def tas53(msg):
    """Aircraft true airspeed, BDS 5,3 message

    Args:
        msg (String): 28 bytes hexadecimal message

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

    if d[33] == '0':
        return None

    tas = bin2int(d[34:46]) * 0.5   # kts
    return round(tas, 1)