英语语法问题请教。。。谢谢？

Question

He took off the French coast in his plane when his enjine failed and he was forced to land on the sea.
请问大家这里的 to land 在句子中做什么成分，用来修饰什么的？谢谢大家的指点说明。。

Answer 1

……he was forced to land on the sea.
1 force sb. to do sth. 迫使某人做某事 （主动语态）
force是及物动词， sb.是宾语， to do sth.是宾语sb.的补足语
2 sb. be forced to do sth. 被迫做某事 （被动语态）
to do sth. 依然是主语sb.的补足语
3 上句中的to land on the sea是动词不定式短语，是主语he的补足语。
……he was forced to land on the sea.(被动语态）
=his engine's failing forced him to land on the sea. （主动语态）追问

谢谢老师的扩深，完全明白了。透透地！