For reasons of convenience, two Wikipedia Lists of US Military Aircrafts are partly reproduced here, together with a
List of US Military Helicopters.
Early machines received a "R" for Rotor designation (R1 - R17) before it changed to "H" for
Helicopter. In 1962, a designation was adopted using a mission code with "H" only remaining as a suffix
(eg: AH: Attack Helicopter, CH: Cargo, SH: Anti-Submarine, UH: Utility, etc). While most previous R designated
machines were re-designated H, six helicopters received a reassigned H
number in 1962. Some USN helicopters did not translated into the H series - see Helicopters in the List of US
Naturally, not all all US helicopters entered the military and these are not mentioned here - the matter is examined on the US Helicopters page