Dornier Do 217

The Dornier Do 217 was a bomber used by the German Luftwaffe during World War II. It was a more powerful development of the Dornier Do 17, known as the Fliegender Bleistift (German: "flying pencil"). Designed in 1937–1938 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 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 and a 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 was used as a strategic bomber, torpedo bomber and reconnaissance aircraft. It was also used for tactical operations, either direct ground assault or anti-shipping strikes during the Battle of the Atlantic and Battle of Normandy. The Do 217 was also converted to become a night fighter and saw considerable action in the Defence of the Reich campaign until late in the war.

The type also served in anti-shipping units in the Mediterranean, attacking Allied convoys and naval units during the Battle of the Mediterranean. In 1943, the Do 217 was the first aircraft to deploy precision-guided munitions in combat, when Fritz X radio-guided bombs sank the Italian battleship Roma in the Mediterranean. After the end of the war, at least one Dornier Do 217 continued in military operational service with the Swiss Air Force until 1946.

Development and design

Early designs and marine plans

thumb|The Dornier Do 17. The Do 217 was to be a larger, improved version in all areas.

At the beginning of 1938, Dornier issued manufacturing specification No. 1323, recognising the need for a twin-engine bomber or long-range reconnaissance aircraft powered by Daimler-Benz DB 601B engines. In February 1938 the Reichsluftfahrtministerium (RLM/German Aviation Ministry) authorized a testing program.

Dornier worked on a version of the Do 17M with the all round vision cockpit of the Do 17Z and a fuselage with a large bomb bay capable of holding a maximum of two and ten bombs. For reconnaissance an Rb 50/30 movie camera was fitted ahead of the front spar of the wing, and an Rb 20/30 was mounted in the second bomb bay. Jettisonable fuel tanks were carried in the forward bomb bay. For smoke-laying, the aircraft could be fitted with two Type S200 smoke generators. Dornier also envisaged the Do 217 as a naval dive bomber, in which case it was to be fitted with twin floats. In April and May 1938, the Do 217 WV1 and WV2 prototypes were produced.

The wing span was to be one metre greater than that of the Dornier Do 17, giving an overall span of . Under the wing a retractable diving air brake was to be installed. To power the aircraft the Dornier office at Manzell favoured two DB 601B engines, which could generate 1175 PS (1159 hp, 864 kW) for take off. The Jumo 211, Bramo 329 and BMW 139 (forerunner to the BMW 801) were also considered. Whichever power plant was selected, the RLM expected the aircraft to have a maximum speed of and weigh fully loaded.

On 5 June 1938 Dornier's overview of its design submitted to the Technical Bureau (Technisches Amt) highlighted some structural differences from the Do 17. In particular, the proposed increase in the bomb load to had to have been a vital factor in the design's acceptance. The fuselage was to be not only bigger but also stronger.

The RLM also had other requirements for Dornier to satisfy. Since 1933 the Kriegsmarine had pressed for the formation of a Naval Air Arm. In January 1938 the Naval Air Arm Inspectorate of the Luftwaffe presented its requirements for a multi-role twin-engined all-metal aircraft which could also conduct maritime operations. On 5 February 1938 it was agreed with the General Staff. The ineffectiveness of horizontal bombing of ship targets had already been noted. At the Erprobungsstelle Travemünde military aviation test centre at Greifswald, training units together with a few naval air units practiced bombing the ship Zähringen with concrete bombs. The results were a two percent hit rate. Junkers Ju 87 dive bombers repeated the assault with a 40% hit rate. The superior accuracy of dive bombing was clearly demonstrated. The Luftwaffe also wanted a machine that could operate as a fighter aircraft to combat enemy aircraft. Essentially they wanted a "sea Stuka" (Junkers Ju 87). The aircraft was to have floats and a range of and a maximum speed of .

Dornier set about designing a floatplane. For hitting targets in the air and sea surface, four automatic weapons would be fitted in the nose. The armament would consist of two MG 17 machine guns (500 rounds of ammunition each) and two MG 204 (aka Lb 204) 20mm autocannon (200 rounds of ammunition) as part of the Dornier Do P.85 project (in German sources these were all classified as "machine guns", since the Luftwaffe considered anything 20mm or lower a "machine gun", rather than a cannon like Western nations, hence the "MG" designation).

For dive bombing capability a dive brake was installed underneath the wing. The power plants were to reflect the speed requirements. It was envisaged as having two DB 601G engines, generating , or two Jumo 211s. The fuel tanks were located in the wing and fuselage which had a capacity for of fuel and of oil. At full weight the Dornier would reach and its effective range was expected to be . Its optimum range at an average cruising speed of at an altitude of , was . The specifications were dated 8 March 1938. Dornier unofficially pursued the project and produced the Do 217W V1 and W V2 prototypes.

By the summer, 1940 the Luftwaffe had been using the Dornier Do 18, Heinkel He 115, Heinkel He 59, Heinkel He 111 and Junkers Ju 88 in maritime operations in the Baltic. At this point, the Ju 88 and He 111 equipped units were ordered to cease providing maritime support en masse. Instead, the Luftwaffe returned to the idea of the Do 217 and its floatplane version as a specialized naval attack aircraft. At the same time more plans were in place to produce extremely long-range aircraft (probably for operations deep in the Soviet Union). It is possible that the data sheet which Dornier gave the designation Do 217G was a part of that project. Unlike the Sea Stuka, a floatplane, the G was to carry an MG 151 mounted in the nose and three MG 15s fitted for defence. The G was expected to reach . It was still designed for a crew of four and equipped with sprung floats which would allow the aircraft to land in rough open seas. The G could also carry the entire variation of the E-1 bomb load it could carry a load twice that of the Do P.85 aircraft. However, the Do 217 E-1s performance was favoured. Nevertheless, the Gs design features figured and influenced the E-4 which went into production as the aircraft that was envisaged to be the backbone of the Luftwaffe's bomber fleet in the Battle of the Atlantic. The first prototype (the Do 217 V1) flew on 4 October 1938, but crashed seven days later during a single-engine flying test. 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.

thumb|Bf 110 using standard 900-litre drop tanks, tested for the Do 217

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 V6 prototype was powered by Jumo 211B engines, but was also tested with DB 601s. The V7 was tested with BMW 139 engines, but as these had been abandoned for use in the Fw 190 fighter as early as 1939, use of the unpopular BMW 139 powerplants was never taken beyond the prototype stage. The V8 was given BMW 801 engines, which became the fixture for the entire E series. The Do 217A and C series were only built in small numbers. Owing to this the following D and F types never advanced beyond the design stage.

The production specifications were ratified on 8 July 1939, with the ultimate goal of the Do 217 having the capability of flying maritime and land operations armed with glide bombs. The four-seat aircraft was adaptable to both land and maritime operations wherein the tactical emphasis was on bombing from a 50-degree dive angle, and it had a maximum speed of . In contrast with earlier specifications for a modified version of the Do 17M, the proposed Do 217E had a new nose section design in which the A-Stand position was armed with a MG 15 machine gun. Additional MG 15s were to be located in the B and C-Stand gun emplacements. The design teams configured the bomb bay to carry two SC 500 and 250 bombs or four SC 250 bomb loads. In addition a LMB II aerial mine, or an F5 Torpedo could be loaded. Instead of the dive brakes being installed under the wings as on the R variant, it was placed on the tail of the aircraft. The design was tested in the E-1 and became the blueprint for all subsequent sub-variants.

The design of the rear and front spar attachments revealed the flanges of the spar were flushed with the wing surface making the most efficient structure. The outer wing leading edges were double-skinned.

The fuel and oil tanks were located in the wing and centre section. The two outer fuel tanks were located next to the outer side of the engine nacelle. The outermost fuel tank contained a fuel capacity, while the tank closest to the engine could accommodate of oil. In the centre section a fuel tank was installed forward of the bomb bay. The early E-series variants were intended to be fitted with a BMW 801B engine on the port side to give counter-rotating propellers. The engines were mounted on welded steel tube mountings at the extremities of the wing centre section. The oil coolers were integral to the front lower section of the BMW-designed cowlings, as used in all twin and multi-engined aircraft that used BMW 801 radials for power. The machine had two oil and five fuel tanks which were protected with rubber and self-sealing coverings. In an emergency, CO<sub>2</sub> could be released into the tanks to extinguish fires. The engines had three-blade, light alloy VDM propeller units. The dorsal gunner was also protected by armour plating.

The Funkgerät or FuG radio communication device compartments were located in the extreme rear of the cockpit, near the leading edge. The automatic pilot panel was located next to the FuG boxes. In the right-rear of the cockpit the piping that was also attached to the de-icing ducts in the wings also entered the cockpit, as part of a single heating system to emit warm air to heat the cabin if needed.

Armament

The defensive armament consisted of an A-Stand (forward firing machine gun position) in the nose with a MG 15 machine gun. In the C-Stand (lower rear gun emplacement) at the rear end of the undernose Bola gondola – a standard feature on many German twin-engined bombers – and a B-Stand position (rear-upper gun post) at the rear of the cockpit glazing, the crew were provided with MG 15 (E-1) or MG 131 machine guns (E-2). In the side of the cockpit, two MG 15s were mounted (one on each side) on bearings. As well as the manual machine gun positions, the E-2 was equipped with a Drehlafette DL 131 rotating turret armed with a 13 mm machine gun. In some instances, a moveable 20 mm cannon was fitted in the nose and a fixed 15 mm weapon was installed in the floor of the nose. The weapons could be controlled by the pilot, via a firing button located on the yoke. To assist in acquiring his target, a Revi C12/C was installed in the cockpit.

The maximum permissible bomb load of the E-series without sacrificing fuel load was of bombs of which a maximum of 3,000 kg could be carried internally. To have the maximum load of 4,000 kg, part of the fuselage fuel tank had to be sacrificed. If long-distance operations had to be flown, drop tanks could be fitted under the wings, which affected speed. Beside the bomb load a LT F5 Torpedo could be carried in its long bomb bay, as well as three aerial mines (the E-1 did not carry the mine load of the E-2). for nautical targets. It was first tested with the E variant.]]

The E series was the initial major production variant, based on V9 prototype, and powered by two BMW 801 radial engines. Deepened fuselage with larger bomb-bay, entered production in 1940.

The V9 had been planned as the prototype for the E-1 variant. The V9 had a fixed MG 151 with 250 rounds of ammunition while the MG 204 was to be installed in the nose. The type was fitted with a dummy run of Lofte 7 and BZA 1 bombing systems. The main armament was to be a single torpedo of either SD 1000 or SC 1800 standard. When the mock up had been given the green light for technical development construction began in the spring, 1940. During September 1940 engine vibration problems were experienced but fixed quickly. During flight tests it was discovered the air brake caused a speed loss of . The V9 underwent heavy tests and was withdrawn to Rechlin, where it acted as a prototype until at least October 1943. During this time it also had trials with BMW 801A and BMW 801G engines.

Do 217 E-0 and E-1

The E-0 was a pre-production bomber/reconnaissance version of Do 217E. It was powered by BMW 801A engines and armed with one forward firing 15 mm MG 151 cannon and five 7.92 mm MG 15 machine guns on gimbal mounts. Continued development led to the Do 217 E-1. The Do 217 E-1 first flew on 1 October 1940. Full production level bomber/reconnaissance variant, similar to the E-0, and followed it into production and service in late 1940, 94 were built. Additional armament consisted of a 20 mm cannon fitted in the nose. Its power plants were BMW 801s of 1,560 PS (). The aircraft could carry an internal bombload of 2,000 kg. Alternatively, it could carry a load of two LMW aerial mines or one torpedo. The E-2 could carry three mines.

The Luftwaffe continued to develop the E series. Not satisfied with the E-1, it perfected a modified version it designated the E-2. Testing was not complete until March 1942. Improvements were added to existing E-1s, which were already being produced by late 1940, and to the prototypes V2 and V4 which would serve as the prototypes for the E-2. The V2 was given the DB 601 engines and a third aircraft, designated V4, was tested with Jumo 211s. Studies of the aircraft began on 15 August 1939, running concurrently with the development of the E-1s. Level, dive and torpedo carrying roles were all examined. Emphasis was also placed on developing a reliable reconnaissance type. These developments were significant as the trials undertaken by the E-1 prototype had not shown any negative characteristics. Level bombing tests were very positive. Only glide-bombing attacks using interception control, and with dive-brakes open, did not quite match the stringent specifications set some four years earlier. According to the test pilots, the aircraft performed well with either the DB 601A, Jumo 211A/B, or even the BMW 801A-1 engines. Pleasing the designers, the test pilots also noted that with all auxiliary bomb racks removed test flights showed at an altitude of 6,000 metres, the Do 217 was quite capable of making an operational range of 2,400 km. With the addition of two 900-litre tanks, it increased to 3,700 km.

The BMW 801 was the preferred powerplant, and although it had been tested by the summer of 1942, the lack of replacements, low production and their use in the Focke-Wulf Fw 190 series prevented large-scale operational testing under combat conditions. In September 1941 flame dampeners were fitted and testing completed. Further innovations were made regarding the installment of reconnaissance equipment, namely the standard Rb 20/30 cameras. During this final phase, plans to construct and designate an E-1b with MG 131 turret was explored, but later shelved. Modifications were also made on the already operational E-1s before the E-2 entered service. One such modification was the installation of MG FF 20 mm cannons, the installation of a hand-held MG 131 in the forward-facing glazing of the cockpit and a MG 131 turret facing aft in the B position (rear cockpit covering the rear). De-icing systems were also installed in the cabin and tailplane for high altitude operations. The Do 217 E-1 and E-2 could reach 535 km/h at 5,300 m and none had a problem with maintaining altitude with BMW 801s, even with weapons, dive-brakes and dampers added, provided it had an all-up-weight of less than twelve tonnes. Machines over thirteen tonnes were difficult to handle and needed experienced pilots at the controls.

The failure of the Heinkel He 111, Dornier Do 17, and Junkers Ju 88 during the Battle of Britain and the Blitz led the OKL to see the Do 217 as the only heavy bomber with the range, bombload and defences for long-range bombing. The E-2 had incorporated all the new design features such as the Drehlafette DL 131 turret and a modified bomb bay which allowed to hold 3,000 kg of bombs. The E-1s originally were given the FuG X, 16, 25 and PeilG V and FuBI 1 radio sets and navigation aids. The E-2 was given the FuBI2. In the next two variants, the E-3 and E-4, the Siemens FuG 101 radio altimeter was also added enabling the pilot to conduct more accurate and safer low-level attacks. The E-1 had Rüstsätz /R1 racks for 1,800 kg of bombs, the /R2 wing rack and /R3s for 50 kg of bombs. Dornier wanted to increase the strength of the racks to increase the size of external loads. A specialist company which had often collaborated with Dornier, Technischer Aussendienst, developed the /R20 rack which enabled heavier loads to be carried. The /R20 enabled fixed MG 81Zs to be installed in the tail cone. The previous lattice air brake was removed; the drag was too much and it bent the fuselage out of shape, making the aircraft unsafe and hastening metal fatigue.

Do 217 E-3 to E-5

In the E-3, additional armour was fitted to protect crew. Armed with forward firing 20 mm MG FF cannon and seven MG 15 machine guns. (Despite the large number of machine guns, the defensive weight of fire was light, with five of the gimbal mounted machine guns to be operated by the radio-operator, who could only use one at a time).

The E-4 was similar to the E-2, which it replaced in production, but with the dive brakes removed. It was fitted with Kuto-Nase barrage-balloon cable cutters in the leading edge of the wings. 258 E-3 and E-4 were built. The E-4 was identical to the E-2, with the exception of the heavy MG FF in the nose. Five of the six positions were flexible, with only one fixed gun; the MG FF installed along the floor, just off centre. The cannon in the nose could be moved. Both were powered by BMW 801L engines.

Do 217 K

thumb|Do 217K-1, with the K-version's standard "stepless cockpit"

To replace the Do 217, the RLM planned for the He 177 A-3 and A-5 to be the long-range carrier aircraft for missiles, owing to the lack of BMW engines to power the Dornier but problems with the engine reliability of the He 177A led to the failure of the plan. The Battle of Stalingrad used up more and more aircrew which prevented them retraining on the Do 217 for glide bomb operations. Owing to the problems with the He 177A, Air Inspector General Erhard Milch returned his attention to the Do 217 and demanded a greater number of improved variants for Precision-guided munition (PGM) operations.

In early 1942, tests on a new and improved, completely glazed cockpit for the Do 217 series had been underway at the Hamburger Schiffbauanstalt (Hamburg Shipbuilding Institute). E-2s were fitted with a new streamlined "stepless cockpit" following its conceptual debut in January 1938 for the He 111P, as this design philosophy became the standard for almost all German bombers later in World War II, which eliminated the separate windscreen panels for the pilot of earlier versions of the Do 217. The lower nose of the K-version also retained the Bola inverted-casemate gondola for a rearwards-aimed ventral defensive armament emplacement, with its forward end fully incorporated with the new nose glazing design. The testing for this new well-framed cockpit glazing format for the later models of the Do 217, was carried out at the Shipbuilding Institute in Hamburg. The design of the cockpit was put to the test using water pressure to simulate a speed of 700 km/h. Only a few of the glass panels failed, caused by inadequate mounting. The cabin design passed the tests easily. Initial flights took place on 31 March 1942 after teething problems had been resolved. The Do 217 K V1 flew with BMW 801A-1s from Löwenthal and Erprobungsstelle Rechlin. This was followed by the ten-airframe pre-production batch, Do 217 K-01 to K-010. Mass production of the Do 217 K-1 began at the Dornier factory at Wismar.

The first prototype, a modified E-2 flew on 31 March 1942, with the aircraft showing higher maximum speed owing to reduced drag. The Do 217 K entered production from September 1942. BMW believed that the type could reach an operational ceiling of 7,000 m, notwithstanding a MTOW of 16.8 tonnes. Tests at Peenemünde in June and July 1943 showed that while the Do 217K could carry and deploy a Fritz-X PGM, it was still controllable.

Do 217 K-1

The Do 217 K-1 was a night bomber version with the 1560 PS BMW 801L engine. It carried the same crew of four in the "stepless cockpit" crew compartment with a revised defensive armament of a twin-barreled 7.92 mm MG 81Z machine gun in the nose, two single MG 81s or twin-barrelled MG 81Z in beam positions, a MG 131 in the B stand position dorsal turret, the DL 131/1C, and another in a ventral position inserted in a Walzenlafette WL 131/1 cylindrical carriage at the rear of its Bola gondola. 220 were built.

Do 217 K-2

This was a specialised anti-shipping version based on the K-1, intended to carry the Fritz X guided bomb, being fitted with pylon-faired hardpoints to allow carriage of two Fritz Xs inboard of the engines and the FuG 203 Kehl guidance system. It had longer-span wings (24.8 m (81 ft  in) compared with 19 m (62 ft 4 in) for the K-1) to give better high-altitude performance when carrying the heavy Fritz-X bombs. 50 were converted from K-1 airframes. The increase in area was to increase high-altitude performance. It was loaded with 350 rounds and controlled by the use of a rear-facing telescope mounted in the forward section of the canopy left of the pilot. Either the gunners or pilot could fire the weapon, which could be jettisoned in case of an emergency to reduce weight.

Level and dive bomber variants – inline-engined

Do 217 M

As the BMW 801 radial engine used by the Do 217K was in great demand for the Fw 190 fighter, the Do 217M, a version powered by Kraftei-unitized installation versions of the largest displacement inverted V12 then in service, the 44.5-litre displacement Daimler-Benz DB 603 liquid-cooled inverted V12 engine, was developed in parallel with the 217K. It shared the new forward fuselage of the 217K, with the first prototype flying on 16 June 1942.

According to RLM plans, production of the M model, which was powered by DB 603 A-1s was due to commence with two aircraft in May 1942 and 10 M-1s in the summer. By March 1943 a production target of 42 aircraft per month was to be achieved. The DB 603 A-3 was chosen as the increased performance handed the aircraft improved characteristics. However, it had not been fully tested and a number of technical problems arose. A Do 217H (a glider-bomber for land operations with E-2 airframe) would be used for endurance testing. This would provide useful testing evaluations for the M-1.

The M V1 was to be the first prototype. It was an E-2 conversion with altered cockpit and DB 603 engines and operated from the central Luftwaffe Erprobungstelle aircraft test centre at Rechlin from September 1942. During the winter, the prototype performed long-range and high-altitude flights. On 16 November it was forced landed for unstated reasons. Different engine-cooling systems were tried and flame retarders added, although the addition of the dampers caused a reduction in speed of 15 to 25 km/h depending on altitude. The first production prototype series M-0 aircraft (M-01) crashed in Lake Müritz, just north of the Rechlin test base, on 9 September 1942, while on an engine test. The M-02 was given wing reduction to 59 m<sup>2</sup>, which became the predecessor of the M-3. The M-03 refined the design with DB 603 A-1 engines but crashed after a mid-air collision with a Dornier Do 215 on 14 May 1943. Six 0-series aircraft (Wrk Nr. 1241 to 1245) were manufactured. Rechlin log books included frequent references to a M-04 from December 1942 to May 1943. This aircraft was apparently used for de-icing and cabin heating tests as well as high-altitude testing with DB603s. Some M-0s were used to evaluate performance with glide bombs (Wrk Nr. 1244 and 1245). These aircraft were named M-0/U1. Each had an ETC 2000 XII, under the fuselage.

Do 217 M-1

The M-1 night bomber version, equivalent to Do 217 K-1 but with DB603A engines, carried similar armament and bomb load to K-1. Daimler-Benz DB 601s were also used on some variants to keep the airframes in service (the shortage of powerplants made this difficult). Mostly though, DB603A-1 engines were used on the M-1, its only major difference from the K series. The M-1/Umrüst-Bausätze 1 (abbreviated "/U1") incorporated the M defensive armament and the lattice air brake of the E-2. The MG 81Z and 131 were to be replaced by the MG 151 in the A-stand position. Problems with the air brakes prevented serial conversions. By November 1943 the M-1/U1 had matured into a night bomber with anti-glare protection in the cabin. The machine was equipped with a MG 131 in the nose, two MG 81Js in the cabin windows and two MG 131s in the B and C stand. 438 M-1 were built by Dornier in Munich and Wismar.

Night fighter variants

Do 217 J

thumb|Nose of prototype Do 17 Z-10 Kauz II night fighter, similar to that of the Do 217 J, equipped with Matratze (mattress) 32-dipole radar antenna for its UHF-band early model [[Lichtenstein radar|Lichtenstein BC AI radar gear]]

In 1941, with Germany under increased night-time attack by RAF Bomber Command and with shortages of the Messerschmitt Bf 110 and the preferred Junkers Ju 88C night fighters, it was decided to supplement the night-fighter force with a version of the Do 217 E, despite its much greater size and 15-ton weight. This aircraft, the Do 217 J, was fitted with a new "solid" nose, similar to that used by Dornier in night fighter versions of the Do 17 and Do 215, with four forward firing 2 cm MG FF cannon and four 7.92 mm machine guns. Dornier encountered many problems in procuring the BMW 801 engines required for the night fighter versions. Junkers had also struggled with BMW deliveries, its Ju 88C variants were to be powered by the BMW as the initial Jumo 211B/F engine plan had been abandoned.

Delays of BMW 801 engine deliveries forced the project to be temporarily abandoned. In November 1941 the directive for the design team had been a J-1 with a Spanner IR system, and a J-2 with Lichtenstein radar. In 1942 the directive changed slightly, and the J-2 was to be fitted with AI radar. Specifically, the Dornier was to be armed with four MG FF fuselage mounted cannon and machine guns for bomber assault, and one MG 131 each in the B-Stand and C-Stand positions for defence from RAF night fighters. Curiously, the night fighter version was ordered to be able to carry eight 50 kg bombs so the type could act as a night fighter and intruder over enemy territory.

The electronic equipment to be installed was listed as the FuG X, 16, 25 Peil G V air-to-ground communications and blind landing devices. The FuB1.1 was also listed as a potential piece, and if possible a FuG 101 radio equipment was to be fitted as standard. It was intended to equip J-1 with the Lichtenstein FuG 202, which had an effective range of 4,000-metre, with three tubes. The weight of the equipment would reduce the performance of the J-1 by 30 – 40 km/h so in January 1942, Dornier opted to install the IR spanner equipment instead of the Lichtensten.

Do 217 J-1

The operational Dornier night fighter, redesignated J-1, before entering operations was powered by BMW 801L engines. It was fitted with a revised crew compartment housing a crew of three, with a solid nose housing four fixed 7.92 mm MG 17 machine guns, with four 20 mm MG FF/M cannon in the forward part of the ventral gondola. It retained the MG 131s in a dorsal turret and ventral position of the bomber, and could carry eight bombs in the rear bomb-bay, with a fuel tank in the forward bomb-bay.

Production had commenced in March 1942, during which eight J-1s were built. In April, 13 followed and 55 were built in May. Despite this start production declined in June and this trend continued until November 1942, when only four were built. Dornier had been ordered to withdraw Dornier airframes for unspecified reasons. Owing to this, by 31 December 1942, only 130 J-1s had been completed. although they were used for early trials of the Schräge Musik arrangement of upward firing cannon, three Js being used for tests in July 1942. The J-2 was only converted from J-1s. The idea of the upward firing cannon had originally come from an engineer, Dr. Poppendieck, in June 1942. engines was produced, with the first prototype flying on 31 July 1942.

N-1 and N-2

thumb|A Dornier Do 217 N-2 night fighter without radar

After testing was satisfied the two variants, the N-1 and N-2, which had two sub-variants, were fitted with FuG 202. The N-1 variants were given two sub-variants which were to follow the design of the E-2/E-4 and the J-1/J-2 with emphasis on range and endurance. Extra fuel tanks were added to the empty bomb bay. For operations over water the heavy night fighters were fitted with lifeboats and radio transmitters. The FuG X with TZG 10 and FuG 16. IFF equipment was the FuG 25s. The N also had the FuG 101 radio altimeter, blind flying equipment FuB1 2 and PeilG V. AI search radar was the FuG 202. The no longer needed bomb release gear remained, bringing the aircraft up to on take-off, so it was barely able to reach . Fuel consumption lightened the load, and the Dornier could reach a maximum operational ceiling of . The speed of the N was a maximum of at . The N-2 was much improved, as it was much lighter and refined. until it was retired from front line use in mid-1944.

The N-2 was originally not to have the Schräge Musik armament configuration or a brake parachute, but it was then decided to fit the armament set for tactical reasons. A semi-rigid brake parachute was also installed for unspecified reasons. The N-2 prototype was a converted E-1, serial 0174, code PE+AW. Communications were improved on the FuG 16 ZY and FuG 214. The B and C cupolas were removed and the positions fared over with Plexiglas and wood. The MG FF guns were replaced by MG 151/20 cannon. The MG 17s in the nose were to be abandoned with more powerful armament, but this was never carried out. To kill the excess weight that had plagued earlier types, the bomb bay, its doors, and the bomb release gear were removed, and changes were made to the control panels. The gaps were replaced by lighter wood parts which reduced weight, allowing heavier armour protection for the crew. The N variant was the most heavily armoured Dornier variant.

The improvements enabled a top speed of (an increase of ) and a reduction from to , which increased ceiling height to .

Although the specifications had originally envisaged a multi-role aircraft which could perform bombing missions, it was to function in reconnaissance roles. The fuselage had to be extended to accommodate the two cameras which could be "accessed directly by the crew" (presumably in flight).

Dornier was ordered to produce three A-0 series machines up to the E variant. This changed to six as the number of reconnaissance machines was inadequate for the military's need. The small production run would consist of six aircraft. The original power plants, the DB 601Fs, could not be installed in time and the lower performance DB 601B engines were assigned to the type instead for the short term. As in the Dornier Do 17, Rb 20/30 and 50/30 cameras were to be installed. The 20/30 would be fitted in the fuselage while the 50/30 camera was to be placed in the cockpit and be jettisonable. For emergencies the aircraft was to have a fuel transfer unit control installed to move fuel from one tank to another.

Dornier completed work on the V6 prototype, the fourth A-0 aircraft. On 15 October 1939 it was flown successfully. The bomb bay had been enlarged and continued testing various weaponry until 1941. It had DB 601P engines installed and its wing was enlarged in early 1941. The DB 601Ps could operate a maximum altitude of 5,800 m and would use high octane C3 aviation fuel. It should have been ready to fly by March, but problems with the engines slowed progress.

A number of the A prototypes served as test beds through the war. The last (V7) flew testing improvised de-icing systems at altitudes of 9,000 metres. In December 1944 the Dornier projects were halted owing to lack of fuel.

The first Do 217 series aircraft, Wk Nr. 2710 flew on tests between September 1940 and March 1941. It crashed on 2 July 1942 at Rechlin. The second C-0 prototype was fitted with dive brakes on the under side of the wings but this configuration was abandoned in January 1941 and replaced by a brake parachute installed in the tail. The third prototype flew on 6 September 1940 and four further machines flew between September and November 1940. The final machine, 2716, flew on 6 November 1940. The eight machines remained at Rechlin in various test bed roles until at least July 1942. The C series project was abandoned and its variants never entered mass production.

Do 217H, L and R

The Do 217 H was a conversion of a Do 217E with DB 601 engines fitted with experimental turbo-superchargers. On 11 October 1942 the first flight was made at 8,000 m. After, 9,000 m flights were reached. In September 1943 the DB603E had improved superchargers, giving better high-altitude performance. The H series continued as test beds for the M series until October, when they were cancelled for lack of fuel.

The L was a variant of the Do 217K with revised cockpit layout and armament. Only two prototypes were built. The R was a Dornier Do 317 with cabin pressurisation systems removed and modified to carry Hs 293 missiles. Only five built.

Do 217P

High altitude reconnaissance/bomber version with two DB 603B engines supercharged by a single Daimler-Benz DB 605T engine, in a so-called Hohen-Zentrale Anlage (HZ-Anlage) installation in the central fuselage, as one example of the Henschel Hs 130E had been fitted with, solely for powering a shaft-driven centrifugal supercharger. Three prototypes, plus three pre-production Do 217P-0 aircraft, armed with six MG 81s. Ceiling of .

Variant list

Do 217 A-0: Pre-production series with two 1,100 PS () DB 601B inline engines, used for reconnaissance missions. Only eight aircraft were built.
Do 217 C-0: Pre-production bomber, DB 601B engines, increased defensive armament. Only four built.
Do 217 E-0: Pre-production bomber with deepened fuselage and powered by two 1,560 PS BMW 801A engines.
Do 217 E-1: Production bomber with five 7.92 mm (.312 in) MG 15 machine guns and one 15 mm MG 151 cannon for defence.
Do 217 E-2: Bomber with dive bombing capabilities, with three 7.92 mm MG 15s, two 13 mm (.51 in) MG 131 machine guns, one 15 mm MG 151, and a bombload.
Do 217 E-3: Level bomber, seven 7.92 mm (.312 in) MG 15s and one forward-firing 20 mm MG FF cannon.
Do 217 E-4: BMW 801L engines.
Do 217 E-5: E-4 with extended wingspan, modified on production line with added Kehl radio control gear to launch Henschel Hs 293 missiles.
Do 217 G: In January 1940 Dornier produced a data sheet for a Do 217 G with BMW 801 engines with the same airframe as a Do 217 E-1. None were built.
Do 217 H: Conversion of a Do 217 E with DB 601 engines fitted with experimental turbo-superchargers.
Do 217 K: Bomber with redesigned forward fuselage with stepped windscreen eliminated, a common World War II German bomber cockpit design concept adopted just before the start of World War II initially on earlier Heinkel bombers (He 111 P and He 177 A). Two 1,560 PS BMW 801L radial engines.
Do 217 K-1: Standard bomber version.
Do 217 K-2: Extended wingspan with Kehl radio gear to carry Fritz X bombs on underwing racks.
Do 217 K-3: Similar to K-2, but capable of carrying both Henschel Hs 293 or Fritz X.
Do 217 M: Bomber; Do 217 K with 1,750 PS DB 603A inline piston engines.
Do 217 M-1: Equivalent to the K-1.
Do 217 M-3: DB 603A-engined equivalent to the K-3.
Do 217 M-5: Kehl radio gear-equipped Henschel Hs 293 carrier with a single missile mounted semi-externally beneath the fuselage.
Do 217 M-11: Similar to the K-2 with extended wingspan, Kehl control gear and Fritz X bombs.
Do 217 J: Night fighter based on the Do 217 E. Solid nose with four 7.92 mm (.312 in) MG 17 machine guns and four 20 mm MG FFs.
Do 217 J-1: Night intruder version.
Do 217 J-2: Dedicated night fighter. Bomb bays removed.
Do 217 L: Modified version of the Do 217 K with rearranged cockpit and defensive armament. Only two built.
Do 217 N: Night fighter based on the Do 217 M. Armament similar to Do 217 J but with improved 20 mm MG 151/20 cannons replacing the 20 mm MG FFs plus the addition of four 20 mm MG 151/20s as Schräge Musik.
Do 217 N-1: Similar to J-2.
Do 217 N-2: N-1 with defensive gun turret and bomb bay equipment removed to reduce weight.
Do 217 P: High-altitude reconnaissance aircraft with two 1,860 PS DB 603B supercharged by a DB 605T in the fuselage (the Höhenzentrale, or "HZ" system) with a ceiling of . Three Do 217 P-0 pre-production aircraft only.
Do 217 R: Dive bomber with increased wing area, greater defensive armament, and dive brakes. Four prototypes built.

Quarterly production 1939–1944:

{| class="wikitable sortable" style="font-size: 9pt; text-align:center"

! Quarter !! Year !! Bombers !! Night fighters

| Fourth || 1939 || 1 || 0

| First || 1940 || 1 || 0

| Second || 1940 || 4 || 0

| Third || 1940 || 3 || 0

| Fourth || 1940 || 12 || 0

| First || 1941 || 47 || 0

| Second || 1941 || 52 || 0

| Third || 1941 || 105 || 0

| Fourth || 1941 || 73 || 0

| First || 1942 || 99 || 8

| Second || 1942 || 164 || 75

| Third || 1942 || 160 || 46

| Fourth || 1942 || 141 || 28

| First || 1943 || 187 || 70

| Second || 1943 || 181 || 64

| Third || 1943 || 135 || 73

| Fourth || 1943 || 1 || 0

Flying the Do 217 M-1

In October 1945 British Captain Eric Brown undertook full handling trials with a Do 217 M-1 WNr 56158 at RAF Farnborough. He recalled a distinctly "underwhelming" experience.

Brown recalled that he took off with full power of some 2,700 rpm and the lightly loaded Do 217 M left the runway at . Brown held a shallow climb, waiting to reach before retracting the undercarriage. Brown timed the time it took to retract, which was between 30 and 40 seconds. Deliveries of the Do 217E started late in 1940, with some aircraft joining another reconnaissance unit, 2 Staffel of Fernaufklärungsgruppe 11, which was also involved in spyflights over the Soviet Union from bases in Romania.

Western Europe

The first bomber unit to receive the Dornier Do 217 was II Gruppe of Kampfgeschwader 40 (II/KG 40) in March 1941, followed by KG 2 later that year. At first these units, based in the Netherlands, were used to carry out minelaying and anti-shipping operations over the North Sea. On the night of 24/25 April 1942, however, Dornier Do 217s of KG 2 took part in an attack on the city of Exeter, the first raid of what was to become known as the Baedeker Blitz. 's Dorniers were heavily deployed during the Baedeker raids, against British provincial cities which were less heavily defended than London, which continued until July that year.

The Do 217 squadrons had little time to recover as on 19 August 1942 the Allies launched an amphibious raid on Dieppe in Northern France, with KG 2 launching almost its entire strength of 80 aircraft in response, losing 20 over Dieppe. It had suffered serious losses of trained personnel during operations during 1942, with the number of combat ready crews in KG 2 falling from 88 at the start of the year to 23 by September.

The Dornier Do 217-equipped bomber units spent most of the rest of 1942 recovering from these losses and re-equipping with the more capable Do 217K and M. Night attacks against Britain re-commenced in January 1943, and continued sporadically throughout the year, often suffering heavy losses. As an example the Do 217 equipped KG 2 lost 26 complete crews during March 1943. The pace of bombing attacks against Britain increased again in January 1944 with the launch of Operation Steinbock, with the Do 217 equipped I and III KG/2 and I/KG 66 being involved, these attacks continuing until

May, with the bomber units again taking heavy losses.

Two Gruppen of the anti-shipping Kampfgeschwader 100 (KG 100) equipped with Do 217s in 1943, with II/KG 100 receiving the Do 217E-5, equipped to carry the Hs 293 guided missile and III/KG 100 the Do 217K-2, with the Fritz-X guided bomb. II/KG 100 made its combat debut against Royal Navy warships in the Bay of Biscay on 25 August 1943, when it near missed the sloop HMS Landguard, while on 27 August, a second attack by 18 Do 217s sank the sloop HMS Egret and badly damaged the destroyer HMCS Athabaskan.

The final actions of Do 217 equipped units over Western Europe was against the allied Invasion of Normandy in June 1944, when the remaining Do 217 equipped bomber units, II/KG 2 and III/KG 100 were thrown into action against the Allied landings. Losses were heavy, with III/KG 100 losing 8 of 13 servicible Do 217s in 10 days of operations. As American forces broke out of the bridgehead at the end of July, III/KG 100 sent its remaining Do 217s to carry out attacks on bridges over the Rivers Sée and Sélune with Hs 293 missiles. They managed a single hit on one of the bridges, which remained in use, while seven Dorniers were lost.

Mediterranean and Italy

Twelve Do 217 J-1 and J-2 variants were acquired by Italian Regia Aeronautica between September 1942 and June 1943 for night fighter operations. One Italian unit was equipped: 235a Squadriglia of 60° Gruppo (41° Stormo). Based at Treviso San Giuseppe, then at Lonate Pozzolo, the unit performed poorly. The unit shot down only one enemy aircraft, and lost one of their own, after nearly a year of activity.

When the Italian Armistice with the Allies was announced on 9 September 1943, the Italian Fleet was instructed to sail to Malta to surrender. III/KG 100, based at Marseille launched an attack from its base at comprising 11 Do 217s armed with Fritz-X guided bombs against Italian warships near Corsica, sinking the battleship Roma and damaging the battleship Italia. The Dorniers were then deployed against the Allied landings at Salerno, damaging the cruisers USS Savannah and HMS Uganda and the battleship HMS Warspite with Fritz X bombs.

Defence of the Reich

Deliveries of the Dornier Do 217J-1 started in March 1942, with night-fighter pilots being unimpressed, considering the type to have poor manoeuvrability and speed. The J-1 was relegated to the training role by summer that year, replaced by the radar equipped J-2 in front-line units. Despite the aircraft's faults, the Do 217 was widely used, being used by 11 night-fighter Gruppen, although it did not completely equip any unit, usually being operated in conjunction with the more popular Messerschmitt Bf 110.

Operators

;

Luftwaffe
Nachtjagdgeschwader 1
Nachtjagdgeschwader 2
Nachtjagdgeschwader 4
Nachtjagdgeschwader 5
Nachtjagdgeschwader 6
Nachtjagdgeschwader 100
Kampfgeschwader 2
Kampfgeschwader 6
Kampfgeschwader 40
Kampfgeschwader 100
Kampfgeschwader 200

;

Regia Aeronautica (Italian Royal Air Force) operated six Do 217-J-1 and six J-2

;

Swiss Air Force operated a single Do 217N-2, interned after landing at Basel in 1944 or 1945 and was in use until at least 1946.

Surviving aircraft

A total of 1,925 Do 217s were produced, however no complete aircraft survives. The largest known relic of this aircraft, a large piece of the rear fuselage, can be found at the Italian Air Force Museum in Rome. One remnant of a Do 217 in the United States is one of the Motoranlage unitized BMW 801ML (BMW 801L) radials, still fully cowled, at the New England Air Museum that used to power a Do 217. The remains of two aircraft then based at Toulouse that crashed over the Pyrenées in July 1944, were being recovered in 2013.