To communicate with a helicopter in sight, raise both arms (forming the letter Y) to indicate "Yes" or "I need help," or stretch one arm up and one down (imitating the letter N) for "No" or "I do not need help". If semaphore flags are available, they can possibly be used to communicate with rescuers. This is important if the helicopter is searching for a missing party to avoid confusion.
Nicola Vähätalo
CC BY-SA 4.0
Nicola Vähätalo