Section 28 Started

Today was the day I started on the fuel line installation. With my previous experience from bending the longerons I was extremely cautious this time to make sure I understood what I had to learn about the techniques involved before doing any serious work. I had never done any plumbing work of any kind beyond using a garden hose and so I had to learn quite a bit. But first I noticed that the Avery tool kit did no come with a little tube cutter and so this mandated a short trip to Harbor Freight to get an adequately sized cutter. Turns out they have a great little inexpensive tool which is perfect for the job. HF #40913 is sold for $5.


Once I had the cutter I started on section 28 and noted that I first had to do some basic installation type of work before getting to bend some tubing. I had to assemble the fuel valve and install some fittings on the fuel pump before installing it on the mounting bracket.
Getting the knob installed on the fuel valve lever was a bit confusing as the instructions asked you to first drill a hole with a #16 bit and then to open it with a #11. Looking a little closer at the drawings and rereading the text, I noticed that you're supposed to drill through the knob with a #16 bit to make room for a screw that will hold the knob on the lever. After that you pull the lever out of the knob and drill its hole open with a #11 to clear the screw. Aha! Funny though that when I tried to open that hole I found that the lever had already been drilled to a #11 by Van's. Duh!


For these fittings I needed the thread sealant Rectorseal No. 7 I had ordered some days ago. It will resist even pure alcohol although I think the fuel pump or the transducer wouldn't survive this. Oh, by the way. The fuel pump was filled with a sh**load of oil of some kind. So when you tip it over and handle it be careful not to spill oil all over the place. Ask me how I know.
I shook and blew most of this stuff out before putting the fittings on. Carefully wiping off the threads of the fuel pump holes before inserting the fittings. I also ran the pump briefly with a 12V power supply to make sure I am not installing dead hardware. Boy, is this pump noisy! A loud tock-tock-tock sound is emitted while it's working. No wonder people install switches to cut this nasty thing off after takeoff.


Here is the fuel pump next to the valve with the fittings installed, ready for installation. To install the valve I needed to turn the fuselage on its side again. Boy, I had forgotten how heavy that piece had become by now. No fun turning this over for just two rivets and clecoing the fuel valve on was no easy task either as the lower firewall section was making access a bit tricky. After banging on a longeron for hours I guess nothing can really deter me anymore ...


Now on to installing the pump. The VAF notes said to not to forget to put the ring terminal through the AN4 bolt before installing it. The instructions still don't mention it. On page 31-05 (Finish Kit) they ask you to remove that bolt again though and to put the ring terminal back(?) on, followed by a cushioned clamp that you insert some installed wires in as well and then tighten it back down again. I don't see why you couldn't thread the wires through the clamp to begin with as you also have to be able to feed them through the snap bushings. So I installed the clamp (part of the Finish kit) now and hope I don't have to take this apart again.


Finally I got to do my first tube bending and flaring. I used a little piece of tube to just play around with the flaring tool and get a feel for a good flare. After doing 5 flares I felt I had a hold on it and I went on and did my first actual production flare on the tube that goes from the tank to the fuel pump. No problem!
Doing the first 90 degree bend I saw a problem though. My bender is not able to do a bend so short after the flare as it was shown on page 28-03. I compensated this in this case by overbending the tube to something around 100 degrees to make it come back on track. The lightening hole it has to go through allows for this deviation. After this, the second 90 degree bend has to be a bit less to match the template but this is all very easy to do if you just hold the bending tool with the tube above the plans and match the layout.


That's how I also did the 15 degree bend. I had a marker on the bender but just matching it with the plans while in the bender was far easier. The last bend then is a bit tricky as you have to measure it and transfer it onto the tube. I always just marked the beginning of a bend on the tube. No L marker or anything. Just align the start of the bend with the 0 degree marker on the static part of the bender and then bend it. Turned out dead on for me all the time.


Now all that was left to do was to put sleeve and nut on, check that the other one hadn't fallen off and flaring the end.


So pretty!
Then it went inside the fuselage and almost completely disappeared under the baggage floors. And here was the only uncertainty I found with this installation. How much torque is too much? I don't have a torque wrench for this application and even if I had, I doubt I had a chance to use it in that confined space. I could hardly use wrenches to get this nut on the fuel pump fitting. And you need 3 hands to tighten the nut as the third one is used to keep the fuel line in place while tightening the nut.


So I decided to do a simple pressure test. I pulled up the flared end of the fuel tank side, covered the outlet of the fuel pump and .... blew into it.
No way! I could feel the pressure building up in there but no apparent leak. I guess there was enough torque on the nut then.

What a nice enjoyable building session, for a change!