A finlet has two main meanings depending on the context:
- In ichthyology (study of fish), a finlet is a small, non-retractable fin usually found on the dorsal and ventral sides between the last dorsal or anal fin and the caudal (tail) fin of certain fishes such as mackerels, tunas, and bonitos. These finlets are rayless in some fish species and are thought to help in swimming dynamics by reducing drag and controlling turbulence around the tail area.
- In aviation, a finlet refers to an array of small fins on the aft (rear) fuselage of an aircraft. These finlets reshape the airflow around the aircraft to improve pressure distribution, reduce flow separation, and thereby reduce aerodynamic drag. The result is improved fuel efficiency, reduced carbon emissions, and extended aircraft range and endurance. These finlets are customized to different aircraft models and can be retrofitted with relatively little impact on the aircraft structure.
In summary, a finlet is either a small fin on certain fast-swimming fish near their tail or a small aerodynamic fin on aircraft to enhance fuel efficiency and reduce drag. Both types serve to optimize flow—water flow in fish and air flow in aircraft.
