Which aircraft designation is used for a helicopter involved in search and rescue?

The correct designation for a helicopter involved in search and rescue operations is "H." In military aviation, the letter "H" is designated for helicopters, and this includes various models specifically adapted for search and rescue missions. These helicopters are equipped with features essential for such operations, including hoists, medical equipment, and sophisticated navigation and communication systems.

Other designations do not correspond to helicopters or do not specifically indicate a role in search and rescue. For example, "K" typically denotes a specific role such as cargo variants, while "O" indicates observation or reconnaissance aircraft, which do not specifically serve in a search and rescue capacity. The designation "N" is not a standard classification in this context. Therefore, the use of "H" acknowledges the helicopter's primary function in search and rescue missions.