Pre-Flight Sump Check and Drain for Header Tank

Discussion in 'Firewall Forward / Props / Fuel system' started by wsimpso1, Feb 3, 2019.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Feb 3, 2019 #1

    wsimpso1

    wsimpso1

    wsimpso1

    Well-Known Member

    Joined:
    Oct 19, 2003
    Messages:
    5,627
    Likes Received:
    2,866
    Location:
    Saline Michigan
    I have a header tank in my design, its bottom is well above the floor. I want to check the tank for contaminants before flight and be able to drain the tank fuel for service. How the heck do you set up the drain valve system that is also somewhat crash safe?

    I can imagine a hard line that exits at the lower chine with a flush valve. That has the disadvantage of being able to tear it open in an emergency landing and dump 10 gallons of fuel right under the cockpit when things come to a stop.

    I was trying to imagine the valve screwed into the bottom of tank, well above the belly, then a thin aluminum line out to an exit with a cable actuator. It is a long ways from the instrument panel to the header tank, so a cable actuation would be nice. At McFarlane's site, they are $800 and up, and most require a rebuildable core. There has to be a better way... I did find boat engine oil remote drain valves, but they are big and heavy... Any suggestions?

    Billski
     
    Last edited: Feb 4, 2019
  2. Feb 3, 2019 #2

    Toobuilder

    Toobuilder

    Toobuilder

    Well-Known Member

    Joined:
    Jan 20, 2010
    Messages:
    4,287
    Likes Received:
    3,034
    Location:
    Mojave, Ca
    Standard drain screwed directly to bottom of tank (well inside the OML); extension tube drain tool reaches up inside fuselage recess. This is how the header on the C-177 is sumped, IIRC. Many deeply cowled, gascolator equipped airplanes do the same thing.
     
    BJC likes this.
  3. Feb 3, 2019 #3

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

    Joined:
    Nov 14, 2009
    Messages:
    5,998
    Likes Received:
    2,001
    Location:
    Rocky Mountains
    Motorcycle style petcock on the bottom of the tank, a short length of braided fuel line, then a small dry-break to the hard line out?
     
  4. Feb 3, 2019 #4

    Marc Zeitlin

    Marc Zeitlin

    Marc Zeitlin

    Well-Known Member

    Joined:
    Dec 11, 2015
    Messages:
    424
    Likes Received:
    571
    Location:
    Tehachapi, CA
    I haven't flown a C-172 in a long time, but IIRC there's some cable inside the oil door that pulls up on a gascolator valve, and you drain the gascolator under the cowl.

    I'm thinking something like this:

    https://www.mcfarlaneaviation.com/products/product/SA3-10-A-D/

    where you don't have the gascolator, but you have some sort of mechanism that a smart guy like you could copy and have a cable that actuates it to drain through a rubber hose down through the floor of the plane. A crash might scrape away the rubber hose, but wouldn't get near the actual tank.

    Maybe Steve's Aircraft:

    https://www.stevesaircraft.com/gascolator.php
    https://www.mcfarlaneaviation.com/media/documents/fuel-gascolator-assemblies.pdf

    would sell you just the drain and the machined lever so you could mount that as you wish.
     
    wsimpso1 likes this.
  5. Feb 3, 2019 #5

    Toobuilder

    Toobuilder

    Toobuilder

    Well-Known Member

    Joined:
    Jan 20, 2010
    Messages:
    4,287
    Likes Received:
    3,034
    Location:
    Mojave, Ca
    The 177 Cardinal has a remote gascolator drain by the oil dipstick as well as a recessed drain for the small header.
     
  6. Feb 4, 2019 #6

    wsimpso1

    wsimpso1

    wsimpso1

    Well-Known Member

    Joined:
    Oct 19, 2003
    Messages:
    5,627
    Likes Received:
    2,866
    Location:
    Saline Michigan
    That gascolator rig gets the function. I will check in with Steve's. Maybe I can work up something with an existing valve, solder an extension on it and an opening mechanism...

    Gotta go look at the C172 and 177 stuff.

    Billski
     
  7. Feb 4, 2019 #7

    mcrae0104

    mcrae0104

    mcrae0104

    Armchair Mafia Conspirator HBA Supporter

    Joined:
    Oct 27, 2009
    Messages:
    2,869
    Likes Received:
    1,883
    Location:
    BDU, BJC
    The 172S I am familiar with does not have the setup Mr. Z mentioned... but then there are a lot of 172 models. The -S has 13 locations to sump. Lawyers must have been involved.
     
  8. Feb 4, 2019 #8

    Marc Zeitlin

    Marc Zeitlin

    Marc Zeitlin

    Well-Known Member

    Joined:
    Dec 11, 2015
    Messages:
    424
    Likes Received:
    571
    Location:
    Tehachapi, CA
    13? That's just crappy design (and I say that as a design engineer). No one in their right mind would design a plane that had 13 "low spots" in the fuel system, even if you weren't going to tell people to sump all of them. Sheesh.
     
    wsimpso1 likes this.
  9. Feb 4, 2019 #9

    Voidhawk9

    Voidhawk9

    Voidhawk9

    Well-Known Member HBA Supporter

    Joined:
    Mar 26, 2012
    Messages:
    179
    Likes Received:
    89
    Location:
    Timaru, NZ
    It's true, 13. One next to each baffle (rib?) in the tank, apparently. Plain ridiculous. I've flown 172-H, N, R, and S, the latter two have 13, the former have 3. No remote cables though.
    Cowl screws also seem to be a consumable item on these, coming loose and falling out all the time. :ponder:
     
  10. Feb 4, 2019 #10

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    5,922
    Likes Received:
    1,506
    Location:
    North Carolina
    I've rigged similar systems for water ball valves in awkward places. Find a valve with a T handle. Slot a piece of tube and that is your extension. No need for a hardline drain, a bit of fuel hose is all you need.
     
  11. Feb 4, 2019 #11

    wsimpso1

    wsimpso1

    wsimpso1

    Well-Known Member

    Joined:
    Oct 19, 2003
    Messages:
    5,627
    Likes Received:
    2,866
    Location:
    Saline Michigan
    Sigh. Every little gadget that must be designed, built, tested, and iterated adds weeks to the build and uncertainty about durability. I was hoping to BUY something that is known to work great, last a long time, and just attach it to the airplane.

    Billski
     
  12. Feb 7, 2019 #12

    Tiger Tim

    Tiger Tim

    Tiger Tim

    Well-Known Member

    Joined:
    Apr 26, 2013
    Messages:
    2,776
    Likes Received:
    1,541
    Location:
    Thunder Bay
    Minimal dihedral dictates checking all four corners of each wing tank to deal with a combination of non-level ramps and post-accident lawyers. That's eight drains right there. I forget where the other five were.
     
  13. Feb 7, 2019 #13

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    5,922
    Likes Received:
    1,506
    Location:
    North Carolina
    At least two drains in your bank account.
     
  14. Feb 7, 2019 #14

    blane.c

    blane.c

    blane.c

    Well-Known Member HBA Supporter

    Joined:
    Jun 27, 2015
    Messages:
    2,893
    Likes Received:
    495
    Location:
    capital district NY
    If water has accumulated in a wing tank lines low spot you would not want to pull that water into the header tank by only having one gascolator or fuel sump. From what I remember of your fuel system diagram you would need at least 3 locations to check for water, one drain at the low spot of each wing tank system probably near the on-off valve preceding the header tank and a gascolator at the low spot after the header tank. Check the wing tank drains first to avoid pulling water into the header tank.
     
  15. Feb 7, 2019 #15

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,139
    Likes Received:
    3,017
    Location:
    Memphis, TN
    Without having to read through the other threads, is the header vented to a main tank or to atmosphere?
     
  16. Feb 7, 2019 #16

    wsimpso1

    wsimpso1

    wsimpso1

    Well-Known Member

    Joined:
    Oct 19, 2003
    Messages:
    5,627
    Likes Received:
    2,866
    Location:
    Saline Michigan
    Header tank is vented back to the tank fuel is being drawn from. Scheme is to pump fuel from the selected tank to the header until it is full, then overflow from up high on the header tank back to the wing. Water not caught in the wings can be pumped to the header... Pickup points on each tank do leave room for some water to accumulate before water will be pumped to the header, then to fuel rail.

    What are you thinking about?

    Billski
     
    Last edited: Feb 7, 2019
  17. Feb 7, 2019 #17

    blane.c

    blane.c

    blane.c

    Well-Known Member HBA Supporter

    Joined:
    Jun 27, 2015
    Messages:
    2,893
    Likes Received:
    495
    Location:
    capital district NY
    If you only sump from header, and there is a place for water to collect prior to entering the header tank it will collect there and when you sump the header tank you will draw the water into the header tank were it will likely mix with the fuel to some extent. It is then possible that it will come out of suspension at the worst possible time. I always sumped my tanks from the highest points first the lowest point last so as not to draw water through the system.
     
    wsimpso1 likes this.
  18. Feb 7, 2019 #18

    blane.c

    blane.c

    blane.c

    Well-Known Member HBA Supporter

    Joined:
    Jun 27, 2015
    Messages:
    2,893
    Likes Received:
    495
    Location:
    capital district NY
    Say moisture in the air has condensed in the wing tanks overnight and dribbled down to the low points in the fuel system, you don't want to mix it up and get it into suspension, Ya want to one eye the plane sneak up on it with your fuel checker gizmo and gently sump from high to low without mixing things up. So check one wing sump then the other wing sump and finally the low sump. Then go about the rest of your business with the plane. Yes sump the fuel first before other stuff so you don't shake the fuel and water up and put the water back into suspension. Well anyway that's the way I did it, I could sneak up on her real good too.
     
  19. Feb 7, 2019 #19

    Toobuilder

    Toobuilder

    Toobuilder

    Well-Known Member

    Joined:
    Jan 20, 2010
    Messages:
    4,287
    Likes Received:
    3,034
    Location:
    Mojave, Ca
    The other thing to consider here is the fact that this airplane will be EFI. Liquid water passes right on through such a system with little detriment. Ice is another matter, but it wont drain anyway. Not saying one should omit sump drains, but EFI is not as operationally critical of water as "typical" recip fuel systems.
     
    wsimpso1 likes this.
  20. Feb 7, 2019 #20

    wsimpso1

    wsimpso1

    wsimpso1

    Well-Known Member

    Joined:
    Oct 19, 2003
    Messages:
    5,627
    Likes Received:
    2,866
    Location:
    Saline Michigan
    I still plan to sump all three tanks. The fuel pickups in each tank are finger screens somewhat above the bottoms of the tanks, so drains at the low point in each tank should get the water before it accumulates to the point of being picked up and moved to the next place in the system.

    Using an existing quick drain with lever and cable to open it and an extension tube to get it from valve to outside of the airframe seems to be the game. One more thing I gotta develop instead of just buy and install. So be it.

    Billski
     
    blane.c likes this.

Share This Page

arrow_white