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Thread: Prop Clearance?

  1. #1

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    Prop Clearance?

    Designing a gear, and am looking for opinions on this paragraph. Do I need to build with 9" at full stuff, flat tires, or just "clearance" at full stuff, flat tires? I'm interpreting as just "clearance" to which I'll add a few inches to be safe.

    (a) Ground clearance. There must be aclearance of at least seven inches (foreach airplane with nose wheel landinggear) or nine inches (for each airplanewith tail wheel landing gear) betweeneach propeller and the ground with thelanding gear statically deflected and inthe level, normal takeoff, or taxing attitude, whichever is most critical. Inaddition, for each airplane with conventional landing gear struts usingfluid or mechanical means for absorbing landing shocks, there must be positive clearance between the propellerand the ground in the level takeoff attitude with the critical tire completelydeflated and the corresponding landinggear strut bottomed. Positive clearance for airplanes using leaf springstruts is shown with a deflection corresponding to 1.5g


    Thanks,

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    skywagon8a's Avatar
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    Quote Originally Posted by gahi View Post
    Designing a gear, and am looking for opinions on this paragraph. Do I need to build with 9" at full stuff, flat tires, or just "clearance" at full stuff, flat tires? I'm interpreting as just "clearance" to which I'll add a few inches to be safe.

    (a) Ground clearance. There must be a clearance of at least seven inches (for each airplane with nose wheel landing gear) or nine inches (for each airplane with tail wheel landing gear) between each propeller and the ground with the landing gear statically deflected and in the level, normal takeoff, or taxing attitude, whichever is most critical. In addition, for each airplane with conventional landing gear struts using fluid or mechanical means for absorbing landing shocks, there must be positive clearance between the propeller and the ground in the level takeoff attitude with the critical tire completely deflated and the corresponding landing gear strut bottomed. Positive clearance for airplanes using leaf spring struts is shown with a deflection corresponding to 1.5g


    Thanks,
    Full 9" with one tire flat, full stuff.
    It says critical tire. Which tire is critical on a single engine tail dragger? For safeties sake I would consider both tires flat, even though the regulation uses tire (singular).

    On a multi engine airplane the critical tire would be on the same side as the respective engine. In that case it is possible for the prop to be even closer to the ground depending on it's relationship to the landing gear.
    N1PA

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