Dornier Do 17/Do 215

The most remarkable characteristic of the new aircraft was the inordinately slim contouring of the fuselage; a pencil-like impression enhanced by a long ogival nose, with, as initially flown, no protuberance other than a shallow flight deck windscreen to mar the lines. This slimness was, in fact, somewhat illusory, as, in planform, the near-cylindrical cross section translated to what can only be described as an inverted triangle, about twice as wide at the top as at the bottom, the sloping sides of which resulted in an abnormally “broad” centre section. Aft of the wing, the fuselage transformed once more from elliptical to circular cross section.
The Do 17 C had provision for two bomb magazines, which, arranged in tandem asymmetrically to starboard, could each accommodate five 50 kg bombs hung vertically. The crew comprised three members consisting of a pilot seated asymmetrically to port, with a navigator/bomb aimer seated immediately aft, and a radio operator/gunner accommodated behind the wing trailing edge. This last-mentioned crew member was intended to operate a dorsal machine gun on an open ring mount between frames 17 and 19, as well as a ventral gun firing through a hatch between frames 19 and 21. This defensive armament was, incidentally, specified in a memorandum, which, following discussions held on 20 May 1933, referred to the guns by the cover-name of Spritzen (syringes)! Four portholes were inserted in each side of the fuselage aft of the wing trailing edge to afford the radio operator/gunner some measure of vision.

Prototypes and Serial Production Variants
Dornier Do 17 V1
On 20th November 1934 the Do 17 C prototype passed the acceptance tests. It was powered by two BMW VI 7.3 engines, each rated at 500 hp (at 1,390 rpm), with maximum power output of 700 hp (at 1,550 rpm). The engines were fitted with three-blade, two-pitch propellers. The aircraft was unarmed. It featured a conventional, single tailfin and four glazed apertures on either side of the fuselage mid-section to offer the radio operator some field of vision.
Three days later, on 23rd November 1934, Dornier’s chief test-pilot Flugkapitän Egon Fath, took the aircraft up for its maiden flight. It was satisfactorily concluded, and by the end of February 1935 the Do 17 C was dispatched to the Erprobungsstelle Rechlin (Test Station at Rechlin, usually referred to as E-Stelle Rechlin). In mid-February 1935, during one of the evaluation flights, the undercarriage failed on landing and the machine was damaged. It was repaired by 18th March 1935 and submitted to a series of tests at Rechlin. By then the aircraft was officially designated Do 17 V1. In late April 1935 another landing gear failure brought the aircraft down for a belly landing. Between 24th and 26th June 1935 the Do 17 V1 was test-flown, along with the Do 17 V2, the other prototype, at Friedrichshafen by two pilots from Rechlin, Flugkapitäne Fleischhauer and Thönes. As a result of those tests, the control surface areas were enlarged, and the landing gear wheel struts were set at a different angle for improved stability on landing.
The results of the tests, carried out up to that point, were discussed during a meeting held on 19th July 1935, and the following refinements were postulated:

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“1. The radio operator and rear gun stations ought to be moved two segments forward, from the section between the 15th and 17th formers to the section between the 13th and 15th formers. 2. The rear bomb bay ought to be moved forward, from the section between the 13th and 15th formers to the section between the 9th and 11th formers.5”
A transparent fairing, which afforded the radio operator a field of vision and fire for his machine gun, replaced the eight glazed apertures, which, after relocation of the radio operator’s station, were no longer of any use. On 30th October 1935 the Do 17 V1, civil registration D-AJUN, returned to Rechlin, where further service evaluations were conducted. On 21st December 1935, during a low-level flight, one of the aircraft’s engines stalled. The V1 clipped the ground with its wingtip and crashed. Of the four-man crew, two were seriously injured. The aircraft was written off. Tests were continued with W.Nr. 686 “Ersatz V1” (V1 replacement), which received the same registration code D-AJUN. It was first flown on 13th June 1936. The aircraft was powered by BMW VI 7.3 engines and fitted with twin tailfins. It was later used as a test-bed for Elvemag (Elektr. Vertikalmagazine) bomb racks, mounted vertically inside the fuselage.

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Dornier Do 17 V2
Unlike the Do 17 C, the Dornier Do 17 A, W.Nr. 257 was to prototype a civilian version. Designated Do 17 V2, it first flew on 5th May 1935. Viewed as essentially a ‘demilitarised’ model, the Do 17 V2 actually differed from the V1 in a number of respects. It was powered by two BMW VI 6.3 engines, each rated at 640 hp at 1,530 rpm, and driving two– or three-bladed, two-pitch propellers. The capacity of each of the two centre section fuel tanks was increased from 500 to 700 litres. Apart from the provision of commercial radio equipment, the flight deck had been extensively revised in conformity with Lufthansa requests, full dual control being introduced and the cabin roof being raised to provide additional headroom and improve forward vision. Other changes included the introduction of cut-outs in the main-wheel well doors, through which the wheels protruded when retracted, and the insertion of rectangular windows in the sloping sides of the fuselage beneath and immediately forward of the wing, the aft portholes being deleted.
Dornier’s factory documentation includes information, rarely mentioned by most authors, that the Do 17 V2 was fitted with three passenger compartments. Hence, it could carry a total of ten, besides its two-man crew. A room was made for two passengers between the pilots’ cockpit and the front spar. Four more could be seated between the front and main spars, albeit in a compartment only 140 cm high! It could be entered via a ladder and a hatch located in the lower part of the fuselage. Four more passenger seats were planned behind the main spar. The machine was test-flown at the factory airfield, whereupon it received the civilian registration D-AHAK “Rhein” and was transferred to Lufthansa for further evaluation. The ensuing tests took only a month, from 8th October to 7th November 1935. Lufthansa rejected the aircraft as unsuitable for its designed role of a fast courier machine. The passenger compartment, with wing spars running across it, was deemed to be too uncomfortable. Another major inconvenience was the fact that the main luggage compartment could only be accessed from the top of the fuselage. The aircraft was returned to Friedrichshafen, where it was turned into a prototype of the Do 17 E bomber.

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