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Installing a Dakota Cub Fuel Valve

Steve Pierce

BENEFACTOR
Graham, TX
So my weekly mission is a 10 minute flight to the local gravel bars and then another hour or so hopping from bar to bar. I usually have little fuel and keep it in one tank but occasionally I go cross country and put fuel in both tanks. Then I head out to my play ground, switch to the lowest tank with the intention of switching to the fullest when I get there and I have a brain fart and forget. I have gotten pretty quick at switching fuel tanks.

I bought a Dakota Cub left, right, both valve over a year ago but hadn't taken the time to put it in so yesterday I decided I was gonna work on my own plane and install the valve. I had already put it in the work hanger and drained both tanks with the tail up. My Super Cub is a 1972 model, almost 13,000 hours, one recover in 1992 and pretty original, still has all the brass Weatherhead fittings on the fuel system.

I pulled the front stick and both front and rear seats to make it easier to get the center interior panel out. My mag switches are still on the side panel and kind of a pain but I removed the switches from the panel leaving the wiring intact. Removed the carb/cabin heat control, trim handle and fuel valve handle along with the covers and then the whole side panel.

I prefer to use 5/8" flare wrench on the Weatherhead tubing nuts but probably not necessary since they are steel. I do back up the fitting with an 11/16" angle wrench close to the base of the fitting because I have had the brass Weatherhead fittings collapse on themselves, they are pretty soft and weak at the openings.
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Once all the fuel lines are disconnected I removed the two screws and nuts holding the valve to the bracket welded to the fuselage and removed the valve. The fittings are not in line with the valve so I measured the angles to make hooking up the fuel lines easier once the fittings are installed on the new valve.
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The new valve is taller in the body and needs an AN914-2D street elbow to get the tee fitting high enough to clear the new valve. I had forgotten this but finally found a brass one in my bin of old fittings.
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I used a big Ford wrench to hold the new valve while I installed the fittings after cleaning them and applying some fuel lube (EZ Turn). You can see the AN style street elbow extends up further than the Weatherhead elbow did.
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I installed the fuel lines first and then the screws that mount it to the fuselage. Makes it easier to get the nuts on the fuel lines started in my opinion. The other part I forgot were the NAS1351-3H10P cap screws that Dakota Cub calls out in their installation instructions to fasten the valve to the fuselage bracket. I didn't have any so I used some drilled head screws to hold the valve until I get them in. The fun part of this is getting two AN960-3 washers between the valve and the bracket on each screw attachment so the break in the fuel valve bracket doesn't interfere with the fuel valve.
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I put some stickem' on the washers and aligned them with an awl and finally got the screws started. Only dropped them three times and lost two washers to the bowels of the belly only to be found when the knife comes out.

Valve installed, everything cleaned and lubricated and ready to install the interior panels which are always a pita. Leaving all the screws loose, several awls and checking all the Tinnerman nuts makes it a little easier.
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I didn't like the Dakota Cub fuel valve sticker that came with the valve so I used an old Cub Crafters sticker I had from a headerless fuel system install that I hadn't used. Problem was is was marked for 17.2 gallons usable on the headerless system and it was old and some letters didn't transfer over. A Sharpie solved that problem.

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This project took about 3 hours but part of that was searching for a fitting and disassembling and washing my seat covers from wet, muddy, sandy dogs on some of my river runs. Can't wait to try out the new selector valve and see how evenly it feeds from both tanks with a stock fuel system.

Sent from my SM-N900V using SuperCub.Org mobile app
 
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Curious if that valve is an STC'd mod or just a minor repair.
Also whether any mods to the fuel system are required.
I've never cared for the "left/right/both" fuel selectors.
In fact, I'll go one further and admit that I like the C150's "on/off" selector best of all!
 
The Dakota Cub fuel valve is an STC'd replacement to the original. No other modification required. I like the both feature but also like the fact that I can select individual tanks as well. I was flying the Slotted winged Pacer that has this same fuel valve and Super Cub site gauges back from Oklahoma a few years ago when we got into some unforeseen headwinds. I was fairly new to the airplane and wasn't too familiar with where the fuel showed in the site gauges for how much was there and decided to see what I had. I switched to the right tank and noted the time. When the engine stumbled I knew roughly how much fuel and had in the left tank and where my optional airports were. You can always leave this valve in the both position which is what the majority of people with this system do.
 
Steve,

As always, VERY nice documentation of a useful maintenance project. I've seen a lot of Cub fuel selectors that could use such an upgrade.

Thanks,

MTV
 
How about when it gets low?
It's politics are still left leaning but with enough differential it equalizes the draw but won't equalize the tanks in flight even when holding up the fuller side. When departing (for fuel) the other day with 1/4 each side it still seemed to pull stronger from the Left. Last week on a round trip to Little Rock I ended up switching to RIGHT only for about the last hour in order to better equalize before switching back to BOTH for landing which is REQUIRED.
 
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It's politics are still left leaning but with enough differential it equalizes the draw but won't equalize the tanks in flight even when holding up the fuller side. When departing (for fuel) the other day with 1/4 each side it still seemed to pull stronger from the Left. Last week on a round trip to Little Rock I ended up switching to RIGHT only for about the last hour in order to better equalize before switching back to BOTH for landing which is REQUIRED.

My cub has this mod as well. I'm still a newby but I've observed the drawing of more from the left tank as well. Generally, I haven't flown long enough distances to be concerned to where I'd switch tanks to try and keep the draw down even. After the cub sits for awhile the tanks even out. I really like having the BOTH feature. My Garmin has a popup notice to 'switch tanks' which I find helpful as a reminder to take a glance at the fuel levels.

jeff
 
One thing to remember is that Kirby's and mine are stock fuel systems with this valve. This is not a headerless system that requires both for take off and landing. I see no reason why the system would not provide fuel as long as there is some in the tanks.
 
One thing to remember is that Kirby's and mine are stock fuel systems with this valve. This is not a headerless system that requires both for take off and landing. I see no reason why the system would not provide fuel as long as there is some in the tanks.

Mine is the same and that's how I understand it.
 
maybe uneven because??? on stock fuel line system, left tank has 2 lines (3/8" rear, 1/4" front) right only has rear 3/8"..........???
 
I have a question about the OFF position.. I keep running into valves that tie both tanks together when in the OFF position.. no flow to carb but if you get a contaminated tank you sure don't want it crossing over while off. Anyone else seen this? Any hi level logic to support the concept?


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Little Cub,
Most of the valves which we use are the inexpensive rotary valves which will be as you have noted. To get a shutoff between tanks and the engine you will need a more expensive valve, like a poppet valve or a separate single action valve for each tank.

Another thing to remember is that the labeling on a valve describes how the fuel flows from the tank(s) to the engine. So the OFF position means no fuel will flow to the engine. If you are concerned with cross feed when parked such as when wings are not level or on floats, just select one tank. If you also want to shut off the flow to the engine you will need a separate shutoff valve downstream of the main valve.

The FAA requirements are that you must be able to stop fuel flow to the engine. The FAA is not interested in what happens before the fuel gets to the shutoff valve.
 
Steve, I just put a Dakota valve in mine, and the little roll pin at the back of the valve was borderline loose. I just wired through it and tied it to the shaft. Frankly I almost took it out so the valve would be complete rotary, but I already had sent out for a custom placard labeled "clockwise for off".
 
Steve, I just put a Dakota valve in mine, and the little roll pin at the back of the valve was borderline loose. I just wired through it and tied it to the shaft. Frankly I almost took it out so the valve would be complete rotary, but I already had sent out for a custom placard labeled "clockwise for off".
None of the ones I have installed have a roll pin.
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Sent from my SM-N900V using SuperCub.Org mobile app
 
I have a question about the OFF position.. I keep running into valves that tie both tanks together when in the OFF position.. no flow to carb but if you get a contaminated tank you sure don't want it crossing over while off. Anyone else seen this? Any hi level logic to support the concept?


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That subject came up recently on our ShortWing forum. A lot of discussion here about having contamination in one tank. http://www.shortwingpipers.org/foru...elector-without-interconnecting-L-and-R-tanks
 
Frank
It could have been as simple as that is what is on the shelf when the plane was built. Might have been done to get more flow/head pressure, or just so some stupid pilot like me will not take off on a empty tank. I am a right/left valve kind of guy. I have standard Cessna both valve in the 180 and every spam can driver I fly with only wants to fly with selector on both at all times. I think a big part of it is what to you first train in, that just sticks to ya.
DENNY
 
They must have changed the pointer attachment since 2010 since I have a screw in the middle
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I have a question about the OFF position.. I keep running into valves that tie both tanks together when in the OFF position.. no flow to carb but if you get a contaminated tank you sure don't want it crossing over while off. Anyone else seen this? Any hi level logic to support the concept?


Sent from my iPhone using Tapatalk

One solution.

One of the great features of this unit is that when the selector is in the OFF position, there is no cross feed between each tank. So if you have your aeroplane parked on a slope, or if one tank is fuller than the other, no crossfeed will occur.http://www.andair.co.uk/product/fuel-selector-fs20x4/


http://www.andair.co.uk/product/fuel-selector-fs20x4/
 
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Interesting valve. Would take a little rework to accommodate the fitting coming out of the back of the valve in a Super cub. I remember looking an Andair's stuff at Sun & Fun many years ago, it was really nice stuff. Back then it seems like it was just he and his son.
 
Problem is that many don't know you run the potential of OFF causing cross flow. Just goofy with the percentage of fuel related accidents!
OFF should simply mean it doesn't flow... ANYWHERE! [emoji6]


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Cessna guys are used to switching from "both" to either R or L to prevent cross flow. Off has never been an issue for me but even with the new zero leak-down FI servos the experts advise it's good practice to get in the habit of turning fuel off at shutdown to prevent any chance of flooding. Damn, that means I'll have to remember to turn it on, too!

Andair is what Back Country supplies with their kits.

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Hehe yeah 'remembering' is the key [emoji15]

BTW we found a boat switch that looks like the ol brass one but the boat guys shut the silly thing off. (Experimental only [emoji56])


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