As key technology, the rotary wing technology is developing by the nations of the world.

因此世界各国都把直升机的旋翼技术当作直升机的关键技术来研制。

youdao

As key technology, the rotary wing technology is developing by the nations of the world.

因此世界各国都把直升机的旋翼技术当作直升机的关键技术来研制。

youdao