The Heinkel He 115 was the most successful German floatplane of the Second World War, and served as a reconnaissance and attack aircraft.
When the Luftwaffe was officially established on 1 March 1935 the Heinkel He 59 was its only twin-engined floatplane. In July the Air Ministry issued a replacement for its replacement. This was to be a twin-engined aircraft that could act as a long range reconnaissance, torpedo bomber, minelayer or fog dispenser,
The first prototype made its maiden flight in August 1937. Early test flights revealed that it was difficult to fly, but Heinkel's designers were quickly able to solve this problem, and the resulting aircraft gained a very favourable reputation for its handling.
The second prototype, V2, was similar to the V1, but with an improved nose, new tail surfaces, and NACA type engine cowlings. V3 had the separate cockpit canopies of the pilot and radio operator replaced by a single glasshouse canopy, while the V4 was the production prototype, with an improved tail and float supports. During the development process the original rather ungainly nose was replaced by the streamlined glazed nose used in production aircraft.
The He 115 was in completion with the Ha 140. After tests in Lübeck Bay early in 1938 the Heinkel design was judged to be superior, and was put into production.
After undergoing flight tests the V1 was modified in preparation for a series of record attempts. The early nose was replaced with a smooth wooden version, the radio operator and observer were both removed (a mechanic was carried), and a streamlined canopy installed. On 20 March 1938 the modified V1 set eight records, carrying a series of loaded from 0kg to 2000kg over 1,000km and 2,000km courses. These records were only held for eight days, before being broken by a CANT Z 509.
The He 115 was an all-metal stressed-skin aircraft, with a slim streamlined fuselage. The mid-mounted wings had a rectangular centre section and tapering outer panels, and carried two BMW 132K engines (based on the Pratt & Whitney Hornet). The three man crew were carried in three cockpits. The observer was located in the glazed nose, with a bombsight and an MG15. The pilot was located just above the wing leading edge, and the radio operator/ rear gunner above the trailing edge. In the prototype the pilot and radio operator had been given separate canopies, but in production aircraft a single 'greenhouse' canopy was used, connecting their positions. An internal weapons bay was installed between the wings, and could carry either a 1,763lb torpedo or three SC 250 bombs (550lb each). The A-1 could also carry two more bombs under the wings.
Ten aircraft in the A-0 pre-production aircraft were built during 1937 and delivered to the Luftwaffe from January 1938. They were similar to the V4 prototype, and were used as reconnaissance aircraft.
The A-1 was built during 1938. It carried a 7.9mm MG 15 machine gun in the nose, and was powered by two BMW 132K radial engines. The torpedo rack was removed, while bomb racks capable of carrying one 250kg bomb were added under each wing, bringing the total to five. Either 34 or 38 were built.
The A-2 was an export version of the A-1. Sweden ordered 18, receiving 12 before the war, while Norway received 12, of which six were delivered.
The A-3 followed the A-1, and was generally similar to the earlier aircraft, but with a revised bomb bay that could carry a 50lt jettisonable fuel tank.
Ten pre-production B-0s were built, carrying enough extra fuel to increase the aircraft's range from 1,242 miles to 2,080 miles.
The B-1 had a stronger fuselage, and a maximum loaded weight of 10,815kg, which allowed it to carry mines or act as a torpedo bomber.
Three modification kits, or Rustsätze were produced for the B-1.
R1: Reconnaissance version with two cameras in the weapons bay
R2: Carried rack for single SC500 or SD500 (1,102lb bomb)
R3: Minelayer, capable of dropping either one 2,028lb LMB III or two 1,102lb LMA III
The B-2 was similar to the B-1, but with reinforced floats with steel ice runners under the floats which allowed it to operate from compacted snow or ice.
The C-1 entered service early in 1941. It carried two rear-firing MG 17 machine guns in the engine nacelles, and a fixed 20mm cannon under the nose. Neither of these additions helped solve its defensive weakness, but the nose gun was useful against ships. The C-1 could use the same three R kits as the B1, as well as the R4, which gave it an SV 300 smoke screen generator.
The C-2 was the C-1, but with the steel ice-runners of the B-2.
The C-3 was a dedicated minelayer. Eighteen were built, and operated with some success at night around the British coast.
The C-4 was a dedicated torpedo bomber. Thirty were built, entering service in May 1941.
A single C-4 was given more powerful engines as the prototype of a planned D series. It had been hoped to use the BMW 800 engine, but this never reached production, and so the D-1 used two BMW 801A 14-cylinder radial engines. Its top speed increased from 183mph to 236mph, but the BMW 801 was earmarked for the Focker-Wulf Fw 190, and so the He 118D never entered production.
Production of the He 118 had to restart in 1942, and continued into 1943, in an attempt to make up for losses. The E-1 carried two MG 81 machine guns, in the nose and dorsal positions, and some carried a 20m cannon. It also had an improved bomb sight.
The E-1 was an unarmed version of the E-1 used for air-sea rescue.
The He 115 was operated by the Küstenfliegergruppen coastal reconnaissance units. KFGr.106, KFGr.406, KFGr.506, KFGr.706 and KFGr.906 are all recorded as using the type, starting with 1./ KFGr. 106, which had eight by September 1939.
During 1939 KFGr.106 and 109 used the He 115 to drop magnetic mines around the British coast. KFGr.506 and 706 used the He 115 during the Norwegian campaign, where it was used by both sides.
KFGr. 106 and 506 used the He 115 during the Battle of Britain, resuming the mine laying operations. The type then began to be phased out in favour of the Blohm und Voss Bv 138 flying boat, and the remaining He 115s were concentrated in Norway, where they took part in attacks on the Arctic convoys, including the successful assault on convoy PQ 17 in July 1942. The last He 115s left front line service in the summer of 1944.
The six aircraft exported to Norway soon found themselves being used against the Germans. At the end of the Norwegian campaign three of the Norwegian aircraft and a captured German aircraft escaped to Britain, where they were given an heavier armament of four forward firing and four rear firing machine guns, and used for clandestine operations. Two went to Malta, from where they were used to drop agents in German occupied North Africa, while two were used for the same purpose over Norway, operating from Scotland. These aircraft were withdrawn in 1942.
Engine: Two BMW 132N 9-cylinder radial engines
Power: 856hp each
Wing span: 72ft 7 1/4in
Length: 56ft 9in
Height: 21ft 8in
Empty weight: 11,684lb
Fully loaded weight: 22, 928lb (Barnes); 29,932lb
Max Speed: 220mph at 11,155ft
Cruising Speed: 183mph
Service Ceiling: 18,045ft
Range: 2,082 miles
Armament: Two 7.92mm MG 15s, one fixed forward firing and one flexible rear firing
Bomb-load: 2,756lb maximum