Heinkel He 51 B-2 single-engine floatplane fighter
In March 1935, Germany officially refused to comply with the Treaty of Versailles clause that restricted the country's military power. And although June 18, 1935 saw the signing of a naval treaty between Germany and Great Britain which stated that the number of Kriegsmarine ships could not exceed 35% of the Royal Navy's combined strength, the path to the German fleet’s quick growth was open. An adequate buildup of naval aviation was immediately required. So, E. Heinkel's suggestion to create a floatplane fighter based on the He 51 was received with favour at the Kriegsmarine Headquarters. It was planned that, if necessary, seaplane tenders could be equipped with such fighters to provide air cover for Kriegsmarine ships at sea and at unfitted anchoring positions.
The Heinkel Flugzeugwerke designers had already laid considerable groundwork for the He 49 V2 floatplane fighter, so the He 51's assembly progressed very quickly. The second prototype fighter was mounted on two single-step, all-metal floats and was designated the He 51w. One production He 51 A-1 fighter was converted into the second prototype He 51 floatplane. After it was equipped with floats, it was designated the He 51 A-2. Its armament and airborne equipment were similar to the land version.
The floatplane fighter passed its tests quickly and showed no problems. The Heinkel company received an order for eight hydroplanes, and a second order for 30 machines followed. By that time, only aircraft of the "B" version were being released, so production floatplane fighters came to be designated as He 51 B-2. Planes of this variant were equipped with underwing bomb racks to suspend six 10 kg fragmentation bombs.
1.Ku.J.St./136, the only Navy fighter squadron that still had a dozen rather obsolete HD 38d aircraft in service, was rearmed with He 51 B-2s in the first half of 1936 and expanded into the I./JG136 Fighter Wing, comprising three squadrons. A combined total of 38 He 51B-2 floatplane fighters entered service with the 1st and 2nd squadrons of Coastal Fighter Group (Kustenjagdgruppe) 136, based in Kiel-Holtenau and Jever.