Bubblehead

Bubblehead

Well Known Member
The only near emergency I have ever had was from a fuel valve not being properly positioned. Yes, by me! The slop in the valve, poor detent mechanism, and poor location of the valve made it very difficult to get it in the right spot. Ever since then I have been picky about fuel valves.

When I bought N247TD last summer, one of the first things put on the "to do" list was replace the stock fuel valve with an Andair unit. I found postings here on VAF, and checked out websites by Jeff Preou, Kevin Horton, Mick in Switzerland, GAPilot, and others. My thanks to everyone who posted information and shared their ideas.

As good as thoe ideas were, it seemed there could be a better way. Take a look at the pictures, and in the next post I'll explain the process. Click on the pictures for a larger view.

Andair and stock valves:


Subpanel:


Subpanel with fuel valve:


Subpanel with fuel valve - rear view. The Andair needs two 45 degree male-female swivels, not just one as shown. The 45 degrees and the swivel function makes it much easier to hook everything up.


New left fuel line (front) with old one (rear)
 
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How to do it

The key is taking out the original fuel valve mount F-883 and using a sub-panel. The sub-panel is made from a new blank fuel panel from Vans, and allows you to position the fuel valve while connecting the outlet line. Then you remove the sub-panel. The outlet line keeps everything in position while you hook up the left and right fuel lines.

Here's how you make the sub-panel.

1) Bolt or cleco the new blank panel to the original fuel panel.
2) Make sure all the screw holes line up, and then drill a matching hole where the old fuel valve stem comes up through the panels.
3) Use a step drill to enlarge the valve hole to about 1-1/16" for the Andair valve. Mark and mount the three valve mounting holes. Rivet three nut plates to the underside of the valve tabs.
4) Removing the subpanel from the fuel panel, and measure and mark a line 5/8" in around the perimeter. Put two parallel lines across the panel at a proper distance for the valve to be fully seated and supported. Then use a jig saw or other tool to cut out the two large cutouts. I drilled holes in the corners of the cut out areas and used a Dremel scroll saw, but there are many ways to do this.
5) One more cut needs to be done. I removed about 1/16" from the entire outside perimeter of the panel to make installation easier. There's a lot to wrestle with and there's no sense making it too difficult to line up the sub panel too. I also opened up all the screw holes in the panel for a little extra clearance.

Two other keys to this method:
1) The left fuel line needs to be a new piece of 3/8" tubing. I have a bending pattern that I will post soon. Basically put a series of 90 degree bends in it but swivel the bending tool each time so the tubing crosses itself with about 1" of clearance. Leave both ends long until the valve is in place. That should line upthe other leg with the fitting on the left side of the valve. Then cut the leg to the fuel tank to a length so the coil is about 1" from the fuselage skin. Then massage the tubing into position to hook up to the left side of the valve. Cut to length, add fitting and sleeve, flare and attach.
2) The right fuel line can be modified and not replaced. I removed several adle clamps along the length of the right line, cut off the flare, and used a spring type tubing bender to massage the tubing over into position to hook up to the right side of the valve. Cut the tubing to length, make sure the sleeve and fitting are on the tubing, flare the end, and hook it up. All the adle clamps go back on, but the last one gets flipped upside down to adapt to the new tubing route.

Spring tubing bender, from the plumbing department at Lowe's:


I will post the tubing diagram and a bill of material here in the next day or so.

If I ever did it again, I would have the sub panel cut by a shop. I have found a company that does that, and several people on this forum do laser cutting. I would also consider using braided hose instead of tubing from the left tank. Tubing worked fine, but it sure took a whole lot of time to figure out!

One other thing I would do different is I would split the sub-panel into two parts. The split would be lateral through the valve mounting hole. That way, the front half of the panel could be screwed into position and left in place while attaching the fuel lines. I might also add a flange forward and aft of the fuel valve to add even more stiffness. I'll add a rendering of that idea in a few days.

The next post will have some pictures that shold make it all come together for you.
 
Pictures of work-in-process and finished product

Original panel and valve:


Original panel removed. Note F-883. Too narrow to mount the new valve and right in the way of everything:


Valve supported and positioned by outlet line. Right side still needs the 45 degree male-female swivel installed:


Line from left fuel tank installed:


Line from right fuel tank installed:


Sub-panel in position:


Final product. Much nicer looking, but more importantly, I know when I change tanks the valve is in the right place!
 
A few caveats, quid pro quos...

OK, here's some free advice.

1) you're messing with gasoline so wipe up any leaks right away and get rid of the rags.
2) use AN caps and plugs over the fuel lines as you disconnect things.
3) I ran most of the fuel out of both tanks before opening the system to minimize fuel spills. If you do this, make sure you fill up the tanks before test flying.
4) Before flying, do an extensive ground run and taxi test, then check for leaks. My engine is an IO-360 and I used the boost pump a lot even with the engine running before fuel pressures got up to normal.
5) I placed the plane back into Phase I during the test flights, and did the first two flights high over the airport. I had a plan prepared and memorized before each flight. The plan was where I would go and what I would do if the engine lost power during each phase: take off, climb out, flight, descent and landing. After 2 hours of flight in all attitudes, with and without boost pump on, and reducing fuel level to 5 gallons on each side I rechecked for leaks and put the plane back into Phase II.

I don't have a way of measuring fuel flow so had to depend on temperatures and fuel pressure to monitor fuel flow. Those of you with fuel flow indicators have a better way to make sure the flow is correct and proper. Those with an EMS that records data can take a look at the data to see if there were unnoticed drops in fuel pressure or flow.

I have now flown a second tank full through 7TD and have continued to watch fuel pressures. Everything looks and acts normal. I really like the new valve and feel more confident when changing tanks. There is no ambiguity with the Andair valve. It was a hassle figuring this out but worth the trouble and expense.

I'll post a few more pieces of information like BOM in the next couple of days.
 
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