Aircraft MACH number

    Args:
        msg (String): 28 bytes hexadecimal message (BDS60) string

    Returns:
        float: MACH number

def mach60(msg):
    """Aircraft MACH number

    Args:
        msg (String): 28 bytes hexadecimal message (BDS60) string

    Returns:
        float: MACH number
    """
    d = hex2bin(data(msg))

    if d[23] == '0':
        return None

    mach = bin2int(d[24:34]) * 2.048 / 512.0
    return round(mach, 3)