Dornier Do 17/Do 215

Dornier Do 17/Do 215

My order reads: ‘Reconnoitre area of Brest-Litovsk – Równe – Sarny – Bielsk, with the emphasis on airfields and railway traffic’. This was to be the first reconnaissance mission behind enemy lines our Staffel was asked to perform.

As we were getting ready, the other crews gathered around us. The day dawned murky, and the hills surrounding Allenstein (Olsztyn) were shrouded by a veil of grey haze.
“If I were you, I would stick to the railway line”, said Junghaus. “You won’t get lost.”
“Well, I’d take along a phrase book, just in case”, advised Niebelschütz. “There are few road signs in Poland, though you could always ask people working in the fields which way to go.”
“Or a policeman!” laughed Klimmer.
Poor chaps! Surely their witty remarks were tainted with envy.
“We’ll do fine, gentlemen”, I assured them. “When we get back, I’ll be counting on you to help me interpret the photos.” As our engines revved up the din drowned the hubbub of their excited voices. I tightened my parachute harness and climbed aboard the aircraft. My crew, Uffz. Kieler and Maiwald, were already inside. I turned around, waved farewell to our comrades and shouted: “I’ll bring you some postcards!” Then the wheel chocks were pulled away and our machine surged forward across the field.
We orbited over the airfield and then began to climb ever higher, finally disappearing into the solid overcast clouds, which extended south as far as the eye could see. We broke clear of the clouds at 1,200 meters, and pressed on with the crystal clear, blue dome overhead. Once at 3,000 meters, we turned south, towards the border. We carefully timed our approach. Twenty minutes later we were supposed to cross the border. It was a thrilling sensation. Down below, hidden under the layer of billowing clouds – which now, illuminated by the sun, resembled a frozen lake surface – lay enemy country. Like a seabed infested with hostile, dangerous creatures. It was time to have a look around. I motioned to the pilot. Kieler nodded in reply and down we went, submerging in the clouds. As we broke clear, I saw flat countryside spreading ahead of us. It was tinged dark brown, with patches of violet, where the heather bloomed. A wide, winding river, and a bridge in the distance.
“That’s the Bug river!” yelled Kieler.
We were flying at 800 meters. I saw flashes below, next to the bridge. Bright, red balls were heading our way. They drifted slowly through the air; I had no problem tracking their advance. They looked like a string of red mice, each with a long, fiery tail – Polish anti-aircraft batteries had opened up!

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I could see we were being bracketed. Those red balls were getting too close for comfort. I pointed my finger skywards. Kieler pulled up the nose of our machine and we ducked into the clouds, continuing on instruments.
So this was our baptism of fire. In fact, quite anticlimactic. I had expected it to be much more dramatic. We flew on, suspended in the opaque, milky void. One could barely see the palm of an extended hand. We had to rely exclusively on the readings of our instruments: artificial horizon, turn and bank indicator, and the clock. If our timing was right, we were over Brest-Litovsk. Again we dropped below the cloud deck. Indeed, I could recognize the distinctive, angled contours of the Brest fortress – a grey-coloured patch, clearly outlined against a brown background. We had ventured too far out to the east and now we had to turn west to take photos of an airfield.
Directly below us, the Bug river leisurely wound its way. I could see sandy shallows under the surface of the clear water. Forlorn and distant, they made me think of the moon’s landscape. Suddenly… red bursts of anti-aircraft shells… At least three Flak cannons were taking pot shots at us. I motioned my hand to direct Kieler’s attention to the nearby airfield. However, he made a far too wide an orbit, perhaps due to a strong head wind, and we strayed to one side of the airfield. In order to take good photographs we had to line up the target and follow a straight course for several hundred meters. “Man, you can do better than that!” I exclaimed.
Finally on our third pass we got it right. The aerodrome was dead ahead. In the meantime, the number of Flak bursts had increased alarmingly. The shells zoomed up, reached the highest point of their trajectory, exploded in a fiery flash and cascaded down. Most of them went off below, but some burst on either side or ahead of us. This time I had a splendid view of the airfield. As soon as I took the photos, we gunned the engines and, dodging the Flak, sped off to the south. Curiously, not a single shell fragment hit us, and no fighter scrambled to intercept us.

The farther we flew on the southerly course, the lighter the sky grew. Solid overcast gave way to broken clouds, and in the breaks we could see stretches of land merrily illuminated by the sunrays. We enjoyed the bucolic scenes below: meadows with large flocks of wild geese grazing on them, peasants toiling in the fields, and dark patches of woodland veiled in mists. From time to time we caught a glimpse of hamlets, their cottages with thatched roofs blurring into the surrounding countryside. We spotted the Kovel railway station, clogged with trains, then passed over Równe and Sarny. Directly behind Sarny lay the Rokitna marshes – a grey, soggy wasteland mottled with white-trunked birches and pools of water. Lying prone, I marked all our findings on the map. Just then the pilot leaned to me and shouted to my ear: “Fighters on our tail!” Simultaneously, the machine gun manned by our radio operator began to clatter. I clambered back to my station and looked behind. Indeed, three Polish PZL 24 fighters boring in on us!1 With their slim fuselages and short, stubby wings they looked very much like agitated hornets. One of them closed the distance to some 400 meters and fired its guns. Strings of white tracers groped towards us. Then the sickening noise of bullets tearing into our machine… and again… time after time. Splinters swished inside the crew compartment. Maiwald, our radio operator, curled up. A stray bullet had torn one of his trouser legs, nicked his calf and embedded itself in the cockpit roof.
One more burst of gunfire found its mark… This time our control surfaces were hit. So this was the real baptism of fire! What a nasty feeling – three against one, and we were just a hapless, hard-working ‘bee’ on a reconnaissance mission! If only we could turn around and return fire… But our task was to reconnoiter at all costs, not to fight.

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Maiwald kept shooting back, whilst Kieler directed our machine into a cumulus cloud, which glided majestically across the blue sky like a white ark. We plunged inside, changed course several times, and popped out on the other side of the cloud. Almost instantly hard, metallic cracks reverberated in the cockpit. One of the Poles had tagged onto our tail and was spraying us with bullets. He was a mere 200 meters away. I felt a surge of fury overcome me. I went towards the rear, pushed Mailwald aside, and grabbed his machine gun. In the meantime Kieler accelerated into a dive, racing for the cloud layer billowing to the north of us. The Polish fighter fell behind and after a few tense moments we were again enveloped by clouds.
Half an hour had passed before we emerged into the clear. We were alone. We took up a north – north-west heading, straight towards our home base. On the way we spotted a freight train moving along the Warsaw-Białystok line. With the adrenaline still pumping through our veins from the recent scrap with fighters, we did not hesitate for long. For only a brief moment did the recollection of Hptm. Kerber’s stern words pass through my mind: ‘Avoid combat at all costs. Delivering the results of your reconnaissance run is of the utmost importance’. But now it was too late. We were racing down, and taking aim at the locomotive. Our forward-pointing gun ripped out a short burst and a geyser of steam shot up from the punctured boiler. The train slowly ground to a halt. We veered around and rushed back, going flat out ‘on the deck’. We were in fact flying so low that I could see treetops bowing under the pressure of our slipstream. We made a second firing pass at the locomotive. Ahead, there was a seemingly endless column of box cars. Several people, apparently brakemen, fled in panic across the fields and away from the train. At the head of the train one man, the engine driver, could be seen. A small, black figure, aiming a rifle at us.
Again our slugs thudded into the bulky, shiny boiler. Suddenly I heard a cracking noise behind my back. Turning around, I saw a hole in my observer’s seat, left by a bullet that had gone right through it to stick in the cockpit roof. The guy with the rifle was a sharp shooter, and a lucky one, too. Had I been in my seat, that bullet would have killed me. One more pass. Incredibly, the guy was still there, standing fast in his bluish, sooty overalls. With the butt of his rifle pressed to his shoulder, he drew a bead on us. For a moment a felt a sense of respect for this tough, selfless man, who dared to duel with our overwhelming firepower. However, his locomotive was already knocked out for good. As we pulled up, it was standing there, like a mortally wounded animal, its boiler bleeding off steam from numerous punctures.
At noon we landed at our airfield. We had been in the air for six hours and ten minutes. Our comrades came running up to greet us and tightly circled our machine. They counted nine bullet holes in the aircraft. We jumped to the ground in high spirits. Everybody asked questions and cheered as if we had returned from the dead. Only the officer responsible for our onboard photographic equipment remained calm. “I hope you bunch of heroes didn’t let my camera get shot to pieces?” he said wryly.2

Design and Development

The Dornier Do 17 was designed and built in the Dornier Werke GmbH plant located in Friedrichshafen on the Bodensee (Lake Constance). The company was founded and owned by one of the most renowned German aviation designers, Prof. Claudius Dornier. He was born on 14th May 1884 at Kempten im Allgäu. The son of a French wine importer and his German wife, Claude Dornier was born and grew up in Bavaria. In 1907 he graduated from the Technische Hochschule (Technical University) at Munich, where he had studied Maschinenbau (mechanical engineering). As a young engineer he first worked for a company designing and building steel road and rail bridges. In 1910, he joined the Versuchsanstalt des Zeppelin-Luftschiffbaues, an experimental facility in Friedrichshafen, which constructed airships. There he dealt with the statics and aerodynamics of airships, refined the construction of airscrews and worked on an advanced, mobile hangar for airships. Shortly before the outbreak of the First World War Dornier designed a massive airship (gas capacity of 80,000 cubic metres) for transatlantic communication. When the war broke out, there was no longer a need for an airship line to the United States of America, and the order was duly cancelled. To compensate for it, Dornier received an offer to design a large, multi-engine flying boat for military use. While designing his flying boat, Dornier relied heavily on steel and duralumin, which made him one of the pioneers of all-metal aircraft construction. His project was designated Rs I. The first prototype was ready in October 1915, but its further development was discontinued before it had a chance to take to the air. It was followed by Rs II, Rs III and Rs IV, which were test-flown. Besides their all-metal construction, Dornier’s flying boats featured engines placed in tandem. This solution was first introduced in the Rs II, due to the lack of more powerful engines. It proved its worth, and was successfully used in many subsequent flying boat designs. Another novelty was the boat’s high-wing configuration with two fuselage-mounted sponsons to improve water stability during start and landing. In 1916 the Zeppelin Werke GmbH plant run by Dornier moved from Seemoos to Lindau-Reutin. There, in 1918, the D I single-seat, all metal fighter aircraft was prototyped, but never made it to series production.
After the armistice had been proclaimed in November 1918, Dornier continued to work in the Zeppelin Werke GmbH at Lindau-Reutin, as well as in the Flugzeugbau Friedrichshafen GmbH in Manzell. In the latter location 20 Zeppelin C II bi-plane observation aircraft were built, of which 19 were delivered to Switzerland.

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Since the war was over, Dornier focused on civilian designs. On 31st July 1919, Dornier’s new flying boat, designated Gs I, with a capacity of six passengers, made its maiden flight. The first air tests revealed its great potential, and the aircraft was publicly demonstrated in the Netherlands. However, the Allied Armistice Committee promptly categorized it as a type of aircraft banned by the Treaty of Versailles and ordered the prototype to be destroyed. Furthermore, Dornier was obliged to discontinue his work on two prototypes of the Gs II flying boat (with a capacity of nine passengers). Watched closely by the Allied Armistice Committee, Dornier strove to design aircraft within the limits imposed on the German aviation industry. One of them was the Cs II Delphin flying boat with a capacity of five passengers, first flown on 24th November 1920. It was followed by its land-based counterpart the C III Komet, completed the next year, and the Libelle I (Dragonfly) open-cockpit, parasol wing, monoplane flying boat.
In 1922 Zeppelin Werke GmbH at Lindau-Reutin was re-named Dornier Metallbauten GmbH. In order to circumvent the constraints forced on the Germans by the Treaty of Versailles, Dornier resolved to open branches of his company in other countries. In Italy he established CMASA (Societa di Costruzioni Meccaniche Aeronautiche S.A.) in Marina di Pisa, which was to manufacture flying boats based on the Gs II design. On 6th November 1922 the prototype of the Dornier Wal (Whale) flying boat was first flown. It was to bring Dornier international fame, and was produced under licence in Japan, the Netherlands and Spain. Besides his branch in Italy, Dornier also founded similar plants in Spain, Switzerland and Japan. The Swiss-based facility, which was located in Altenrhein, across Lake Constance from his main office in Germany, became Dornier’s premier construction plant for flying boats. There, the Dornier X was built, then the largest flying boat in the world, powered by 12 engines (mounted in six separate tandem nacelles on top of the wing). The first prototype of this giant design (of 56,000 kg take-off weight) lifted off from the surface of Lake Constance for its maiden flight on 12th July 1929. In the ensuing years two more machines of this type, based on orders from Italy, were built.
More experimental designs by Dornier followed. Among them was a twin-engined night bomber, ordered by Japan and designated Do N, which was later produced in cooperation with the Kawasaki company. On 31st March 1930 the first of two prototypes of the Do P four-engined heavy bomber was test-flown. Then, on 17th October 1931, a prototype of the Do Y three-engined bomber took to the air for the first time.

In 1931 Dornier set about designing the Do F twin-engined bomber. It was first flown on 7th May 1932 in Altenrhein. Its fuselage was of all-metal, stressed-skin construction. The wings were fitted with metal spars and ribs, and covered partially with fabric. The aircraft was powered by two 600 hp Bristol Jupiter radial engines, produced under licence by Siemens. The Do 11 (which was the official designation for the Do F) was included in the 1932-1938 expansion plan for the German Air Force. The production of the Do 11 and Militär-Wal 33 flying boat was undertaken by the Dornier company (which around that time was re-named Dornier-Werke GmbH) in 1933.
When, in January 1933, the National Socialists seized power, the German Air Force entered a period of rapid expansion. On 5th May 1933 the State Ministry of Aviation (Reichsluftfahrtministerium or RLM) was formed, with Hermann Göring at its head, and Erhard Milch as the State Secretary for Aviation. The RLM quickly devised a new expansion programme, which aimed at creating a fleet of 400 bombers – the Luftwaffe’s main striking force – by the end of 1935.
A technical specification for a Kampfzerstörer, a fast assault/bomber aircraft, was created in Obstlt. Wilhelm Wimmer’s Waffenprüfwesen (weapon test division), which was part of the Heereswaffenamt (Ordnance Department) of the Reichswehrministerium (Reich Defence Ministry), as early as July 1932. At that time Germany was still under close scrutiny from the international community. Hence, Gen. Lt. von Vollard-Bockelburg, then at the head of the Heereswaffenamt, concealed the aircraft’s intended role by issuing specifications for a Schnellverkehrsflugzeug für die DLH (fast communication aircraft for the DLH)3. However, there was no doubt that the design was to be a combat aircraft. Its civilian use was of minor importance, and allowed only if the aircraft could be quickly and inexpensively re-converted to its military version. Invitations to tender were sent to three companies: Dornier, Junkers and Heinkel. The design bureaus eagerly accepted the challenge to create an aircraft that would meet the demands stated by the Army. Thus, three bombers were designed: the Dornier Do 17, the Junkers Ju 86 and the Heinkel He 111.

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Of the three producers, Dornier seemed the least concerned about the aircraft’s secondary use as a civilian machine. His design, which incorporated all the latest achievements in aerodynamics, featured an unusually slim, long and narrow fuselage, which could accommodate two bomb bays, but had hardly enough room for its six passengers. In March 1933 Dornier prepared a full-scale wooden mock-up. On 17th March 1933 it was demonstrated to representatives of the Reichskommissariat für die Luftfahrt (Reich Commissariat for Aviation). On 5th May 1933 the newly established RLM took over the responsibilities of the Reichskommissariat für die Luftfahrt. Immediate control over the development of new aircraft designs was placed with the Abteilung Technik (technical division) of the Allgemeines Luftamt, the civilian department of the RLM, under Obstlt. Wilhelm Wimmer.
On 23rd March 1933 Erhard Milch, the Staatssekretär der Luftfahrt of the RLM, placed an order with Dornier for two aircraft designated Do 17, one in military configuration, and the other for Lufthansa. It was stressed that the civilian version was to be easily modified for military use. The first prototype of the military version was designated Do 17 C, W.Nr. 256 (later Do 17 V1). The prototype of the civilian version was initially designated Do 17 A, W.Nr. 257 (later Do 17 V2). Both aircraft were to be powered by BMW VI (Do 17 C) or BMW VI 6.0 (Do 17 A) inline engines. On 2nd October 1933 Dornier proposed a third prototype powered by Hispano-Suiza 12Ybrs engines, which was to serve as a ‘fast airliner’. On 4th November 1933 the RLM signed the contract, and the aircraft received the designation Do 17 D.
The Do 17 was a markedly advanced design for the first half of the thirties. The airframe was composed of four main sub-parts: the fuselage front and rear sections, the wings and empennage. Its fuselage was a metal monocoque of built-up frames and intermediate stiffeners notched to receive channel-section stringers, and its wing was a two-spar trapezoidal structure, the spar booms being thick duralumin extrusions of asymmetrical section, the girder-type spar bracing utilising duralumin members of broad channel section, from which the main ribs were built up, and the intermediate ribs had a tubular bracing. Wing skinning was flush-riveted light metal, apart from the undersurface of the wing between the spars, for which fabric covering was employed.
The Do 17 C prototype was designed to feature the classic, single tailfin configuration, whilst the Do 17 A prototype was to be equipped with twin tailfins, successfully used by Dornier on his Do 23 bomber. All fuel was housed in the wing centre section, between the engine nacelles and the fuselage, and the main undercarriage members retracted aft hydraulically and mechanically into the tails of the engine nacelles.

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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