The Heinkel He 111 is a German airliner and medium bomber designed by Siegfried and Walter Günter at Heinkel Flugzeugwerke in 1934. Through development, it was described as a wolf in sheep's clothing. Due to restrictions placed on Germany after the First World War prohibiting bombers, it was presented solely as a civil airliner, although from conception the design was intended to provide the nascent Luftwaffe with a heavy bomber. Perhaps the best-recognised German bomber of World War II due to the distinctive, extensively glazed "greenhouse" nose of the later versions, the Heinkel He 111 was the most numerous Luftwaffe bomber during the early stages of the war. It fared well until it met serious fighter opposition during the Battle of Britain, when its defensive armament was found to be inadequate. As the war progressed, the He 111 was used in a wide variety of roles on every front in the European theatre. It was used as a strategic bomber during the Battle of Britain, a torpedo bomber in the Atlantic and Arctic, and a medium bomber and a transport aircraft on the Western, Eastern, Mediterranean, Middle Eastern, and North African Front theatres. The He 111 was constantly upgraded and modified, but had nonetheless become obsolete by the latter part of the war. The failure of the German Bomber B project forced the Luftwaffe to continue operating the He 111 in combat roles until the end of the war. Manufacture of the He 111 ceased in September 1944, at which point piston-engine bomber production was largely halted in favour of fighter aircraft. With the German bomber force virtually defunct, the He 111 was used for logistics. Production of the Heinkel continued after the war as the Spanish-built CASA 2.111. Spain received a batch of He 111H-16s in 1943 along with an agreement to licence-build Spanish versions. Its airframe was produced in Spain under licence by Construcciones Aeronáuticas SA. The design differed significantly only in the powerplant used, eventually being equipped with Rolls-Royce Merlin engines. These remained in service until 1973.
Development
Conception
After its defeat in World War I, Germany was banned from operating an air force by the Treaty of Versailles. German re-armament began earnestly in the 1930s and was initially kept secret because the project violated the treaty. Early development work on bombers was disguised as a development program for civilian transport aircraft. Among the designers seeking to benefit from German re-armament was Ernst Heinkel. Heinkel decided to create the world's fastest passenger aircraft, a goal met with scepticism by Germany's aircraft industry and political leadership. Heinkel entrusted development to Siegfried and Walter Günter, both fairly new to the company and untested. In June 1933, Albert Kesselring visited Heinkel's offices. Kesselring was head of the Luftwaffe Administration Office: at that point Germany did not have a State Aviation Ministry but only an aviation commissariat, the Luftfahrtkommissariat. Kesselring was hoping to build a new air force out of the Flying Corps being constructed in the Reichswehr, and required modern aircraft. Kesselring convinced Heinkel to move his factory from Warnemünde to Rostock – with its factory airfield in the coastal "Marienehe" region of Rostock (today "Rostock-Schmarl") and bring in mass production, with a force of 3,000 employees. Heinkel began work on the new design, which garnered urgency as the American Lockheed 12, Boeing 247 and Douglas DC-2 began to appear. Features of the He 111 were apparent in the Heinkel He 70. The first single-engined He 70 Blitz ("Lightning") rolled off the line in 1932 and immediately started breaking records. In the normal four-passenger version, its speed reached 380 km/h (240 mph) when powered by a 447 kW (599 hp) BMW VI engine. The He 70 had an elliptical wing, which the Günther brothers had already used in the Bäumer Sausewind before joining Heinkel. This wing design became a feature in this and many subsequent designs they developed. The He 70 drew the interest of the Luftwaffe, which was looking for an aircraft with both bomber and transport capabilities. The He 111 was a twin-engine version of the Blitz, preserving the elliptical inverted gull wing, small rounded control surfaces and BMW engines, so that the new design was often called the Doppel-Blitz ("Double Lightning"). When the Dornier Do 17 displaced the He 70, Heinkel needed a twin-engine design to match its competitors. Heinkel spent 200,000-man hours designing the He 111. The fuselage was lengthened to 17.4 m (57 ft) from 11.7 m (38 ft) and wingspan increased to 22.6 m (74 ft) from 14.6 m (48 ft).
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