Pitot and AOA plumbing - when?

[DaleB]

I'm about to the point of putting the lower inboard skin on the left wing. I have not yet decided on what avionics will go into the plane, so itmay end up with a Dynon, Garmin or someone else's pitot or pitot/AOA. It will probably be heated, but not for sure. The only real decision I've made is to buy a Safe Air 1 pitot mast, which arrived today.

My question is... do I need to run pitot and AOA tubing now, before closing up the wing? It seems like if I plan to use the holes in the inboard ribs up near the main spar web (not sure if Van's punched those, or the original kit owner) I should run the tubing through them. Which brings up the next question; does one normally have fittings at the wing root so the pitot and AOA lines can be disconnected from the fuse? Seems like you'd have to in order to take the wings off.

School me on pitot and AOA lines, please! I don't want to be kicking myself later on.

 

[rleffler]

If you run conduit in the wings, running the lines at a later time isn't an issue.

I ran the Van's 3/4" conduit in my RV-10 and I pulled my AFS AOA tubes after the fact through them.

You may want to pre- run the pitot tube line. If you are thinking about running a plastic line for the pitot, you'll want to test whichever pitot you choose to see how the output tubes heat up (or not). I ran aluminum tubing in the wings and transition to plastic at the wing root.

That answers your question about wing root / fuselage transition for the pitot. I ran my AOA tubes all the way to the EFIS. But AFS did supply fittings that can be installed in the wing root to assist with the transition if so desired.

There is no "right" answer to your question.

 

[Aiki_Aviator]

Tube runs

As Bob said, no right answer here...

I did however run all the tubes for the Pitot and AOA before I closed up so that I could have them run independent of the wiring conduit.

I had them run through their own grommets and as such managed the lines separately all the way to the wing root. I chose to install a Gretz heated pitot so it made sense for me to do the lot. Part of the analysis was per below:

My questions were:

1. Am I going to have AOA?: Yes, so might as well run the lines
2. Am I going to have a Pitot?: Yes, so run the lines.

Based on the above, I ran the lines before I closed up so that I did not have to deal with any fiddly stuff later and I knew that the wings were basically done. More a procedure and process thing for me...

 

[Airhead]

I just finished installing my wings and pitot/ aoa lines. The 3 access panels made this easy. I had the mast installed early as you are planning, but waited for running the plastic tubing, using the pre-punched holes, with straight coupling fittings just inside the fuselage at the wing root. The tubing made an easy 90 degree bend as it passed in through the the lower edge of the aileron rod hole. I added slip over tubing as chafe guard.

 

[flion]

My $0.02 - if you will be using Safeair 1 tubing, they include enough connectors that you can do one at the fuselage. There are bulkhead pneumatic connectors available for the Safeair tubing (Automation Direct) but they are straight only, so you'd probably want to install them in the wing root rib. It's just as easy to use a right-angle union mounted inside the fuselage with one end going through the side, and you don't have to negotiate a turn with the tubing.

The AOA might be another matter. The AFS AOA Sport and Pro use 1/8" ID tubing. They include barb "bulkhead" fittings (no real bulkhead attachment but epoxy works) but the connection to a Safeair system is hokey and neither company has a real solution. The choice is to take a Safeair union and install a barb fitting into it or to take the AFS fitting (a modified standard union) and attach a couple of SafeAir adapters. Personally, I am doing the former. It's not very hard to do but it'd be real nice if Safeair would offer one as an accessory so we don't have to do a hack job on those beautiful components.

Dynon AOA uses standard fittings, so the same approach as the pitot works there. If you are undecided and don't want to have to snake the lines later, you can always just leave the skin off for now. I have fitted but not riveted the bottom skins on my RV-10 because I am still wiring the servos, pitot heat, etc. My plan is to fit the wings up, test all the connections (mechanical, electric, and fluid), and then remove them and do the skins before reinstalling and final test. I've already run my tubing, but I'd have access later, even if I hadn't. Another approach (easy with the Safeair tubing) is to just go ahead and run both types and leave a bit coiled up for attachment later. I may yet do that myself; I've got a Gretz pitot but if I change my mind and install a Dynon later I could use the AOA in my Dynon EFIS as a backup for the AOA Pro.

 

[DaleB]

Yeah, what I'd really like to do is run the tubing from fittings mounted at the wing root, to fittings mounted near the pitot. That way I wouldn't have any loose tubing flopping around. It looks like the Dynon pitot/AOA and the Garmin GAP-26 are physically about the same (even if they aren't interchangeable), so the same fittings would work for either one. I'm not looking at AFS at this time, so that's not an issue.

I think I'll start looking at fittings and tubing to figure out what I need. Thanks for the input, guys! Now... if only I hadn't tipped over TWO parts bins last night and covered the garage floor with screws, nuts, bolts, half a million washers, and about 1/3 my inventory of pulled rivets. At least it wasn't the regular rivets!!

 

[DaleB]

Just as a sanity check... for those of you who know more about AN fittings than I do, would this materials list be what I want if I decide to use aluminum tubing inside the wing?

• ACS 03-40300 tubing, 3003-0 VERSATUBE 3/16" OD
• AN832-3D bulkhead unions for the pitot end, with AN924-3D and AN818-3D nuts and AN819-3D sleeves
• AN833-3D bulkhead elbows for the wing root end, also with AN924-3D and AN818-3D nuts and AN819-3D sleeves

Edit: Also, I see Dynon talks about a 1/4 to 3/16 reducer. Is there any reason I should use 1/4" pipe in the wing rather than 3/16? Garmin makes no mention of plumbing sizes. I figure I'll probably need to switch to 1/4" plastic in the fuselage, but don't know why I'd need to run 1/4" in the wing (other than the snap bushings are 1/4" ID).

 

[hayabusa]

Dale,
I`m at the same point as you and I`m using the safeair1 plumbing kit, dynon unheated AoA pitot and gretz pitot mount.
I just fitted the centre spar and seat ribs from the fuse kit to my left wing temporarily so I could confirm all the things you are asking (for my situation). I ended up drawing up an interface drawing for wing to fuse so I know where to drill the holes in the fuse to pass everything through neatly and respect edge distances etc in the fuse parts.

My safeair plastic pitot and AoA tubes use the tooling holes in the wing ribs along the back of the spar. They pass behind the aileron bellcrank using a small plastic anchor riveted to the spar using the existing 1/8 tooling hole. Where they exit the root rib they curve 90 degrees aft, clear under the aileron pushrod lightning hole and connect to 90 degree fittings in the fuse skin.

I literally spent hours working out the most simple, safe, and reliable design to suit my circumstances. Don`t be surprised if you end up spending hours on it too!

 

[DaleB]

Thanks, Hyabusa. I've gone back and forth between plastic and aluminum for the wing tubing. So far all I've done is think about it and snap the plastic bushings into the holes just aft of the spar.

Knowing that the plumbing inside the fuse will be plastic, I'm thinking I may as well use it all the way out to the pitot. I'll have to transition from 3/16 aluminum to 1/4 plastic, may as well do it there. I'll take another look at the SafeAir1 kits.

 

[High_Flyer]

there is no need to close your wings before fitting them to the fuselage, if you delay the riveting of the bottom wing skins you don't have to commit to one or another pitot choice. One you've decided on avionics and pitot you can install the hardware in the wing and then close them.
Just my 2 cents...