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Thread: Ram air fuel cap

  1. #1
    Join Date
    Jan 2014
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    Culpeper
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    Default Ram air fuel cap

    I read with interest Ralph Widman's "The News" article in April, May, June 2014 issue about a Ram air cap for the PA-22 right tank. He states that a Wag Aero cap @ $10 with a 1/4" copper tube in it, bent to the relative wind will allow the right tank to be used until dry. It appears to be a fix which requires no STC or 337. Is this correct?

  2. #2
    Join Date
    Jun 2008
    Location
    Roseville, CA
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    442

    Default

    Is such a cap required? I can run my right tank until the engine stumbles, land, and put 18.0 gallons into it. Is this a fluke, or will these aircraft all do this?

    Kurt
    Ex-Vice President

    63' Colt

  3. #3
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    Jan 2014
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    Culpeper
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    Default

    I'm referring to the limitation of no take offs and landings with less than 1/3 of a tank on the right side. Ralph said that the ram fuel cap corrected the shortcomings of the fuel plumbing on the right side and that the limitation would no longer apply. Can I get anyone to confirm this?

  4. #4
    Join Date
    Mar 2012
    Location
    Searcy
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    66

    Default

    Quote Originally Posted by Taildragon22 View Post
    Can I get anyone to confirm this?
    I'll go out on a really thick, big, and heavy limb and say no

    Besides how much gas is 1/3 of a tank? Is there any situations where getting off the ground with that much gas is actually going to get you somewhere you couldn't just drive to in the car and bring back 5 gallons of gas to put in it?

  5. #5
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    Mar 2014
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    Delta, OH
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    Default

    No, not without FAA approval.

    The Placard on the instrument panel is required in the Type Certificate Data Sheet and cannot be removed or changed without FAA approval.

    I would be cautious about even putting on a modified fuel cap without approval.

    Rick
    Last edited by RickF; 06-08-2014 at 10:46 PM.

  6. #6
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    Mar 2014
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    Delta, OH
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    Default

    Quote Originally Posted by 61Chuck View Post
    Appendix A to FAR Part 43, major alteration, airframe. Basic change to the fuel system. Hard to argue that.
    The point is he cannot just make the change without some kind of paperwork.

    Typically a 337.

    Rick

  7. #7
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    Jan 2014
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    Default

    The article is on page 57-60 in the "The News" and after re reading, a 337 is not stated but implied since he was going to do a re plumb of the fuel system on the right side which does requires a 337. To answer other questions, 1/3 of a tank equates to 6 gallons or about 45 minutes of flying at full rich settings on the 150hp engine, leaned out, it's almost an hour. And yes, I would rather operate an aircraft without restrictions on the fuel system especially in the pattern.

  8. #8
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    350

    Default

    I you have a question about how and what Ralph did on this fuel cap, drop him an email. His address is at the beginning of the article. After talking to him on Saturday at our chapter meeting, I believe he indicated that the FSDO told him it would be a minor alteration. This puts the liability on whom ever is makeing the mod and relieves the FSDO of any responsibility. This same type of cap is common on many cubs and super cubs. This mod doesn't change in any way the flight requirement on the right tank of use in leval flight only with less than 1/3 of a tank. Ralph is an I/A and understands the rules.
    The reason Ralph needed to add pressure to his right tank is that un be known to him there waws a blockage in the fuel line up near the selection valve. He found this out much later. He still uses the ram air cap, however, because it improves the fuel flow from the right tank under all conditions.

    Tom Anderson

  9. #9
    Join Date
    Jan 2014
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    Culpeper
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    Default

    I've got to say I love this forum format. The picture is becoming clearer with everyone's help. I've had several mechanical fixes over the years that have solved the immediate problem but not the underlying cause. The cause was only found after a tear down. If I can summarize, the ram air cap is a necessity for a spider infested fuel selector. Without the spider a normal cap works fine and the TCDS restriction remains in place. With the ram air cap and a 337 and without the spider, the fuel flow is improved in all flight condition and TCDS restrictions still apply. So my next question would be, if the right side is re plumbed via 337 and a Maule fuel selector with left, right, both, off is installed could the TCDS restriction be removed for that A/C via FSDO?

  10. #10
    Join Date
    Mar 2014
    Location
    Delta, OH
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    I would make sure that the removal of the placard is stated in the context of the work performed on the 337.

    Rick

  11. #11
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    350

    Default

    I highly doubt that any FSDO would remove the TCDS restriction with anything less than an STC. Even with Frank Sperandeo's fuel mod which eliminates the cross tube under the pannel, the restriction remains in place. The concern is that at steep angles of attack flow from the right tank could be reduced enough to cause engine starvation. I have not found it to be an issue, but it only takes once. The Maule fuel valve would make a difference, but I still doubt the FAA would do it without the testing required for an STC.
    Tom Anderson

  12. #12
    Join Date
    Mar 2006
    Location
    Peachtree City, GA
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    21

    Default

    I tried the caps from Wag-Aero. They are well made however on my Pacer the tank cover fuel filler neck hole was too small of diameter to allow the lugs on the cap to recess below the tank cover level as the cap is tightened. These caps have about 1/2 "lugs or Knobs" beyond the diameter of the basic cap. It's very nice too help turn the cap in slippery conditions or with gloves but I would have had to widen the tank cover opening or modify the caps to work on my airplane. If your tank filler neck extends up higher than mine it would probably work fine. I ended up buying the TSO'd ones from Atlee Dodge. If you want the total diameter measurement of the Wag-Aero cap let me know.

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