helicopter的复数形式是直接在单词后加s，第三人称单数形式是helicopters，过去式形式是helicoptered，过去分词形式helicoptered，现在分词形式helicoptering。
例句：
1、The helicopter made several passes over the village before landing.
直升机在村落上空盘旋数次才降落。
2、The rescue helicopter made another sweep over the bay.
救援直升机在海湾上空又搜索了一遍。
3、The helicopters appeared as two black dots on the horizon.
直升机像两个小黑点出现在地平线上。
4、Stay well away from the helicopter when its blades start to rotate.
直升机的螺旋桨开始转动时，尽量离远点儿。
5、A helicopter was scrambled to help rescue three young climbers.
直升机接到命令，紧急起飞前去营救三个登山的年轻人。
