What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Garmin AOA pitot retrofit

maus92

Well Known Member
I'm installing the unheated Garmin AOA pitot using a Gretz mount in my flying RV-8A. The existing pitot is the bent tube that I assume was standard in the circa 1998 kit. It attaches to the hard line with an elbow, and exits the wing into the airstream just forward of the middle inspection plate (bell crank access) adjacent to the forward inboard corner of the plate.

Question: Where should I install the new pitot? There is some consideration of potential interference with the tie down eye, therefore should I move the pitot to the vicinity of the inboard inspection plate, or is that too close to the prop wash?

Question: Since this is a retrofit, should I drill out some rivets and try to fasten one side of the doubler plate to the rib, or is it OK just to use the doubler on a field of skin without attaching to some structure?

Question: Generally, what color tubing is used for the AOA and pitot lines?
 
We placed the Gretz mount in the next bay outboard of the old pitot tube and used the pitot hole to mount the Garmin OAT probe. Access for riveting is through the inspection access just outboard and adjacent to the old pitot tube. It's requires a few improvisations but very doable.

Yes, we drilled out some rivets so that we could mount the doubler plate (joggle) to the wing spar flange (per the drawing).

We used red tubing for pitot, white for AOA, but that's entirely at your discretion. I don't think there's a standard, that I'm aware of anyway.

I'll try to take a picture for you tomorrow when I'm out at the hangar.
 
Last edited:
Thank you!

So you went for the outboard inspection plate... was that to avoid the prop wash?

How did you extend the pitot hard line? Soft tubing mated to the hard line, or an entirely new run?

I was thinking about using the old hole for the OAT... glad to hear that it works!
 
Not just to avoid prop wash, but generally it's a good idea to go outboard, but just to get it out of the way of the bellcrank, etc.

Used the old pitot plastic tubing for the AOA and ran a new red plastic line for the pitot. Stein has all of the transitions you need, P515, AN816, 818, 819. The photo will definitely make things clearer, so I'll make a note to put one up tomorrow evening for you.
 
Thanks for the photo. Did you shorten the metal air tubes on the pitot? Also, the OAT probe looks like you added a washer to cover the old pitot tube hole. Is it a shoulder washer or a flat washer? Was it difficult to buck the rivets when working through the inspection port? How did you mark the holes on the doubler plate? Did you remove the existing rivets and mark through the holes?

Thanks!
 
Questions for Pat

We placed the Gretz mount in the next bay outboard of the old pitot tube and used the pitot hole to mount the Garmin OAT probe. Access for riveting is through the inspection access just outboard and adjacent to the old pitot tube. It's requires a few improvisations but very doable.

Yes, we drilled out some rivets so that we could mount the doubler plate (joggle) to the wing spar flange (per the drawing).

We used red tubing for pitot, white for AOA, but that's entirely at your discretion. I don't think there's a standard, that I'm aware of anyway.

I'll try to take a picture for you tomorrow when I'm out at the hangar.


Pat,

Great job and thank you for posting. I too have the old style pitot and want to upgrade so as to install AoA.

You indicate you placed the Gretz in the next outboard bay.

Question 1: How did you know exactly where to cut the airfoil shaped hole for the Gretz mount in the bottom of your wing while still ensuring the doubler plate (Joggle) holes would still correctly line up with the rivet holes in the spar and the lower skin?

Question 2: Did the doubler plate come pre-drilled for attachment to the wing skin and the spar or did you have to drill those holes?

Question 3: Is there sufficient room to stick your hand and the Gretz though the inspection hole and the rib hole and get it in there or did you have to use a tool or jig?

I really like the idea of placing the OAT probe in the location of the old pitot.

Thank you for the picture and response.
 
Charlie,

Bob actually did the install, but I can tell you basically how it was done. You want to position the doubler against the wing spar flange and drill through the previously drilled-out rivet holes. Once you have drilled all the #40 holes through the doubler on the inside, reposition the doubler on the outside and cleco it to the outside wing skin. This will allow you to roughly trace the airfoil shape of the cutout on the wing skin. Cut out this hole but leave a little for final trim with a file when you put the doubler back inside the wing.

As for drilling through the pre-drilled doubler holes (yes, it comes with the holes pre-drilled), we used an angle drill on the inside, and, yes, there's pretty good access through the two holes. We positioned the doubler right up against the rib and added a small .032 X 3/4 X 3/4 angle against the rib and the doubler to further support the Gretz mount. You can probably see the rivet pattern in the photo.

When it comes time to mount the pitot tube, you can easily reach in with your hand and guide the 3/16" aluminum tubes and gently bend them as you feed them into the mount. We gradually shaped the aluminum tubes to the position shown in the photo. We reached in with the flaring tool and easily were able to flare the end of both aluminum tubes as shown.
 
Last edited:
Thanks for the photo. Did you shorten the metal air tubes on the pitot? Also, the OAT probe looks like you added a washer to cover the old pitot tube hole. Is it a shoulder washer or a flat washer? Was it difficult to buck the rivets when working through the inspection port? How did you mark the holes on the doubler plate? Did you remove the existing rivets and mark through the holes?

Thanks!

We did not shorten the tubes, no reason to, they are about the right length after the bend (as shown in the photo).

The OAT probe is actually smaller than the hole, so we took an AN960 flat washer that fit perfectly in the hole, was just the right thickness, and acted as a shim. We did have to slightly enlarge the hole in the washer so the probe would fit.

First you have to figure out how many rivets you have to drill out where the doubler will nest on the wing spar flange. Once you have drilled out these rivets, put the doubler in position and you can use a Sharpie to mark these holes on the doubler and check them for proper spacing. Once satisfied of the spacing, you can drill through the removed rivet holes into the doubler and cleco as you go. Setting the rivets is not difficult. It helps to use a small tungsten bucking bar.

Hope this is clear.
 
Last edited:
Thank you Pat

Pat,

Thank you very much for your very detailed response to the questions regarding the pitot install. This looks doable, even for someone who didn't build the plane (me).

I'm still trying to decide between the AFS Pro and the Garmin AoA, but either way I go this gives me perspective on the pitot mod.

I have a retired fire fighter friend with a beautiful RV-10 who's been schooling me letting me follow his panel upgrade and teaching me along the way. He would be a tremendous resource for me on this modification.

Mike...

Thanks again Pat.
 
Pitot mount

Charley,

Heres some more pics of my install. I had an AP friend admonish me to leave a service loop to be able to remove the probe, Heater element etc through the inspection plate. It's tight but can be done. Dynon alreay had a service bulliten on their AOA unit and the heater and probe had to be removed to comply. After the skin is on It's very difficult to get in there to service. Mine is in the bay outboard of the inspection cover plate.

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81335

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81817

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81390
 
Last edited:
Charley,

Heres some more pics of my install. I had an AP friend admonish me to leave a service loop to be able to remove the probe, Heater element etc through the inspection plate. It's tight but can be done. Dynon alreay had a service bulliten on their AOA unit and the heater and probe had to be removed to comply. After the skin is on It's very difficult to get in there to service. Mine is in the bay outboard of the inspection cover plate.

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81335

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81817

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81390

Mark,

Thank you for the additional pictures of your RV-7 pitot install as well as the tip about the service loop.

That rib hole looks large enough to get in there and do the necessary drilling, riveting and installing that Pat described.

Did you install a support bracket 3/4" X 3/4" angle to the doubler like Pat described?
 
I use high temp chemical resistant silicone rubber tubing for joining Nylo tubing to aluminum tubing, it may not look as nice as the fancy fittings but it's much less likely to leak and no flaring is required.
 
Charlie,
I purchased the pitot mast from Avery. The instructions have you put 3 rivets In the leading edge of the mast through the wing spar and skin, and two rivets in the rear of the mast directly through the skin. When the skin is on it has more than enough strength to support the pitot probe and is very rigid.
 
Charley,

Heres some more pics of my install. I had an AP friend admonish me to leave a service loop to be able to remove the probe, Heater element etc through the inspection plate. It's tight but can be done. Dynon alreay had a service bulliten on their AOA unit and the heater and probe had to be removed to comply. After the skin is on It's very difficult to get in there to service. Mine is in the bay outboard of the inspection cover plate.

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81335

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81817

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=81390

FYI, my antivirus is reporting that it's blocking an infection from the site that hosts your photos.
 
Us too.

We did this same thing just a few weeks ago. Much like Pat did, but we used the Safe-air pitot tube and their tubing kit from Avery. It worked very well, had all the instructions in the kit's and all we had to do is pull out the old 1/4 Van's line and follow the same rout with the new plastic tubing.
The second question. Safe-air kits, use white for static, blue for AOA., and green for pitot. We like the quick connect fittings and hope they last a long time. Hope this helps. Yours as always. R.E.A. III #80888
 
An update on the retrofit: I've cut the hole for the mast. It not the best job in the world - I might need to fill it ever so slightly... Anyway, I've run into a problem with the rivets. I've drilled and dimpled the skin and doubler plate based on the recc's of several builders both here and on my field: holes with #40 bits, and dimpled with a 3/32 pop-rivet die set. The problem is that CherryMax rivets are not available in 3/32 sizes - they start at 1/8 it seems. Should I enlarge the holes for the larger rivet size and re-dimple? Or should I try to use solid rivets? I don't own an air rivet gun or a hefty compressor. I'm sure I could borrow an air gun and bucking bar, but I'm concerned that my $100 Lowes compressor is inadequate for the job.... OTOH, it's only like 10 - 15 rivets that need to be driven, and I'm pretty sure I can get access for the bucking bar through the inspection plate...

I'm looking for recc's or suggestions, thanks!
 
What we did.

We wanted to be able to remove the Safe-Air mast if needed down the road so we dimpled for number 6 screws in 6 places 4 on the corners and 2 in the middle of the long sides. It worked very well looks good and can be serviced any time we need. Oh the three at the leading edge of the Safe-Air mast that go through the spar lip are screws now too. It is your call.
Yours as always. R.E.A. III #80888
 
An update on the retrofit: I've cut the hole for the mast. It not the best job in the world - I might need to fill it ever so slightly... Anyway, I've run into a problem with the rivets. I've drilled and dimpled the skin and doubler plate based on the recc's of several builders both here and on my field: holes with #40 bits, and dimpled with a 3/32 pop-rivet die set. The problem is that CherryMax rivets are not available in 3/32 sizes - they start at 1/8 it seems. Should I enlarge the holes for the larger rivet size and re-dimple? Or should I try to use solid rivets? I don't own an air rivet gun or a hefty compressor. I'm sure I could borrow an air gun and bucking bar, but I'm concerned that my $100 Lowes compressor is inadequate for the job.... OTOH, it's only like 10 - 15 rivets that need to be driven, and I'm pretty sure I can get access for the bucking bar through the inspection plate...

I'm looking for recc's or suggestions, thanks!

Find someone on your field with riveting experience and a compressor to help. I would finish the job with the #3 rivets, it can be done fairly easily for someone with experience. CherryMax rivets are total overkill for this job and you can avoid the redo of the dimples, etc., by just going with what you've got. :)
 
Find someone on your field with riveting experience and a compressor to help. I would finish the job with the #3 rivets, it can be done fairly easily for someone with experience. CherryMax rivets are total overkill for this job and you can avoid the redo of the dimples, etc., by just going with what you've got. :)

I did just that: the local guy who recc'd the CherryMax solution earlier determined that my compressor could handle the riveting job. He dug around in his vast hanger (actually the same size as mine, but filled to the gills with all sorts of collected parts and tools,) and came up with an assortment of "antique" but functional air tools and bucking bars. Together, we installed a doubler for my belly VHF antenna that was somehow overlooked during its initial construction, and riveted the new Gretz pitot mast. It turned out well - only had to redo one rivet, but we did chip some paint which was expected....

On a related note, has anyone tried to chrome their Gretz mast? Might look cool.
 
Garmin Heated Pitot/AOA Location

Here's the photo taken today. Let me know if you have any questions.


Pat,

I saw this post and will doing a panel retrofit soon using Garmin G3X touch screens. I currently have the standard Van's 1/4" tubing pitot that I will be replacing with a Garmin heated Pitot/AOA and using the Gretz mount. I like your idea using the old pitot hole for the OAT sensor however I was wondering if the fact that you mounted the new pitot with the Gretz mount near the outside inspection plate if it interferes with your tie down and chains when securing your plane?
 
We wanted to be able to remove the Safe-Air mast if needed down the road so we dimpled for number 6 screws in 6 places 4 on the corners and 2 in the middle of the long sides. It worked very well looks good and can be serviced any time we need. Oh the three at the leading edge of the Safe-Air mast that go through the spar lip are screws now too. It is your call.
Yours as always. R.E.A. III #80888

I know it's an old thread but I see you're still posting on the forum. Do you have any pictures? I like the idea of using screws for this installation and I noticed you live close too.
 
Back
Top