What does the LCAC hand signal of the left hand above head rotating in a circular motion signify?

The hand signal of the left hand above the head rotating in a circular motion specifically indicates the instruction to start the starboard Auxiliary Power Unit (APU). This signal is used primarily in the operation of the Landing Craft Air Cushion (LCAC) to ensure clear communication among crew members.

When this signal is given, it communicates a request to initiate or activate the starboard APU, which is critical for various operations, including generating power to the craft's fans and propulsion systems. It is essential for crew members to understand these visual signals to maintain safety and efficiency while operating complex equipment like the LCAC. Mastery of these hand signals contributes to effective teamwork and the smooth execution of maneuvers during operations.