Which capstan drive arrangement requires a flexible coupling between the reduction gear output shaft and the capstan head input shaft?

Correct Answer: Option B — The drive arrangement where the drive motor, electric brake, gear reducer are mounted on the deck below the weather deck, and only the capstan head is located on the weather deck.

When the drive machinery is mounted on a separate deck from the capstan head, the shafts are not perfectly aligned. A flexible coupling is mandatory to accommodate minor misalignments, prevent excessive bearing loads, and protect the gear reducer output shaft from bending stresses during operation.