螺旋桨变距是指改变（）。

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 （ ） ．

The airspeed required to sustain an aircraft in straight and level flight depends on （ ） ．

Lift is proportional to the square of the airplane’s velocity. If an airplane’s speed is reduced by one half, lift （ ） ．

Lift is proportional to the square of the airplane’s velocity. If an airplane’s speed is doubled, lift increases （ ） ．

The indicated airspeed of a stall varies with （ ） ．