Aircraft true airspeed, BDS 5,0 message

    Args:
        msg (String): 28 bytes hexadecimal message (BDS50) string

    Returns:
        int: true airspeed in knots

def tas50(msg):
    """Aircraft true airspeed, BDS 5,0 message

    Args:
        msg (String): 28 bytes hexadecimal message (BDS50) string

    Returns:
        int: true airspeed in knots
    """
    d = hex2bin(data(msg))

    if d[45] == '0':
        return None

    tas = bin2int(d[46:56]) * 2   # kts
    return tas