Dornier Do 17 (1934)

Officially, the twin-engine Dornier Do 17 was developed for Deutsche Lufthansa as a fast “mail aircraft”. In fact, this high-speed aircraft was planned for military use right from the start. The development contract issued by the German National Association for the German Aviation Industry (Reichsverband der Deutschen Luftfahrtindustrie)gave clear instructions that Dornier had to design two prototypes, only one of which were intended to meet the criteria of Lufthansa. A high-speed aircraft was created that was designed on the basis of the latest aerodynamic principles and manufactured using advanced production engineering methods. The narrow cylindrical fuselage precluded commercial use of the aircraft from the outset and earned the plane the nickname of “Flying Pencil” (fliegende Bleistift). After a long series of delays, the first prototype, the Do 17 V-1, took to the skies for the first time on 23 November 1934. In fact, this was a purely military test aircraft, albeit unarmed. Testing proved to be extremely satisfactory. On 5 May in the following year, the Do 17 V-2 took off on its maiden flight. This was the prototype for a ten-seater commercial airline. Inevitably, the aircraft demonstrated impressive flight performance but proved to be completely unsuitable for carrying passengers commercially. Indeed, Lufthansa’s commercial flight tests therefore only lasted a month. Some of the subsequent prototypes and pre-production aircraft were fitted with different engines and were primarily designed as military aircraft. The aerodynamic design was the principal factor in ensuring that the prototypes of the Do 17 achieved speeds that were often higher than the standard fighter aircraft of the time. The first public demonstration of this prowess was by the Do 17 V-8, fitted with two Daimler-Benz DB 600 A-0 engines delivering takeoff power of 1,100 hp at the Zürich International Air Show in July 1937. The aircraft designated Do 17 MV1 achieved a maximum speed of 425 km/h and won the Alpine Race.

One year previously on 30 May 1936, the Do 17 E-0 had already taken off as the first aircraft of a future military version for volume production. The main difference from the previous prototype aircraft was the defence armament. It was fitted with two BMW VI 7.3 engines, each delivering 750 hp power. The aircraft in the E Series (E-1 to E-3) were designed as bombers and a total of 268 aircraft of all versions came out of the assembly plants, including planes built under license by Henschel and HFB. Many of these aircraft saw action during the Spanish Civil War. In parallel to the E-1 version, Dornier also developed its own reconnaissance version, the Do 17 F-1. From spring 1937, a total of 15 of these aircraft were delivered and some were also deployed in Spain. The Do 17 F-2 had virtually the same design and it appears to have been a one-off. The two pathfinders Do 17 LV 1 and LV 2 also remained one-offs.

The Do 17 Ka 1 was developed from the Do17 E-1 for export to Yugoslavia and this aircraft took off on its maiden flight on 6 October 1937. The use of French Gnôme & Rhône 14 K engines, each delivering 870 hp power was the most significant difference. This difference also applied to the Do 17 Kb 2 fitted with French Gnôme & Rhône 14 NO engines, each delivering 980 hp power. Similar to the Do 17 E, the two reconnaissance versions Do 17 Ka 2 and Ka 3, again fitted with Gnôme & Rhône 14 engines, were also developed. Dornier supplied 36 aircraft of all versions before production under license started up in Yugoslavia at the state company Drzauna Fabrika Aviona in 1939. Some 60 aircraft were manufactured there prior to the commencement of hostilities.

Volume production of the Do 17 M-1 started up in mid-1937 and this version gradually began to replace the Do 17 E. 200 aircraft left the production hangars fitted with two Bramo 323 A engines, each delivering power of 900 hp. Again, Dornier derived the reconnaissance version Do 17 P-1 and P-2. They were mainly distinguished from the Do 17 P through installation of BMW 132 N-1 high-altitude engines, each delivering power of 910 hp. 330 aircraft were built in the two versions, virtually all of them being manufactured at Siebel, Henschel and HFB under license. The Do 17 R was a reconnaissance aircraft derived from the Do 17 M with two 1,100 hp DB 60 B engines, but only four aircraft were delivered.

On 1 March 1938, the first Do 17 Z took off on its maiden flights. Introduction of the Z Series (Z-0 to Z-7 and z-9 and Z-10) turned the Do 17 into a truly multipurpose aircraft, deployed for a range of different uses from bomber through long-distance reconnaissance aircraft to night fighter, depending on the version. The most striking differences with previous versions were newly designed nose area, reinforced defence armament and increase in crew strength to four men. The versions Z-1 to Z-3 were bombers, as was version Z-5. Apart from the first versions, all the aircraft were fitted with two Bramo 323 P-1 engines, each delivering power of 1010 hp. They remained the fastest versions of this type, despite the continual increase in takeoff weight. In particular they saw action in the air battle over England and the versions Z-3 and Z-5 were substantially modified to meet the requirements. The Do 17 Z-9 was the last bomber version, specifically designed for low-level attacks.

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