line with flared on nut and installed a fitting to match inside the wing.  Cheap and easy to replace.  Not sure if I have pictures but I will look.

https://www.autozone.com/brakes-and-traction-control/steel-line/ags-poly-armour-steel-line/85322_0_0

cut the tube to length discard the other end or save it for a spare.

Edited 20 Jan 2019 by wypaul

[wypaul 448]

Here is the only picture I could find.

[sioux201 84]

 To Hard to explain, I brazed  nuts on a 3/8 tube with a quarter inch ID ,  tapped through for 832 bolts to pinch the quarter inch aluminum Peto tube  thatwill slip inside

[Turbo 162]

For what it's worth, the Pitot tube probe head need not be very far below the wing's lower surface.  It just has to be clear of the viscous boundary layer of the wing's lower surface.  This is typically very thin, like a few hundredths of an inch, unless, of course, the flow under there is separated (not too likely!).  It senses the total pressure, i.e. the sum of static pressure and ram, impact, or dynamic pressure.  The total pressure is totally unaffected by the static pressure field around the wing - as long as it's clear of the viscous boundary layer around the wing at that location.  The total pressure is very easy to measure correctly, as the probe can even be misaligned by, say, 10 degrees, and the total pressure error will be less than 1%.  Align the probe tip parallel to the aircraft centerline and parallel with the wing's lower surface at the probe tip location, and you're good to go.  I say all this since a large standoff increases the chances of the probe being damaged.  The IAS is reckoned from the difference between total and static pressure.

The real airspeed error comes from the static pressure measurement, which is fiendishly difficult to get right.  What do they do on our airplanes?  Just leave the static port on the ASI open to the cockpit pressure, and live with the very systematic error.  We could calibrate out this error if we could get a good static pressure.  Static pressure is influenced by the airplane's presence, so getting a good one involves  putting the static pressure probe sufficiently far away to zero those effects, and somehow nulling out the AOA & yaw effects.

-Turbo, reired Boeing aerodynamicist and former associate professor of aerospace engineering, Avid C owner