the ca.165 had a narrow fuselage featuring an enclosed cockpit. the undercarriage was fixed with spatted wheels. a unique feature of the ca.165 was the retractable radiator, which the pilot could deploy for optimum performance, or retract depending on the flight conditions: completely open in climbs, or closed in level flight and dives. in this way, it was similar to the morane-saulnier m.s.406. when deployed, the radiator significantly increased the drag on the aircraft, but increased engine performance and reliability.