What designation was given to the first helicopter accepted by the Navy on 16 October 1943?

The designation given to the first helicopter accepted by the Navy on 16 October 1943 is YR-4B. This particular helicopter was based on the Sikorsky R-4 and marked a significant point in naval aviation as it was the first operational helicopter used by the U.S. Navy. The YR-4B played a crucial role in establishing the use of helicopters for various tasks, including search and rescue operations, transport, and utility missions during World War II.

Its development and acceptance also laid the groundwork for future advancements in helicopter technology and operational tactics within the Navy, making it a pivotal moment in aviation history. In contrast, the other designations listed refer to helicopters that were introduced at much later dates or were not the first accepted by the Navy.