AOA Installation

I have a couple of questions for anyone flying with one of Advanced Flight Systems' AOA instruments. I just got my 'A' kit today so I can install it in the leading edge of my wing while the wing is still under construction.

1. The AFS manual says that the best location for the pressure ports is the outboard wing bay. I also have the Duckworks landing lights mounted there. Have any of you placed the ports in other locations? I'm mainly wondering whether the small gap between the plexi lens cover and the leading edge skin would cause any airflow problems for the pressure ports.

2. I'm not clear on the location or size of the drain hole in the bottom of the leading edge skin. I know I need to drill a hole to insert the drain tool into so that I can let water out of the air/water separator attached to the top of the skin, but there is no fitting running from the drain to the bottom of the wing. Am I just supposed to drain the water into the leading edge bay? If so, what size drain hole did you drill?

Thanks for the help.

Craig Schwartz
RV-8 Wing Kit
Santa Rosa, CA

The AFS manual says that the best location for the pressure ports is the outboard wing bay. I also have the Duckworks landing lights mounted there. Have any of you placed the ports in other locations? I'm mainly wondering whether the small gap between the plexi lens cover and the leading edge skin would cause any airflow problems for the pressure ports.

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I had this exact question about six years ago and discussed it with Jim Frantz. He wasn't sure, but thought it might be a problem. On his advice, I moved the ports in one bay and the system works well.

I did one other thing that is unusual, however. I reasoned that the AOA was a backup to the airspeed indicator, so I didn't want a single point of failure in the system. I put a second blade type pitot-static head on the other wing to give the AOA its own source--I didn't tap into the main pitot-static system at all.

I really like the AOA, and it is my primary speed reference for approaches.

I have a short video clip here that includes a landing with the AOA. It may be too compressed to really tell what's going on, but the lights are arranged left to right just above the attitude indicator on the EFIS. The "Angle-angle-push" sounds just before the wheels touch.

homepage.mac.com/flyeyes/iMovieTheater24.html

James Freeman

1. I have the AOA ports on the left wing in the specified locations, and also a Duckworks landing light in the same bay. My unit works as advertised. I think this is a non-issue.

2. There is a long (7 inches or so?) machined black plastic piece which attaches to the upper drain port and protrudes from the lower wing skin. Perhaps you didn't get this in your kit? A picture would be worth 1K words, but unfortunately I don't have one. Maybe someone else does?

Thanks for the replies. I saw the plastic fitting you are talking about in the video that came with the kit. The part wasn't included, and when I called AFS to ask about it I was told that it was no longer part of the kit.

Craig

Black plastic thingy?

I also did not find such a plastic "tube". But in anticipation of a problem finding the drain fitting when sticking the rod in the wing in the blind, I found an arrow shaft that looks like it will work. That is if I can figure out how to attach it to the metal drain valve (epoxy, or something). My idea was to have it attached to the drain plug and serve as a "guide" for the rod inserted in the little bitty hole in the skin.

The previously supplied machined plastic tube sounds like a better solution. Wonder why they stopped supplying it?

It is amazing but I have also been wondering about putting the Duckworks lights in the same bay with the AOA port! Now I think I will put them both in the last bay and quit worrying about it.

Craig23 said:

The part wasn't included, and when I called AFS to ask about it I was told that it was no longer part of the kit.Craig

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Curious. Did they tell you why?

The guy I talked to said that some builders use tubing they find themselves to accomplish the same task. I gave in to my impatience tonight and installed the pressure ports in the outboard bay. It was actually very easy to locate the right spot for the drain hole. I just eyeballed it by looking into the bay from the tip end of the wing, and lining up the long pin used to open the drain valve along the axis of the air/water separator, then marking where it crossed the bottom of the leading edge skin. A #40 pilot hole 4.75 inches inboard from that spot allowed the pin to engage the drain valve perfectly. Now I just have to find some tubing that will fit around the drain valve to use as a guide for the pin. I thought of using pro-seal to bond the tube to the delrin plastic above the valve. I was also thinking of trying to pro-seal the tube to a washer that is in turn pro-sealed to the skin around the drain hole. That way the pin would have a guide to get it to the drain valve and any water would drain straight out of the wing instead of getting into the leading edge around the landing light.

What do you guys think. I'd love to hear other solutions.

My Solution

Here's what I came up with guys. I found some anodized aluminum tubing that fit perfectly over the water drain valve in the top pressure port. It slides freely but there's no free space for it to rattle around. I cut and filed the tube to the right length, and bonded it with sealant to a washer. I then bonded the washer to the bottom of the leading edge skin, centered on the #30 drain hole. I didn't bond the top of the tube to the pressure port, so it is free to move as the skin flexes. If I did it right, there should be a picture of the installation attached. With the guide installed, it is much easier to insert the long pin and open the drain valve. I also don't have to worry about water draining out into the wing. The only problem I can anticipate is that I can't remove the drain valve if it starts to leak air into the top pressure port. The valve looks to be the same type used on the fuel tanks. I contacted Advanced Flight Systems and they said they were not aware of any valves needing replacement in their AOA systems. If I have to do it, I can access the bay through the wingtip and cut the tubing off to get to the valve.

There are numerous free apps for resizing images, including www.irfanview.com. The extra-wide image makes the thread very difficult to read.

But thanks for posting the picture. That looks like a good solution. Do you remember the size of the tubing?

Dave

image sizes

Here is an online utility to resize your images before posting:

http://www.resize2mail.com/

Thanks for the info about resizing the image. It was the first one I've posted. What size works best for these forums? The tubing I used was 3/4", but I can't find any of my extra to tell you the thickness. I found it at a local hardware store.

An image width less than about 800 pixels would be good.

Or it looks like ImageShack provides an automatic thumbnail.
Just use the link next to "Thumbnail for forums (1)".
It will display a thumbnail with a clickable link to the full size picture.
Like so:

My AOA kit did not include that plastic tube either, so I spoke to Jim Franz about it. He stated that many people did not like the end of the tube extending below the wing skin. They now include a short rod that is inserted into a hole below the drain to push the drain fitting. I was concerned that water would run down the rod and collect on the inside of the bottom skin, but Jim felt that so little water will actually enter the #60 hole, that this was not an issue. I did not like the idea of an unsupported hole in the skin, so I machined a small disk out of Delrin that I fastened over the hole in the same manner that the AOA discks are attached.

I also asked Jim about inter ference with the airflow due to Duckworks landing light and he did not fell it would be a problem. I know of one 8 with the AOA in the standard location with DUckworks lights and it seems to work fine.