Does anyone hsve the numbers for usable fuel in the 5 gallon wing tanks? Curious at 15-20deg pitch down how low the fuel level can get before the pickups are uncovered.
Chris
Remember, in aviation death sentences are administered by the laws of physics, not the FAA.
Depends on how you plumb them. You should have a header tank that will fill from the wing tanks and keep things running in the event the fuel pickup is unported. You can also have multiple fuel pick up points in each tank. One forward and one aft. if you are skidding or slipping, one tank will still be filling the header tank. The header tank can be one or two gallons with a central sump or flop tube for pickup. Usable fuel will depend on your installation (dihedral, angle of attack, pickup location, etc.). Joe
Depends on how you plumb them. You should have a header tank that will fill from the wing tanks and keep things running in the event the fuel pickup is unported. You can also have multiple fuel pick up points in each tank. One forward and one aft. if you are skidding or slipping, one tank will still be filling the header tank. The header tank can be one or two gallons with a central sump or flop tube for pickup. Usable fuel will depend on your installation (dihedral, angle of attack, pickup location, etc.). Joe
A few years ago I made a study of usable fuel difference between the plastic 5 gal and 7 gal tanks at different pitch angles. I dug up the summary sheet (attached), but I can't find the backup work.
My (personal) conclusion was the 7 gal tank wasn't necessarily very efficient for useful fuel capacity because it tended to collect an enormous amount of fuel up front in the pitch down position. As Joe mentioned there are plumbing solutions that would resolve that. Jim
There are some variables in this scenario. You may be doing a glide approach with power at idle and a flight path tilted at 6 degree down, or a partial engine assisted approach with flight path at 3 or 4 deg down, but your wing tank may actually be level (or may only be tilted nose down by 1 degree,) due to the positive incidence and also a positive angle of attack. I think for most phases of flight except for final approach, the wing tank is tilted a few degrees nose up. Just thinking out loud. I could be wrong.
Joe, I was just trying to figure out where the pickup / outlet should be located. Your suggestion to have two separate pickups, one at the front and one at the back would be most ideal. But if I were to have only one outlet, then where should that be located?
If you are fabricating your own tank, an angled bottom with a single pick up at the lowest point would be ideal as in :
Do you know what I can use for a pickup that has a 5/16 barb on the TEAM fuel tanks? I see they made a little doubler plate in the back corner to receive fuel..
A small Gallon or two header tank that gravity feeds to the engine, an overflow line from it back to the main tank, and the pump constantly overflowing it, just my two cents
Many ultralights have no Facet pump. The pulse pump does the fuel feed.
I have a different issue altogether. My CG is at 12 inches back from Leading edge. I had to add almost 6.25 lbs of weight inside the rear fuselage, under the stabilizer. This moved the CG back by just 1 inch to 13 inches. Can't afford to add any more weight.
I would still like the CG to move back by one more inch to at least 14 ". I have a 5 gal poly tank inside the forward fuselage. Not sure if this is what is called a header tank.
I am thinking of adding a small 1.5 gal tank behind my seat. Unfortunately it can only be fitted inside the turtle deck at my neck / head level. (Already ordered a small tank.)
The plan is to fill forward main tank with no more than 2 or 2.5 gal. 1.5 gal fuel is available in auxiliary tank.
I was thinking of adding a facet pump. But on second thought, I felt it may not really be necessary. The pulse pump should do its job.
I am doing all this by trial and error. Has any other builder tried to solve CG issue by dispersing fuel to the back ?
I am thinking of adding a small 1.5 gal tank behind my seat. Unfortunately it can only be fitted inside the turtle deck at my neck / head level. (Already ordered a small tank.)
The plan is to fill forward main tank with no more than 2 or 2.5 gal. 1.5 gal fuel is available in auxiliary tank.
Your plan is certainly feasible but it does introduce a potential problem. You have to be very aware of the fuel level in the front tank so that when you are running it "low" you don't run it "empty". You say that you would never do such a thing....well, if you do you won't be the first pilot to accidentally run a tank dry. Managing the switching of tank valves has been a factor in many accidents.
BTW, how far will the CG move aft with 9 lbs of fuel behind you?
Replace the weight you installed in the tail with an atv battery (the same weight pretty much), and install a facet pump from the front tank to the back tank with the back tank overflow routed to the front tank. The front tank will run empty first and you can use all of it and not have to worry about switching valves. Have two little posts to hook up a battery tender to charge up while it's parked. An atv battery should be able to empty a few tank fulls.🤷🏻♂️
but perhaps you could fit your 'header' tank low and somewhere that's CG neutral or aft of CG, and then drain your main tank into it. You wouldn't need to worry about having to switch tanks as the 'header' tank will be the one the engine gets its fuel from. That's the setup I have on my Max, where I have the standard tank, and an 11 ltr tank bolted under the fuselage just under the seat. I've attached a diagram showing the approximate location of the tankage, and a couple of photos of the tank in place.
Regarding adding extra tankage, you could always do what I've seen done on a Fisher 404, where the builder/owner fitted it with a bomb shaped tank between the undercarriage legs. I've attached a photo of it so you can see how it's been fitted.
I've also added a couple of photos of a tank that can be used either under the fuselage, or one under each wing.
Aircraft Spruce sell them for $135, and here's a link to their ad on their website.
So basically what I am considering doing at this point is placing a small 1 or 1.5gal tank behind the seat that the wing tanks will gravity feed into and then pumping from there. The only issue I foresee is currently the low point in my fuel system is the gascolator at the bottom of the firewall and placing a new tank behind the seat makes that tank then the lowest point. Currently, gravity pressure from the wing tanks keeps the gascolator full whereas with the header tank below the seat the system will be relying on the engine driven diaphragm pump to keep the gascolator filled and the air out.
am I just overthinking the whole thing?
Chris
Remember, in aviation death sentences are administered by the laws of physics, not the FAA.
Water can be sucked up 33ft by vacuum alone, and petrol is only 0.7 as heavy as water, so in theory a vacuum pump could lift it around 40ft or so. As such I'm sure that lifting the fuel for your 'max around 30 inches won't be too hard for the engine driven vacuum pump. By the way, I don't think you're overthinking it, you need to take into consideration all possibilities when designing a reliable fuelling system.
One day on a long cross country in the RANS S6 one wing tank got completely dry.That was scary as there was no seperate on/off for the individual tanks.Nothing happened though.The engine kept running on the Right wing tank.Still wondering why the engine did not quit.
I use the "football" wing strut tanks on my Quad City CH-I. I ran fuel line inside the strut tube fairings to a manifold on the floor under my legs. I can select either or both tanks. The "thumper" pump has no problem sucking the fuel to the carbs, but I installed a Facet pump inline for backup.
An "in-line' Facet pump for backup! Now THAT'S a statement sure to open a can-o-worms on this suspiciously quite site. Hope everyone is keeping clear of the CHINA FLUE/KUNG FLU/ WOO HAN BACK HAND FLU. That's right....I said it!!!! LOL
It hit where I work a couple months ago, but it's food processing so we couldn't shut down. Out of 138 people, by the time we were finally able to get tested after the first person was hospitalized, well after many people were falling sick, 43 tested positive (many of the early ones sick had recovered by that point). In the end out of them all, 6 were hospitalized, two in intensive care and intubated. One of them was in his early sixties with diabetes, still in the hospital and will be on oxygen for life, the other one is 33 with no previous medical problems spend 6 weeks in a coma, then extensive physical therapy to be able to walk again because his muscles had atrophied while he was in the coma. He got released on July 3rd, and when I talked to him on the phone Friday he was excited he was able to walk 80 feet that morning before having to catch his breath, will probably be disabled for life.
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