As early as 1927, the German navy initiated a secret program for the buildup of a naval air arm. The catapult-capable HD 30 'ambulance aircraft' was not eventually built in series. Although this aircraft belongs to the RDL test site at Travemünde, this is not Travemünde, nor the Heinkel factory in Warnemünde. The city is Kiel before WWII, with the St Nikolai Church, and the catapult was evidently installed in the naval port - not at Holtenau. Photo from: Nationaal Archief (Netherlands)