Как по Английски будет 바지 밑으로 날아가다

phrase

Rely on instinct rather than logic or knowledge.

Примеры использования:

I was flying by the seat of my pants because i'd never managed anybody before

idiom

To do something difficult without the necessary skill or experience

Примеры использования:

I had no idea how to do it – i was just flying by the seat of my pants.