当着陆航空器在航向面内时，则航向指示显示（）。

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 （ ） .

Because of their high fuel consumption at low levels, （ ） prefer to remain at higher altitudes when they fly.

“Crank down the gears” means （ ） .

“Make a gear up landing” means to make a landing （ ） .

When an aircraft was in emergency after taking off, it should （ ） before landing.