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Modified fuel caps

in 912 / 914 Technical Questions 8 years ago
Just interested to know if anybody has any idea why my inspector insisted i modify my already vented fuel caps on my CH701 to include a pipe facing forward into wind. He was going on about pressurized fuel tanks, I'm not saying he's wrong it's just that I can't really see what the point is! High wing aircraft fuel flowing down to the engine (a 912ul) why do I need and more pressure going into the fuel tanks. Does anybody else do this mod or is it just my inspectors thing!

Thanks for anybody's thought's on the post.

Stephen

  • Re: Modified fuel caps

    by » 8 years ago

    Hi Stephen,

    I did a research project on an FD CT years ago. Tried all kinds of vents. The original ones where straight up. Tried all positions with these. Then I tried the 90 degree swept forward ones that like you say would pressurise the tank. Then we just tried a flat cap that had vents holes and running vent tubes out that the wing tips. Many planes from yesteryear had these swept forward 90 degree vents. Maybe your inspector is old school, but a really doubt they are mandatory.

    Bottom line not a single one made any difference. I will give this one caveat. The 90 degree swept forward and taller than the stock straight up ones would help keep fuel from wanting to splash or overflow out with full tanks.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Modified fuel caps

    by » 8 years ago

    Thanks Roger for your time and trouble. I think it's the old school thinking as you said!I did have a CH601hd that I built before the 701 and that plane had flanged vented caps inside the wing under an access hatch, never had a problem with fuel flow with that arrangement in the ten years I flew that plane either.
      
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  • Re: Modified fuel caps

    by » 8 years ago

    Depending on the inspector's attitude it might be quicker and easier to add them then once signed off do what you want. I hate to say it that way, but some aren't very flexible and it may take a long time to contest the mod.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Modified fuel caps

    by » 8 years ago

    You're quite right Roger, infact that is what we did in order to get the permit to fly we have since been using the modified caps because he made us drill holes in the caps and fit the pipes as he wanted. However we have now flown the aircraft for about 30 hours and although we now have some replacement caps I was reluctant to use them due to being concerned about why we had to mod the caps in the first place.
      
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  • Re: Modified fuel caps

    by » 8 years ago

    Hi Stephen,

    Run your own test and get real time facts.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report
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