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Thread: How I almost Wrecked My Super Cub Today

  1. #1
    Administrator Steve Pierce's Avatar
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    Default How I almost Wrecked My Super Cub Today

    I bet that got your attention. The event sure did get mine and figured I better tell the tale so someone else isn't as fortunate. So normally I fly around with 6-12 gallons of gas in my Super Cub. My playground is 7 miles from my airport and I like being light when playing. On several occasions when running the stock fuel system and stock valve I would forget to switch tanks when needed and run a tank dry. That is an un-nerving feeling and I am very quick to switch to the tank with the fuel but my fear was to have this brain fart and the engine quitting at the most inopportune time like climbing out of a short strip with no where to go. A few years ago I decided to install the Dakota Cub fuel valve which has a Both position but does not require you to replumb the entire fuel system like their STC'd headerless fuel system and the one from Cub Crafters. There are limitations since you are feeding out of one line on the right tank it does tend to burn out of the left tank faster and therefore on cross country flights I use left and right tank selection periodically to balance the fuel load. Thread on installing my Dakota Cub fuel valve. https://www.supercub.org/forum/showt...Cub-Fuel-Valve

    Yesterday morning SJ flew down to Wichita Falls to do an insurance check out with Tony in Mac's amphib Super Cub so I put on 20 some odd gallons of fuel to fly the 60 miles up to see him and explore the Brazos River that had crested the night before at almost 27 feet, (flood stage is 21 feet) which means the playground is gonna be new. I took off and switched over to the right tank with the intent to switch back over to both before I landed. Needless to say I didn't and after hanging out through lunch and flying the river back to Graham I put the airplane back in the hangar and didn't think about the fuel valve. This morning I took off and flew the river to the end of our normal route, pulled up out of the river in a left hand banking turn and the engine quits. Oh, forgot to switch back to Both position on the fuel valve so I reach down to turn the valve, it won't turn. CRAP. Put a lot of force on it and it still won't turn. WTF. Fly the airplane. There is a row of trees and a spotty field full of mesquite just beyond them. I am thinking, glide past the trees if I can, pull flaps and find a line between the mesquite. Problem is I don't see a line that doesn't include any trees. I'm gonna have to rebuild my airplane. CRAP. I don't want to tear up my plane, no options. I grab the handle and crank on it and it goes to Both, engine restarts and I feel my heart racing. Holy smokes. I get some altitude and rotate the valve a little, it is smooth but then hits a tight spot. To heck with that, back to Both and I will jack with it on the ground. Having had these valves apart all I can think is that an o'ring has come loose and bound up in there.

    I get back to the airport and taxi down to my work hangar and start draining fuel. I pull the fuel valve placard and remove the snap ring holding the spool in the valve. I installed the handle, slip a ziplock bag over the assembly to catch the detent springs and balls and pulled on it, it won't come out. Oh yea, there is a limit screw on the back that engages the rotation stop machined in the back of the valve body to meet the part 23 regulation about only being able to turn the fuel valve off in one direction. Crap, I gotta pull the valve out of the airplane.

    Ignore the dog hair, my dogs usually fly with me on my adventures.

    Attachment 56087
    I get the valve out and I notice that the limit screw is bent and later realize it has backed out as well. How did that happen. Only thing I can think is I got a little rodeo with it turning it all the way to the Left tank or to Off but can't recall doing that.
    Attachment 56088



    Attachment 56089
    I get the bent screw out and the spool out of the valve body, no smoking gun. Put some EZ Turn on the spool, install it in the valve body and it all works great. What the heck. I call Mark Erickson at Dakota Cub to see if he has ever heard of this, he has not. While talking to him and relaying my story I realized what happened. The screw backed out of the spool while in the Right position. It backed out so much that the head hit the rotation stop when I tried to go back to Both the Limit screw head wouldn't allow the spool to rotate. When I got real forceful with it the screw bent allowing the spool to rotate to the Both position. Not sure if the Loctite let go allowing the limit screw to vibrate out or what. I ended up leaving the limit screw out since I didn't have an MS35265-48 screw which has a lower profile head than normal. I don't have to meet part 23 and if I do I can install stops like Cub Crafters does with bushings and AN3 bolts on the cover plate of the fuel valve. Refueled, tested and flew some more with everything working normally. So that was my excitement for Sunday morning. Hopefully it is educational to someone else and this was a freak incident.

    Witness marks from the Limit Screw on the Rotation Stop on the back of the Fuel Valve Body.


    Attached Files Attached Files

  2. #2
    akflyer's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    The pic doesn't show any evidence of locktite having been on there. Is it possible that it wasn't used? Glad that it ended the way it did and both you and the bird are in one piece!

    Another great reminder to not get complacent and to use at a minimum GUMP. I have gotten lazy in the pacer a few times and when I get to the tie down and shut down I realize I am still on the right tank from cruise flight. Every time I do that I get a kick to the junk wake up call.

  3. #3
    walt.buskey's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    Steve, so your DK valve's been in there about 5 years? How many flight hours?

    Looks like that screw could be observed with a mirror once the cover's off... (maybe I'll just have a look-see....)

    Glad you were able to get out of a tight spot!

  4. #4
    Stephen's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    Steve, glad it worked out for you.

    My stupid fuel starvation occured over water at 900 feet, with my wife along. I'm not sure which of these variables are worse. It was a problem with miss aligned sight gauges...anyway. I survived by rocking the wings and pumping the throttle to get several more short lived engine starts so that I could make it to land. Glad I had my big tires on that day.

    It took a few months before my hart would not race when I pulled the power off. I added a fuel monitor gauge to my panel and wear a life jacket flying over water.

    All good lessons, if we survive.
    Last edited by Stephen; 06-07-2021 at 02:39 PM.
    "You can only tie the record for flying low."

  5. #5
    Pacerfgoe's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    I bet that got the blood pumping through your veins....good story.

    I agree with akflyer that it doesn't look like there was ever any Loctite on that screw, is there any evidence to the contrary?

    I have to admit I once got lazy and didn't do the prelanding checks in my Pacer and landed uneventfully.....on the ground after shutdown I noticed that I was still on the tank that had 2 hours plus burned out of it....I was pretty much on fumes.
    Forrest Miller

  6. #6
    RRHall's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    Quote Originally Posted by Stephen View Post
    Steve, glad it worked out for you.

    My stupid fuel starvation occured over water at 900 feet, with my wife along. I'm not sure which of these variables are worse. It was a problem with miss aligned sight gauges...anyway. I survived by rocking the wings and pumping the throttle to get several more short lived engine starts so that I could make it to land. Glad I had my big tires on that day.

    It took a few months before my hart would not race when I pulled the power off. I added a fuel monitor gauge to my panel and wear a life jacket flying over water.

    All good lessons, if we survive.

    In my case it would definitely have been having the wife along. I would have had multiple audible alarms going simultaneously.

  7. #7
    Stephen's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    Quote Originally Posted by RRHall View Post
    In my case it would definitely have been having the wife along. I would have had multiple audible alarms going simultaneously.
    I hear you. When we made it to a field, I tried one more time to get it going and get a little closer to home. She not so politely said "get this plane on the ground, NOW".

    Maybe I'll stick with dogs....like Steve does.
    Last edited by Stephen; 06-07-2021 at 03:47 PM.
    "You can only tie the record for flying low."

  8. #8
    Gilbert Pierce's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    It seems to be a problem mainly confined to those who have really big tires. There has to be a connection there somehow somewhere.

  9. #9
    Administrator Steve Pierce's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    Quote Originally Posted by Gilbert Pierce View Post
    It seems to be a problem mainly confined to those who have really big tires. There has to be a connection there somehow somewhere.
    Hmm, really? Short memory? I seem to remember little tires covered by wheel pants having a similar outing as Stephen. I remember watching her walk away from the airplane from the air and could tell her mood.

  10. #10
    Old3pacer's Avatar
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    Default Re: How I almost Wrecked My Super Cub Today

    Wow!
    Great story, good telling, fine outcome!
    I appreciate you sharing, all of the experiences.
    I have been a bit slack on my gumps check last few flights but you have given me reason to approach
    it with renewed vigor. Glad you were able to 'persuade' the valve to continue to function and
    correct the issue without bending the plane.

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