Any thoughts on this stc? My IA is pushing for it in the rebuild to get rid of the header tanks in the cockpit and save a small amount of wieght. All the fuel lines must be replaced (or will be) anyway. I’m not thrilled about losing any fuel capacity, but it will free up some space under the panel and give both to the fuel selector. Just looking for your thoughts both for and against.
I have the headerless arrangement in my -12, with the original two valve arrangement, and have not experienced any downside in the 47 years I've owned the plane.
I have close knowledge of a fuel starvation crash on take-off that had the headerless fuel system, sorry but I'll keep my header tanks with the multi-function valve and a HD header for the front one (just in case) and stock in the back.
Remember, These are the Good old Days!Farmer Ted thanked for this post
I agree with Gordon. I've had the headerless/two valve system in my -12 for 30 years with no problems. I leave both valves on all the time and thus don't have to worry about forgetting them. One tank may feed faster than the other, but once a tank gets low, the other develops more head pressure and catches up.
I can imagine that happening - - My system has both forward and rear ports on the left hand tank, but not the right. Consequently it is placarded left tank on for takeoff and landing. For me that means to always have some gas in the left tank, and both tanks on for takeoff and landing. My thinking is that a header tank only delays the effect of any fuel supply disruption, and also delays resumption of gas flow to the carb once that disruption is corrected.Originally Posted by OLDCROWE
The header will let you get higher before the music quits and hopefully have a positive outcome.
Remember, These are the Good old Days!DENNY liked this post
What is the real reduction in weight when any increase in unusable fuel is taken into account? CubCrafters FX-3 with headerless system carries 30 lb of "unusable" fuel. It also has the stand pipe vented fuel caps that piss fuel over the wing if the tanks are anywhere near close to full.
Not when the silence is the first indication of a problem.
Gordon
N4328M KTDO
First off, if you are calculating fuel load to include header tanks, ya might want to reconsider.
That being said, I like the headerless system. But, as pointed out above, it needs to be installed correctly. That means correct vent lines, fuel caps, selector, and front AND rear ports on the right tank. If it's done halfway, bad stuff will happen. I've heard of fuel starvation incidents but it was generally traced down to no front port installed on the right tank, or incorrect caps/vent lines that lead to a vacuum in one tank or other.
Web
Life's tough . . . wear a cup.
If you do a search the topic you will see a lot of good info. I prefer not to have a both system. The main reason is fuel management. If you are reliant on electric gauges or sight tubes it is truly hard to judge remaining fuel in a long flight. Do you have 2 gal or 4 gal left per tank? Even with a fuel flow meter on long trips I fly my right tank until the engine coughs. At that point I know I have 18 gal left and it is all in one tank making remaining fuel easier to flight plan the last two hours in case I loose fuel flow. If you think about it, without a front header tank and six gallons of fuel split between two tanks it would not be hard to have fuel starvation with a hard climb much like current stock system on Right tank only.
DENNY
I think you might have meant descent with the absence of front tank port(s)?fuel starvation with a hard climb . . .
Gordon
N4328M KTDO
A system with a BOTH selection does not necessarily prevent the fuel management techniques you describe. I have over 1,000 hours in my PA-28 with LEFT, RIGHT, OFF selections. I never ran a tank dry but I often ran one tank down to 5 gals then used most of what remained in the other. Nice to know that last 5 gals was available.
My FX-3 has LEFT, RIGHT, BOTH, and OFF selections. Sometimes I use LEFT or RIGHT, sometimes I use BOTH. It's nice to have the choice.
There is no inherent fault with either the stock or the header less fuel system. Period. Any problems noted with either system are purely a function of the pilot not understanding the characteristics and limitations of the installed system, assuming the system was installed correctly.
I’ve flown with far more pilots in Super cubs who had no clue how their system was designed than I have with pilots who fully understood their fuel system.
Theres an old saying: “The Super Cub is a really safe airplane, it can just barely kill you.” Even simple aircraft have systems, and many of those systems can hurt you.
Install whatever system you like, then fully understand the characteristics of that system. And, if you’re flying someone else’s Super Cub, don’t assume it’s the same as yours.
MTV
HD header for the front tank? On this 1960 the right tank feeds the aft header and the left feeds the front header tank, what is the HD header, I’m curious.
The header tank should not have to fill for fuel to flow out of it. The fuel stopped flowing out of the header tank at the bottom level of the outlet, any fuel added will simply continue to flow through. Head pressure will change but it will flow.
DENNY
It doesn't have to completely fill, of course. But it does need to fill a little bit. And that is a delay, even if a small one.
Yes fill a little bit then go looking for the outlet plus air filled fuel line/gascolator/carb. Boost pumps can help shorten the wait.
Gary
Farmer Ted,
I think the "HD" means Heavy Duty header tank.
https://fadodge.com/header-tank-front/
Back to what Denny said, what sight gauges may indicate
Or fuel computers are reading, may mean nothing. The tryed and true method that works in ALL Cubs regardless of the fuel system. Jump into an unfirmilar Cub, after you fill it full of fuel. T/O
And when climbing thru 500' switch to "One" tank at that time, and 'Note the time' on your watch exactly! Set your rpm to an exact amount, you use for cruise flight. Fly the Cub until it quits at altitude, and switch to the full tank. Look at your watch to know EXACTLY how long it ran on the first tank, Now you know within a very few mins how long it will run on the other tank, assuming you maintain that same rpm. Engines very wildly, in the time on one tank: I have flown lots of Cubs rigged up about the same, that were as short as 1:50 min! : To say as long as 2:30 min, before they quit on standard 18 gal tanks. So until you have established exactly how long a tank last with one perticular Cub with one engine, one carburetor, one prop, etc. You just don't know what it does exactly. You do this and land the airplane regardless of fuel system; 10 min "before the first tank quit" and you will likely NEVER run outta fuel.....( But you will be dam close) If your cutting it this close, you can't use a long nose down decent to land, unless you have a 'front outlet port' on that tank your coming in on.
Good luck.
E
This is what all the old Polar Bear guides did before headed out over the ice for Russia.
Last edited by TurboBeaver; 10-19-2022 at 04:36 AM.
Did the CC STC on our L21 back in 2016 when we went to 160hp. Wouldn't have done it with out adding the fuel port in the right tank.. I actually thought it was required by the STC.
I like the BOTH position and use it 100% of the time. I know how long I can stay airborne and am very conservative when it comes to fuel planning. The airplane does a lot of Tailwheel Training and not having to be concerned with when to switch tanks takes an element of risk away.
Just my 2 cents, but I would install it on any Super Cub I owned...
Bob D
Heavy Duty Super Cub header tanks are 3 lbs each and the clamps for both tanks weigh 1/2 lb.
My previous Cub had the stock header tank system and my current Cub has the Dakota Cub headerless fuel system. If you like to run down to less than 2 gallons of gas you probably want the stock system and heavy duty header tanks.
Previous threads on the subject. Google "headerless fuel system site:supercub.org"
https://www.supercub.org/forum/showt...ss-Fuel-System
https://www.supercub.org/forum/showt...ss-Fuel-System
Good advice, with one addendum: If you’re playing this game, make DAMN SURE that you can get fuel out of each tank individually before you run one tank out of gas. I know of at least one case where that didn’t happen, and one tank was not useable. Rare, but will ruin your day.
MTV
That cross flow through the top crossover tube on sidehills is another issue. Having pressed hard on all the virtues of a stock cub system, I fly the 180 on both all the time. MTV hit the nail on the head any system will work fine as long as the pilot knows how to use it correctly. DENNY
Atlee Dodge made them, but I don't see them on their site anymore. In my opinion they are far more crash resistant than the stock tanks.
Remember, These are the Good old Days!
A correctly installed top crossover vent tube will be connected to the outboard top of each tank. When done in this manner there will only be air entering the crossover tube. The downhill tube will fill with fuel to the fuel level only. There will be no cross flow.
NX1PA
I have header tanks…can’t see a downside to them. I did install the Dakota Cub valve, it has a both selection and I have started using that 90% of the time.
If I’m running minimum fuel for the mission then I’ll use the L or R function.
Dakota Cub valve is a great piece of engineering. Dump an AD and get a new function. STC is included with the valve.
They are still listed on their website. Select products then on the right side "fuel systems" and the header tank is right there.
The Super Cub vent tube is plumbed into the top of the sight gauge and the cross vent only becomes an issue when parked on a side slope.
Obviously a poor design.
NX1PA
Designed to retrofit. You can put a valve in the vent line and turn the fuel to a single tank when you park on a side slope. I don't park with one wing low full of gas very often myself so it hasn't been an issue.
Steve Pierce
Everybody is ignorant, only on different subjects.
Will Rogers
I'm re doing a headerless install. they routed the lines how they seemed fit, and even used a cessna fuel selector. It's a nightmare
What is the purpose of this modification and why was it supposed to be an improvement over Piper's system?
NX1PA
If a fuel cap vent clogs up, the vent line is supposed to allow air into the tank, from the opposite tank (which, hopefully, does NOT have a clogged vent).
I like your idea of venting from the outboard side of the tank. Still allows a second vent path but would be immune to fuel cross feed. Something to have welded on next time the tanks are out.
Web
Life's tough . . . wear a cup.
The lowest point on the cross vent should be at the tanks, so that any condensation can't collect and freeze. For the experimental -12 I'm working on, the cross vent will connect to the outboard ends of the tanks to prevent side-hill issues, but will probably have to be lower in the middle. I'll run the gascolator vent to the lowest point.
Gordon
N4328M KTDO
Gascolator vent?? IF your engine has a fuel pump it will draw air.
That crossover vent is very unlikely to ever collect any condensation. If that is a concern, you could incorporate a clear portion in the center for a visual check.
NX1PA
The fuel pressure will be the same at the vent line junction as at the fuel supply line at the gascolator. The head with fuel flowing will be less than the static head, but still non-zero. The gravity head is sufficient to generate excess fuel flow through the fuel supply lines at maximum power in adverse airframe attitude. So I don't see how the vent line would suck air. It's sure worth thinking about in detail though. Thanks.
Edit: A basic rule I think should be followed is to have every high-point vented and every low point drainable.
Gordon
N4328M KTDO
Maybe less parts count when they were building Super Cubs around data plates or maybe to simplify the fuel system with a both position.
Gets rid of the header tanks and allows for both. I think I saw something in the regs about needing crossover with a both valve. I have been distracted and forgot to change tanks coughing a tank at 10 ft on both take off and on landing. I can change the tank usually before the second cough so it has never been an issue. If you have a lot going on I can see how the both would help. DENNY
Failure to attend to fuel level has bit a few folks, and killed a couple. One thing I’ve never been able to understand is why the same does not seem to be true of the Cessna 206, which also has a right/left/Off selector. Maybe 206 drivers just don’t talk about it.
MTV
As I recall the original selling point was to eliminate the header tanks especially the front as they had been known to rupture in a crash. They are very thin walled and easily crushed; splitting along the seams.
That is why the heavy duty tank was developed.
The thought of fuel dumping into your lap will cause you to loose sleep.
Ed
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