Pitot tube installation

[BravoGolf]

I am considering using a boom style pitot tube on my Patrol. I have considered using the AN5812 style pitot tube and mount but I like the look of a boom style. There are three options that I can find for a boom.

1. Build my own using the AN5816-1 "sharkfin" style. I like the look (old aircraft) of this pitot static system, but I would need a third party AOA system.
2. Using the Dynon boom. This supports AOA but is not drilled to drain water like the Dynon AN5812 style. I would need to add some water capture capability to the pitot / AOA lines.
3. Use the Steen boom. This does not support AOA as well, so back to a third party AOA.

Has anyone tried using an AN5816-1 style pitot static boom? If so, any problems with accuracy?

While on the topic of booms, does anyone have any photos of the retention device used to attach the boom to the leading edge of the spar. Eric has a few images on his CD, I was hoping to see how others might have solved this design. A few mention it on websites but don't show any photos of where it is attached to the spar. I'm planning on the fourth "bay" in from the tip or just outside the aileron support frame.

Thanks

 

[Battson]

I strongly advocate for the Dynon style of AOA which is integrated with the headset audio.
I firmly believe this would save lives every year if installed more widely, no contest with a basic stall warning or visual-only AOA.

 

[BravoGolf]

I have the Dynon AOA pitot tube on my RV . I was just looking for other options that keep the look of an older tail dragger while keeping the AOA functionality. Advanced Flight sells a stand alone AOA system that has audio, but that means two additional tubes running into the wing and its not cheap.

 

[haribole]

Hi Scott, Not sure if this is still relevant for you, I am using the 5816-1 pitot tube in a boom, and so does Russ Erb. I am not flying yet, so can't comment on the accuracy, but surely Russ can.

 

[BravoGolf]

I hoping to see someone's installation. In the meantime I have done been looking at older aircraft that have a boom style pitot tube. I have Russ' CD and looked at his installation. In the end I purchased a Dynon boom style pitot tube and have decided on a mount that is a cross between a Cessna 195 and Bell 206. Both use a mast that supports the pitot tube and I am just finishing the design and waiting on the appropriate parts. In short there will a base mount on the spar (similar to the Steen Aero) and a second support mount about 1/2 way between the spar and the leading edge.

 

[Nev]

Scott did you go ahead with the boom pitot mount ? Any pictures? I’m searching for a way to mount mine.

 

[BravoGolf]

Nev,

I went through a few variations before settling on the AeroSteen pitot tube. It bolts to the forward spar much like the one in Bearhawk book.



https://secure.steenaero.com/Store/s...68CF89D388401B

I tried fabricating a mount for the Dynon tube but decided to abandon it in favor of the AeroSteen product. Here is what I attempted to fabricate. Using 6061 I brazed a mount together which would bolt to the forward spar. A barrel (again 6061) to hold the Pitot tube would bolt to the mount and then using set screws the Pitot tube is held in the barrel. The barrel gives the additional length necessary, gives a manner to mount the Dynon tube and allows the whole thing to be disassembled should there be any damage (kids swinging on the tube.) In its final version the barrel extended through the leading edge about 3" and the Pitot tube another 6". Not pictured is a slot cut in the side of the mount so the two pressure lines (pitot and AOA) can be connected. I brazed four or five to get a couple that I liked and then put a few in a vise to beat until they failed. Brazing seemed strong enough to handle this task, but if you can weld aluminum that would probably be a better choice.



Inside the leading edge I added a Z angle piece of aluminum riveted to the nose rib on the other side of the flange. I actually moved the stiffener from one side of the nose rib to the other, so the Z angle is riveted to that stiffener. I mounted two nut plates to the Z angle to screw a strap to secure the barrel of the Pitot tube for additional strength. All of the that drove the location of the hole in the leading edge. All this was done before riveting the leading edge skin in place.




Sorry for the long post. There will still be an AOA capability but not using the Dynon product. I am using the OnSpeed product and a second pressure tube for that installation.

Scott

 

[spinningwrench]

I ordered a Gretz Pitot tube Mount Bracket to go along with a Garmin GAP 26 Pitot/AOA Tube for mounting on my Patrol project today.

 

[Nev]

I ordered a Gretz Pitot tube Mount Bracket to go along with a Garmin GAP 26 Pitot/AOA Tube for mounting on my Patrol project today.

Do they do a mount for a boom type pitot ?

 

[spinningwrench]

The Gretz mounting bracket comes straight down from the bottom of the wing and the Garmin AOA pitot tube plugs in and turns at a right angle. You can see both items at Aircraft Spruce.

 

[BravoGolf]

Nev,

I did a lot of research and I don’t believe anyone makes a mount for the Dynon boom pitot tube. That’s why I went down this road

 

[Nev]

Here my “proof of concept” for a mount.
My plan is to widen the two holes in the rectangle extrusion and weld the tube into it. I’ll cut away more of the rectangle extrusion and bolt that to the main spar. The hose clamp holds the Pitot in place nicely.

Interested in feedback/comments.

 

[jaredyates]

Will you bolt through both sides of the extrusion? I used a 1/8 bar stock in that position. Seems like as it is you'll be tightening against the cross section which could lead to deforming it. You may want to make provisions to raise and lower the part that meets the spar, so that you can adjust to get the angle right. If you haven't already drilled the leading edge of the wing, my recommendation would be to switch to the other type of tube.

 

[BravoGolf]

If you are placing it outboard of the flap the spar web in that area does not have any additional material other than the caps. So there is a little flex in the material. I riveted a doubler to the spar web underneath where I mounted the Pitot tube. Even with the doubler there was still a little flexibility at the tip of the tube. Enough flex that I added to the Z angle to the nose rib. I considered adding an additional reinforcement outside the skin, something similar to what is installed on many helicopter Pitot tube installations. In my case the Z angle added sufficient strength that I decided that was not necessary. There is more flex in my Dynon angle mount on my RV than on this installation.

 

[Nev]

Thanks Jared, I would cut the square extrusion away at the ends so the bolts are only through the rear part.

When you say the other type of type, which type do your mean ?

 

[jaredyates]

The l-shaped type. It's much more common and supported, and it's available in a heated option.

 

[Nev]

Thanks Jared.

 

[Paul Johnston]

3/8 aluminum 5052- leftover fuel line-18”and threaded on one end-attached block on main spar with threaded hole to accept pitot tube. I keep a couple spares-easy to replace. Works perfect