In 1934 the prototype was built and on 22 June transported to Puck - a base of the Naval Aviation Squadron ("MDLot"). It appeared there, that it was tail-heavy on water, and it demanded some modifications, like lengthening engine nacelles towards front. It first flew on 8 April 1935 (some sources: 10 April). Initially the plane was kept in secret. The design was found satisfactory, but it had also faults, like moving of centre of gravity during flight and low fuselage rigidity. The prototype was modified then and returned from the factory for further trials on 30 October 1935.