ILS的航向指针居中，则说明着陆航空器（）。

The main purpose for extending the flaps is to （ ）.

（ ） carpet may be required for emergency landing.

（ ） is responsible for the use and management of SSR codes.

“Wind shear” is a kind of （ ） .

Automatic direction finding (ADF) is an airborne （ ） the ground direction finding system.

ADS is a means for（ ）.

Before providing radar service, air traffic controller should（ ）to the aircraft.

By using VOR and DME, a pilot knows he is on the correct course and his （ ） to the VOR/DME station.

When propellers are rotated, they generate a force called （ ）.

The difference between NDB and VOR is （ ） .