直升机尾桨的主要作用是（）。

To initiate a turn, the pilot use the （ ） and （ ） in combination.

Which of the following does not go with all the others?

Which word does not go with all the others?

Which of the following is a primary control system?

Which of the following is an assistant control system?

Which of the following is not part of empennage?

Which word does not go with all the others?

Which word does not go with all the others?

Which word does not go with all the others?

Which word does not go with all the others?