def jorgensen_eta(fineness_ratio: float) -> float:
    """
    A fit for the eta parameter (crossflow lift multiplier) of a fuselage, as described in:

    Jorgensen, Leland Howard. "Prediction of Static Aerodynamic Characteristics for Slender Bodies
    Alone and with Lifting Surfaces to Very High Angles of Attack". NASA TR R-474. 1977.

    Fits performed in /studies/JorgensenEtaFitting/

    Args:
        fineness_ratio: The fineness ratio of the fuselage.

    Returns: An estimate of eta.

    """
    x = fineness_ratio
    p = {
        '1scl': 23.009059965179222,
        '1cen': -122.76900250914575,
        '2scl': 13.006453125841258,
        '2cen': -24.367562906887436
    }
    return 1 - p["1scl"] / (x - p["1cen"]) - (p["2scl"] / (x - p["2cen"])) ** 2