Category: Fuel Tanks

Fuel Tank Drama Continues…

October 22, 2021 – I have given up on my right tank fuel quantity issue, for now…

I got a new sensor from Van’s. I installed it, reinstalled the tank, ands started the fuel calibration again. Believe it or not, no help. The sensor and float move just fine, and electrically it works. but when it’s in the tank, there is still no apparent movement (i.e. voltage change) when I add fuel.

I tried bypassing my wiring; running a wire from pin 21 of the Dynon EMS to the sensor. That was no help. I also double-checked the ground.

OK. I’ve had enough. I decided to go scorched-earth, and reconfigure the tank back to the fixed pickup tube and relocate the float sensor to it’s normal place in the inboard bay of the tank.

I removed the tank again, and ordered the pickup tube with a screen and the anti-rotation brackets from Van’s.

I removed the access plate on the inboard rib, to see if I could tell if the float was hanging up. I was able to stick something through and move the float. I also checked the resistance while I was moving it. I couldn’t find anything wrong.

I cut an access hole in the back baffle of the tank as needed to get access to the bay.

Here’s the flop tube inside the tank.

I removed the flop tube and the float from the next bay over. I left the small mods that are installed with the flop tube; there’s a twisted strap that keeps the flop tube from hanging up in the next rib, and there’s a small trap door that acts as a check valve to keep fuel in the inboard bay so fuel doesn’t slosh outboard and starve the flop tube.

I drilled the hole in the inboard access plate for the sensor…

…and when I got the pickup tube, I located that hole, then secured the tube in place along with the anti-rotation bracket.

So here’s everything in place:

The float does not and cannot hang on anything. It also doesn’t touch either the top or the bottom.

I made the panels to close the tank back up and installed them.

Two days later, I pumped up the tank with a bike pump and used soapy water to look for leaks. Absolutely nothing…

I plugged the hole at the leading edge where the flop tube was mounted, and where fuel exited the tank. I used an AN fitting with two AN caps and thoroughly sealed them inside and out…

I also had to make a new fuel line to the fuselage since the location was different…

I installed the tank, and proceeded to begin the calibration.

Guess what?… It still doesn’t work.

Well, I was able to get a “calibration”, but I had to thump the top of the tank with my fist to get the sensor voltage to change after each 2-gallon addition.

I filled it to 21 gallons, and the Dynon accepted the calibration.

I proceeded to drain 10 gallons from the tank to put in the left tank. The indicated quantity did not change.

My drain valve was dripping, so I drained the rest of the fuel so I could check the o-ring on the drain. I did expect to find a piece of aluminum stuck there, and I did. I reinstalled the drain. With an empty tank, Dynon still indicated 20+.

OK. This airplane needs to be flown, so I decided I’ll not hit my head against the wall any more, and just manage the fuel for the time being.

I may call Van’s at some point, and probably will end up ordering another sensor, but maybe not until the condition inspection next year.

Time: 24:30

Work after First Flight

October 8, 2021 – I took care of the items that were noted during the first flight.

Chuck suggested that I remove a little bit of the dam in front of the #1 cylinder, because it was getting a little warm.

I also took care of some of the items that were related to configuration on the Dynon. Battery voltage showed a steady 14.5 volts, yet was annunciated in yellow. I changed the parameter for the yellow to 15 volts. I also had a yellow caution band on the RPM gauge. Chuck questioned whether it had to be there. I called Aerosport Power, then Hartzell. Based on my engine and prop combination, there was no restriction, so I changed the parameters for that sensor in Dynon to remove the yellow band.

My airspeed issue was because I reversed the AOA and Pitot connections at the tube. My transponder guy came out, found that, and he also pumped up the airplane from the pitot tube back. No leaks and an accurate indication.

I also had a slight yaw issue, where the ball was a little bit to the right. I installed a temporary tab, and we will investigate further during the next flight.

After the first flight issues were taken care of, and because my pilots are on vacation, I decided to pull the right fuel tank to try to address my calibration issue.

Yay. What joy to remove the bolts that attach the tank to the wing spar…

I took out the float sensor. It electrically checked out, but it seemed a bit stiff. I decided to go ahead and order a new one from Van’s.

I have since installed the new one. I’m going to give the sealant time before I put fuel to it.

I moved on to the interior.

I’ve had to make some small mods because of things that I have done differently in the airplane.

This small panel wraps around the air vents. Since I made my own air vent brackets, I had to make a cut about 1″ long to accommodate…

The big side pockets fit under the armrests. Since I installed the J-stringer sections to stiffen the armrests, I had to modify these…

Time: 12:30

Fuel Calibration—-Yay and Nay!

September 15, 2021 – I started fuel tank calibration.

I jacked up the tail to level, and started the calibration on the left wing. In hindsight, I kind of did this maybe the hard way, but it worked.

I bought 5 gallons of fuel at a time (my hangar has fuel), and transferred that to a marked 1-gallon jug. I did the Dynon procedure, where you tell it how much is full, then click “Add” every two gallons.

Here’s the screen as fuel got added:

Got to 21 gallons and clicked “Full”. I rebooted the Dynon and got a good reading. Actually it doesn’t read above 15 gallons or so, but that’s a “feature”.

Now to the right wing.

I drained the left tank 5 gallons at a time and started the transfer to the right tank.

Maybe it’s  worth noting that the right tank has a flop tube for fuel pickup, which moves the fuel float to the next bay outboard in the tank. As  I started filling the right tank, the readings didn’t change.

The first time I tried this, I got to 12 gallons, went around to press “Add” on the screen, and saw that the Dynon system had shed its load because the battery couldn’t keep up. Oh, well, just as well. I really didn’t want to get all the way to 21 gallons with this problem. But the next day I decided to try again. Same problem. I filled up to 21 gallons. The Dynon asked me if I wanted to use that calibration, even though it wasn’t successful. I answered yes, but after I restarted, the right side still showed the annunciator for CAL. My inspection is scheduled, so I asked my DAR as well as the test pilot if this was going to be an issue. They both said no, so I’m going to defer this until after the airplane flies.

I’m assuming I’ll need to pull the tank.

So I drained 10 gallons from the right side, and put them in the left. My test pilot asked for 1/2 tanks for first flight. Oh, by the way, I bought a battery-powered pump from Harbor Freight. Took no time to drain a 5-gallon can.

Time: 6:20

Wing Tasks

February 23, 2021 – With the wings on, I started doing various tasks that need to be done while the wings can still come off.

Fuel Tank Attach

After quick verification that the wings were in the correct position from the previous drilling 5 years ago, I drilled the fuel tank attach brackets. This was a simple matter of using a drill bushing to center the hole in the fuselage bracket slot.

When the wings come back off, I’ll install the nutplates for the attach bolts.

Fuel Lines

The next step is the fuel line connections. These are the vent lines and the main fuel feeds from the tanks. The right tank is routed differently because I have a flop tube installed there. The main fuel connection from the left side is a straight shot into the fuselage.

Wing/Fuselage Fairings

There are fairings all the way around the wing root that enclose the gaps you see in the above pictures.

There is a short section underneath where the fuselage skin is attached to the wing skin on each side. I used a hole-finder to start these holes, then enlarged the holes up to the correct size for the screws.

The next part is the large wrap-around panel that wraps around the leading edges of the wings.

These panels have pre-punched holes that match open holes in the wings. Holes do need to be match-drilled to the skins of the fuel tanks.

Time: 6:00

Tanks mounted!

April 18, 2011 – After a little finesse on the outboard end of each tank, I installed them. I’m sure they’ll have to come off again at some point, but now things look pretty aircrafty.

You’ll recall that I had some pillowing of the skin between the screws where the tak joins the fixed leading edge:

After a little lovin’ here’s roughly the same spot now:

I’m pretty satisfied with this unless I see something a whole lot better on other airplanes.

Here’s the left wing with the top skins clecoed on:

Riveting the top skins will be the next big project. In the absence of help, I want to do things like paint and install the landing light brackets; things like that.

Time: 2:10

Fuel tanks done!

April 18, 2011 – Last Thursday I found one more rivet for the left tank baffle that was leaking. I removed the rivet and did the shop-vac thing again. I went to Minneapolis over the weekend with my son to check out a school, and got back last night. This morning was the leak check, and I’m happy. I have a couple things to do around the house, and I’m going to try to check the fit of the tank later today. I hand-worked the skin between the screw holes on the outboard end. We’ll see how that goes. If it works out, I’ll remove the right tank and do the same thing.

Time: :45

Right tank complete!

April 13, 2011 – My right tank is complete and (maybe permanently) in place!

I went back to Addison and leak checked the leaks that I repaired last night. Here’s something: the trick with the shop-vac worked! That was in the right tank and it all checked out. The left tank, however, had another leak. It was the one in the previous post with the leak in the corner at the baffle/rib/skin joint. That one checked out, but I found another at about the center of that same end at the attach for the end z-angle. It may have been that the one leak yesterday was so big that other leaks didn’t show up.

So I brought everything home, including the regulator setup. I did the shop-vac thing again. The sealant hasn’t set up yet, and I’ll be out of pocket for the next few days, so things should be nice and dry by the time I get back.

I installed the wiring for the fuel float sender in the right tank. I had to do this now because the float is attached to the baffle and will be inaccessible when the tank is installed.

Then I mounted the right tank. Screws and bolts line up and go right in, and everything looks aircrafty.

One issue I see, and this appears to be very common, is that I have slight pillowing between the screws at the tank/leading edge junction.

I’ll research and address this later. It does go all the way around the tank edge.

I also clecoed the top skins to the left wing in preparation for their installation.

Time: 2:40

Fuel tank leak check

April 12, 2011 – Today I leak-checked the tanks. I took the tanks to Addison where my friend Kato had some of the equipment to do the job.

We hooked up the regulator and gauge to the vent fitting.

We put 2 PSI to the tanks and sprayed soapy water.

We found three leaks. Two were rivets, one of which is for the baffle (no sweat there). The other is a rib fastener just forward of the baffle.

The other leak was in the other tank, and was a bit bigger. Turns out I left a hole in the corner between the outboard rib, the baffle and the skin.

That was easy to fix because luckily, it is in the same bay as the fuel filler point. I put sealant on the outside, and I taped a long q-yip to a long screwdriver, put some sealant on the end, and reached in and applied it in the corner on the inside.

I brought the tanks home, and attempted a poor man’s fix on the internal rivet. I placed the hose of my shop-vac in the filler hole, and it fit perfectly. I held the hose there tightly while I applied some thinned sealant to the outside of the rivet. We’ll see if it did the job. The rivet leaks were both very small.

Time: 2:15

Right fuel tank closed!

April 5, 2011 – In preparation for closing of the right tank, I had to install the flop tube. I had to clean up the 9/16″ hole where the fitting passes through the inboard rib and the T-405 and T-410. I ran a reamer through there by hand.

I then put sealant on the fitting where it goes through the rib, and tightened the jam nut on the outside, making sure the tube rested in the anti-rotation bracket.

I placed the tank in the cradle and cleaned the mating surfaces with acetone.

Shown below are the tank, and then the baffle with the float sender installed.

I did adjust my countersink a few thousandths deeper and ran over all the baffle holes through the skin, because my left tank rivets sat a little proud of the skin. These are much better.

Time: 2:30

Left tank rivets

April 3, 2011 – After cleaning the sealant from the rivets for the baffle on the left tank, I found that many of them were sitting a bit proud of the surface. Since I never change the depth of my countersink, I can only assume that the difference is the sealant.

I went down both rows and gave the rivets some love with the gun and a light bar. They’re better. Not baby-bottom smooth, but better. To fix the problem for the right tank, I did adjust my countersink.

Time: :25

Installed left tank baffle

March 29, 2011 – After a little bit of clean-up work on both tanks, I decided to bite the bullet and close the left tank. I mixed up the sealant and put a bead along the rivet lines and the aft edges of the ribs, then I put the baffle in place and clecoed it to death.

I installed the upper and lower pop rivets in each rib, then I sealed and clecoed the z-angles in place, making sure they were oriented correctly. The pop rivets were installed wet, by dipping them in the sealant.

To install these I had to modify my trusty pop riveter that I bought when I started my airline career 23 years ago. Kinda hated to do it.

Just for good measure, I cap-sealed the pop-rivets.

Then I used a squeezer to install all the upper and lower skin rivets and the -4 button-head rivets on the upper and lower ends of the inboard and outboard ribs. I still need to install the z-angles on those ribs.

Time: 4:20

Right tank work

March 22, 2011 – I finally got all the center ribs installed in the right fuel tank. I’m getting a little tired of mixing a batch of sealant every time I need to do something, but the end is near.

I also did some of the smaller items that will lead to being able to close the right tank. I installed the fuel float sender in the baffle for the right tank, because of the flop tube. Luckily, the float cleared the stiffener right below it.

I safetied the flop tube to the fitting that will feed fuel out of the tank…

I installed the anti-hangup strap to the second rib. This strap will deflect the flop tube in case it gets close to this corner.

Then I installed the anti-rotation bracket for the flop tube. I used a bracket that Van’s includes in the kit. These brackets are for the fixed fuel pickup tube that I have installed in the left tank. I just cut the top off so the flop tube fitting would lie in the bracket.

Then my friend Joe stopped by, so we riveted the splice straps in the leading edges. This is where the fuel tank attaches at the outboard end. Just for giggles, we test-fitted a tank on the wing. No pictures on that yet until it’s time to install…

Time: 8:00

Left tank fuel pickup tube

March 18, 2011 – I took a few minutes to address the problem with the fuel pickup tube I discussed in the previous post.

After discussing the problem with someone else, I decided to use a finger screen; a solution I always preferred over the sawed inlet holes per the plans. I cut the tube off at the last inlet hole that I had made. I then cut the fitting off of a finger screen that was donated to the cause.

I located the screen with the access panel installed, then made a mark through the screen onto the tube. I drilled a hole laterally for .020 safety wire, and slid the wire through the screen and the tube.

I took the access panel out, and wrapped the safety wire in opposite directions, as tightly as I could.

I coated the joined area between the tube and the screen with sealant.

With the extra sealant, I installed the float in the panel, and put it all in place.

Time: :40

More left tank stuff

March 16, 2011 – Today I installed the left tank fuel sender and the T-405 attach angle.

The sender float wire gets bent to reach its full up and down travel within the tank. I used the measurements provided by Van’s on the added sheet that came with the kit. I bent the center angle at 3 1/4″, and then the short 3/4″ section that goes into the sender. That bend was also 3 1/4″ from the center bend. I slid it into the sender and checked travel. I had to adjust the bend just a hair because the float didn’t quite reach the bottom of the tank. Then it was time to measure resistance through the sender. My old faithful meter decided to give it up, so I borrowed one from a friend. The readings were just about what they needed to be.

I also installed the T-405 attach angle and the T-410 doubler on the inside of the inboard rib leading edge. Kinda messy, but not too bad.

I do have to slightly rework the left tank fuel pickup tube. I made it too long, so it will not allow the baffle plate to be installed. I cut it to shorten it, but I’m not sure it will withstand recrimping the end. I may have to make a new one.

Time: 2:40

Left tank miscellaneous

March 15, 2011 – Since the center ribs for the left tank got done in the last post, I installed some of the necessary items to eventually prepare for closing.

I installed the T-410 doublers on the outboard ribs for both tanks.

I installed the outboard rib in the left tank.

I then installed the snap bushings, the fuel vent line and the fitting in the inboard rib.

I then installed the inboard rib for the left tank. I still have to install the T-410 doubler and the T-405 mount bracket at the leading edge.

Time: 4:25

Continued fuel tank rib installation

March 13, 2011 – Today I also continued installing fuel tank ribs. I made an off-hand remark to my wife Lenora (LJ) about needing help with some riveting, and she said OK!! After a quick lesson on handling the rivet gun, we got started. Shot the last two ribs in the left tank, and I said we could stop if she wanted. She said “It’s kinda fun, let’s keep going”. After I picked my jaw up off the floor, we put the right tank on the table and got two of those ribs done. Once she got the hang of it, she was a machine. She did a great job.

Time: 5:40