飞行员遇到云雾无法用肉眼观察时单凭仪表操纵的仅靠仪表飞行的未经目击的仅靠仪表操纵地盲目地飞行单靠仪表的操纵
When pilots encounter clouds and fog that they cannot observe with the naked eye, they fly solely by instrument control, fly blindly without being witnessed, and fly solely by instrument control
以上为机器翻译结果，长、整句建议使用 人工翻译 。