Mel

Mel

Legacy Member
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Does someone have a Dynon AOA pitot that can give me some information?
Place a drill bit in each of the pitot and angle of attack holes and measure the angle between the two.
 
Should be very doable

Mel said:
Hey, let's hold off and see if it works first.
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Mel, below is the post I made about flying the Dynon AOA with the LRI probe:

http://www.vansairforce.com/community/showthread.php?t=36346

The LRI probe indicates AOA on the Dynon very nicely. Below is a sketch of the LRI probe with angles and dimensions:

http://www.ch601.org/resources/aoa/print/angleattack.jpg

There is a significant error on this drawing, however. The lower port runs straight out the end of the probe instead of having the angled opening as shown. This is a 45 degree angle between the high and low pressure ports. As drawn the probe would not present the differential pressure needed for the AOA indicator.

If you only want an AOA probe, I see no reason why a modified standard Vans pitot tube (aluminum tube with AN fitting) wouldn't work fine, just bend it down to a 45 degree angle and let the Dynon firmware do its thing. To include pitot in the same mast as AOA will take a little more work.....but we have faith in you. :)

I haven't tried using the high pressure (upper) LRI port for pitot. I suspect getting a pitot port to indicate accurately at various AOA is more difficult than the AOA side of the probe. The Dynon firmware should be able to accommodate variable AOA readings within its calibration routine.
 
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My plan is to add another line similar to the std pitot just aft of it with the new line angled down for the AOA pick-up. It may not look pretty, but it will be cheap (just like me). By doing it this way, I can experiment by bending the tube a little at a time. If it works, and I don't see any reason why it shouldn't, I'll work on looks later. I pulled the left tank and ran the new line today.

Yeah Sam, I had seen you previous post and am aware of the error in the drawing. But not being sure of the reliability of the pitot port, I thought I would try to match Dynon's angles as much as possible.
 
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2nd pressure port angle

Mel,
I imagine you have already seen the NACA tn-4351 that documents some AOA probes.

I though it was interesting that the probe with the two ports @ 90 degrees had the best slope of the delta P ratio curves ( in other words, the best feedback gain ).

I will go out on a limb and say that a roughly 60 degree angle used by Dynon is probably a reasonable compromise that provides for the utilization of a horizontal pitot port for airspeed.

Keep us in the loop. I was just about ready to stick a chunk of refined bauxite on the mill to make my LRI probe. Thanks to you and Jim for noting the LRI probe drawing issue. I had assumed :)rolleyes:) that the normalcy of the two probe faces was overiding the drilled angle of the holes, and this drawing was a result of practical experience.

Your idea of a separate angled tubing pitot is refreshingly simple. :)
 
rzbill said:
I will go out on a limb and say that a roughly 60 degree angle used by Dynon is probably a reasonable compromise that provides for the utilization of a horizontal pitot port for airspeed.
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My reasoning for using the same approximate angle as Dynon is to keep it within their calibration parameters.
 
Good Plan

With the feedback of an LRI probe lower port working with the Dynon, it looks like you have a fairly wide range of angles that will do the duty. Good luck!

BTW, does this project fit into the "Oh, I'll just do this change during my annual" category????:D
 
Funny you should mention this,

rzbill said:
BTW, does this project fit into the "Oh, I'll just do this change during my annual" category????:D
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Actually I had just put the airplane back together after the annual condition inspection. Flew a little on the first and decided to pull the left tank and run another line. Just took one day. Now everything is done except fabricating the AOA probe.
Caught my wife's cold so I'll get back on it in a few days.
The airplane will fly like it is, so no hurry.
 
Mel,

Measured 3 Dynon pitots today...mine and guccidude1's old (unheated) and new (heated). Two showed 62 degrees, and the third showed 65 deg. Might have been a little misalignment of the drill bits on the third, since the other 2 showed the same as SMO's in his earlier post.

Good luck, and looking forward to see what you fabricate!

Cheers,
Bob
 
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