DME系统的地面设备是（）。

An autopilot is essentially a stabilizing system which （ ） the controls during flight.

“（ ）” is the height above the ground or water of the base of the lowest layer of cloud below 6000m covering more than half the sky.

“Indicated speed” is （ ） .

Radar works on an （ ） principle.

“Radar” means Radio Detection and （ ） .

Flight information centers shall provide flight information service and （ ） service within the regions.

Inertial navigation systems are （ ） devices.

The term knots when referring to speed means （ ） per hour.

A compass needle points to the （ ） .

The height of the mercury column will decrease by nearly one inch for each （ ） ascent.