 Ten were to be essentially similar to the SET 3 but feature various refinements including a redesigned undercarriage, and another ten similar to these but armed with machine guns for pilot and observer.Apart from these standard production models, a number of "one-off" aircraft were developed, including the 41 and 41S - a night-flying trainer and a combat-trainer respectively.Ionel Ghica flew the special 31G named "Foisor" on a long-distance flight from Bucharest to Saigon between 30 March and 16 April 1932, covering in 2 days, 14 hours, and 25 minutes.