Chief Aux tank replaced & installed!

Fuel tanks, systems and parts
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flyingfool
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Chief Aux tank replaced & installed!

Post by flyingfool »

Well due to contaminated tank of I think old sloshing compound. I had to remove the tank. I was able to purchase a "clean" tank last year. I finally got around to getting it replaced.

Quite a job. A few lessons:

1) Your hands and arms will look like you got into a fight with a wild cat when you are done with this project.

2) Remember when removing the aux tank that there is a filler neck support attached to the BACK of the bulkhead former. if yo do not, when you remove the tank you will break something. Ask me how I know! Fortunately it was fragile built enough that only a few nails bent and allowed it to be removed without breaking or damaging the plywood bulkhead.

3) Model A fuel gauge gaskets they sell do NOT fit the Chief Aux tank. The larger gasket I was able to trim the inside diameter of the neoprene gasket to allow it to seat properly. I had to reuse the original gaskets that go on each side of the "glass" which is actually plastic of some sort. The model A gaskets are too small inside and outside diameter. If I was going to do it over I may just try and get a sheet of gasket material and trace and cut new gaskets from scratch!

4) You can remove and replace the aux tank with the headliner only partially removed. In my case I had to remove both rear windows in order to get the headliner unattached to the first wire support holding the headliner in place in front and above the rear tank. Not fun but better than removing the ENTIRE headliner.

5) when installing the tank, Getting that filler neck support screwed back into place is a real trick and royal pain. At least in my case. This is because you can not get to the back side of the bulkhead. (unless the airplane is without fabric) I made a new support so that the part that mates up with the back of the bulkhead was thicker and extended all the way to the bottom of the plywood former. You have to put the neck support onto the filler neck and put the tank into place. Then I made with a thin piece of metal with a 90 bend in it. I was then able to get under the filler neck support, lift it up, and pull it back and up tight against the backside of the plywood support. I was then able to get the screws into place. Much easier said than done. Without having the rear windows out it would have been nearly impossible to do!

6) For the convenience of the next individual (hopefully not me!) if they have to remove the tank. I wrote on the tank warning them to remove the screws for the filler neck support FIRST so they do not break anything.

I do have some picture of the project but I'm not sure they reveal much if someone would want a few pics I could see which few may be of interest.

7) Also unless you are made of money. It makes sense to do this work yourself. it took me "only" about 8 hours to get the tank installed. Probably took about 6 hours to be careful not to ruin anything to get it out. So at A&P shop rates that would have been a wad of cash. And it is almost entirely completely grunt work that you do not need A&P skills to do. Inspection along the way and at completion however is required and well worth the time & money. But I'd rather pay for 1 hour rather than 15 to 20 hours!

Next steps:

I currently have about a gallon or so in the tank making sure that my fuel line connections do not leak. I'm leaving it over night. My next step is to fill it and calibrate a dipstick one gallon at a time and also record the gas gauge levels at each point. I will then leave this overnight and again check for leaks with full head pressure. And if no leaks schedule my A&P to inspect and sign off the work. This is pretty simple stuff but still want to ensure everything is up to snuff!

The final step just for my own curiosity. I want to raise the tail to a level flight condition. And with the main tank 1/4 full. I want to time how long it takes to drain into the main tank. This will only be an estimate as when flying there are several other variables. Such as how level I can remain flying, the differential in pressure between the tank cap at the top of the fuselage in potential lift sucking and the vent line which is at the bottom of the fuselage which kind of points into the slipstream (pressurized?). Not to mention the lack of fuel burn from the main tank which changes the idiosyncrasy between the head or differential in fuel pressure between the main and aux tank. I will then have to go out and fly it and time how long it takes at cruise. I will then make a chart or table and put it into the glove box. Along with my other measurements of dip stick markings for fuel in inches so that if I ever loose my dipstick, I can use any stick and a tape measure!

Hopefully none of you will have to go through this unless you are restoring your Chief and have the fabric off etc. But when restoring. I would recommend that you keep in mind the ability to be able to remove the tank. I would also suggest possible holes in the plywood bulkhead in order to grab or position the filler neck support. Also leaving enough of a scallop between stringers to leave room to put a couple fingers between the top of the bulkhead and the fabric. This would have added dramatically the ability to deal with the filler neck support!

That is all for now. Just thought I'd add my experience that may help some others!
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joea
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Re: Chief Aux tank replaced & installed!

Post by joea »

Good info.

Have to tell you that in actual use the drain rate is VERY slow. You almost are afraid that its not draining and its getting closer and closer to the main tank being empty, but finally it keeps going down.

Joe A
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Re: Chief Aux tank replaced & installed!

Post by flyingfool »

I know. That was what was reported on the fAA e-mail list a couple weeks ago.

I'm still just curious. As I've stated. It seems that on my chief there is some sort of bump or something that may be made of wood where the aux vent line exits the bottom of the fuselage. It is wood from the inside. And it is mostly covered with fabric on the outside. It appears and I'm hoping the fuel overflow drain/vent and that it is pointed forward. My hope is that it will allow positive pressure from the prop blast & slipstream the aux tank and aid in quicker draining. But that is all just a hope.

I wonder if anyone has tried a NON venting fuel cap on the aux tank. I wonder if there is still low pressure (lift) at the aux tank cap location that actually creates suction and thus less ability for the weight of the fuel to flow. Steve Wittman said that the center section of the fuselage between the wings on his tailwind created lift and is part of the reason he was able to get more performance out of the short winged tailwind. While the chief is by no means a tailwind, the concept still may apply. It seems to me, how the aux tank is vented from below would provide ample venting without the need for a vented fuel cap! Maybe this would aid in speedier draining of the aux tank???
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