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ON THE COVER The shape of things to come. The colours of the two fuselage bands around this Junkers D.I must remain speculative but the camouflage colours are confirmed by contemporary reports as described fully on pages 32 and 33. (Painting by Brian Knight G An A of the Guild of Aviation Artists)

Above, subject of the cover painting, this unidentified Junkers D.I was found abandoned by the Allies at Hombeek, Belgium on January 21 1919. Further photographs of this machine appear on page 21.

Opposite page: Junkers D.I (J9/I) production prototype flown by Leutnant Krohn in the Second Fighter Competition of June 1918.

Price 5.45 (UK net)

FOREWORD The revolutionary all-metal monoplanes designed during WWI under the direction of Professor Hugo Junkers were the progenitors of a long and incredibly successful line of aeroplanes several examples of which, in the form of the ubiquitous Ju 52 '7ante./u'trimotor, are still flying to this day. The J.9/D.I monoplane, subject of this DATAFILE, arrived too late to influence the fortunes

of the German Army Air Service and any operational activities were limited to post-war fighting in Poland yet it is deserving of an important position in German military aviation history. In a period of wooden, wire-braced, fabric-covered biplanes and triplanes, the products of Junkers Werke stand apart as being ahead of their time in several respects. RL Rimell, March 1992.

DATA Published by Albatros Productions, Ltd., 10 Long View, Chiltern Park Estate, Berkhamsted, Hertfordshire HP4 1BY, Great Britain. Copyright 1992 Albatros Productions, Ltd. Printing in Great Britain. ISBN No. 0 948414 41 3 Exclusive distribution to North American hobby and craft shops, museums and book shops by Bill Dean Books, Ltd., PO Box 69, New York 11357, USA. (Tel: 1-718 767 6632). Designed, edited and produced by R L Rimell. Co-publisher: A M Hogan. Colour profiles by R L Rimell. Scale drawings by Ian Stair. Mono origination, printing and binding in Great Britain by The Magazine Printing Company Limited, Enfield, Middlesex, EN3 7NT. Colour origination by Columbia Offset (UK and Singapore). The contents of this publication are strictly copyrighted and may not be reproduced or transmitted in any form whatsoever, either in whole or in part, without the prior, written consent of Albatros Productions, Ltd. Acknowledgements All period photographs reproduced in this book are from the PM Grosz archive unless otherwise accredited.

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JUNKERS D.I Peter M. Grosz

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AN INTRODUCTION

Above, the revolutionary Junkers J 1 all-metal monoplane during airscrew thrust measurement at Doberitz on December 3 1915.

Centre, the Junkers J 1 in front of the hangers at Doberitz prior to the first ground test by Ltn. Theodor Mallinkrodt on December 12 1915. The streamlined belly radiator was typical of Junkers' innovative engineering.

Right, surrounded by a number of curious onlookers, the Junkers J 1 was photographed on January 18 1916 at Doberitz on the occasion of performing its first series of extended flights.

In an air war dominated by wood-and-fabric biplanes, the appearance of an all-metal aircraft was a technological breakthrough of the first magnitude not unlike the appearance of jet-engined aircraft in World War II. The Junkers all-metal, cantilever-winged aircraft of World War I were the creation of Professor Hugo Junkers (1859-1935), a brilliant scientist who in his extraordinary creative lifetime amassed over 1000 patents in the fields of thermodynamics, instrumentation, internal combustion engines and aircraft structures. His work was characterised by meticulous theoretical investigation to lay a solid foundation before embarking on the path of engineering development. In his aeronautical endeavours Junkers was fortunate to be able to gather an extremely competent team of scientists and engineers who with exemplary speed put his ideas into practice.

In 1987, Junkers was appointed professor of thermodynamics at the Technische Hochschule Aachen, where his interest in aviation was aroused by his association with Professor Hans J Reissner, who in 1907 was engaged in the development of a canard monoplane fitted with single-surface duraluminum wings. Junkers'

fertile mind began to analyze the problems of flight and he came to the conclusion that the primary goal of aircraft design should be the elimination of parasite drag. To this end, in 1912 Junkers invented the 'thick-wing' concept in which the engine, passengers and structural members were contained within the airfoil body (patented February 1 1912). It was typical of Junkers that he continued to delve deeper into the realm of aerodynamics by building a wind tunnel in his Frankenberg laboratory. In April 1914, Junkers embarked on a systematic programme to study the relationship of airfoil shape, camber and thickness which by 1919 encompassed some 4000 tests with 400 models.

By late 1914, Junkers' experimental work had reached a stage at which he was convinced that an all-metal monoplane fitted with a cantilevered 'thick wing' was a viable proposition. Because duraluminum-forming techniques were relatively crude and required further study, and to avoid delay, Junkers chose ferro-magnetic steel (0.1 to 0.2 mm thick) as the structural material. It was readily available in large sheets and could be welded with ease. After constructing a model wing of 2.8 metre

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span, Junkers approached the War Ministry on February 2 1915 for funds to build an all-metal aircraft, but the request was turned down. Theoretical investigation and metal-forming experimentation had made sufficient progress by July 1915 for Junkers to obtain funds from the War Ministry to construct a flying prototype. After completing the load tests on December 3 1915, the Junkers J 1, a truly revolutionary cantilever-winged monoplane, performed a short hop during ground trials on December 12 1915 and the first proper flight on January 18 1916.

Realizing that metal aircraft had military potential Idflieg supported further development by providing funds for the construction of six all-metal monoplane fighters, designated the Junkers J 2 (E.250-255/16).(1) The Junkers J 2 performed the maiden flight on June 11 1916. Unfortunately this sleek fighter with many modern features was grossly overweight to the detriment of climb performance and manoeuvrability. Although it excelled in speed, the J 2 was unfit for operational service. Nevertheless much important knowledge concerning metal design, forming and assembly techniques was gained. Forced to re-evaluate his design, Junkers concluded that an 'iron' aircraft was a dead horse no matter how aerodynamically perfect it was. He wrote that:

.. .'we had to choose a new material light-weight metal. But not only the choice of iron had resulted in high weight. We had built too heavy because we wanted a safe aircraft and partially because we had not extracted the optimum structural strength from the material'

In Summer 1916, Junkers and his team began the methodical examination of fatigue life, heat treatment, metallurgical and forming properties of duraluminum. Since the metal could not be welded satisfactorily, new techniques for forming, fastening, and riveting had to be devised. Special machines and tooling were designed to manufacture profiled shapes for use as structural members. Although some of metal-working methods had been developed for airship construction, Junkers broke new ground at almost every step.

The first aircraft to employ what was to become the classic Junkers construction technique using corrugated duraluminum was the Junkers J 3 monoplane, a private venture project. The fuselage and wing had been completed when in late November 1916 Junkers was forced to abandon the project because the military refused to provide funding. Idflieg was more interested in all-metal, ground-attack biplane prototypes for testing and flight evaluation.'(2) Junkers regarded the construction

Above, the Junkers J 2 (E.251/16) powered by a 120 hp Mercedes D.II engine on the flightline at Adlershof in July 1916. Built of thin ferro-magnetic steel, the J 2 was grossly overweight. Climb performance and manoeuvrability suffered accordingly.

Centre, the improved Junkers J 2 (E.252/16) during flight evaluation at Adlershof in Autumn 1916. To improve performance it is believed this machine was powered by a 160 hp Mercedes D.III engine. The fine lines, well-cowled engine and belly radiator were a product of wind-tunnel investigations.

Left, interior of the Junkers factory on November 16 1916 with E.250/16 (white fuselage on floor), E255/16 (left rear), J 1 (hidden behind E.255/16), E.253/16 (centre) fitted with a wing of increased span and E. 254/16 (right).

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Opposite page: Test pilot Arved Schmidt performed the maiden flight of the Junkers J 7 on September 18 1917.

Opposite page (centre): Junkers J 7 (second version) after standard ailerons were installed, photographed on October 12 1917. The barely discernible lettering on the outer wing leading edge reads 'nur hier anfassen' (only touch here). On the inner leading edge it says 'nicht gegen den Flugel ?lehnen?'(don't lean on the wing). The tripod-mounted instrument is an airspeed indicator. The wheel cover reads 'Junkers & Co Dessau'.

Above, this is as far as the assembly of the all-duraluminum Junkers J 6 progressed before being terminated to concentrate all effort on the Junkers J.I (J4) ground-attack biplane. The intended powerplant was a 160 hp Oberursel U.III twin-row rotary engine.

Centre, the Junkers J 7 (D.I prototype) photographed on September 13 1917 shortly before the maiden flight. The radiator was readily interchangeable to determine the optimum configuration before installing a permanent nose radiator. Belly and ear radiators had been prohibited on combat aircraft as of November 10 1916.

Right, Junkers J 7 photographed on September 13 1917. The rotating wing-tip ailerons proved unsuccessful and were replaced after the first flight tests. The long exhaust pipe was another Junkers innovation. Testing was performed at Halle where a tent hangar was erected to store the aircraft.

of a biplane an unfortunate regression, but his disappointment was mitigated when in December 1916 Idflieg ordered three prototype monoplanes.

The Junkers J 7 - the D.I. Prototype Work on the Junkers J 7 single-seat fighter and the J 8 two-seat fighter was started in late Spring 1917.(3) Wind tunnel tests had shown that when the wing was positioned below the engine, an additional lift increment was generated by the slipstream. Furthermore, the low wing would absorb the forces in event of a crash thus protecting the pilot. For Junkers it was a bold move, as he explained in 1923:

. . . 'for the first time, I risked placing the wing below the centre of gravity. Many an experienced pilot expressed the strongest scepticism over this new arrangement. It was thought that the machine would tip over'...

The most difficult design problem involved the

wing-fuselage juncture which Junkers patented on March 23 1918. The complex central structure that supported the engine, fuel tanks, wing attachment points and cockpit was not an inspired design as Junkers later admitted.

The Junkers J 7 was constructed from specially-shaped profiles and covered with corrugated duraluminum sheet, employing structural techniques that had been tested and perfected in the J 4. The outer corrugated skin made the wing very resistant to torsional deformation. Unlike the J 4, which still retained some fabric-covered surfaces, the J 7 was all-duraluminum. Flight testing of the J 7 began on September 17 1917 when Junkers test pilot Feldwebel Arved Schmidt performed high speed ground runs which uncovered some tail heaviness. On September 18, Schmidt performed extended hops and flat turns. The prototype, according to Schmidt, 'made a good impression and possessed no serious faults,' but

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the unique, rotating wing tip ailerons were 'somewhat overbalanced'. In spite of the high drag of the large provisional radiator mounted over the engine, a respectable speed of 124 km/h was recorded while climbing. On October 2-3 1917, Schmidt reached an altitude of 5000 metres (16,405 ft) in 17 minutes with the unballasted fighter weighing 713 kg (1572 lb). With a military load of 100 kg, the time was 24.1 minutes. It was obvious that the Junkers J 7 was an aircraft of great promise.

After a new wing with conventional ailerons was installed, the J 7 prototype was ready for further evaluation on October 10 1917. Naval aces Leutnants Gotthard Sachsenberg and Theo Osterkamp, given an opportunity to fly the J 7 on October 22 1917, were able to outclimb the Albatros D.1II with ease and were substantially faster in level flight. They found the fighter stable and solid with good visibility from the cockpit, but the manoeuvrability suffered because of the 'improvised' ailerons. Both pilots became outspoken supporters of the Junkers fighter, especially for operational service in the wet weather conditions of the Flanders Front. On December 1 1917, Schmidt tested new ailerons, a modified rudder and

nose radiator and reported greatly improved flight characteristics. Tony Fokker damaged the J 7 on December 4 when he turned turtle upon landing.(4) The J 7 was easily repaired in time for inspection by Hauptmann Schwarzenberger of Idflieg, who felt the type was sufficiently interesting to enter in the forthcoming First Fighter Competition. For the event, another new wing fitted with aerodynamically-balanced ailerons was installed. Powered by a new Mercedes engine the J 7 was test flown and fine-tuned by Schmidt and Fokker on January 15 1918.

During the Competition (January 20-February 12 1918) the J 7 was flown by various Front-line

Centre left, another view of the Junkers J 7 (second version). The high headrest was to protect the pilot in event of a nose-over. The small fixture under the tailplane is a handgrip. October 12 1917.

Centre right, the Junkers J 7 (third version) was fitted with a new wing, ailerons with aerodynamic balances, a new rudder, a conventional exhaust pipe and a faired, nose-mounted radiator. The undercarriage has also been modified. It is being readied for flight at the First Fighter Competition at Adlershof, January 20-22 1918.

At foot, after Fokker's forced landing on January 22, the lightly damaged Junkers J 7 was flown to the factory for further modification. The J 7 (fourth version) is shown here fitted with a new wing of increased span and longer ailerons without balancing surfaces. The photographs are dated February 2 1918. The pilot is Arved Schmidt.

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pilots including Manfred von Richthofen. Several reports stated that the J 7 possessed the best climb and speed among the in-line engined fighters, although in sharp turns the wings vibrated unpleasantly. On January 22 1918, with Fokker aloft on a demonstration flight, the airscrew disintegrated and the J 7 was slightly damaged on landing. It was flown to Dessau on January 26 to modify the wing; returned to Adlershof on February 3 and again damaged, repaired and ready for further trials on February 9 which were completed on the 17th. The fact that the structure survived accidents that could have demolished wooden aircraft and the ease with which repairs were made were significant advantages of metal construction. The last known tests were recorded on March 17-23 1918 by Junkers test pilot Leutnant Krohn:

'On take-off the aircraft (J 7) accelerates quickly and leaves the ground in a comparatively short time. It reacts instantaneously to the controls. After ten

degrees of control-stick movement, which suffices for an 80-degree bank, the control becomes very heavy. In a spiral the aircraft reacts quickly to the controls. On the whole the aircraft is at least as manoeuvrable as the new Albatros Dili or D.V I dived at 250 km/h (155 mph) airspeed without any vibration in the wings'.

After a final aileron modification, Krohn reported normal reaction to the controls that he now felt were well balanced.

The much-modified J 7 prototype was accepted by the Fliegertruppe during the week of March 25 1918 and used as a demonstration and training machine. The J 7 was demonstrated at the Second Fighter Competition in July 1918 alongside the recently-completed Junkers J 9 and D.l production prototype that was entered in the Competition. Notwithstanding its engineering excellence, Front-line pilots remained sceptical of the low-winged Junkers monoplane. The prejudice surrounding the type is best expressed by

Above and right, for Summer operation, the Junkers J 7 (fifth version) had a larger radiator installed. The long-span ailerons are shown to good advantage. Note that the wheel covers now carry the Jfa logo. The photographs are dated March 23 1918.

Schwarzenberger (the Idflieg fighter expert) who denigrated the 'all-metal aircraft hullabaloo as a fashionable sickness'.

The Junkers J 9 the D.I production prototype But to its credit, Idflieg continued to support the Junkers all-metal aircraft. Junkers had began work on the improved J 9, the D.I production prototype, in February 1918. The prototypes (designated J 9/1 and J 9/II) were built, the first was to be ready for tests on April 15 1918, the second would follow in short order. While airframe changes from the J 7 were minimal, the major design effort concentrated perfecting the J 9 airframe for high volume production. On March 21 1918, Idflieg representatives met with Junkers to discuss purchasing six fighters for evaluation. Junkers replied that this was impossible, because if the aircraft proved successful, of which he was certain, then it would be difficult to make up lost time. Metal aircraft, unlike wooden ones,

required an extensive machine tool park and factory preparation to reach an acceptable output. This in turn required advance financial support by the military. Junkers asked for, and on May 8 1918 received, an open contract for 100 all-metal aircraft of which the first 20 were ordered as D.I fighters. The ambitious production schedule called for delivery of six fighters in June and 14 in July. Conventional fighters, such as the superlative Fokker D.VIII and SSW D.IV(5) represented strong competition, but the visionary Junkers shrugged off the challenge when he wrote in May 1918 that wooden aircraft were a negligible factor and these manufacturers would soon be fighting for their existence: 'Junkers all-metal aircraft are the aircraft of the future.'

The maiden flight (Einfliegen) of the first D.I fighter (referred to in Junkers records as the J 9/I) is believed to have been performed on May 12 1918 (not in April as commonly reported) when Junkers test pilot Krohn put the prototype through its paces, including

Foot of page 6, above and centre, the Junkers J 7 in its final form with over-painted Maltese crosses, probably photographed at the Second Fighter Competition in May-June 1918. The indentation behind the radiator was a Junkers innovation to increase the airflow by means of a Venturi nozzle. The ease with which the duraluminum could be damaged is demonstrated by the dented port wingtip.

Left, the all-metal Junkers aircraft had little problem with inclement weather. The Junkers J 7 was inspected by members of various aviation organizations and the press on a visit to Doberitz on July 24 1918.

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Above, the Junkers D.I (J 9/I) production prototype in full military markings and armed with two Spandau machine guns. This machine was flown by Leutnant Krohn in the Second Fighter Competition on June 6, 10 and 14 1018 at Adlershof where these photographs were taken. The inverted vee strut leading from the undercarriage to the fuselage centre line was eliminated on production machines.

Centre and right, the Junkers D.I (J 9/I) production prototype on the Junkers airfield at Dessau, photographed on July 8 1918. The corrugated metal covering was interrupted at the fuselage mid-point (behind the pilot's right arm). In production aircraft the side fuselage covering was composed of a single sheet of corrugated metal.

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sharp turns, inverted flight and loops with complete satisfaction. For the second Fighter Competition in May 1918, Junkers readied the J 9/I (D.I) powered with the 160 hp Mercedes D.IIIaii engine just received from the factory. Because of the higher compression ratio, the engine gave superior high-altitude performance matching that of the BMW.IIla engine. In the climb competition the J 9/I surpassed all other Mercedes-powered fighters with the exception of the Rumpler D.I. It is interesting to note that the Fokker V 21 and V 23 wooden monoplanes, also entered in the Mercedes category, weighed 853 kg and 848 kg respectively, marginally heavier than the 835 kg of the J 9/I fighter. The fighter was a striking example of Junkers engineering skill in the design and realization of light-metal construction.

To complete the record, the second Junkers D.I prototype (J 9/II), powered by a 195 hp Benz Bz.IIIbo V-8 engine, made its appearance in June 1918. It also was scheduled to appear in the Second Fighter Competition, but problems with the experimental Benz engine kept the J 9/II from competing. Information regarding the flight trials is unavailable.

On the final days of the Fighter Competition Front-line pilots were invited to test the various fighters. Their opinions, voiced in two conferences convened on July 6 and 14 1918, would in a large degree determine which fighters would go into production. Keeping in mind that throughout the post-war years and into the Thirties, fighter development was heavily biased in favour of the biplane, it is easy to understand why the low-wing Junkers D.I failed to receive much support. On July 6 1918 the following was recorded:

'Oberleutnants Goering and Loerzer support the eventual development of the Junkers D.I as a special machine for attacking observation balloons. The new design embodied in the Junkers D.I is, in the opinion of all, a total failure.'

The second conference reiterated that position. But 'total failure' was too harsh a criticism for a fighter that had demonstrated superior performance and flight characteristics. The only real drawback, according to the Austro-Hungarian liaison officer, was the lack of downward vision from the cockpit. This needs explanation. Contemporary German fighter

Below, the Junkers D.I (J 9/ II) was powered by a 195 hp Benz Bz. IIIbo V-8 engine. Note the modern belly radiator. The protrusion on the front cowling is believed to be a header tank. Recurrent problems with the temperamental Benz engine prevented the fighter from participating in the Second Fighter Competition as had been scheduled. This photograph is dated June 20 1918.

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Right, Junkers D.I (J 9/11) showing the elongated fuselage, belly radiator and outer wing panel attachment points.

Centre, Hugo Junkers (on far left with bowler hat) discussing the Junkers D.I (J 9/II). This photograph, taken after July 8 1918, shows that the Benz-powered fighter required further study of the cooling system by mounting a temporary radiator over the engine for flight evaluation.

Below, the Junkers D.I (Jco) 5180/18 was the first production machine from a batch numbered 5180/5189/ 18 ordered in May 1918. The interior fittings were inspected and critiqued on September 1918 as part of the type-test procedure. Because it had been slightly damaged, the flight trials could not be performed. It appears that this version has the longer fuselage.

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tactics favoured attacking from above in a high-speed dive and disengaging quickly to avoid entanglement with vastly superior numbers of Allied fighters. Such tactics required excellent downward visibility that in the Junkers D.I was partially blocked by the wide fuselage and the broad wing. On the plus side, the invulnerability of metal construction to ground fire (amply demonstrated by the Junkers J.I)

made the Junkers D.I an ideal candidate for the always risky task of attacking heavily-defended observation balloons. Old habits die hard and the conservative Front-line fighter pilots preferred a biplane fighter or one with a wing above their head and not below it.

While this information disturbed Junkers, on August 21 1918, Idflieg showing more faith than the fighter pilots, placed a second order for 100

Left, the new Junkers assembly building showing four nearly-completed Junkers DJ production machines, the disassembled J 7 and the tail of the J 9/I prototype. The four D.I machines shown here seem to have a longer fuselage and it is believed these were shortened before the aircraft left the factory. Photograph is dated August 8 1918.

Centre, Junkers assembly hall in August 1918. At far left are wings of E.255/16, the fuselages of E.253/16 and J 1. On the right are four D.I. production airframes, one in front of the door and three in line. The disassembled J 7 and J 9/I are in the right foreground.

Below, Junkers built one D.I powered by a 185 hp BMW.IIIa engine for participation in the Third Fighter Competition held at Adlershof between October 10 and 28 1918. This version has the elongated fuselage which suffered from vibration and a larger wingspan that reduced manoeuvrability.

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all-metal aircraft and called down 10 Junkers D.l fighters.(6) Idflieg commander Wilhelm Siegert urged Junkers to give priority to the D.I because only in 'the crucible of combat' could the true value of the low-wing monoplane be determined.

On August 1 1918, the static test machine and three D.I fighters with fuselages stood ready for shipment. A further three were in final assembly and a remaining five were scheduled for delivery in early September 1918. Two D.I fighters were sent to Adlershof for static load testing and flight evaluation. The load tests began on August 3 and ended on September 13 1918. The metal sheeting around the wing root had to be reinforced three times before the wing passed the load test requirement. Other parts were of adequate strength. The type-test machine, Junkers D.I(Jco) 5180/18 was approved for the Front on September 9 1918, pending of course the results of the flight tests.

Evaluations Junkers entered a D.l, fitted with a longer fuselage and increased wingspan, in the Third Fighter Competition (October 10-28 1918) that was limited to fighters powered by the BMW.IIIa engine. Flight testing at Junkers was completed

on October 10 1918. The D.I had the second best rate of climb exceeded only by that of the Albatros D.XIII. The D.I was faster than the Fokker V 36 biplane fighter, but above 4000 metres the Fokker V 29 parasol was faster. One pilot reported that the D.l, 'reacted too slowly to the aileron controls and climbed poorly in a turn. The vibrations in the rear fuselage were unpleasant. Visibility for formation flying and dog-fighting was poor. Only manoeuvrable when flying slowly'

From photographic evidence it appears that the first D.I production aircraft to be completed (see photograph on page 11 dated August 8 1918) had the longer fuselages and wings. As demonstrated by the BMW-engined D.I above, this configuration suffered from unpleasant fuselage vibrations and had poorer manoeuvrability. It is probable that instead of leaving for the Front after type-test approval, the four or five completed D.I fighters were rebuilt with a shorter fuselage and wingspan. At any rate, from a photograph dated October 2 1918 showing four D.I fighters on flat-cars (page 14) we may assume these were the first D.I fighters dispatched to the Front from Dessau, possibly for the Flanders sector.

It was here that in January 1919, five D.I fighters were found by Allied Armistice

Above and right, on October 2 1918 a D.I. was slightly damaged after hitting a ground obstruction resulting in undercarriage collapse on landing. The number '11' can be seen below the tailplane. This is the short fuselage version. Further details are lacking.

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inspection teams. Four ('one in good condition, one good enough to study and two wrecked') were found abandoned at Hombeek in Belgium. Another semi-intact D.I was inspected at the Evere airfield near Brussels. Whether any of these monoplanes were flown in combat is open to question. One D.I at Hombeek was decorated with a two-colour band behind the cockpit and the Evere machine had been struck, 'by several bursts of machine gun bullets'. The US Air Service reported, '... no one was found who had ever seen one of these airplanes in flight' but continued that, 'some of the RAF pilots, however, were sure that it had been used in service'. With both Sachsenberg and Osterkamp keen to have the D.I in their squadrons, it is within the realms of possibility that some marine squadron members might have taken the D.I aloft on training flights.

During the war, a total of 40 D.I fighters had been ordered from Junkers & Co (Jco) of which 27 were completed through February 1919 when military production was stopped. Having delivered their first D.I fighter in June 1918, the Junkers-Fokker company (Jfa) eventually received orders for 20 aircraft of which 13 were built, giving a total of 40 D.I fighters that were completed between June 1918 and February 1919. Junkers all-metal

monoplanes saw operational service in the post-war conflict between invading Bolshevik troops and the German Freikorps defenders in the Baltic countries. Both the Junkers D.I and the two-seat CI.I flew air-support missions with the Kampfgeschwader Sachsenberg under the command of Leutnant Gotthard Sachsenberg, a long-time booster of all-metal Junkers aircraft. Upon his return to Germany in 1919, Sachsenberg wrote to Junkers that he had requested and received approximately 30 Junkers aircraft of which half were D.I fighters. He continued:

'The Junkers aircraft have proven themselves beyond all expectation. The weather resistance of the aircraft is so great that it was possible to allow the aircraft to stand for weeks on end in the open during snow, rain and thaw of the March season. A tarpaulin cover over the propeller and engine sufficed to provide protection. Since neither tents nor hangers were available, no other aircraft except the Junkers would have been able to serve in Russia at that time... the advantage of the weather resistance, the exceptional speed and the invulnerability of the aircraft outweigh the small disadvantages. In crashes and emergency landings relatively little occurred... the Junkers aircraft, with

Two further views of the crashed D.I reveal under surface details not always clear on other photographs note plain black unoutlined Balkenkreuz.

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Below, four Junkers D.I (Jco) loaded on flat-bed trucks for delivery to the Front. Whereas wooden aircraft would be fully protected by a tarpaulin, the Junkers wing and airframe required no protective covering.

At foot, at least three Junkers D.I fighters of the Kampfgeschwader Sachsenberg in the airship hangar at Wainoden in early 1919. As long as the engine and airscrew were covered, the airframe was impervious to the elements.

improvement, will without doubt, take first place as a combat type.'

The development of the Junkers all-metal aircraft in World War 1 provided the foundation upon which Junkers built a successful aircraft business. The rugged and serviceable Junkers 'corrugated' aircraft provided reliable transport in the desert, Arctic and jungle regions for many years.

Author's note The material above was adapted from The Way to the World's First All-Metal Fighter, by Peter M Grosz and Gerard Terry, Air Enthusiast, No.25, August 1984. The author would like to thank Peter M Bowers and Francis P Garove for use of their Junkers photographs.

Notes (1) Being the second Junkers design, it was known as the Junkers J 2. The military designation, either E..I or E.II, cannot be verified from existing

military or company records. In official records the individual J 2 aircraft were referred to by their serial number.

(2) Because the armour-plated Junkers J.I could absorb heavy ground fire and bring its crew safely home, it was highly regarded at the Front. All told. 227 Junkers J.I biplanes were delivered between February 1917 and January 1919.

(3) The Junkers J 5 and .1 6 single-seat fighter projects were not built.

(4) Fokker's association is explained by the fact that at IdfUeg's insistence Hugo Junkers was 'forced' to establish the Junkers-Fokker Werke AG (Jfa) on October 20 1917. It was felt that Fokker's production expertise was essential to counteract Junkers' penchant for experimentation and lack of production know-how. The union was not a happy one.

(5) See WINDSOCK DATAFILES Nos 25 and 29, available from the editorial address see inside rear cover for details.

(6) Both Junkers (Jco) and Junkers-Fokker (Jfa) were involved in the production of the D.I. Exactly how the production orders were assigned by ldflieg\s not known, but there was a good bit of competition between Jfa and Jco for production orders. Junkers were determined not to let Fokker get the upper hand. As it was in late 1918, Junkers was on the verge of purchasing Fokker's share in Jfa. A little known fact is that in July 1918, Idflieg awarded Hansa-Brandenburg a provisional contract for 50 Junkers D.I fighters that was cancelled when the war ended.

14

Left, three Junkers D.I fighters in the Wainoden airship hangar, March 1919.

Below, a trio of Junkers D.I (in the foreground) and three Cl.I in the background of Kampfgeschwader Sachsenberg being serviced in preparation for take-off.

15

Above, Junkers D.I of a German post-war flying unit.

Right, a mixed group of German airmen and mechanics pose with a Junkers D.I at Peterfeld, October 9 1919.

Below, using airship ground-handling rails as wheel chocks, this Junkers D.I is ready to start in front of the airship hangars at Wainoden.

16

Drawn and traced by IAN R STAIR 1992 IAN R. STAIR and ALBATROS PRODUCTIONS LTD 17

One of the four abandoned Junkers D.I found by Allied inspection teams at Hombeek, Belgium on January 21 1919. This particular aircraft appears to have a short fuselage. The initials on the wheel cover 'Jko' should correctly read 'Jco', showing that the aircraft was built by Junkers and Co.

20

The two-colour stripe around the fuselage of this Junkers D.I, also discovered at Hombeek, gives rise to the speculation that the aircraft may have seen combat service. For the difference between the short-fuselage and long-fuselage version, compare the 3/4, rear view with that of the Junkers D.I (Jco) 5180/18.

21

THE JUNKERS D.I IN DETAIL The design of the complex fuselage-wing interface caused Junkers much difficulty and he did not consider it an ideal solution, although he received a patent for this invention on March 23 1918. With exception of the tubing, all of the duraluminum profiles were manufactured by Junkers.

22

Opposite page: Cockpit photographs of all World War I aircraft are rare. This photograph of the J 7 cockpit, taken on April 27 1918, shows the port side with the dual throttle lever marked 'Gas' and the spark advance below marked 'Zundung'. Although no photographs exist of machine gun(s) mounted on the J 7, it appears a trigger lever is affixed to the joystick. Left, two views of a Junkers D.I at Evere reveal the triangular structure inside the wing. Seven duraluminum tubes attach to corresponding fuselage points.

Below, as part of the type test, that took place between August 23 and September 13 1918, an airframe was tested to destruction. Here (inverted) the wing covering has been removed to reveal the failure areas. The wing was built up from a series of spanwise tubular spars interconnected with triangular bracing. In order to pass the strength requirements for diving conditions, the wing had to be strengthened at the root.

23

WING SECTION SHOWING THE SEVEN TUBULAR SPARS.

DETAIL INSIDE WING TIP (STARBOARD)

The drawings reproduced on this and following pages are from the 1920 Ministry of Munitions' report on captured Junkers D.I monoplanes. Although the quality of the originals is poor, they have been reproduced as carefully as possible. On the premise that a faded illustration is better than no illustration at all we make no excuses for their inclusion. (RLR)

JUNCTION OF UPPER SPARS.

24

Below, Junkers D.I at Evere. Close-up of the engine section provides detail of the clean fuselage covering. The wing stub has the marking 'Mi 6' which may be some form of works number. The markings 'Mi 7' and 'Mi 34' have been found on other D.I airframes.

25

BULKHEAD TO REAR OF POWERPLANT.

Below, Allied inspection teams photographed this Junkers D.I at the Evere airfield outside of Brussels on January 21 1919. The fuselage had been over-painted with a, 'chocolate-brown colour except underneath where white pigment has been applied. The wings are painted a pale green with irregular patches of mauve on top and white underneath. The tail planes and elevator are white above and below'. It is possible that the all-white tail was some type of unit marking.

BULKHEAD TO REAR OF PILOT'S SEAT.

BULKHEAD TO REAR OF B'.

FORWARD FUSELAGE INTERNAL STRUCTURE.

FUSELAGE CROSS SECTIONS SHOWING FORWARD FORMERS.

CONTROL GRIP DETAIL.

26

CONTROL COLUMN AND RUDDER BAR DETAIL.

Below, Mercedes D.IIIa engine installation in another Junkers D.l wreck found at Evere.

CONTROL SURFACE MECHANICAL DETAILS.

A=AILERON CONTROL (HINGE).

B=AILERON CONTROL (PIVOTED ARM).

C=ELEVATOR KING-POST.

/ LEFT, NINTH BULKHEAD SHOWING RUDDER POST RIVETED TO UPPER SECTION.

RIGHT, RUDDER POST BRACKET.

DETAIL SHOWING BOLT-ON TAIL ASSEMBLY

DETAIL OF LOWER ATTACHMENT LINKS; SHOWN AT IMMEDIATE LEFT

AILERON CONTROL DETAIL.

27

On these pages, photographs of the Junkers D.I before and after restoration by the Musee de l'Air in France. The number on the wing stub reads 'Mi 34', the meaning of which is not known.

28

29

30

31

Above, the J 9/D.I as currently displayed at La Grand Gallerie, Le Bourget wearing spurious green and brown (!) camouflage .. .

Opposite page, left, and below, more views of the Musee's unique D.I before its restoration offer useful reference for scale modellers.

COLOURS AND MARKINGS 1) Below, this Junkers D.I prototype was built by the Junkers-Fokker company as the 'Jfa' on the wheel cover shows. According to factory records this aircraft was delivered during the week of June 17 1918. The side fuselage covering the rear of the engine mount back to the detachable tail is composed of one sheet. Power was supplied by a 160 hp Mercedes D.IIIa engine. For the initial flight trials armament was not installed.

2) Upper photo on page 33, Junkers D.I (Jco) 5185/18 in full camouflage markings at Adlershof during flight trials. The metal strip covering the wing-fuselage joint has been removed for inspection. According to reports of aircraft found after the war, the wing was, 'painted pale green with irregular patches of light mauve on top, and white underneath'.

The camouflage and markings of the Junkers J 9/D.I are not easy to establish with any degree of certainty. The sole known survivor see Appendices was restored in 1973, its present colour scheme differing from the original finish of mauve and green sprayed upper surfaces and pale blue under surfaces, the entire rudder being white. The official report of a D.I found abandoned at Evere, near Brussels, in November 1918, and subsequently published in Flight during 1920, stated: . . . 'the body is painted a chocolate brown colour, except underneath, where a white pigment is applied. The wings are painted a pale green with irregular patches of light mauve on top, white underneath. The tailplanes and elevators are white above and below. 'JUNK D.I' was painted on the fuselage side but had been obliterated by the chocolate paint'... 'Closer examination revealed the fact that under the layer of chocolate paint on the body was a layer of pale green colour and a similar colour could be seen on the tailplane wherever the white had peeled off. The chocolate and white were all flat, unvaried colour'...

As several writers have since observed, the subject aeroplane had been abandoned and left in the open for several months during the Winter period so it may be assumed that the colours were subjected to weathering and/or fading. The green, nonetheless, was not a dark

green for according to the Musee de l'Air their specimen, which still retained much of its original paint, was painted mainly in 'Forest Green'.

It is known that most Junkers machines had only a thin layer of paint sprayed on (the metal did not corrode) so this, too, would have resulted in some fading. It is likely that the scheme of sprayed medium green and mauve irregular patches on all upper surfaces with very pale blue or white beneath was fairly standard for all Junkers machines from the J.4 armoured biplane onwards. The sprayed patterns do not appear to conform to any one standard pattern therefore variations between individual machines were wide.

It may be of pertinent interest to quote from an official report on a captured Junkers i.4 in 1918:

...'The machine is thinly painted (ie, sprayed on) in matt colours. The upper surfaces of the (wings) have irregular masses of the usual green and mauve tints, while the underside is painted a bluish-white colour. The struts and wheels are green as is the armoured portion of the fuselage'...

An existing J.4 (J.I 586/17) owned by the National Aviation Museum in Canada is similarly finished but all lower surfaces are painted a pale 'sand yellow'; approximating to clear-doped fabric perhaps? Rudder is

32

compiled by R L Rimell

unpainted with the plain black Balkenkreuz applied directly to the metal skinning.

The final form of narrow Balkenkreuz was applied in the usual eight positions on the Junkers D.l with the chord-wise arms of wing crosses often extending over leading and trailing edges. Serial numbers, when applied, where painted in large black characters forward of the fuselage crosses, and sometimes repeated in smaller size on each wing tip

underside. Jfa logos often appeared on wheel disc covers.

Since original colours of the extant WWI Junkers are either overpainted or considerably faded it is not possible to provide accurate colour standards/references for these aeroplanes. The colours quoted are based on known German camouflage dopes used on various other types and should be considered as a guide only.

3) At foot, Junkers D.I (Jco) 5180/18 in full camouflage scheme.

33

REAR COVER PLATES 3) JUNKERS D.I 5180/17 This long-fuselaged D.I was the first production

1) JUNKERS D.I PROTOTYPE machine from the batch 5180-5189/18 ordered This prototype was built by the Junkers-Fokker in May 1918. It also sports the mauve/green/ company as indicated by the logos applied to bluish-white scheme with narrow Balkenkreuz the wheel covers. The machine is unpainted in the usual positions. and presents a clean natural duraluminum Source: photograph on page 33. finish with grey-painted wheel covers. Source: photograph on page 32.

2) JUNKERS D.I 5185/18 Methuen colour notations This typically finished D.I carries the mauve/ Dark Green green/bluish-white scheme as described above. 25D8/26F3/27D4/29D5/29E4/30E6/30E8 The camouflage pattern was sprayed over the Lilac (Mauve) upper surfaces and does not appear to be 15D4/15E2/15E3/17F8/18D4/18D6 standardised. Pale Blue Source: photograph page 33. 24B4/25B5

SOURCES FOR COLOUR STANDARDS Methuen Handbook of Colour For the convenience of modellers, Methuen colour references, wherever possible, have been quoted and can be found in the Methuen Handbook of Colour by A Kornerup and J H Wanscher published by Methuen and Co., Ltd., a book which provides over 1260 colour samples.

Munsell Book of Color Munsell has two primary colour books, each with removable colour chips (sizes noted below): Munsell Book of Color, Glossy Finish Collection (1976 Edition). This two binder set contains 1490 colour chips, each 11/16" x 13/16" (a supplementary set is also available). This set costs approx $640.00, plus postage and tax. Munsell Book of Color, Matte Finish Collection (1976 Edition). This binder contains 1270 colour chips, each 5/8" x 7/8". This set costs approx $500.00, plus postage and tax.

Munsell also sells a wide variety of other colour-related products explained in a full-colour catalogue available from: Munsell Color, 2441 N Calvert St., Baltimore, MD 21218 USA.

Federal Standard No.595a FS 595a, Colors, Vol. 1. This is really the only FS 595a item required and is available for only $5.50 postpaid. The book contains 550 3/4" x 1/2" lacquer colour chips glued to the pages. Additional chips which have been added since the latest change of page are available as 3" x 5" chips for 15c. each.

Also available is a "colour fan" containing 550 (2" x 5/8") silkscreened representations of FS 595a colours. Since the patches are silkscreened, the colours are somewhat less reliable than those available in Colors, Vol 1; however, it's easier to transport and actually compare to a real colour value than the 3-ring binder Vol 1. The fan is available for $6.00, postpaid.

Also available is a boxed set of 558 3" x 5" cards protected in separate envelopes. The eight colours added to FS 595a by Change 9 (29 May 1985) are not included in this set, but are available separately at 15c. each. The US Federal government considers these 3" x 5" cards to be the only contractually acceptable references for colour matching. The basic set is available for $80.00, postpaid.

Prices shown are for US orders. Foreign orders must add 25% for handling and shipping. All items are available by payment in advance (personal cheque OK if from US bank; International Money Order or cheque in US dollars for foreign orders) from: GSA Specifications Section, Room 6039, 7th and "D" Streets, SW, Washington, DC 20407, USA.

Publishers' note The above data is believed to be correct at press date but readers should confirm details of price and availability prior to ordering.

APPENDICES BIBLIOGRAPHY Junkers Nachrichten, August/September 1942. Flight, Vol. 20, April 1920; (Three issues: April 1, 8 and 15). Junkers all-metal Monoplane; Engineering Division Air Service Technical Orders, October 1919. Profile Publications No. 187, The Junkers Monoplanes by H Cowin, Profile Publications, Ltd., 1967. 'The Way to the World's First Ail-Metal Fighter' by P M Grosz and G Terry, Air Enthusiast 25, August, 1984.

34

SPECIFICATIONS

Type

Span: Length: Height: Wing area: Weight (empty): Weight (loaded): Max Speed: (160 hp Mercedes D.IIIa) Climb: (160hp Mercedes D.lllaii)

Junkers D.I (1st version)

9.00m 6.7m 2.6m 14.8sqm 655kg 835kg

176km/h

0-1 km: 3min l-2km: 2.8min 2-3km: 3.7min 3-4km: 5.8min 4-5km: 9.3min

Junkers D.I (late version)

9.00m 7.25m 2.6m 14.8sqm

JUNKERS D.I SURVIVORS France (1 ) Musee de I'Air et al L'Espace, 93350 Le Bourget. Junkers J9 (D.I) D.5929/18, sole known-survivor. Currently on display at Le Bourget's La Grand Gallerie following 1973 restoration.

Left, two views of the world's only known D.I survivor. The upper illustration shows the Junkers as currently displayed.

35

JUNKERS D.I MODEL KITS

Top left, Blue Max 1:48 Junkers D.I and, at right, 1:72 Warbirds vacform version. {Models/photos, RLRimell)

The Junkers J9/D.I is quite well represented in small scale model form with at least eight kits released over the past few years.

One of the first 1:48 kits was from Lone Star Models of New Mexico which featured fuselage halves, wings, tailplane, rudder, engine, radiator and axle fairing in resin while the remaining parts were a combination of several materials. The kit included vacform seat and gun troughs, extruded plastic aerofoil for the undercarriage struts, white metal wheels, exhaust pipe, control column and machine gun sans barrels; these latter supplied as brass etched parts along with an airscrew boss.

Major components stand up well to comparison with photographs in this book and although a certain amount of flash and some pitting is simple enough to correct, refinement of all the corrugated surfaces will be more difficult. Even in 1:48 the corrugations are somewhat overscale and one remedy may be to apply generous coats of primer to reduce the ribbing detail prior to painting. Such work becomes even more important when markings are considered since very few commercial transfers, solvents notwithstanding, are going to sit snugly over the untreated ribbing detail. Detailed instructions provide useful building tips while exhaustive notes assist construction of the etched brass gun jackets provided.

The most recent 1:48 Junkers D.I kit to appear is the injection-moulded version from Blue Max. Moulded in grey, the kit is very well detailed with the corrugations of the fuselage and flying surfaces neatly rendered while trailing edges are as thin as the toolmaking will allow. A complete Mercedes engine is supplied along with bearers and firewall while fine metal parts take care of the guns, exhaust system,

carburettors and manifolds. Wings are in two halves and require careful treatment of their mating surfaces before joining. They feature an incorrect tapering trailing edge (in planform) which requires mild trimming as the original trailing edge was parallel with the leading edge as shown in the drawings reproduced in this DATAFILE. Transfers are supplied along with detailed painting and assembly instructions.

The Junkers in 1:72 First of the 1:72 scale Junkers D.I kits was the vacform produced under the Warbirds label by Gordon Stevens of Rareplanes' fame. Since the distinctive corrugated skin of the original aircraft was so prominent it is to their credit that Warbirds produced the effect quite superbly in 1:72 scale. Once the various parts are removed from the sheet and carefully cleaned up, there should be few problems with assembly. Cockpit interior parts are supplied but can always be improved upon. The sides can be closely scored 5 thou plastic card panels (representing corrugations) and cemented in place. Some longerons and spacers can also be added if desired note that the basic interior colour would be medium silver/grey. There's very little useful criticism that can be made; the only filling required is along the upper fuselage to wing join and around the tailplane platform, and even so this is minimal. Overall the kit is accurate and needs little in the way of extra detail.

The Pegasus D.I is another very good replica of the type with extremely neat corrugations despite the small scale. Released in 1986, this kit remains one of the most authentic versions in 1:72.

NON-FLYING MODELS

Kit Name

Junkers D.I Junkers D.I Junkers D.I Junkers D.I Junkers D.I Junkers D.I Junkers D.I Junkers D.I

Manufacturer/date

Vintage Aero Models, 1986. Lone Star Models, 1989. Blue Max, 1990 Fun-Model, 1991. Warbirds, 1981. Cramer-Craft, 1984? Czechmasters, 1986. Pegasus Models, 1986.

Scale

1:48 1:48 1:48 1:48 1:72 1:72 1:72 1:72

Remarks

Vacform/resin; release uncertain. Resin with metal parts see review. Injection-moulded see review. Resin no sample available. Vacform see review. Vacform limited edition. Resin limited edition. Injection moulded see review.

36

1) JUNKERS D.I PROTOTYPE, 1918.

2) JUNKERS D.I 5185/18, 1918.

3) JUNKERS D.I. 5180/18, 1918.

Printed in Great Britain.