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Thread: header or not

  1. #1

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    header or not

    When I started my 12 project, there were no header tanks in the fuel system. I'm upgrading to either an 0-320 or 360. I've already put in Dakota 24 gal tanks and Dakota fuel selector, but haven't started plumbing yet. Someone a while back said if I didn't have a header to begin with, then don't worry about it. Should I install one (or two) or should I just not worry about it. What's the advantage other than a little extra gas? I added another door (seaplane) and the STC requires belly sumps. I'm trying real hard not to go experimental.

  2. #2
    mike mcs repair's Avatar
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    no headers.....

  3. #3
    Gordon Misch's Avatar
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    Tom, I did not use header tank(s). Two reasons:

    First, that is extra gas right over my legs in the event of a wreck.

    The other is that I think the header can actually operate in opposition to its intended purpose, at least as I understand. I think the intended purpose is to ensure gas feeding the carb in the event of temporarily unporting a main tank. However, if a tank is unported due to being low on fuel (or out of fuel), after switching tanks when the engine quits, it will take longer for gas from the other tank to reach the carb, because it will have to partly fill the header tank on the way to the carb. In this scenario more rapid recovery will occur without a header.

    In the case of a low tank unporting in a steep descent, including a port at the front of at least one tank remedies that automatically.
    Gordon

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  4. #4
    Bugs66's Avatar
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    Not. Use the CC system.

  5. #5
    Iflylower's Avatar
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    I like headers. Just a little more fuel and you can't unport.
    "There are three things in life that people like to stare at: a flowing stream, a crackling fire and a Zamboni clearing the ice." Charlie Brown

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  6. #6
    Bugs66's Avatar
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    I am curious, is there any evidence of a header-less fuel system using CC's design un-porting? I have never once stumbled my engine in over 300 hours. Been in many different descent angles, fuel levels.

    Also more tanks means more weight and complexity.

  7. #7
    nanook's Avatar
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    I like headers. When you are landing up a steep grade, there is always positive fuel pressure above the carb. The forward mounted header is always above the carb. Unless you are going straight nose up...

  8. #8
    Steve Pierce's Avatar
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    The PA12 had two fuel valves. If you use the CC STC you do away with the two fuel valves. Is there another way to get this approved?
    Steve Pierce

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  9. #9
    mike mcs repair's Avatar
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    Quote Originally Posted by Iflylower View Post
    ... and you can't unport.
    thats not really true at all..... you just have the volume of the header to use....

  10. #10
    mike mcs repair's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    The PA12 had two fuel valves. If you use the CC STC you do away with the two fuel valves. Is there another way to get this approved?
    the dakota valve with both is STC for the -12 ...... and their drawing shows basic routing... http://dakotacub.com/images/stories/...Supplement.pdf

  11. #11
    nanook's Avatar
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    Actually Mike, you can't unport a header. You can run it out of fuel though. The whole idea of the header is to get you through the odd unusual attitude that may unport or starve the carb feed. Gravity feed fuel system have some inherent shortcomings. Envision where your aft main tank feed is located (in relation to your carb fuel feed fitting) when you are landing on a steep uphill landing area. Also in any steep high power climb. (high fuel demand). The less fuel you have in the tanks the lower the head pressure. That being said, av8rtom, I maintain and fly a PA-12-150 that has the same double doors and no headers. The fuel system is field approved with big Dodge tanks double plumbed fore and aft. One "both" fuel selector. Both aft lines have a belly quickdrain, because of the left door cutout. I haven't had any fuel starvation issues, but, I don't take it to some of the places I hunt with the PA-18 with Dodge tanks and headers.
    Last edited by nanook; 11-07-2013 at 12:24 PM.

  12. #12

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    I have had my 12 since '75 with ho header and I like it that way. I have the two valve shut off system. I have heard, over the years, of pilots taking off with the gas turned off, using the gas in the header tank and then crashing when the header ran out of fuel. If I start to taxi with the valves off, the engine quits in about 100 feet while I am still taxiing. If I really believe that I am extremely low on fuel on a return to an airport I am just very careful in how I bank and descend. I do have a label on the top of the panel which states "no header".

  13. #13
    jgerard's Avatar
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    I like headers because when low on fuel and flying uncoordinated such as slipping or skidding or making rapid changes in pitch, roll, or yaw you don't un-port the fuel pickup. It provides more safety when getting wild while low on fuel. 99% of the pilots would never need that ability but I like having it. You have to look at what is considered unusable fuel. With a header less systems I believe it's about 5 gal per side and it's even worse with bigger fuel tanks. Part of certification requires testing to determine min fuel required to operate in unusual attitudes. Even though header less tanks will empty dang near every drop a fuel in normal conditions the unusable fuel quantity is significantly higher than the stock header system. I also don't care for the cross feed on a header less system, I like two separate tanks. I don't buy the sales pitch that removing headers from the cockpit makes crashing any safer. Most crashes yank fuel lines apart regardless of headers and no one bitches about all the other airplanes that have nose tanks. Rule number one is don't crash


    Jason
    Last edited by jgerard; 11-08-2013 at 12:52 AM.

  14. #14

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    I know of a cub with DC 24's and a CC header-less system that got a whole lot lower than that, once upon a time that is...
    Remember, These are the Good old Days!

  15. #15
    SteveE's Avatar
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    Hmmm, 2/10's left and still runnin,,, barely as I'm told.

  16. #16

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    Quote Originally Posted by SteveE View Post
    Hmmm, 2/10's left and still runnin,,, barely as I'm told.
    on ocassion
    Remember, These are the Good old Days!

  17. #17
    PerryB's Avatar
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    Quote Originally Posted by Bugs66 View Post
    I am curious, is there any evidence of a header-less fuel system using CC's design un-porting? I have never once stumbled my engine in over 300 hours. Been in many different descent angles, fuel levels.

    Also more tanks means more weight and complexity.
    With the CC system, the only way you're ever going to un-port is to run completely out of fuel. Its an excellent system. At least one port is always going to be covered.

  18. #18
    aktango58's Avatar
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    Quote Originally Posted by PerryB View Post
    With the CC system, the only way you're ever going to un-port is to run completely out of fuel. Its an excellent system. At least one port is always going to be covered.

    BULLSH!T.

    Leave at least the front header in. There are a couple of reasons why, Jason has explained one.

    If you really challenge yourself and your cub you will find times when you need to be uncoordinated, slipping, skids, abrupt pitch changes... part of the fun. In a slip you put the upwind wing down, and where does your fuel go??????? Right, to the outboards portion of the tank. Where are the ports?

    Now do that on low fuel...

    Also when you are real low on fuel the stock 12 will not feed fast enough to keep the engine running. But using a fuller tank and letting the fuel flow to the header tank you can then switch and run till the header is dry, thus using the last gallon or two out of a tank.

    Don't think you will need that? That is fine. But like a shoulder harness, if you ever do...
    I don't know where you've been me lad, but I see you won first Prize!

  19. #19
    Gordon Misch's Avatar
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    Also when you are real low on fuel the stock 12 will not feed fast enough to keep the engine running.
    Based on nearly 30 years (ok, only 28 years) with my -12, I'll quote the gentleman from Haines --- "BULLSH!T".
    Gordon

    N4328M KTDO
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  20. #20
    Bugs66's Avatar
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    Quote Originally Posted by aktango58 View Post
    BULLSH!T.

    In a slip you put the upwind wing down, and where does your fuel go??????? Right, to the outboards portion of the tank. Where are the ports?
    ...
    With a "Both" system and front back ports, almost impossible to un-port. I don't see it un-porting in your scenario. Also if you are running on fumes, why are you doing aggressive play time with the Cub?

  21. #21
    Gordon Misch's Avatar
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    Quote Originally Posted by Bugs66 View Post
    With a "Both" system and front back ports, almost impossible to un-port. I don't see it un-porting in your scenario. Also if you are running on fumes, why are you doing aggressive play time with the Cub?
    +1, given at least a little usable fuel in each tank.
    Gordon

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  22. #22
    cubdriver2's Avatar
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    12 has alot less dyhideral then a 18. Might not work as well as a 18 does?

    Glenn

  23. #23
    skywagon8a's Avatar
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    Quote Originally Posted by Bugs66 View Post
    With a "Both" system and front back ports, almost impossible to un-port. I don't see it un-porting in your scenario. Also if you are running on fumes, why are you doing aggressive play time with the Cub?
    Ditto, provided that there are two fuel outlets in each tank. There needs to be an outlet at both the front and rear inboard corners with all four lines feeding the "both" position of the valve. Personally, I would like to be on the ground before the fuel gets that low. If not, I would be very careful about letting the fuel slosh in the tanks.

    The headers are important when there is only one outlet per tank and are useful in both steep nose up and nose down conditions.
    N1PA

  24. #24
    nanook's Avatar
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    It unports in a flat spin, high centrifical force....might be the least of your worries at that point though....

    A scenario in Alaska to consider. There is a psychosis that manifest itself around Aug. 9th every year. It involves little white sheep that hide way up in high places. Alaskan pilots put minimal amounts of fuel in their cubs so they can operate at elevations where they probably wouldn't be, if they were of sound mind. Flying amongst those windy turbulent peaks with minimum fuel, you can end up in some pretty unusual attitudes in mountain induced turbulence. I'll keep my forward header tank, just in case...

  25. #25

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    Nevermind. Discussing flat spin recovery on the internet is a bad idea.
    Last edited by Carey Gray; 11-08-2013 at 11:10 AM.

  26. #26
    skywagon8a's Avatar
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    I have been in a flat spin (not a Cub) and the only thing that I could do to stop it was to increase power. Without the power there was no air flowing over the tail rendering the controls useless.
    N1PA

  27. #27

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    Nevermind. Discussing flat spin recovery on the internet is a bad idea.
    Back to header tanks---or not.
    Last edited by Carey Gray; 11-08-2013 at 11:11 AM.

  28. #28
    aktango58's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    Based on nearly 30 years (ok, only 28 years) with my -12, I'll quote the gentleman from Haines --- "BULLSH!T".
    Gordon, run one tank dry, switch tanks.

    wait five minutes, switch back. You have fuel again and run for a while...

    What, never tried it? Then don't say I am wrong.
    I don't know where you've been me lad, but I see you won first Prize!

  29. #29
    mike mcs repair's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    12 has alot less dyhideral then a 18. Might not work as well as a 18 does?

    Glenn

    they have ~same dihedral ... 3" +/- 1/8"

    MODEL PA-12 RIGGING PROCEDURE
    .....
    #2 Dihedral Angle: Stretch a length of string from wing tip to wing tip along the top of the wing at the front spar location. Measure down from the string to the top of the fuselage front wing hinge fitting a distance of three inches. Adjust the front lift strut fork fittings in or out to produce this dimension.

    To check for equal dihedral in each wing, use a 30" level, held spanwise against the underside of the wing at the front spar location. Note the amount of off-level on one wing and see if the other wing has the same amount of off-level. Adjust the front lift strut forks in on one side and out on the other to get the same amount of off-level in both wings. Check the 3" dimensions after this adjustment to see that it has not been affected by the equalizing adjustments."
    ......
    http://www.supercub.org/forum/archiv...p/t-34286.html


    pa-18
    Dihedral Angle: To check Dihedral angle at the front spar, proceed as follows: Stretch a string along the top of the wings above the front spar, from wing tip to wing tip,and draw it tight.
    Check the dimension vertically from the string to top of fuselage front spar wing hingefitting. For correct dihedral this dimension should be 3 1/8 inches.
    I think they left out the +/- on that one??...
    http://www.fadodge.com/fad_pdfs/Corr...20SuperCub.pdf

  30. #30
    mvivion's Avatar
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    Quote Originally Posted by PerryB View Post
    With the CC system, the only way you're ever going to un-port is to run completely out of fuel. Its an excellent system. At least one port is always going to be covered.
    Which is why the CC 18 180 has six gallons of unuseable fuel, according to the TCDS? Apparently SOMEONE found SOMETHING there that suggested fuel starvation in certain attitudes.

    As Nanook suggested, it's not just fully unporting a tank that's of concern, it's also how much fuel pressure arrives at the carburetor in certain pitch attitudes. A steep climb coming out of someplace you probably shouldn't have been anyway isn't where you want that O 360 to be hungry for gas.

    notice the fuel cap "snorkels" required on some of the 180 conversions? Does that suggest a possible fuel pressure issue?

    i like headers. That said, if there were none installed in a plane, I probably wouldn't install them.

    MTV

  31. #31
    nanook's Avatar
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    I can't see myself getting out of an aft CG flat spin pulling the power back.

    Doing long survey flights in the cub with Dodge tanks, I would milk everything I could out of the right tank. It would sputter and I would switch left. After a while I would switch back and it would run for a while again, this was to make sure you could make it to the next fuel cache on the left tank....

  32. #32
    Bugs66's Avatar
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    I am glad we still have our annual traditions in place at SC.org. This place wouldn't be as fun without traditional topics of "header/no-header", "big tires/no-big tires", "flaps/no-flaps". Which reminds me, we are overdue for a Husky bashing topic.

  33. #33
    aviationinfo's Avatar
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    Who knew this could be such a controversial topic?

    I agree with Mike V---- don't bother with adding the header if it isn't already in there. Make sure that you have ports in at least one tank that cover the front and rear of the tank though.

    A friend of mine (in a J-5) had drained all the fuel out of his tanks to have some leaks repaired. The header (in the front) was also drained. When they were ready to fly they forgot about the possibility of an air lock occurring in the header---he took off and had an engine fail at 50 feet. Got it on the ground ok but lost a couple of years off his life. I don't recall how his system is vented but it played a role.

    I would guess that most of us don't operate at attitudes that require a header unless perhaps the airplane is used for work. My 12 has a header that the previous owner installed because he thought it would be helpful for the initial takeoff run on floats. I don't see that he was correct. Save the weight and the plumbing.
    Aviationinfo

  34. #34
    courierguy's Avatar
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    In the experimental world, several of us are using a tapered header tank, WITH a sight gauge. Both wing tanks plumbed direct to the header, no shutoffs between. One outlet in each tank.

    The way it works, I'm told.... is you fly along until the right wing tank sight gauge shows empty, as that tank always empties first, it is of no concern. Then, you start watching the left tank's level, and about 30 minutes after the last of the visible fuel disappears from it's sight gauge you starting looking around behind you every few minutes (or seconds, depending on the terrain, WX, and amount of fuel remaining) and now when you see the gas level start to drop in the header, and assuming you're flying behind a Rotax 912S, you still have 1 hr to 45 minutes of flight time left. The header holds 4 gallons. The taper of the tank is such that some report flying along (and taking off) with only a gallon OR LESS in the header, but, they knew exactly that that was the situation, no guess work about how much fuel was sloshing around in the mains or how accurate the electric gauge was. The end result seems to be more range, one guy flies 8 to 9 hrs between re-fueling with this setup, resulting in far less fuel stops, just due to the total awareness of the actual fuel remaining. In a real pinch, when some are cutting it real close, like sub 1 gallon remaining, the observed fuel remaining in the tapered header drains quicker and quicker, as the tank volume is less so the fuel seems to drain quicker, this visual effect must be allowed for or it will cause severe consternation they say. When the last of the fuel in the header is gone, there is not a drop left in the airplane anywhere, so at least the resulting deadstick landing probably won't result in much of a fire.

  35. #35
    PerryB's Avatar
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    Quote Originally Posted by aktango58 View Post
    BULLSH!T.

    Leave at least the front header in. There are a couple of reasons why, Jason has explained one.

    If you really challenge yourself and your cub you will find times when you need to be uncoordinated, slipping, skids, abrupt pitch changes... part of the fun. In a slip you put the upwind wing down, and where does your fuel go??????? Right, to the outboards portion of the tank. Where are the ports?

    Now do that on low fuel...

    Also when you are real low on fuel the stock 12 will not feed fast enough to keep the engine running. But using a fuller tank and letting the fuel flow to the header tank you can then switch and run till the header is dry, thus using the last gallon or two out of a tank.

    Don't think you will need that? That is fine. But like a shoulder harness, if you ever do...
    Ok "BULLSH!T", let me admit to making the assumption that both tanks were selected. If anybody can figure out how to unport them all, I'll buy them a steak. Crashing doesn't count. P.S. You and Mike should be scolding Gordon, Bugs and Skywagon because they agree with me too.
    Last edited by PerryB; 11-08-2013 at 09:13 PM.

  36. #36
    Gordon Misch's Avatar
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    Quote Originally Posted by aktango58 View Post
    Gordon, run one tank dry, switch tanks.

    wait five minutes, switch back. You have fuel again and run for a while...

    What, never tried it? Then don't say I am wrong.
    Tried it? SOP for max range given a full or near-full second tank. It cross-feeds through the cross-vent.

    If the fuel valves don't leak, and if there isn't enough fuel in the second tank to cross-feed thru the vent to the first tank, you're wrong.

    But so what? That is independent of the presence or absence of a header tank.

    And besides, that's not even what I said BS about, which I still stand by.
    Last edited by Gordon Misch; 11-08-2013 at 10:04 PM.
    Gordon

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  37. #37
    gbflyer's Avatar
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    You guys that run that low on fuel on purpose must have a big ol' pair. Where do you fit them in?

  38. #38
    mvivion's Avatar
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    Again, unsporting aside, why does the CC18-180 have six gallons unuseable fuel? The answer is fuel availability at all "normal" flight attitudes.

    Thats what header tanks are for, and that's a lot of useless gas to haul around....36 pounds worth.

    Granted, the CC header less fuel system STC on the PA18 doesn't require that much unuseable.....so, is that because of CAR 3 vs FAR 23 certification? Seems to me the systems are basically identical? CC tanks in the CC18 180 though.

    MTV

  39. #39
    nanook's Avatar
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    I never cared much for the CCs Goose Neck type fuel cap. To me that says that they had feed problems. Not enough head pressure or volume delivered. Probably at full power applications.... Also those things attract bugs, moisture and ice.

  40. #40

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    I am looking at doing a CC system when I recover BUT there are some issues I do not like. The top crossover tube will give you problems if parked on a side hill, It can be like a Cessna with fuel draining out the low wing. The both selector will cross contaminate if one tank has bad fuel, also make fuel management harder. Both tanks are connected in the off mode also. CC system without top crossover and stock valve would be what I would like. Just have to pay attention to where my fuel is and what angle I am flying at. Stock system sounds pretty good. Lots of good points have been brought up, now just pick what you like and go for it.
    DENNY

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