The K-3 was an improvement on the K-2. The most significant change was the substitution of a Kinner C-5, 210hp engine for the Continental A-70, 165hp plant. The Kinner boasted 210hp at 1900 rpm. The weight of the engine was reported "under 190kg." The low weight-to-horsepower ratio was somewhat in favor of the Kinner. The K-3 used an 2.69m propeller. Optional items were a "coupe top" and a safety nose skid which protected the propeller in case of a noseup.

The horizontal tail plan form was changed for a more pleasing rounded shape on the elevators and stabilizer.

Records indicate that six were built. Two K-2s were modified to K-3s. One went to the South Pole with Admiral Byrd. This was donated by the Pep Boys of auto parts stores fame. It was N 12615. Two were sold to Japan. Standard equipment was: adjustable metal propeller, Heywood air starter, navigation lights and "Hotshot" (dry) battery.

G.Townson "Autogiro. The Story of the Windmill Plane", 1985

Technical data for Kellett K-3 Engine: 1 x Kimmer C-5 pistone engine, rated at 210hp, gross weight: 1089kg, empty weight: 747kg, useful load: 341kg, max speed: 177km/h, cruise speed: 145km/h, landing speed: 24-32km/h, rate of climb: 300m/min