In response to a Lufthansa specification of 1933 for a six-passenger mail plane, Dornier designed a shoulder-wing all-metal monoplane to be powered by two 660 hp (492 kW) BMW VI engines. Three prototypes of this Dornier Do 17 were built in 1934, but although the airline carried out an evaluation programme early in the following year, the aircraft's slim fuselage provided such limited passenger accommodation that all three were returned to the manufacturer. The design had military potential, however, and a fourth prototype (Do 17 V4) with twin vertical tail surfaces and a shortened fuselage was flown in the summer of 1935. Among development prototypes, the fifth was powered by 860-hp (641-kW) Hispano Suiza 12Ybrs engines, the seventh mounted a 7.92 mm (0.31 in) MG 15 machine gun in a dorsal blister, and the tenth was fitted with 750 hp (559 kW) BMW VI engines. The initial production versions were the Do 17E-1 which, developed from the ninth prototype, had a glazed and shortened nose, and carried a 1,102 lbs (500 kg) bomb load, and the Do 17F-1 reconnaissance aircraft with increased fuel capacity and two cameras. Both of these models made their operational debut with the Legion Condor in Spain during 1937. Their performance was such that they had little difficulty in avoiding contact with the obsolescent aircraft then serving with the Republican air force.

Introduced publicly at the 1937 International Military Aircraft Competition held at Dubendorf, near Zurich, the Do 17 VS prototype (or Do 17M Vl) powered by two 1,000 hp (746 kW) Daimler-Benz DB 600A engines soon gained the nickname 'Flying Pencil' because of its slender fuselage. More significantly, it was able to better the performance of international fighters taking part in the contest. Following this demonstration at Dubendorf, Yugoslavia showed interest in the type and the Do 17K was developed for that nation, being similar to the Do 17M but powered by two 980 hp (731 kW) Gnome-Rhone 14NI/2engines. The type was to be licence-built by Drazavna Fabrika Aviona at Kraljevo, the three versions produced being the Do 17Kb-1 bomber, and the Do 17Ka-2 and Do 17Ka-3 reconnaissance aircraft with secondary bombing and attack capability respectively. Two prototypes of a proposed pathfinder version which did not enter production were built under the designation Do 17L, these being powered by two 900 hp (671 kW) Bramo 323A-1 radial engines because of a shortage of Daimler-Benz DB 600s. The same Bramo powerplant was used for the thirteenth and fourteenth prototypes to develop the airframe/engine combination for the production Do 17M-1, which could carry a 2,205 lbs (1000 kg) bombload and was armed with three 7.92 mm (0.31 in) MG machine guns.

A photo-reconnaissance version of the Do 17M entered production under the designation Do 17P, powered by two 875 hp (652 kW) BMW 132N radial engines and carried Rb 20/30 and Rb 50/30, or Rb 20/8 and Rb 50/8 cameras in the Do 17P-1 production series. Two aircraft were built as engine test-beds under the designation Do 17R, one with 950 hp (708 kW) Daimler-Benz DB 60OGs, and the other with 1,000 hp (746 kW) Daimler-Benz DB 601As. They were followed by three DB 60OG powered high-speed reconnaissance aircraft which had the designation Do 17S-0. Used for test purposes, these had an extensively glazed nose and the airframe incorporated a bulged section in the underside of the forward fuselage, accommodating a gunner in a prone position to operate an aft-firing MG 15 machine-gun. These experimental reconnaissance machines were followed by a small production batch of 15 pathfinders, comprising three Do 17U-0 and 12 Do I7U-1 aircraft, the five-men crews of which included two radio operators to handle the new and comprehensive communications and navigation radios.

Major production version was the Do 17Z, which appeared in several variants and was built to a total of some 1,700 between 193940. They included the Do 17Z-0 which, powered by two 900 hp (671 kW) Bramo 323A-1 engines and armed with three MG 15 machine guns, was otherwise similar to the Do 17S. The Do 17Z-1 had an additional nose-mounted MG 15 but was underpowered and restricted to a 1,102 Ib (500 kg) bombload; this situation was rectified in the Do 17Z-2 which with 1,000 hp (746 kW) Bramo 323P engines could carry a 2,205 lbs (1000 kg) bombload and up to eight MG 15 machine guns. Some 22 examples of the Do 17Z-3 reconnaissance aircraft were built, each equipped with Rb50/30 or Rb20/30 cameras, and they were followed by the Do 17Z-4 dual-control conversion trainer. Final bomber variant was the Do 17Z-5 which, generally similar to the Do 17Z-2, differed by having flotation bags in the fuselage and in the rear of the engine nacelles. Do 17 production ended with a single Do 17Z-6 Kauz 1 (screech owl 1) long-range intruder and night-fighter which incorporated a Junkers Ju 88C-2 nose housing a 20-mm MG FF cannon and three MG 15 machine-guns. However, for the nine Do 17Z-10 Kauz 11 aircraft that followed anew nose was developed which housed four MG FF cannon and four 7.92 mm (0.31 in) MG 17 machine guns; when deployed as night- fighters they were equipped with Lichtenstein Cl radar and Spanner-11-Anlage infra-red detection apparatus.

Export versions of the Do 17Z were planned under the general designation Do 215, the first to be developed being the Do 215A-1, with 1,075-hp (802-kW) Daimler-Benz DB 601A engines, which was ordered by Sweden in 1939. With the outbreak of World War 11 the 18 aircraft were embargoed and following conversion to Luftwaffe requirements were delivered for use as four-seat bomber/reconnaissance aircraft under the designations Do 215B-0 and Do 215B-1. Two examples of the Do 215B-3 were delivered to the USSR during 1940, and the Do 215BA was a reconnaissance version, similar in configuration to the Do 215B-1, but carrying Rb 20/30 and Rb 50/30 cameras. Final variant was the night-fighter/intruder Do 215B-5 which had an unglazed nose, similar to that of the Do 17Z-10, but housing two 20-mm MG FF cannon and four 7.92 mm (0.31 in) MG machine-guns.

Dornier Do 17s played a significant role in the early phase of World War 11, used first on 1 September 1939 when the invasion of Poland began. They played only a small part in the Norwegian campaign, but were used extensively in the invasion of France and the Low Countries, against Allied convoys in the English Channel and targets in England during the Battle of Britain. Deployed in the invasion of Greece, Yugoslavia and the Soviet Union most had been withdrawn from first-line service by late 1941.

Do 17E and F

The prototypes had mounted the excellent Dailmer-Benz DB 600 engines, but these were constantly in short supply. Production started instead with the BMW V1 radial engine, creating the Do 17E-1 bomber and Do 17F-1 reconnaissance versions. The bombload of the E-1 was a measly 500kg, and the two defensive MG15 machine guns were in a hut on the roof and a small hatch in the floor that offered almost no angle of fire.

Do 17K

After seeing the Do 17M at the Zürich air races in 1937, the Yugoslavian Air Force bought licence rights for production at Drazavna Fabrika Aviona. They equipped it with the considerably better Gnome Rhône 14N engines and added a 20mm Hispano cannon and three 7.92mm Browning machine guns. Seventy had been produced by April 1941 when the country was invaded by German forces. Most were destroyed but two of them fled the country with a load gold on board.

Do 17L and M

The Do 17L-0 and Do 17M-0 were developed in parallel as replacements for the earlier E and F's, the L being the reconnaissance version. Both were designed around the more powerful Daimler Benz DB 600A engines, delivering about 1,000hp. Two L and one M versions were built as prototypes, both with another MG15 in the nose.

The feasibility of the schnellbomber was tested at the International Military Aircraft Competition at Zürich in 1937, where the Do 17M prototype finished ahead of all the fighters in the competition.

The the supply of the DB 600 was extremely limited, and priority had to be given to the Messerschmitt Bf 109. Production versions of the basic M model airframe where then fitted with the new BMW Bramo 323A-1 Fafnir of 900hp, which gave reasonable performance and raised the bombload to 1,000kg. The resulting Do 17M-1 was produced in small numbers and operated until the first year of the war, when they were withdrawn and sent to training units.

Do 17P

The L version would not be able to enter production with the DB 600, and the Bramo engine was rather thirsty and left the M models with too short range for use in the reconnaissance roll. The BMW 132N radials of 865hp were selected instead, which had lower fuel consumption for better range. This Do 17P-1 was produced in some number, but why this version was not called the L-1 is a mystery.

Another two prototypes with DB 600 engines were produced as the Do 17R-0, but did not enter production.

Do 17S and U

When the Soviet Polikarpov I-16 monoplane arrived over Spain where the Do 17P's were being tested, the woeful armament clearly needed an upgrade. A completely new pod-like cockpit was designed for the plane to give the crew more room and better visibility. The roof was extended upward over the line of the fuselage, sloping down to meet it just in front of the wing. The dorsal gun was moved to the rear of the pod where it had a considerably better field of fire. Likewise, the floor was dropped under the fuselage and the ventral gun moved to the back of the pod, allowing it to fire directly to the rear. The changes in the roof and floor made the whole front of the plane much larger. The aircraft now looked much more like the Junkers Ju 88 than previous models, and was no longer referred to as the flying pencil.

Three prototypes with the DB 600 were constructed as the Do 17S-0 reconnaissance versions, but did not go into production. An additional fifteen Do 17U-1 pathfinder models were built, similar to the S but adding an additional crewman (to five) to operate the complex radio equipment. The U models were to fly in ahead of other bombers on night missions, using the radio equipment to locate the target and drop flares on it. They were personally requested by KG 100 as experimental models for this role.

Do 17Z

Wide-scale production finally settled on the definitive Do 17Z models. At first a batch of Z-0's were built with the Fafnir for testing, the DB 600 again proving to be too hard to come by. These were quickly replaced with the Z-1 model, which added another gun for the bombardier, but the additional weight of the nose and guns meant the bombload was reduced to 500kg.

This was addressed in the major production model, the Do 17Z-2. The Z-2 mounted the new 323P version of the Fafnir with 1,000hp, and the extra power allowed the bombload to be increased back to 1000kg. Once again, the armament was upgraded by adding an additional pair of guns firing out of the sides of the upper part of the pod, but the three guns were all fired by a single gunner, meaning that two of them were always dead weight. Although the performance was reasonable, the extra power reduced the fully loaded combat range to a tiny 205 miles.

Modifications of the basic Z-2 model included the Z-3 reconnaissance version, the Z-4 dual-control trainer, and the Z-5 which included float cells in the fuselage and engine nacelles in case it was forced down on water. Some 537 Z-2's were produced before the lines shut down in July 1940.

At first, the plane could use its 265mph maximum speed to stay away from biplane fighters, and its light armament was almost enough for the later planes it met in Spain. But by the time it met British planes, notably over England during the Battle of Britain, it was hopelessly outclassed, typically eight guns to one. It could still sometimes outrun the Hurricanes in a slight dive, but since the Fafnir engine was good only at low altitudes they instead switched terrain-following mass raids which worked fairly well. Even then the Do 17's were butchered over England; for all the trouble spent developing the Do 17, the Luftwaffe was better off without it. Production ended in 1940 and the surviving planes were handed off to allied nations over the next two years.

Do 17Z-10 Kauz

After bomber production ended in 1940, the Z model was modified with a "solid" nose from the Ju 88C and fitted with one 20mm and three 7.92mm MG15's to be used as night fighters. One prototype was constructed as the Z-6 Kauz I (screech-owl), and then the design was futher modified with a custom nose with four 7.92 mm MG17 machine guns and four 20 mm MG-FF cannon. Only nine of these Do 17K-10 Kauz II designs were built, fitted with both a Lichtenstein C1 radar and the Spanner-II infra-red detection system. The later proved to be essentially useless, and was not used on later night fighter designs.

The Z-10 served for two years in the night fighter role, where they were used in Josef Kammhuber's defensive system known as the Kammhuber Line. Each fighter was assigned a single "cell", with three strips of such cells running from Denmark to the middle of France. Within each cell a direction center on the ground tracked both the Kauz and a single target, guiding them until the target was visible in the Spanner. RAF Bomber Command were able to ascertain the nature of the line, and sent all of their bombers in a single "stream", thus overwhelming the defences. The Z-10s were then replaced with more capable planes mounting their own radars.

Do 215

The Do 215 was developed as an export version of the Do 17Z series, but fitted with the much more powerful 1,075 hp Daimler-Benz DB 601A engine. Performance was greatly improved, with top speed increasing to 280 mph and service ceiling to over 31,000 ft.

Eighteen Do 215A-1 were built for export to Sweden in 1939, but were embargoed and instead put into service with the Luftwaffe as the Do 215B-1 and Do 215B-2. Two aircraft were sent to the Soviet Union as Do 215B-3s, otherwise unchanged. The Do 215B-4 was a reconnaissance aircraft similar to the Z-3. The Do 215B-5 Kauz III was a night fighter, similar to the Do 17Z-10. In total another 101 planes were completed as Do 215's.

Specifications (Dornier Do 17Z-2)

Type: Four or Five Seat Medium Bomber

Design: Dornier Design Team

Manufacturer: Dornier-Werke GmbH and Drazavna Fabrika Aviona

Powerplant: (Z-2) Two 1,000 hp (746 kW) BMW Bramo 323P Fafnir 9-cylinder single row radial engines. (E-1) Two 750 hp (559 kW) BMW V1 7,3 12-cylinder Vee engines. (Do 215B-4) Two 1,100 hp (820 kW Daimler-Benz DB 601Aa 12-cylinder engines.

Performance: (Z-2) Maximum speed 255 mph (410 km/h) at 4,000 ft (1220 m); service ceiling 26,905 ft (8200 m); cruising speed 186 mph (300 km/h) at 13,125 ft (4000 m). (E-1) Maximum speed 221 mph (355 km/h) at 4,000 ft (1220 m); service ceiling 16,730 ft (5100 m). (Do 215B-4) Maximum speed 292 mph (470 km/h) at 4,000 ft (1220 m); service ceiling 29,503 ft (9000 m); climb to 3,280 ft (1000 m) in 2 minutes 18 seconds.

Range: (Z-2) 721 miles (1160 km) with full bombload. (E-1) 622 miles (1000 km) with full bombload. (Do 215B-4) 1519 miles (2445 km) with full bombload.

Weight: (Z-2) Empty equipped 11,464 lbs (5200 kg) with a maximum take-off weight of 18,937 lbs (8590 kg). (E-1) Empty equipped 9,921 lbs (4500 kg) with a maximum take-off weight of 15,520 lbs (7040 kg). (Do 215B-4) Empty equipped 12,731 lbs (5775 kg) with a maximum take-off weight of 19,400 lbs (8800 kg).

Dimensions: (Z-2) Span 59 ft 1/2 in (18.00 m); length 51 ft 10 in (15.80 m); height 14 ft 11 in (4.55 m); wing area 592.0 sq ft (55.0 sq m). (E-1) Span 59 ft 5/8 in (18.00 m); length 53 ft 3 1/2 in (16.25 m); height 14 ft 2 in (4.32 m). (Do 215B-4) Span 59 ft 1/3 in (18.00 m); length 51 ft 9 5/8 in (15.80 m); height 14 ft 11 1/2 in (4.55 m).

Armament: (Z-2) Up to seven 7.92 mm (0.31 in) Rheinmetall MG 15 trainable machine guns in the windscreen, nose, dorsal and ventral postions plus an internal bombload of 2,205 lbs (1000 kg). (E-1) One 7.92 mm (0.31 in) forward firing MG 15 machine gun in the starboard side of the cockpit. One 7.92 mm (0.31 in) MG 15 machine gun in the lower nose. One 7.92 mm (0.31 in) MG 15 machine gun in the rear cockpit. One 7.92 mm (0.31 in) MG 15 rearward firing machine gun in the lower rear window plus an internal bombload of 1,102 lbs (500 kg). (Do215B-4) Two 7.92 mm (0.31 in) MG 15 forward firing machine guns in the windscreen. Two 7.92 mm (0.31 in) MG 15 trainable machine guns in the nose. Two 7.92 mm (0.31 in) MG 15 trainable lateral firing machine guns in the side windows. One 7.92 mm (0.31 in) MG 15 machine gun in the dorsal position. One 7.92 mm (0.31 in) MG 15 machine gun in the ventral position plus an internal bombload of 2,205 lbs (1000 kg).

Variants: Do 17E-1 (bomber), Do 17F-1 (reconnaissance), Do 17K/Kb-1/Ka-2/Ka-3, Do 17L, Do 17M/M-1, Do 17R, Do 17P/P-1, Do 17S-0, Do 17U/U-0/U-1, Do 17Z (major variant), Do 17Z-0/Z-1/Z-2/Z-3/Z-4/Z-5, Do 17Z-6 Klaus I, Do 17Z-10 Klaus II, Do 215 (export variant), Do 215A-1/B-0/B-1/B-3, Do 215B-4 (reconnaissance), Do 215B-5 (night fighter).

History: First flight (civilian prototype) 23 November 1934, (Do 17Z-2) early 1939, (Do 215V-1 prototype) late 1938, (Do 17Z-1) first delivery January 1939, (Do 215A-1) December 1939, (Do 17Z series) production terminated July 1940, (Do 215 series) January 1941.

Operators: Germany, Italy (Regia Aeronautica), Croatia, Spain, Yugoslavia, Finland.