Martin Foray (Updated: 3/20/2016):
After World War 1, Germany's war making capacity was extremely limited following the terms of the 1919 Treaty of Versailles that lay most of the blame for war at the feet of the German Empire. As such, the nation was allowed no military aircraft, submarines (nor warships of any kind) or tanks. Her internal defense was handled by a small standing army and armored cars for policing duties. This all changed when Adolf Hitler rose to power and was handed the Chancellery before ultimately taking total control as dictator. In an effort to curb unemployment and secure the faithful of the middle class as well as build up his war machine, he put Germans to work in factories making his weapons of war.
In the years leading up to total war in Europe, the German propaganda machine took control of the minds of the German people. It utilized whatever greatness was found in German discoveries and creations and set forth to create a bloated image of the New Germany. Such was the case in aircraft development where designs began appearing that promoted particular strengths in their respective civilian guises. It was not long before the military value of these designs was noticed by both German authorities and outside parties such as Britain and France. With that said, many of the rebuilding German Luftwaffe's early aircraft became nothing more than conversions of these commercial-minded models. While these systems excelled in their original forms, limitations soon shown over the life of such systems when converted to their military cousins - the Dornier Do 17 proving no exception.
Dornier Do 17 Origins
The Dornier Do 17 series of aircraft actually began as a dedicated commercial venture in 1932. Dornier constructed a mailplane with limited passenger seating capacity that utilized a slim fuselage, two engines set upon a high-mounted monoplane wing assembly and a single vertical tail fin. The flight deck was held at the extreme forward of the aircraft and the passenger cabin was actually two split areas - a two-seat arrangement fitted behind the cockpit and a four-seat arrangement installed aft of the main wing spar. An internal cargo hold managed goods for transport. The initial Do 17 V1 prototype went airborne in 1934. Dornier then delivered a pair of similar prototypes to Lufthansa for evaluation but these were rejected particularly for their split passenger cabin arrangement. The Do 17 lay in limbo before a Dornier test pilot considered the airframe for a military bomber venture for the German Luftwaffe. Dornier engineers then re-envisioned the type by removing the passenger and cargo holds, installing an internal bomb bay and splitting the single vertical tail fin into two smaller vertical tail fins (the latter move served to ensure an unfettered vantage point for a dorsal machine gunner). Defensive armament was added to complete the revision. Dornier then produced five additional prototypes to fit this design scheme and the militarized Do 17 was born.
The Dornier Do 17 is Born
At the time of its inception, the Do 17 was an excellent performing airframe. She proved faster than any fighter development of the time and her handling was fighter-like in itself. Pilots appreciated her rugged status and her flight handling characteristics for an aircraft of this type were exemplary. The German Luftwaffe accepted the type into service and production began on two similar models - the Do 17E-1 and the Do 17F-1. The Do 17E-1 was a dedicated medium bomber capable of an 1,100lb internal bomb load while the Do 17F-1 was a dedicated reconnaissance platform doing away with the bomb load in favor of adding two downward-facing reconnaissance cameras (Rb 50/30 and Rb 75/30 types) and extra internal fuel for increased operational ranges. Both of these mounts were fitted with BMW VI inline liquid-cooled inline engines delivering 750 horsepower and production was limited.
Dornier Do 17 Walk-Around
In her completed production form, the Do 17 still maintained much of her original mailplane/passenger origins. All of the flight positions were held in the forward portion of the airframe. As such, much glazing was added to help improve respective vantage points. Wings were shoulder-mounted along the thin fuselage and fitted ahead of amidships. Wings were straight in design and tapered off at the tips. Each wing fitted a radial piston engine in streamline nacelles along their leading edges. The fuselage tapered off into the empennage to which a double vertical tail fin configuration was affixed. This supplied the dorsal gunner a wider field of fire. The undercarriage was of a traditional arrangement with a pair of main landing gear legs and a tail wheel - all were fully retractable into the engine nacelles (main legs) and the tail section.
The glazed nose housed a crewmember with access to a forward-facing machine gun. The lower flightdeck floor was a gondola-type appendage with a rearward, downward-facing machine gun meant to counter enemy attacks from below and the rear. A dorsal gunner was situated at the rear of the flight deck with access to a machine gun to cover the all-important rear and upper quadrants of the Do 17. Side gunners managed machine guns meant to stop broadside strikes from incoming enemy fighters. In all, the basic Do 17 crew had access to four machine guns in early models and up to eight machine guns in later models. Machine guns were of the MG 15 series of 7.92mm caliber. Bomb loads ranged from 1,000 to over 2,000lbs for the life of the aircraft (depending on variant). Needless to say, fighting conditions aboard any Do 17 airframe were relatively cramped.
First Combat - the Spanish Civil War
It was not long before many of the early German military creations received their formal baptism of fire. Spain became embroiled in a civil war that became known simply as the Spanish Civil War (1939-1939) that pitted the forces of the Republic government against the rebellious Nationalists. Germany sided with the Nationalists and committed their new Do 17s bombers, Junkers Ju 87 dive bombers, Messerschmitt Bf 109 fighters and Panzer light tanks. Both production versions of the Do 17 eventually made their way to the battlefront as part of the "Condor Legion". In combat, the types were exceptional and surpassed the qualities of the fighters that sought to destroy them. Their bombing nature made them lethal opponents and the design was deemed to have passed its initial test.
Work had already begun on improved forms of both Do 17 production models. These became the Do 17M and Do 17P designations respectively. Both versions were intended to fit the much improved Daimler-Benz DB600A series engines of 1,000 horsepower but precedence was handed over to fighter development. As such, the Do 17M was given Bramo 323 Fafnir nine-cylinder, air-cooled radial piston engines of 900 horsepower while the Do 17P was fitted with the BMW 132N series. These newer designs were given larger internal space with room for over 2,200lbs of stores and improved defensive armament based on combat experience gained in the all-important Spanish Civil War. Again, these versions were limited production aircraft.
The Do 17S appeared next and was a high-speed reconnaissance platform that never materialized into a serial production model. Another reconnaissance version, the Do 17U was produced in three prototypes and twelve operational models and (as in the Do 17S) introduced a stepped cockpit, increasing internal space and, thusly, the operating crew to five personnel. Both were fitted with the Daimler-Benz DB600 series as well as improved defensive armament.