page_title: Dornier Do 217
section_title: Focus on a heavy bomber
hierarchical_section_title: Dornier Do 217 / Development and design / Focus on a heavy bomber
caption_attribution_description: English: Three-side drawing of German Dornier Do 217E bomber, 1943.
context_page_description: The Dornier Do 217 was a bomber used by the German Luftwaffe during World War II as a more powerful development of the Dornier Do 17, known as the Fliegender Bleistift. Designed in 1937 and 1938 as a heavy bomber but not meant to be capable of the longer-range missions envisioned for the larger Heinkel He 177, the Do 217's design was refined during 1939 and production began in late 1940. It entered service in early 1941 and by the beginning of 1942 was available in significant numbers.
  The Dornier Do 217 had a much larger bomb load capacity and had much greater range than the Do 17. In later variants, dive bombing and maritime strike capabilities using glide bombs were experimented with, considerable success being achieved. Early Do 217 variants were more powerful than the contemporary Heinkel He 111 and Junkers Ju 88, having a greater speed, range and bomb load. Owing to this it was called a heavy bomber rather than a medium bomber. The Do 217 served on all fronts in all roles. On the Eastern Front and Western Front it operated as a strategic bomber, torpedo bomber and reconnaissance aircraft.
context_section_description: At the end of August 1938 arguments against the floatplane version arose in favour of a land based aircraft to serve as a torpedo bomber in the Battle of the Atlantic, with its more numerous potential applications, were accepted. At the beginning of January 1939 the RLM stopped all work on the marine dive bomber version, as its estimated performance was not adequate.
  On 8 July 1939 Dornier issued a manufacturing specification for a glide bomb-deploying version for full maritime use. It was to be equipped with unitized BMW 801 engines. In contrast to the earlier description of the design, the Do 217 E had a new nose and the nose, cockpit rear, and ventral positions carried one MG 15 each. The design was to carry a maximum bomb load of two SC 500 and two SC 250 bombs. It was also possible to carry an aerial mine or torpedo, for which the bomb bay had been substantially extended rearwards in the ventral area of the rear fuselage, nearly 70% longer in proportion than what the earlier Do 17Z had possessed. 
  A "clamshell"-like dive brake was fitted aft of the tail, with rear-hinged single dorsal and ventral "petals" to deploy using a jackscrew during anticipated dive bombing missions. These features increased the design's weight to 10,500 kilograms (23,100 lb). Dornier had intended the speed to be in the region of 530 kilometres per hour (290 kn).
  Superficially a scaled-up Dornier Do 215, and initially powered by the same engines, the Do 217 was actually considerably larger and totally different in both structural and aerodynamic design.
  The first prototype (the Do 217 V1) flew on 4 October 1938, but crashed seven days later during a single-engine flying test. The aircraft had been piloted by Rolf Koeppe, a flight commander at the central Erprobungsstelle facility at Rechlin. A Dornier mechanic, Eugen Bausenhart was also on board.
  It was found to be underpowered and was not manoeuvrable when compared with contemporary bombers. Instability was a problem at first, but modifications such as fixed Handley-Page leading edge slots along the leading edges of the vertical stabilizers helped to improve flight stability.
  The second prototype flew on 5 November 1938. After arriving at Friedrichshafen in June 1939, further evaluations were scheduled to take place. Plans were made to install unitized Daimler-Benz DB 603 engines to enable the aircraft for high-altitude reconnaissance. This meant the fitting of a pressurized cabin. When Daimler-Benz failed to supply the engines, development came to a standstill. On 29 October the RLM ordered the aircraft to be scrapped, or a new use found for it.
  A third prototype flew on 25 February 1939 with Jumo 211A engines in place of the DB 601s. On 15 August 1939 and 23 January 1940, the aircraft was flown to Rechlin, where it was tested in night flying trials. A number of the flights were to assess the performance of the new Siemens navigation aids under development. At the same time, Dornier also carried out fuel jettisoning and drop tank trials using the standardized 900 l capacity, vertical-finned drop tanks pioneered by the Bf 110D extended-range heavy fighter. As with the Do 17, the test team tried several tail configurations with the Do 217 V3. single, double and triangular-planform assemblies were tried. These designs were used in the Do 217 M-3, M-9 and Dornier Do 317.
  The same units were used on the fourth prototype V4 which flew in April 1939 at Friedrichshafen and Rechlin. The Jumo proved to be superior, and the designers deemed them to be essential if the desired performance was to be achieved. In February 1941, the V4 began trials with the dive brake which was installed in the tail. This was to satisfy a demand for the Do 217 to conduct dive bombing missions. It also was fitted with a brake parachute to test the ability of the Dornier to conduct short landings. The parachute brake was also considered in use as a dive brake.
  The V5 prototype was fitted with them and flew in June 1939. Later it was retested with DB 601s and was the third of six aircraft given the official designation Do 21
caption: Outline of the Do 217E
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