英语语法分析

For example, all a VFR pilot has to do to enter Class C airspace is establish two-way radio contact with ATC.

例如，VFR 飞行员进入 C 类空域所要做的就是与空中交通管制建立双向无线电联系。

No explicit permission from ATC to enter is needed, although the pilot must continue to obey all regulations governing VFR flight.

尽管飞行员必须继续遵守有关视觉飞行规则的所有规定，但无需获得空中交通管制的明确进入许可。

However, this purely visual system was useless in bad weather, and, by the 1930s, radio communication was coming into use for ATC.

然而，这种纯粹的视觉系统在恶劣天气下毫无用处，到了20世纪30年代，无线电通信开始用于空中交通管制。