Chief constructor Ernst Heinkel of the Caspar Werke of Travemünde, Germany, designed a two-seat multi-purpose fighter for the Swedish navy. The unarmed prototype, fitted with a 360 hp Rolls-Royce Eagle, was built in Germany. The fuselage was developed from the Hansa-Brandenburg W 37. Designated by Caspar as S.I and registered D-292, it was first flown in 1922. In Sweden it received the designation Type 31, but was sold to Norway in 1923, where it came on the civil registry as N-23 owned by L. Lier of Oslo. It crashed on August 15, 1924.
Caspar produced parts for another five aircraft that were assembled in Sweden by the newly formed Svenska Aero at Hästholmen in Lidingö. These were fitted with 240 hp Armstrong Siddeley engines, and a fixed machinegun and a double machinegun on a flexible mount. These were designated Type 32. Caspar produced another two unarmed S.Is for the Reichsmarine (German Navy), although they received civil registrations, D-450 and D-830.
At his own works Heinkel produced another ten aircraft, all fitted with a 360 hp Rolls-Royce Eagle IX engine, and differing from the previous aircraft only in detail. Built in 1923 but because of the restrictions all ten were dismantled and transported to Stockholm. Stored after testflights (Pilot Carl Clemens Bücker, first flight 11/7 1923) at the company Svenska  Aero AB. First in 1926 the embargo was taken away and the aircraft were returned to Germany. Used by the Severa later called Luftdienst GmbH. Of those D-1045 and D-1047 were only withdrawn from use in October 1933.
Type Two-seat reconnaissance floatplane
Engine 1 Rolls-Royce Eagle IX
Dimensions Length 12,66 m, height 3,90 m , span 17,48 m, wing area 52,6 m2
Weights Empty 1863 kg, loaded 2400 kg
Performance Max. speed 183 km/h at sea level, climb to 2000 m 13,9 min., to 1000 m 6,1 min.,sevice ceiling 3800 m, landing speed 84 km/h, endurance 4,6 h, range  800 km
Armament 1 machine gun used by the observer
Type Werk.Nr Registration History
205 D-938 Severa, July 1929 Luftdienst GmbH. Crashed 25/3 1930
207 D-939 Severa, July 1929 Luftdienst GmbH
February 1934
208 D-945 Severa, July 1929 Luftdienst GmbH. Crashed 12/9 1929
203 D-1045 Severa, July 1929 Luftdienst GmbH. Out of service October 1933
206 D-1046 Severa. Crashed 28/10 1927
211 D-1047 Severa, July 1929 Luftdienst GmbH. Out of service October 1933
202 D-1134 Severa, Febr. 1929, Im March 1930 used to test landings on snow covered ground at E-Stelle Travemünde. Febr. 1932 to DVS. In May 1933 engine changed to BMW Va
209 D-1199 Severa, Dec. 1929 with a Junkers L5 engine. Luftdienst GmbH
210 D-1282 Severa, Crashed 16/4 1929
204 D-1474 Severa, July 1929.  Luftdienst, Febr. 1933 engine changed to Junkers L5. April 1933 to DVS. Out of service June 1937