航空活塞发动机正常使用的燃油是（）。

Flaps increase lift by （ ） ．

Which word is not used in describing the shapes of the wing?

V2 is defined as the （ ） .

Which of the following is not true?

If the airplane has fixed landing gear, it is considered to be in a clean configuration when the （ ） ．

An airplane is in a clean configuration when the （ ） ．

In training airplanes, configuration normally refers to （ ） ．

Which of the following is not true?

The ability of the airplane to fly slowly is especially important during the （ ） ．

When properly used, flaps （ ） ．