Wind-Assisted Propulsion Systems (WAPS) are moving from pilot projects to commercial deployment, yet no mandatory, internationally accredited training standard exists for the seafarers operating them, and crew preparation relies on non-regulated, manufacturer-led familiarisation. This study assesses operational competency needs based on serving crew members rather than desk-based analysis. A sequential case study combined onboard observation with a structured questionnaire administered to 28 seafarers at a shipping company operating Flettner rotor vessels; the 16 respondents with hands-on rotor experience represent an estimated 5–10% of the global population of such officers. Over 93% of active operators report regular manual intervention or close monitoring, and 56% experience recurring conflicts between their professional judgment and manufacturer-provided system recommendations, challenging the assumption that automation minimises the human element. A lack of holistic understanding of vessel behaviour under aerodynamic forces emerges as the primary obstacle to safe operation, and seafarers prioritise stability and COLREG compliance over efficiency. The study maps the competency areas requiring formalised training and proposes a modular, STCW-aligned curriculum to inform ongoing IMO deliberations on training for wind-propelled ships.