Dornier Do 17

The Dornier Do 17 was one of the Luftwaffe’s most distinctive aircraft, and one of the most recognisable silhouettes of the early Second World War. Nicknamed the “Flying Pencil” by the British because of its long, slim fuselage, the Do 17 was a fast, twin-engine light bomber that had been designed in the 1930s as a high-speed mail plane and adapted for military service. When it first flew in 1934, it was faster than most fighters of its day, and the Luftwaffe believed it would be almost impossible to intercept. The Do 17 fought in the Spanish Civil War, in the invasion of Poland, in the Battle of France, and in the Battle of Britain, where its slim shape became a familiar sight over southern England. But by 1940, fighters had caught up with it, and its light defensive armament and small bomb load made it increasingly vulnerable. The Luftwaffe gradually withdrew the Do 17 from front-line bombing and replaced it with the faster, more capable Junkers Ju 88. About 2,139 Do 17s were built, and the type continued to serve in secondary roles — as a reconnaissance aircraft, a night fighter, and a glider tug — until the end of the war. The Do 17’s story is the story of an aircraft that was ahead of its time when it was designed, and behind the times when it was needed most.

1. Key Facts

Role	Light bomber; also reconnaissance, night fighter, glider tug
First flight	23 November 1934
Introduced	1937
Number built	About 2,139
Crew	4 (pilot, bomb aimer, radio operator, gunner)
Engine	2 × Bramo 323P 9-cylinder radials, 1,000 hp each (Do 17Z)
Max speed	About 410 km/h (255 mph)
Range	About 1,160 km (721 miles)
Armament	6 × 7.92 mm MG 15 machine guns; up to 1,000 kg (2,205 lb) of bombs
Operators	Luftwaffe; also Bulgarian, Croatian, Finnish, and Spanish air forces
Fate	Withdrawn from German front-line service by 1942; last operators retired in the early 1950s

2. Development

Origins as a Fast Mail Plane

The Do 17’s origins lay in a 1933 requirement from the German airline Lufthansa for a fast mail plane that could carry mail and a small number of passengers at high speed. The Dornier company, which had built the giant Do X flying boat, designed a sleek, twin-engine monoplane with a long, slim fuselage and a shoulder-mounted wing. The aircraft was built under the cover of a civilian project, because Germany was still forbidden by the Treaty of Versailles from building military aircraft, but its designers always intended it to be adaptable as a bomber. The first prototype flew on 23 November 1934, and it was immediately clear that the aircraft was fast: it could reach 400 km/h, faster than any fighter then in service. Lufthansa was not interested in the aircraft as a mail plane, because its cabin was too small, but the Luftwaffe was very interested in it as a bomber.

From Mail Plane to Bomber

The Luftwaffe ordered the Do 17 into production as a bomber in 1936, and the first military version, the Do 17E, entered service in 1937. The military Do 17 had a glazed nose for the bomb aimer, a bomb bay in the fuselage, and defensive machine guns in the nose, the dorsal position, and the ventral position. The aircraft’s slim fuselage gave it a small frontal area and low drag, which made it fast, but it also gave it a cramped interior and a small bomb bay. The Do 17’s bomb load of 1,000 kg was modest, and its defensive armament was light, but the Luftwaffe believed that its speed would protect it. The Do 17 was one of the three main bombers of the Luftwaffe’s early war, alongside the Heinkel He 111 and the Junkers Ju 88, and it was the fastest of the three.

The Spanish Civil War

The Do 17’s first combat service came in the Spanish Civil War, where the Condor Legion used it as a bomber and as a reconnaissance aircraft. In Spain, the Do 17 proved to be fast and difficult to intercept, and it carried out bombing raids on Republican positions with relatively few losses. The lessons of Spain were encouraging: the Do 17’s speed seemed to confirm the Luftwaffe’s belief that a fast bomber did not need heavy defensive armament. But Spain was a limited war, fought against an enemy with few modern fighters, and the lessons did not hold in the Second World War, when the Do 17 faced the RAF’s Spitfires and Hurricanes. The Spanish experience gave the Luftwaffe a false confidence in the Do 17 that would cost it dearly in the Battle of Britain.

Production and the Do 17Z

The main production version of the Do 17 was the Do 17Z, introduced in 1939, which had more powerful Bramo 323P engines, a redesigned nose with better visibility for the bomb aimer, and improved defensive armament. The Do 17Z was built in several sub-types, including the Z-2 bomber, the Z-3 reconnaissance version, and the Z-10 night fighter. Production was centred on the Dornier factories at Friedrichshafen and Munich, and it was always limited by the competing demands of other aircraft programmes. About 2,139 Do 17s were built in total, including the early Do 17E and Do 17F versions and the later Do 17Z. Production ended in 1940, when the Luftwaffe decided to concentrate on the Ju 88, which was faster, carried a bigger bomb load, and was easier to build.

3. Design

The Flying Pencil

The Do 17’s most distinctive feature was its long, slim fuselage, which gave it the nickname “Flying Pencil”. The fuselage was a narrow, oval-section structure, only about 1.5 metres wide, with a glazed nose at the front and a tapered tail at the rear. The slim fuselage reduced drag and made the aircraft fast, but it also made the interior extremely cramped: the crew of four sat in a narrow cabin with little room to move, and the bomb bay could carry only 1,000 kg of bombs. The aircraft’s wings were shoulder-mounted, with a span of 18.00 metres, and they carried the engines, the fuel tanks, and the main undercarriage. The Do 17’s clean lines and slim shape made it one of the most elegant aircraft of the war, but its elegance came at a price: the aircraft was difficult to fly, uncomfortable for its crew, and limited in what it could carry.

Engines and Performance

The Do 17Z was powered by two Bramo 323P nine-cylinder radial engines, each producing 1,000 hp. The Bramo 323 was a development of the Siemens-Halske Sh 22 engine, and it was reliable but not powerful enough to give the Do 17 the performance it needed. The aircraft’s top speed of 410 km/h was fast for a bomber in 1937, but by 1940 it was slower than the Spitfire and the Hurricane, and it could not outrun the fighters it faced. The Do 17’s range of about 1,160 km was adequate for operations over France and southern England, but its service ceiling of 8,200 metres was lower than that of the fighters it faced. In practice, Do 17 crews flew at medium altitude, where they were vulnerable to fighters attacking from above and to anti-aircraft fire from below. The aircraft’s performance was a disappointment in combat, and it was one of the main reasons for the type’s withdrawal from front-line service.

Crew Positions and Defensive Armament

The Do 17’s crew of four consisted of a pilot, a bomb aimer, a radio operator, and a gunner. The pilot sat in a cockpit at the front of the aircraft, with a good view forward but a poor view to the rear. The bomb aimer sat in the glazed nose, where he operated the bomb sight and a forward-firing machine gun. The radio operator sat behind the pilot, and the gunner manned the dorsal and ventral gun positions. The Do 17’s defensive armament was six 7.92 mm MG 15 machine guns, mounted in the nose, the dorsal position, the ventral position, and the side windows. The MG 15 was a light weapon with a limited rate of fire, and the Do 17’s guns were no match for the eight-gun armament of a Spitfire or a Hurricane. The aircraft’s crew knew that their guns could do little more than force an attacking fighter to be cautious, and that their survival depended on fighter escort and on flying in formation.

4. Technical Specifications

The figures below are for the Do 17Z-2, the main production bomber version, and are typical values from Luftwaffe manuals and post-war reference works.

	Do 17Z-2
Length	15.80 m (51 ft 10 in)
Wingspan	18.00 m (59 ft 1 in)
Height	4.50 m (14 ft 9 in)
Wing area	55.0 sq m (592 sq ft)
Empty weight	5,210 kg (11,486 lb)
Loaded weight	8,590 kg (18,938 lb)
Max takeoff weight	8,850 kg (19,511 lb)
Engines	2 × Bramo 323P radials, 1,000 hp each
Max speed	410 km/h (255 mph) at 4,000 m
Range	1,160 km (721 miles)
Service ceiling	8,200 m (26,900 ft)
Bomb load	Up to 1,000 kg (2,205 lb)

Dimensions and Weights

The Do 17 was a medium-sized light bomber, with a wingspan of 18.00 metres and a loaded weight of about 8,590 kg. Its size reflected its role as a light bomber: it was smaller than the He 111 and carried a smaller bomb load, but it was faster and more manoeuvrable. The aircraft’s fuel capacity was about 2,400 litres, enough for a range of 1,160 km, which allowed it to reach targets in southern England from bases in France. The Do 17’s bomb bay could carry up to 1,000 kg of bombs, typically four 250 kg bombs or eight 50 kg bombs. The aircraft’s small bomb load was a limitation, and it meant that the Do 17 had to fly more sorties than the He 111 to deliver the same weight of bombs on a target.

Performance and Limitations

The Do 17’s performance was adequate in 1937 but inadequate by 1940. Its top speed of 410 km/h was no longer faster than the fighters it faced, and its climb rate and service ceiling were inferior to those of the Spitfire and the Hurricane. The aircraft’s light defensive armament and lack of armour made it vulnerable to both fighters and anti-aircraft fire, and its losses in the Battle of Britain were heavy. In the Battle of France, Do 17 units lost about 10 percent of their aircraft, and in the Battle of Britain, loss rates were higher. The Do 17’s limitations were well understood by the Luftwaffe, and the type was gradually withdrawn from the bombing role and used instead for reconnaissance, night fighting, and training.

5. Armament

Machine Guns and Defensive Positions

The Do 17Z-2 carried six 7.92 mm MG 15 machine guns, mounted in the nose, the dorsal position, the ventral position, and the side windows. The MG 15 was a drum-fed machine gun with a rate of fire of about 1,000 rounds per minute, but it had a limited ammunition supply and a short effective range. The Do 17’s guns were hand-aimed, and the gunner had to stand in the cramped fuselage to fire them. The aircraft’s defensive armament was its greatest weakness: six light machine guns were no defence against a modern fighter, and the Do 17’s crew knew that if a Spitfire or a Hurricane found them, they had little chance of survival. The aircraft’s defensive armament was a reminder that the Do 17 was designed in the 1930s, when bomber crews believed that speed alone would protect them.

Bombs and the Bomber Role

The Do 17’s bomb load was up to 1,000 kg, typically carried as four 250 kg bombs or eight 50 kg bombs in the bomb bay. The aircraft could also carry smaller bombs and flares for night operations. The Do 17’s bomb load was small compared with the He 111’s 2,000 kg, but it was adequate for attacks on airfields, bridges, and shipping, which were the Do 17’s main targets in the early war. The aircraft’s bomb sight was a simple device, and its bombing accuracy was poor, especially at high altitude and high speed. In practice, Do 17 crews often attacked at medium altitude, where they were vulnerable to fighters and anti-aircraft fire. The Do 17’s bombing role was a disappointment, and the aircraft’s small bomb load was one of the reasons for its replacement by the Ju 88.

6. Variants

Do 17E, Do 17F, and Do 17Z

The Do 17E was the first production bomber version, with BMW VI engines and a crew of three. The Do 17F was a reconnaissance version with extra fuel tanks and cameras. The Do 17Z, introduced in 1939, was the main production version, with Bramo 323P engines, a redesigned nose, and a crew of four. The Do 17Z was built in several sub-types, including the Z-2 bomber, the Z-3 reconnaissance version, the Z-5 floatplane version, and the Z-10 night fighter. The Do 17Z was the version that fought in the Battle of Britain, and it was the aircraft that most people think of when they think of the Do 17. The Do 17Z’s improved engines and better visibility made it a better aircraft than the earlier versions, but its performance was still inadequate against modern fighters.

Night Fighter and Later Versions

The Do 17Z-10 was a night-fighter version fitted with a solid nose containing four machine guns and a Spanner infrared detection system. The Z-10 was one of the first German night fighters, and it served with night-fighter units in 1940–1941, before being replaced by the more capable Bf 110 and Ju 88 night fighters. The Do 17 was also adapted as a glider tug, a target tug, and a trainer, and it served in these roles until the end of the war. The Do 217, a larger and more powerful development of the Do 17, entered service in 1940 and became the Luftwaffe’s main medium bomber, but it was a new aircraft rather than a version of the Do 17. The Do 17’s design had reached the limits of its development, and the Luftwaffe moved on to newer aircraft.

7. Combat Record

Poland, France, and the Low Countries

The Do 17’s combat record began in the invasion of Poland in September 1939, when Do 17 units flew bombing and reconnaissance missions against Polish targets. In the invasion of France and the Low Countries in May–June 1940, Do 17 units attacked French and Belgian airfields, bridges, and troop concentrations, and they suffered moderate losses. The Do 17’s speed and manoeuvrability were assets in the fast-moving campaign, and the aircraft’s crews found that they could operate effectively when they had fighter escort and when the enemy’s air defences were weak. The Do 17’s service in Poland and France was a success, and it encouraged the Luftwaffe to believe that the aircraft would be equally effective against Britain.

The Battle of Britain

The Battle of Britain in the summer and autumn of 1940 was the Do 17’s hardest test, and the one that exposed its weaknesses. Do 17 units based in France flew daylight raids against RAF airfields, radar stations, and London, and they suffered heavy losses to Spitfires and Hurricanes. The Do 17’s light defensive armament was no match for the RAF’s fighters, and its small bomb load meant that it had to fly many sorties to achieve a useful effect. On 18 August 1940, “the Hardest Day” of the battle, Do 17 units lost 10 aircraft in a single day. By the end of the battle, the Do 17 had lost about 130 aircraft, and the Luftwaffe had concluded that the type was no longer suitable for daylight bombing. The Do 17’s failure in the Battle of Britain was a turning point for the Luftwaffe’s bomber force, and it led to the decision to replace the Do 17 with the Ju 88.

Later War: Reconnaissance, Night Fighting, and Withdrawal

After the Battle of Britain, the Do 17 was withdrawn from front-line bombing and used mainly for reconnaissance, night fighting, and training. Do 17 reconnaissance aircraft flew over Britain and the Soviet Union, photographing enemy positions and reporting on troop movements. Do 17 night fighters flew against RAF bombers over Germany, and Do 17 glider tugs towed gliders carrying troops and supplies. The Do 17’s later service was useful but unglamorous, and the type gradually disappeared from the Luftwaffe’s inventory. By 1942, the Do 17 had been withdrawn from front-line service in Germany, although it continued to serve with the air forces of Germany’s allies, including Finland, Bulgaria, and Croatia, until the end of the war.

8. Operators

Luftwaffe Service

The Do 17’s principal operator was the Luftwaffe, which used it in bomber, reconnaissance, and night-fighter units. At its peak in 1940, the Do 17 equipped about 15 bomber squadrons, and it was one of the three main bombers of the Luftwaffe. The type also served with Luftwaffe reconnaissance units, which used it to photograph enemy territory and to report on the movement of Allied forces. The Do 17’s service with the Luftwaffe was the aircraft’s main operational career, and it was in Luftwaffe service that the Do 17 fought its most famous battles, in Poland, France, and the Battle of Britain.

Other Users and Post-War Service

The Do 17 was also used by the air forces of several of Germany’s allies, including Finland, Bulgaria, Croatia, and Spain. The Finnish Air Force operated the Do 17 as a bomber and reconnaissance aircraft in the Continuation War against the Soviet Union, and it used the type with considerable success. The Bulgarian Air Force operated the Do 17 as a bomber, and the Croatian Air Force used it in anti-partisan operations. The Do 17’s service with these air forces continued until the end of the war, and the last Do 17s were retired in the early 1950s. The Do 17’s post-war career was short, because the aircraft was obsolete by 1945, but its service with Finland and other air forces showed that it could still be useful when it was used carefully.

9. Legacy

Assessment

The Do 17’s legacy is that of an aircraft that was ahead of its time when it was designed and behind the times when it was needed. Its speed when it first flew in 1934 had been remarkable, and its slim, elegant shape had made it one of the most advanced aircraft of the 1930s. But by 1940, fighters had caught up with it, and its light defensive armament and small bomb load made it vulnerable. The Do 17’s failure in the Battle of Britain was a lesson for the Luftwaffe: a fast bomber was not enough, and a bomber needed heavy defensive armament, armour, and a large bomb load to survive. The Do 17’s successor, the Do 217, was a larger, more powerful aircraft that addressed many of the Do 17’s weaknesses, but it too was overtaken by events. Historians generally rank the Do 17 as a good aircraft that was used in the wrong role at the wrong time, and as a symbol of the Luftwaffe’s early confidence and its later difficulties.

Survivors and Memory

Only one complete Do 17 survives today: a Do 17Z-2 that was recovered from the Goodwin Sands off the coast of Kent in 2013, where it had crashed in 1940. The aircraft, which had been shot down during the Battle of Britain, was raised from the seabed and is now preserved at the Royal Air Force Museum at Cosford. The recovery of the Do 17 was a major event in aviation archaeology, and the aircraft is the only surviving example of its type. The Do 17 is remembered in Britain as the “Flying Pencil”, the slim, elegant bomber that flew over southern England in the summer of 1940, and it appears in films, model kits, and museum displays. For historians, the Do 17 is a reminder that the Battle of Britain was fought not only by fighters, but by the bombers that the fighters were trying to stop.

10. FAQ

Why was the Do 17 called the Flying Pencil?

The Do 17 was nicknamed the “Flying Pencil” by the British because of its long, slim fuselage, which resembled a pencil. The nickname was a reference to the aircraft’s distinctive shape, which was unlike any other bomber of the war: a narrow, oval-section fuselage, only about 1.5 metres wide, with a glazed nose at the front and a tapered tail at the rear. The slim fuselage reduced drag and made the aircraft fast, but it also made the interior extremely cramped and limited the bomb load. The nickname stuck, and the Do 17 is still remembered in Britain as the “Flying Pencil”, the slim, elegant bomber that flew over southern England in the summer of 1940.

How fast was the Do 17 when it first flew?

The Do 17 was faster than most fighters of its day when it first flew in 1934, with a top speed of about 400 km/h. This speed was the reason the Luftwaffe ordered it as a bomber: it was believed to be too fast for fighters to catch, and too fast for anti-aircraft guns to hit. The Do 17’s speed was remarkable for a bomber in 1934, and it reflected the aircraft’s origins as a fast mail plane designed for Lufthansa. But by 1940, fighters had caught up: the Spitfire and the Hurricane were faster than the Do 17, and the aircraft’s speed was no longer a defence. The Do 17’s story is the story of an aircraft that was ahead of its time when it was designed, and behind the times when it was needed most.

How many Do 17s were built?

About 2,139 Do 17s were built in total, including the early Do 17E and Do 17F versions and the later Do 17Z. Production was centred on the Dornier factories at Friedrichshafen and Munich, and it was always limited by the competing demands of other aircraft programmes. Production ended in 1940, when the Luftwaffe decided to concentrate on the Junkers Ju 88, which was faster, carried a bigger bomb load, and was easier to build. The Do 17’s production total was modest compared with the Heinkel He 111, of which more than 6,000 were built, and the Ju 88, of which more than 15,000 were built.

What was the Do 17’s role in the Battle of Britain?

The Do 17 flew daylight bombing raids against RAF airfields, radar stations, and London during the Battle of Britain in the summer and autumn of 1940. It suffered heavy losses to Spitfires and Hurricanes: its light defensive armament was no match for the RAF’s fighters, and its small bomb load meant that it had to fly many sorties to achieve a useful effect. On 18 August 1940, “the Hardest Day” of the battle, Do 17 units lost 10 aircraft in a single day, and by the end of the battle the type had lost about 130 aircraft. The Luftwaffe concluded that the Do 17 was no longer suitable for daylight bombing, and it withdrew the type from the bombing role.

What replaced the Do 17?

The Do 17 was replaced in the bomber role by the Junkers Ju 88, which was faster, carried a bigger bomb load, and was easier to build. The Ju 88 became the Luftwaffe’s main medium bomber, and it served throughout the war in bombing, reconnaissance, and night-fighter roles. The Do 17 continued to serve in secondary roles, such as reconnaissance, night fighting, and training, until the end of the war. The Do 17’s successor in Dornier’s own line was the Do 217, a larger and more powerful development that entered service in 1940, but the Do 217 was a new aircraft rather than a version of the Do 17.

Where can I see a Do 17 today?

The only surviving Do 17 is a Do 17Z-2 at the Royal Air Force Museum at Cosford in England. The aircraft was recovered from the Goodwin Sands off the coast of Kent in 2013, where it had lain since being shot down during the Battle of Britain in 1940. The recovery was a major event in aviation archaeology, and the aircraft is the only complete example of its type in the world. The Do 17 is preserved as it was found, and it is displayed at Cosford alongside other Battle of Britain aircraft. For historians, the Do 17 at Cosford is a tangible reminder of the summer of 1940.

11. Sources

• Do 17 general histories, including accounts of the aircraft’s development, its service in the Spanish Civil War, and its combat record in the Battle of Britain.
• Dornier company histories and the development of the Do 17 from a civil mail plane to a military bomber.
• Green, William, Warplanes of the Third Reich.
• Smith, J. Richard and Kay, Anthony, German Aircraft of the Second World War.
• Bungay, Stephen, The Most Dangerous Enemy: A History of the Battle of Britain.
• Wikipedia, “Dornier Do 17”, consulted for production figures and technical data, cross-checked against specialist sources.