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Thread: Anything special to watch out for with running a tank dry in flight?

  1. #1

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    Anything special to watch out for with running a tank dry in flight?

    It will just restart again when you switch to the other side, right?

    I have a corroded fuel drain which needs replacing.

    Cheers,

    David
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  2. #2
    skywagon8a's Avatar
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    Quote Originally Posted by BritishCubBloke View Post
    It should just restart again when you switch to the other side, right?

    I have a corroded fuel drain which needs replacing.

    Cheers,

    David
    Corrected your word. Just be over the airport if in doubt.
    N1PA
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  3. #3

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    Be safe. Drain it on the ground.
    Sorry for the dumb questions, I'm an FNG!

  4. #4

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    Why do you have to do it in flight? Fly the tank close to empty, land, siphon the tank nearly dry and then run it out on the ground. A whole heck of a lot safer.
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  5. #5

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    Drain on the ground through the gascolator.

  6. #6
    Steve Pierce's Avatar
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    I do it all the time, switch tanks when it stumbles and it is running perfectly again. It does make a lot of people nervous. I can change a quick drain pretty quick with a full tank.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  7. #7

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    Maybe I will just do that. It is probably the fourth or fifth time this has happened in 16 years of ownership and it is always the right tank drain, never the left. There is never water in the fuel, so I can't figure it out. Any idea why, Steve?

  8. #8
    Scouter's Avatar
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    Quote Originally Posted by BritishCubBloke View Post
    It will just restart again when you switch to the other side, right?

    I have a corroded fuel drain which needs replacing.

    Cheers,

    David
    I would say it’s the most important. I have run one empty at altitude it sure gets your attention
    most of the time I just leave it in both.

    This was the end of Folsom Air in Maine. They were a long time bush charter.
    One tank full and one empty and fuel selector in the wrong tank
    3 guys dead
    https://www.highbeam.com/doc/1P2-11765306.html

    jim

  9. #9
    RaisedByWolves's Avatar
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    I didnít think Iíd like the both Dakota fuel valve after flying the stock piper for a while, itís one less thing to worry about now. Leave it on both and forget it


    Sent from my iPhone using Tapatalk
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  10. #10
    skywagon8a's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I can change a quick drain pretty quick with a full tank.
    Quote Originally Posted by BritishCubBloke View Post
    Maybe I will just do that. It is probably the fourth or fifth time this has happened in 16 years of ownership and it is always the right tank drain, never the left. There is never water in the fuel, so I can't figure it out. Any idea why, Steve?
    Steve's method will briefly cause a large outflow of fuel. This relatively high flow will draw any contaminants which normally may not drain out. If the tank is run dry in flight there will not be enough fuel remaining in the tank to do this flushing.

    Even though running the tank dry in flight while over the airport is perfectly safe, Steve's method will be more productive in your objective. Likely be done with less elapsed time too.
    N1PA
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  11. #11
    Steve Pierce's Avatar
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    I am a tool junkie and found this on the Matco truck. Works great for pulling those quick drains without an armpit full of fuel.
    Click image for larger version. 

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    Sent from my SM-N900V using SuperCub.Org mobile app
    Last edited by Steve Pierce; 05-02-2018 at 08:21 AM.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  12. #12
    behindpropellers's Avatar
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    On long flights I always run left tank for an hour and then drain the right tank until dry. Then land on the left tank.

    Tim
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  13. #13
    cubdriver2's Avatar
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    Take the cap off and tape the hole closed, sump it a couple times to create a vacuum before removing

    Glenn
    Last edited by cubdriver2; 05-02-2018 at 12:08 PM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  14. #14
    cubdriver2's Avatar
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    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  15. #15
    hotrod180's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    Cute and no doubt handy, but at $66 pretty spendy.
    I just tie rags around my wrists.
    Found out the hard way the first time I changed out a quick-drain
    that it's a pretty good way to get an armpit full of gas.
    Cessna Skywagon-- accept no substitute!

  16. #16

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    David
    I run my right tank dry a lot for fuel management issues. I try to do it over country I can land if possible. If I am working on fuel drain I usually cough it a few times to get out a much fuel as I can. As far as reoccurring drain problem, I had the same issue. My right tank had the low profile drain and after 4 years and several of the small washers replaced I noticed that what was happening was the valve was seating on the neck of the valve. This is a pipe thread and that should not happen. Basically the fuel lube I was using was acting like a seal in the threads, but after a few months it would give up and I would get a small weeping from the valve. I thought it was from the o ring or a some dirt that was the problem. I replaced the low profile valve with a normal one and have had no problems for a year. So check valve and make sure the threads are where the seating occurs. Hope I explained this properly. Best of luck.
    DENNY

  17. #17
    Steve Pierce's Avatar
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    Quote Originally Posted by hotrod180 View Post
    Cute and no doubt handy, but at $66 pretty spendy.
    I just tie rags around my wrists.
    Found out the hard way the first time I changed out a quick-drain
    that it's a pretty good way to get an armpit full of gas.
    That is for 6 of them. I knew I didn't pay that much.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  18. #18

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    I have regularly ran tanks dry on all sorts of airplanes, everything from Navajos to PA18s. HOWEVER that is on airplanes that have no issues with the fuel system. YOUR situation is deeply different. You have corrosion on the drain which means there could be flakes in the intake that could get drawn in and clog the gascolator or the line leading to or out of it. I would get the tank down a ways, but I would not run it dry. To great a risk unless you do it over an airport and you feel proficient at dead stick landings.

    As to why it is always the right one, I would look at the bonding. You most likely have a battery going there with fuel as the electrolyte.

  19. #19
    hotrod180's Avatar
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    FWIW during the OPEC embargo (1979-ish) we had gasoline rationing, in Calif anyway.
    You could fill up every other day, based on your license plate number, and there was always long lines.
    I owned an older Chevy pickup with saddle tanks. The tanks had not been used in a long time,
    but I figured they were just the thing to get me through the no-gas days.
    I'd fill the aux tanks, then run them dry before switching to the mains (just like an airplane).
    Well, like I said, the saddle tanks hadn't been used in a long time--
    every time I ran them dry, it would suck out debris from the bottom of the tank which would clog the finger screen at the carb inlet.
    I got pretty good at leaping out of the cab, opening the hood, and removing/shaking clear/reinstalling that screen...
    all while people were yelling and honking at me to get out of the way.

    Bottom line is, you don't want that happening in the air.
    Cessna Skywagon-- accept no substitute!
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  20. #20
    JP's Avatar
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    I gotta chuckle. Headed to the WAD one year with Cliff (yes, that one) off to my right. Running on my right small tank. Fully concentrating on keeping an eye on Cliff. He's been know to wander. My right tank runs dry. Right over the willywags of New Hampster. That little adrenaline surge. Followed by a tank switch. Purrs back to life.....
    JP Russell--The Cub Therapist
    1947 PA-11 Cub Special
    www.bloomerrussellbeaupain.com

  21. #21

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    Only the ground.
    Remember, These are the Good old Days!
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  22. #22
    cubdriver2's Avatar
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    Quote Originally Posted by BritishCubBloke View Post
    It will just restart again when you switch to the other side, right?

    Cheers,

    David
    If your with you wife when it quits and your seated side by side she will punch you in the right shoulder when the silence happens, seated tandem you will have to resize your cap a notch larger.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  23. #23

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    Quote Originally Posted by cubdriver2 View Post
    If your with you wife when it quits and your seated side by side she will punch you in the right shoulder when the silence happens, seated tandem you will have to resize your cap a notch larger.

    Glenn
    It quits all at once to, it goes from cruise to quiet in a microsecond, LOL, from noisy to complete silence. Flick of the wrist and its running back at cruise again, although as others said Im not sure I would run it dry with rust on the drain

  24. #24

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    Let us know what you find when you pull the drain.
    DENNY

  25. #25

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    For fuel tanks, carb heat, power changes, or mag checks, etc... I would say don't change anything unless you are over land (or water) you are ready to crash into. That also means get those things set where you want them before you go over that place, so you don't have to touch it while you are over it. Most things break (including cylinders and fuel selectors) when you change them. Just what I was taught.. and I believe it to be true...from what I've seen. I believe changing tanks after they run dry is a practical way to maximize the utility of you airplane - it just requires thought as to when and where..I don't like to do it unless I have a good reason. That said, I do it in every airplane new to me (with the previous caveats) so I know exactly when and where that tank will be done fueling the plane. I don't fly many that are new to me so that may be a luxury you folks don't have. If that were the case I'd just keep the tanks full.
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  26. #26

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    What is the fitting into which the fuel drain screws that then screws into the tank? Anyone have a part number? The drain is locked into it. The tank will need to be emptied completely and these two unlocked in a vice.

  27. #27
    skywagon8a's Avatar
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    That sounds like an adapter to change from a pipe thread to a straight thread or vice-versa for the drain valve. Sounds like you need to remove the whole assembly. Check the threads in the tank and get the proper drain valve. This adapter could be the cause of your issue with the valve.
    N1PA
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  28. #28
    Steve Pierce's Avatar
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    Piper used a reducer bushing in the bunge welded into the tank. I usually just install the larger quick drain instead of having two set of threads as leak sources.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  29. #29
    cubpilot2's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Piper used a reducer bushing in the bunge welded into the tank. I usually just install the larger quick drain instead of having two set of threads as leak sources.
    Trivia for the day.....

    https://www.aircraftspruce.com/catal...faircav160.php. 1/4”. NPT. PUSH TYPE. Some can be tripped with upper door window. PITA

    https://www.aircraftspruce.com/catal...squickdv11.php. 1/4”. NPT. Twist / lock type. Longer and will hit upper door, but wont spill fuel. Not fun to hit your head on..... Cure is to install big tires.

    https://www.aircraftspruce.com/catal...afairflush.php. SA14. Is 1/4 NPT. Flush mount. Can not be tripped by upper door. Only PITA if you can’t find your sump checker. (Never happens in Alaska bush)

    AD 85-06-04. Was what appears to have caused the existence of the adapter bushing with the Piper kit and flush mounted valve. AD allows for an FAA approved equivalent, so doesn’t mandate a flush mount. (If you already had something you didn’t have to change. Just install placard.)
    Ed
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  30. #30

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    Click image for larger version. 

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    Managed to change the drain valve by securely grabbing the reducer bushing and using a torque wrench to give enough moment. This is the reducer bushing. I am using the Piper part number for the valve, but the parts catalogue doesn't seem to show the bushing. Anyone know what it is? Steve? Or what is the part number for the larger drain valve?

  31. #31

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    x2

    Quote Originally Posted by OLDCROWE View Post
    Only the ground.

  32. #32

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    OK, found it, thanks everyone. What a resource this site is. Thank-you, Steve Johnson.

    http://rgl.faa.gov/Regulatory_and_Gu...2?OpenDocument

    (d) For Models PA-11, PA-16, PA-18, PA-18A, PA-20 and PA-22 series airplanes which have wing fuel tanks incorporating a 1/4 NPT drain boss, install drain valve Piper P/N 491-806 or FAA approved equivalent in accordance with the following procedures:

    (1) Drain fuel tank.

    (2) Remove the inspection cover located approximately 4 inches outboard of the butt rib and approximately 5 inches forward of the rear spar.

    (3) Remove the fuel tank drain plug.

    (4) Install reducer/adapter Piper P/N 453-616 (AN912-1D) and fuel drain valve P/N 491-806 or FAA approved equivalents per Figure 2 of this AD.

    (5) Add a 3/4 inch diameter hole in the inspection cover at the quick drain location.

    (6) Add fuel, check for leaks, check for proper operation of the quick drain valve and install inspection cover.

  33. #33

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    Is my part AN912-1D or AN912-3D Does anyone know? Does it matter? Shall I just order both? (They are only $6.)

  34. #34
    cubdriver2's Avatar
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    Quote Originally Posted by skywagon8a View Post
    That sounds like an adapter to change from a pipe thread to a straight thread or vice-versa for the drain valve. Sounds like you need to remove the whole assembly. Check the threads in the tank and get the proper drain valve. This adapter could be the cause of your issue with the valve.
    But that fitting gives you something to put a wrench on when removing the quick drain, other wise you would be torquing the tank bottom everytime you messed with the drain

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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