4.1 一般规定 ................................................................................................................................ 81 4.2 在冰区航行船舶的要求 .............................................................................................................. 82 4.3 恶劣环境条件 ............................................................................................................................ 82 4.3.1 上层建筑结冰 ...................................................................................................................... 82 4.4 附近冰区的迹象 ...................................................................................................................... 84 4.5 独立航行船舶 ...................................................................................................................... 85 4.5.1 进入冰区 ...................................................................................................................... 85 4.6 冰区破冰船 ............................................................................................................................. 86 4.6.1 与破冰船通信 ............................................................................................................. 86 4.6.2 护航开始前须报告................................................................... 88 4.6.3 破冰护航作业 ...................................................................................................... 88 4.7 E FFEC