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Thread: Fuel Line

  1. #21

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    Quote Originally Posted by steveinindy View Post
    Kind of like HEMS pilots
    USED to be, maybe. now i'm paid to say NO.

  2. #22
    rwanttaja's Avatar
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    Quote Originally Posted by cdrmuetzel@juno.com View Post
    at the risk of being misinterpreted because print doesn't convey a wink and a nod very well,

    remember that P-51 pilots were paid to take crazy risks.
    And here I thought that my checks were just 30 years behind. :-)

    I can appreciate Steve and others' arguments for keeping the fuel out of the fuselage. I certainly grant the safety benefits.

    But for the fuselage fuel tank to make a difference, I have to crash. After that, to make a difference, the crash has to be such that the fuel tank is broached. After that, the crash has to be such that I am incapacitated. And after that, the fuel has to be ignited.

    I certainly agree with the possibility... we had an accident in the Fly Baby community about ten years ago that went about 95% through this sequence.

    http://www.bowersflybaby.com/safety/horsten.html

    Fuel-System mechanical problems or pilot fuel-system management issues contribute to about 8% of homebuilt accidents, but of course, the above sequence can occur in any accident. It's impossible to quantitatively compare the approaches... Reduce (slightly) the overall number of accidents due to fuel system or fuel management problems, or reduce (slightly) the risk of burning to death if you crash, if the fuel tank is ruptured, if you're trapped, and if it catches fire.

    Good subject for arguing over a couple of beers at the bar, but impossible to settle (short of a thumb-wrestling tourney).

    Putting the fuel tanks in the wings results in a more-complex aircraft. If you don't install something, you can't install it wrong, the parts can't wear and fail, and later maintainers can't botch the wrenchwork.

    Adding the complexity to move the fuel tank out of the fuselage reminds me of ballistic parachutes. It takes more building effort to install, it reduces performance, it makes things more complex to maintain, and really is only useful in a fairly narrow range of circumstances.

    But if you DO encounter those circumstances...you'd really wish you'd accepted the complexity.

    Ron Wanttaja

  3. #23
    steveinindy's Avatar
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    but some drifted way off the question you asked.
    Sorry about that.

    USED to be, maybe. now i'm paid to say NO.
    Ah....I guess it depends on which service you fly for but I hope the approach your company takes continues as a permanent trend even after the attention from all the deaths a few years back fades out. I never want to attend that many funerals of friends in a single year ever again.

    But if you DO encounter those circumstances...you'd really wish you'd accepted the complexity.
    Points taken. However, I honestly believe that given a little time, I could build a crash resistant fuel tank that could be safely put into an aircraft like the Fly Baby.

    I mean, we already have a design that exceeds the US Army standards for helicopter fuel tanks. It's going into our LSA design. One of the tests we're planning is to build a break-away rig for the bed of a pickup truck and to slam this tank (filled with water) into a scrapped telephone pole (one of the local energy companies has offered to donate one for the test) at a speed probably close to 65 mph. It's designed (on paper) to withstand a 80+ mph impact but I'm not sure we could safely test that with the gear we have available to us. Honestly, the fuel tank and seat designs were the only reason I even bothered with an LSA design. It's nothing more than a testbed for subsystems that will be scaled up for our real project. It's just a heck of a lot cheaper to abuse and destroy a dozen or so 6 gallon tanks than to do the same to even the smallest tank for the larger design.
    Unfortunately in science what you believe is irrelevant.

    "I'm an old-fashioned Southern Gentleman. Which means I can be a cast-iron son-of-a-***** when I want to be."- Robert A. Heinlein.



  4. #24

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    I worked with a friend with Kitfox and 912 engine and I have a 912 in Pulsar. If you are using mogas, stay away from blue vinyl lines and use automotive fuel hoses as they are formulated to withstand mogas with ethanol. I have never had an issue with auto hoses but replace them every 5 yrs and my CA mogas has 10% ethanol. Never saw any sign of deterioration but do it as precaution and it's both easy and inexpensive to do. There is no preload issue or fatigue issue with a rubber line as you can have with aluminum tubing nor a weight hit as with braided SS with AN fittings. I would go with what is safe and convenient to install and maintain.

  5. #25
    BushCaddy's Avatar
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    Some people never finish their airplanes because they search for perfection and it doesn't exist. Some people over-analyze and over-engineer every aspect and that's ok...it's their choice and perhaps they prefer building to flying...that's ok too. But it's not for me. In the real world the more pragmatic approach is take what has consistently worked in certified designs and incorporate them into your aircraft w/o over-complications and added potential points of failure. There is nothing unsafe or unreasonable about unshielded hard alumium fuel lines in the cockpit...just about every high wing airplane flying has them. No airplane can be 100% safe in every circumstance because it's an impossible task. At some point you just have to take what has succeeded time and time again in the past and move on.

    My $.02
    Don...
    BushCaddy N2C
    http://www.donsbushcaddy.com

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