O.Thetford, P.Gray German Aircraft of the First World War (Putnam)

Siemens-Schuckert D III (Short)
   This short-span D III prototype (serial 7550/17) first flew on 22nd October 1917. It was one of a series of tubby, rounded-fuselage prototypes that eventually led to the D III and D IV production series. The airframe is seen here undergoing static load testing of the wing structure after the flight test programme had been completed. Engine, 160 h.p. Siemens-Halske Sh III. Span, 8.5 m. (27 ft. 10 3/4 in.). Length, 6.0 m. (19 ft. 8 1/4 in.). Area, 19.4 sq.m. (209 sq.ft.). Weights: Empty, 500 kg. (1,100 lb.). Loaded, 750 kg. (1,650 lb.). Climb, 6,000 m. (19,680 ft.) in 26.2 min. Duration, 2 hr. Armament, twin Spandau machine-guns.


Siemens-Schuckert D III (Long)
   Another D III prototype (serial 7551/17), with wings of longer span but narrower chord, which resulted in the machine having less wing area than the short-span D III. This prototype was again modified and competed in first D types Competition. Engine. 160 h.p. Siemens-Halske Sh III. Span, 9.0 m. (29 ft. 6 3/8 in.). Length, 6.0 m. (19 ft. 8 1/4 in.). Area, 18.02 sq.m. (195 sq.ft.). Weights: Empty, 500 kg. (1,100 lb.). Loaded, 750 kg. (1,650 lb.). Climb, 5,000 m. (16,400 ft.) in 17.5 min. Duration, 2 hr. Armament, twin Spandau machine-guns.


Siemens-Schuckert D III
   Although dealt with in the main text, this illustration is included here to show the continuous development of a single airframe (7551/17). Modified from the D III (long), the cowling arrangement may now be seen to be less austere and that ailerons have been additionally located at the lower wingtips. It first flew in this form on 20th December 1917, and then crashed while at Adlershof for first D types Competition in January 1918. Data as for D III (long).


Siemens-Schuckert D III and D IV

   Ultimate successor of the S.S.W. D I was the D.III/ D.IV series, which appeared almost a year later, after development through a series of D.II prototypes, and represented a line of advanced and original thought from the drawing-board of Dipl. Ing. Harald Wolff (who was appointed chief designer after Steffen was killed) and his assistant, a young engineer named Hauck.
   With the relative success of the various D.II prototypes a pre-production order for 20 D.IIIs was placed by Idflieg during the last weeks of 1917; followed by an order for 30 more in February 1918. During April and May some 41 S.S.W. D.IIIs were channeled to the Western Front for operational trials. Most were received by Jagdstaffel 15 of the Jagdgeschwader 11 commanded by Haupt. Rudolph Berthold. A good deal of trouble was experienced with piston seizure, and it became obvious the Siemens-Halske Sh.III engine with which these D.IIIs were fitted was not yet ready for operational service. This shortcoming was seized upon by opponents of the D.III, one of whom had been Hermann Goring, in an endeavor to discredit it completely and have it condemned. Berthold none the less had achieved several victories on the D.III and saw its potentialities; it was largely through his intelligent and objective report on the type that development continued.
   The Siemens-Halske Sh.III engine was a more powerful, eleven-cylinder development of the earlier Sh.I engine, retaining the same characteristic of crankshaft rotating in one direction at 900 rpm. and the crankcase and cylinders rotating in the reverse direction also at 900 rpm., thereby achieving an actual engine speed of 1,800 rpm. Although advantageous in some respects, this system had its disadvantages. Being a more powerful and bigger engine than the Sh I, the Sh III tended to run a lot hotter, and this effect was magnified by the slow speed at which the cylinders rotated, compared with a normal rotary, resulting in a considerable reduction in the amount of air cooling. Coupled with the low-grade castor oil available to the Germans at this period of the war, recurrent piston seizure after some seven to ten hours running seemed inevitable. The redeeming feature of the engine was that its power did not drop off at high altitude and held good prospects. The D.IIIs were withdrawn from the Front during May 1918 for the fitting of improved engines and some airframe modifications.
   One such re-engined D.III, with a Rhemag built Sh IIIs, was piloted by the Siemens test pilot Rodschinka, to the extraordinary height of 8,100 m. (26,568 ft.) in exactly 36 min. These aircraft were then returned to operational service during July 1918, when, by virtue of their superb climbing powers, they were used mainly as interceptors by Kampfeinsitzer Staffeln 4a, 4b, 5, 6 and 8 for defense of the Fatherland.
   Fritz Beckhardt, a friend of the late A. R. Weyl, flew Siemens-Schuckert fighters to good account with Kest (the abbreviated Kampfeinsitzer Staffel) 5, his aircraft being characterized by the painting on the fuselage sides of a large Hakenkreuze (swastika). On a single sortie during September 1918 he managed to shoot down a pair of French Breguet B 14s operating at a height of more than 23,000 ft. The Breguets were by no means sitting ducks, as Ernst Udet was able to testify when he had been shot down by one earlier in the year and was only saved by his parachute.
   When in December 1917 Idflieg gave the first D.III order, it also requested development of the D.IV and placed an order for three prototypes. A D.V development was similarly requested, but as this was virtually a two-bay version of the D.IV, and offered no improvement, it proceeded no further. Although the S.S.W. D.III had excellent climbing abilities, its maximum level speed was not comparable, being only about 180 km.h. (112-5 m.p.h.). In an endeavor to achieve improved performance a redesigned top wing of new section and reduced chord was experimentally fitted, and in this guise the aircraft was re-designated D.IV. There was also some revision to the cowling arrangement, in which the lower half was almost completely cut away to give additional cooling to the cylinders. The spinner was also impressed with four cooling louvers in order to scoop cooling air on to the crankcase. Apart from these modifications, the two types differed little. In performance an immediate increase in level speed to 118 m.p.h. was obtained and the rate of climb substantially improved. By March 1918 a production order had been given for the D.IV, but it was not until August of that year that it became operational; first deliveries went to Jasta 14 and to the Marine Jagdgeschwader commanded by Osterkamp. Later Kest 2 and Jasta 22 received some D.IVs, but production rate was largely controlled by engine availability, and by the Armistice not all the 280 machines that had been ordered had been delivered. Not even the famous Richthofen Geschwader (after an initial antipathy) had been able to get its belated request for the type fulfilled.
   The D.III/ D.IV fighter series, the first-and last-S.S.W. original rotary engined design to see service with the German Air Force, differed radically in appearance from all previous production fighters. Its stocky, barrel-like fuselage was of considerable strength and continued the circular section dictated by the engine throughout its length. In the initial production machines the Sh.III engine was completely enclosed in a close-fitting circular cowl, and the four-bladed propeller - of fairly coarse pitch - was fitted with a large diameter spinner. This combination left an insufficient aperture for the entry of cooling air, and later the cowling was drastically cut away in the lower half, thereby exposing the front engine-bearer spider frame. The fuselage consisted of a basic structure of spruce longerons and circular plywood bulkheads additionally reinforced with diagonally mounted ply formers, which, when the three-ply skin was attached, resulted in an extremely strong structure. The panel between the front undercarriage legs was of sheet metal liberally endowed with louvers to allow the exhaust to escape; the top panel between the center-section struts was similarly covered. Handgrips adjacent to the cockpit and tail plane were fashioned by the simple expedient of cutting away a small rectangle of the plywood skin and exposing the longeron, which could be grasped. All fin surfaces were of wooden framing and constructed integrally with the fuselage, and were likewise plywood skinned. The vertical fin was of asymmetrical section, which helped to counteract a tendency to swing on take-off as a result of the considerable torque moment of the big engine. The balanced, angular rudder and the one-piece balanced elevator were of welded steel-tube construction and covered with fabric.
   In the D.III the upper wing was of considerably greater chord than the lower. Both were based on twin hollow box-spars, and the plywood ribs with pine capping strips were closely spaced and, with the plywood sheeting of the leading edge back to the front spar, dispensed with the necessity for false ribs to preserve the aerofoil section. In the D.IV an improved aerofoil section was introduced and the upper wing reduced in chord to 1 m.: the same as the lower wing. Overhung, horn-balanced ailerons, of parallel chord (those of the D.IV were slightly tapered towards the tips) were fitted at all four wingtips and imparted a brisk rate of roll to the machine. They were operated through torque tubes in all wing panels by a positive linkage which made it unnecessary for them to be linked externally by either struts or wires. As in the steering surfaces, they were of welded steel tube and covered with fabric.
   A conventional vee-type undercarriage was fitted, although the vee struts were fabricated from alloy tube instead of the more usual steel tube, and were wrapped with alloy sheet fairings. The wheels were sprung with spiral steel springs. A substantial ash tailskid was hinged to the under fin and bound at its upper end with elastic cord. Interplane struts were of wood and wrapped with fabric for additional strength, as were also the center section struts.
   Flight characteristics of the series were such as to demand constant vigilance from the pilot; there was no stall warning and a spin rapidly developed. Nevertheless, although with such a powerful engine the torque was considerable, it could be handled by any pilot of good average skill. The counter-rotation of the crankshaft and cylinders did nothing to lessen torque (as has been supposed), but did compensate the gyroscopic reaction. This was extremely beneficial, as it gave no fore-and-aft change of trim between right- and left-hand turns, as was normally the case with rotary-engined fighters.
   Without doubt these Schuckert machines were the best German fighters to reach operational status, yet they were probably the least known. For some odd reason, manufacture of the type did not cease until the summer of 1919, and one D.IV survived in Germany until as late as 1926.
  
  
Description: Single-seat fighter.
Manufacturer: Siemens-Schuckert Werke G.m.b.H. Siemensstadt, Berlin and Nurnberg (Ssw.).
   D.III D.IV
Power Plants: One 160 h.p. Siemens-Halske Sh III and IIIa 11 cylinder geared rotary engine.
Dimensions:
   Span 8.43 m. (27 ft. 7 3/8 in.) 8.35 m. (27 ft. 4 3/4 in.)
   Length 5.7 m. (18 ft. 8 1/2 in.) 5.7 m. (18 ft. 8 1/2 in.)
   Height 2.8 m. (9 ft. 2 1/4 in.) 2.72 m. (8 ft. 11 in.)
   Area 18.82 sq.m. (203.5 sq.ft.) 15.12 sq.m. (163.25 sq.ft.)
Weights:
   Empty 534 kg. (1,175 lb.) 540 kg. (1,190 lb.)
   Loaded 725 kg. (1,595 lb.) 735 kg. (1,620 lb.)
Performance:
   Max speed 180 km.h. (112.5 m.p.h.) 190 km.h. (118.75 m.p.h.)
   Climb to:
   1,000 m. 1.75 min. 1.9 min.
   2,000 m. 3.75 min. 3.7 min.
   3,000 m. 6.0 min. 6.4 min.
   4,000 m. 9.0 min. 9.1 min.
   5,000 m. 13.0 min. 12.1 min.
   6,000 m. 20.0 min. 15.5 min.
   Ceiling 8,000 m. 8,000 m.
   Duration 2 hr. 2 hr.
Armament: Two fixed Spandau machine guns firing forward.
  

Siemens-Schuckert D IV
   This photograph continues the evolution of the 7551/17 airframe. After the crash at Adlershof in January 1918 the machine was rebuilt with a new serial (7554/17) and the type redesignated D IV. Again the aircraft crashed, as may be seen above, and was yet again rebuilt, this time with reduced span, and designated D IVa. Engine, 160 h.p. Siemens-Halske Sh III. Span, 9.0 m. (29 ft. 6 3/8 in.). Length, 6.0 m. (19 ft. 8 1/4 in.). Weight: Loaded, 695 kg. (1,529 lb.). Climb, 6,000 m. (19,680 ft.) in 18 min. Duration, 2 hr. Armament, twin Spandau machine-guns. When rebuilt as D IVa, span was reduced to 7.5 m. (24 ft. 3 3/8 in.), and climb to 6,000 m. took 30 min.


Siemens-Schuckert D IIe
   Yet another airframe with a long and complicated history. The D IIe (serial 7553/17) was originally built with dural-girder wing spars and unbraced wings. The I-type interplane struts may be noted, which help to distinguish from the other S.S.W. prototypes. On test flight the wings were found to flex considerably and bracing cables were then added. Eventually the machine was rebuilt to D IV standards and sent to Geschwader II in spring of 1918 for operational assessment; it was again returned to factory, modified and reengined and ferried back to Geschwader II again in July 1918. Engine, 160 h.p. Siemens-Halske Sh III. Span, 8.2 m. (26 ft. 10 7/8 in.). Length, 60 m. (19 ft. 8 1/4 in.). Area, 154 sq.m. (166 sq.ft.). Weight: Empty, 500 kg. (1,100 lb.). Duration, 2 hr. Armament, twin Spandau machine-guns.


Siemens-Schuckert D V
   Although no photograph has been traced, details are included for completeness. The S.S.W. D V was a development of the D II/D IV series with two-bay wing bracing. Three prototypes were scheduled (7556-7558/18) and completed by August 1918: 7557/18 competed in the second D types Competition, was flown by Muller with climb figures quoted below: Engine, 160 h.p. Siemens-Schuckert Sh III. Span, 8.86 m. (29 ft. 0 7/8 in.), length, 57 m. (18 ft. 8 3/8 in.). Area, 15.1 sq.m. (163 sq.ft.). Weights: Empty, 514 kg. (1,131 lb.). Loaded, 734 kg. (1,615 lb.). Climb, 1,000 m. (3,280 ft.) in 1.8 min., 3,000 m. (9,840 ft.) in 7.3 min. 6.000 m. (19,680 ft.) in 28.8 min. Armament, twin Spandau machine-guns.

J.Herris Siemens-Schuckert Aircraft of WWI (A Centennial Perspective on Great War Airplanes 12)

SSW D.II to D.V

   The SSW D.II through D.V are discussed together because all were variations on the same basic design. Although there were many detail differences, the key distinctions between types were the wings.
   Expecting the eleven-cylinder 160 hp Sh.III engine Siemens-Halske was developing, in November 1916 Idflieg ordered three D.II prototypes (D.IIa 3500/16, D.II 3501/16, and D.IIb 3502/16) for flight trials.
   Two D.II fighters, completed in January 1917, gathered dust at the factory until early June when a Sh.III flight-test engine was at last delivered. SSW quickly installed the new engine and flight trials began on June 7. After a period of laborious experimentation with both two- and four-bladed propellers to maximize performance, Lt. Hans Muller, a 12-victory ace and company test pilot, performed an astonishing climb of 7,000 meters in 35.5 minutes on August 5, 1917. Muller flew the D.IIb prototype powered by an experimental, overcompressed Sh.III engine. Claiming an unofficial world record, a pleased SSW management gave Muller a bonus of 1,500 Marks.
   On October 7, 1917 Idflieg ordered nine fighter prototypes (numbered D.7550/17 to 7558/17) to explore the possibilities of this new combination. These had lighter, stronger airframes specifically designed for the new Sh.III engine. These prototypes were continually modified (wing span, airfoil type, tail surfaces, etc., were all changed) in the quest for better performance and handling characteristics, as shown in the table.

SSW Fighters at the First Fighter Competition

   On December 26 1917, Idflieg ordered a pre-production batch of 20 D.III fighters (D.8340-8359/17), at the time the customary number for front-line evaluation and, in this case, for the First Fighter Competition. Entered in the Competition, which started January 20, 1918, were SSW prototype fighters D.7551/17, 7552/17, 7553/17 (ready January 24) and series D.III 8340/17. Made possible by the Sh.III engine, SSW pilot Hans Muller demonstrated the fighters' impressive performance and maneuverability. As an example, on January 21 D.7552/17 climbed to 6,000 meters in 21.5 minutes.
   Regardless of their exceptional climb performance, the new SSW fighters were not yet perfected. In particular, they had challenging handling qualities, especially on landing, and required expert piloting. Front-line pilots, accustomed to more docile fighters, experienced difficulty flying the SSW fighters.
   On January 23 Muller took 7553/17 up for its first flight. The aircraft proved extremely nose heavy and required full elevator and throttle to maintain level flight. Coming in to land, the engine failed at 1,000 meters. In spite of full elevator, the nose-heavy fighter dived toward the ground. At the very last moment Muller regained control, touched down sharply, and buried the nose in the sand with only minor damage! Director von Siemens, impressed by Muller's flying ability, was of the opinion that if the accident had occurred at the small SSW airfield rather than huge Adlershof, the fighter would have been totally destroyed.
   Also on January 23, Oblt. Bruno Loerzer, an experienced fighter ace, flew D.7552/17 for evaluation. He misjudged the landing ('the tail wouldn't come down'), had to go around the airfield again, and finally stalled in and flipped over, severely damaging the aircraft.
   On January 24, Muller was taxiing the 'wireless' D.IIe 7553/17 when the undercarriage wire bracing failed, a failure attributed to substandard material.
   On January 25, Lt. Hans von der Osten flew D.7551/17. Reporting unsuitably high propeller revolutions, heavy control forces, poor maneuverability, and landing problems, Osten compared the SSW D.III to the Fokker D.VII prototype as 'an elephant to a mosquito'.
   On January 26, after a high-altitude flight, Lt. Busse fared badly when D.7551/17 turned over upon landing in the sandy terrain, severely damaging the airframe and engine. By then it was obvious to everyone that the SSW D.III prototypes, with their touchy controls and tall undercarriages (required by the large two-bladed propeller), demanded a degree of flying skill beyond a typical fighter pilot's ability. The landing problem was greatly improved by changing to a four-bladed propeller which, being of smaller diameter, permitted shortening the undercarriage. Overall handling qualities were improved by modifications to the ailerons and tail surfaces. With impressive speed, D.III D.8340/17, which had not yet flown, was given a new elevator and undercarriage and returned to the Competition on January 28.
   The spectacular climb rate of the rotary-engined fighters powered by the Sh.III and Goebel Goe.III engines was accompanied by good speed. On January 23, various fighters piloted by company and frontline pilots went aloft for 'parallel competition'. Muller in SSW D.III 8340/17, and making the first flight in this first production D.III, competed with Manfred von Richthofen flying the Fokker D.VII prototype (V11 or V18) and Lt. Hans Klein in an Albatros D.Va powered by the new 180 hp Mercedes D.IIIau high-compression engine. The SSW D.III was substantially faster than the Albatros and marginally faster than the Fokker below 2,000 meters.
   With most of the attention going to the prototype Fokker D.VII, which was declared the winner of the competition, SSW Director von Siemens thought the SSW prototypes did not receive appropriate recognition for their performance and opined, "one has the feeling that Richthofen's sympathies, as before, lie with Fokker!"
   During his inspection of the Siemens factory on January 24, Richthofen stated, "all aircraft at the Competition were too slow; the rate of climb was of secondary importance." This opinion was shared by Loerzer and the other combat pilots. SSW responded by proposing the SSW D.IV that, given a smaller upper wing chord and reduced wing area, sacrificed climb performance for increased speed. Interestingly, the performance specifications show the D.IV as having better climb rate than the D.III at high altitudes, indicating individual variations in conditions and piloting technique were greater than inherent design differences for climb performance.
   On March 1 1918, Idflieg, on the basis of the competition results, ordered 30 D.III fighters (1600-1629/18) followed by 50 D.III (3007-3056/18) on March 23 and 50 D.IV (3060-3109/18) on April 8. Due to the priority of the faster D.IV, on June 8 Idflieg changed the March 23 order to 30 D.III (3007-3026/18 & 3037-3046/18) and 20 D.IV (3027- 3036/18) fighters.


Initial Combat Experience

   From March 16 to May 18, SSW shipped 41 D.III fighters and one D.IV to the front, with most going to Jagdgeschwader II (See Table). Hptm. Rudolf Berthold, CO of JG II, during a squadron visit by SSW designer Bruno Steffen on April 22 1918, praised the D.III's 'brilliant' rate of climb, but requested increased speed, maneuverability, and airframe strength. The D.III and Sh.III engine combination was considered 'faultless' and had gained the 'trust of the pilots'. Maintenance of engine power at higher altitude was appreciated. The sole D.IV was reported 'in all respects-superior to the D.III'.
   Prohibited from flying over the front, JG II pilots intercepted and shot down two high-flying Breguet 14 bombers. But after seven to ten hours, the engines began to fail. They overheated, pistons seized, and piston heads disintegrated, falling into the crankcase. Even the Le Rhone rotary, which had a good reputation for reliability, showed similar symptoms when tested with Voltol, a synthetic castor-oil replacement. Investigation revealed that wrong viscosity oil had been delivered in incorrectly-marked barrels. On May 23 Berthold urged "the Siemens fighter be made available again for frontline use as quickly as possible for, after elimination of the present faults, it is likely to become one of our most useful fighter aircraft."
   All the crippled SSW fighters were returned to the factory in May 1918 for engine replacement and extensive modifications. On June 19 Idflieg required that the existing D.III fighters and those in production receive the following major changes: a new rudder shape, rounded (not pointed) aileron balances (and rounded elevator balances on future production machines), shortened wing span, larger cockpit opening, new propeller pitch to maximize speed, a cut-away cowling, and a smaller propeller spinner.
   Operational use of the Sh.III engine was prohibited pending successful completion of the demanding 40-hour endurance test, which was not achieved until July. Although the early-production Sh.III engines were unreliable, the revised Sh.IIIa, the version that passed the endurance testing and also known as the Sh.III neu, was a reliable engine. Furthermore, the Sh.III(Rh) engines built under license by the Rhenania Motorenfabrik AG (Rhemag) were also reliable. Eventually, about 40% of SSW fighters were powered by Rhemag-built engines. The availability of Rhemag-built engines coupled with the Siemens-Halske Sh.IIIa engine passing its endurance test permitted deliveries to the front (five D.III and one D.IV) to re-start on July 22 after a two-month interruption.


SSW D.V

   Aircraft D.7556-7558/17 were the SSW D.V prototypes; these aircraft were ordered along with the D.III and D.IV prototypes on October 7, 1917. D.V. 7556/17 performed its first flight on June 14, 1918 and D.V 7557/17 participated in the Second Fighter Competition. Using essentially a D.IV fuselage, the D.V differed in being fitted with duralumin wing spars and 'wireless' two-bay wings. The three completed D.V. fighters were slated for home defense service but the Armistice intervened. Unfortunately, no photographs of these aircraft have surfaced.


SSW at the Second Fighter Competition

   From the perspective of SSW, the Second Fighter Competition served primarily to compare production SSW fighters with the latest German prototypes. Eight SSW fighters, some powered by the Sh.IIIa engine and many fitted with the above modifications, were entered in the Second Fighter Competition that was held from May 27 to June 28 1918. Siemens reported that, 'because of significant weight increase and reduced wing area, the climb rates were somewhat reduced: 6,000 meters in 25-28 minutes.' With respect to speed and maneuverability, the aircraft, 'showed up very favorably against the competition'. In the front-line pilots' de-briefing sessions (July 6 and 14), among the Sh.III-powered fighters the SSW D.IV, fitted with four ailerons, was chosen over the less-maneuverable Pfalz D.VIII, the pilots' second choice, which was recommended for home-defense duties. Accordingly, on July 26, Idflieg ordered 60 SSW D.IV fighters (6105-6209/18), followed by 50 fighters (9000-9049/18) on September 10, 100 (11500-11599/18) on October 16, and 100 at the end of October 1918.


The SSW D.III & D.IV in Action

   SSW delivery records show that from July through November 1918, at least 136 SSW D.III and D.IV fighters were delivered to combat units. In general the D.III, due to its potentially higher climb rate, was supplied to the home-defense squadrons (Kampfeinsitzer Staffeln - Kests 2, 4a, 4b, 5, 6 and 8) and the faster D.IV to the Western Front: JG II, Jasta 14, Jasta 22, Jastaschule 1, and Marine Jagdgruppe. The few available combat reports universally praised the Siemens fighters but not without some criticism, especially from units having flown the more benign Fokker D.VII. Both the D.III and D.IV needed more flying skill for they were exceptionally maneuverable, very sensitive on the controls, and, unlike the docile Fokker D.VII, spun with little warning.
   Therefore Muller and Lt. Bruno Rodschinka, both SSW test pilots, visited operational units to instruct on the SSW fighters and gave flying demonstrations in them that were generally considered the finest exhibition of low-altitude aerobatics ever seen by service pilots. Their efforts produced the necessary confidence in the types, as did the initial victories. Naval Lt.z.S. Theo Osterkamp shot down a D.H.4 at 6,000 meters on August 21 while Muller was present. At Kest 8 Rodschinka downed two D.H.4 bombers out of 24 on September 7. A pilot of Kest 8 wrote on October 2, after two British aircraft were downed, that, 'we all now have the Siemens and are very satisfied... the Siemens is much superior to Allied aircraft and the Sh.III engine operated without complaint.' Even Jagdgeschwader Richthofen, who had been adverse to the Siemens fighters, after a demonstration by Hans Muller on October 5 requested 'twelve good D.IV fighters and a further twelve as soon as the first are shipped.'
   Lt. Lenz, CO of Jasta 22, reported on October 3 that the D.IV was, 'superior to all aircraft at the front in climb, maneuverability, and speed above 4,000 meters'. At that altitude, 'it was impossible to fly formation with the Mercedes-engined Fokker D.VII'. Pilot training was mandatory since many were unfamiliar with the SSW fighters' rotary engine and their high landing speed. Above 5,000 meters the high wing loading became noticeable in turns and required, 'watchfulness and opposite rudder'. Spin recovery was quick and effortless. The pilot's field of view was quite good, except straight down due to the round fuselage.
   Although Germany had difficulty finding sufficient aircraft to meet the Armistice stipulations, it appears SSW fighters were held back because only a few were turned over to the Allies. Of the 44 D.IV fighters completed by SSW after the war, from December 1918 through July 1919, some were sent to Flieger Abteilung 431 of the Grenzschutz Ost, but most were placed in storage at Reichswehr depots at Johannisthal, Liegnitz, Thorn, and Doberitz before being destroyed in accordance with the Treaty of Versailles. At least one of the D.IVs shipped to Thorn later turned up in the hands of Flieger Abteilung 424 in Lithuania in 1919.


SSW Fighter Prototypes Ordered October 7,1917
Type Serial # Notes
D.IIc kurz D.7550/17 8.5 m span, first flight October 22, 1917. Later redesignated D.III 7550/17 and became the static test airframe for the D.III production series.
D.IIc lang D.7551/17 9.0 m span, first flight November 15, 1917. Redesignated D.III, it became the true prototype of the D.III series. It participated in the First Fighter Competition. After being damaged, it was rebuilt as D.IV 7554/17 with a span of 8.35 m. Again damaged, it was rebuilt as D.FVa 7554/17 with a span of 7.4 m. It was accepted on May 4 and participated in the Second Fighter Competition in June.
D.III D.7552/17 Made its first flight December 20, 1917, and participated in the First Fighter Competition. 8.7 m span, wing area 21.6 m2, 6 m long, 500 kg empty weight.
D.IIe D.7553/17 It was fitted with a wireless wing cellule with duralumin wing spars. During test flights the wings flexed too much and full wire bracing had to be fitted. Participated in the First Fighter Competition. Later converted to D.IV 7553/17 and delivered to JGII in April for evaluation in combat. Engine problems required its return to the factory, where it was modified and fitted with a new engine. It was returned to JG II in July 1918. Original span 8.2 m, length 6 m, 500 kg empty weight.
D.IV D.7554/17 Was rebuilt from 7551/17; see above.
D.IV D.7555/17 Prototype for the D.IV, made its first flight June 18, 1918. Delivered to Adlershof in August as the D.IV static test airframe. Span 8.2 m.
D.V D.7556/17 D.IV fuselage with 2-bay wireless wings, duralumin spars. First flew June 14, 1918.
D.V D.7557/17 Participated in the Second Fighter Competition.
D.V D.7558/17 Slated for home defense like the other D.V fighters but the Armistice intervened.


Siemens-Schuckert D-Type Fighter Specifications
D.I D.III D.IV D.V D.VI
Engine 110 hp Sh.I 205 hp Sh.III 205 hp Sh.IIIa 205 hp Sh.III 205 hp Sh.IIIa
Armament One, later two guns Two guns Two guns Two guns Two guns*
Span, Upper 7.50 m 8.40 m 8.35 m 8.86 m 9.37 m
Span, Lower 6.30 m 8.40 m 8.35 m na
Chord, Upper 1.30 m 1.46 m 1.0 m
Chord, Lower 0.8 m 1.0 m 1.0 m na
Length 6.00 m 5.85 m 5.58 m 5.7 m 6.50 m
Wing Area 14.4 m2 18.84 m2 15.12 m2 12.46 m2
Empty Weight 430 kg 534 kg 540 kg 514 kg 540 kg
Loaded Weight 675 kg 725 kg 735 kg 725 kg 710 kg
Max. Full Weight: 735 kg 740 kg 735 kg 734.5 kg 735 kg
Maximum Speed: 155 km/h 180 km/h 190 km/h 220 km/h
Climb: 1,000m 3.5 minutes 1.75 minutes 1.9 minutes
2,000m 8.0 minutes 3.75 minutes 3.7 minutes
3,000m 14.5 minutes 6.0 minutes 6.4 minutes
4,000m 24.3 minutes 9.0 minutes 9.1 minutes
5,000m 45 minutes 13.0 minutes 12.1 minutes 17.4 minutes
6,000m 20.0 minutes 15.5 minutes 16 minutes
7,000m 22 minutes
Ceiling: 8,000m 8,000m 8,000m
Duration: 2.5 hours 2 hours 2 hours 2 hours
Notes:
   1. Although the Sh.III and Sh.IIIa developed slightly over 205 hp, contemporary publications usually stated their power at 160 hp, the power developed by the initial prototype engines.
   2. SSW D.III climb times from official German Baubeschreibung figures. SSW D.III with Sh.IIIa engine had these times to altitude: 5,000 meters in 10.5 minutes, 6,000 meters in 15 minutes, 7,000 meters in 22.5 minutes, and 8,000 meters in 34.5 minutes.
   3. SSW D.IV climb times from G.P. Neumann figures.
   4. Lt. Lenz recorded 14.5 minutes to 6,000m during an operational sortie in his SSW D.IV during which he shot down two British airplanes.
   5. SSW D.VI armament is that projected for production; the two prototypes were unarmed.


SSW D.III & D.IV Production Orders
Order Date Siemens # Quantity Military # Type
17 Jan. 1918 11054 20 D8340-8359/17 d.hi
1 March 1918 11080 30 D1600-1629/18 D.III
22 Apr. 1918 11111 30 D3007-3026/18 D3037-3046/18 D.III D.III
22 Apr. 1918 11122 20 D3027-3036/18 D3047-3056/18 D.IV D.IV
7 May 1918 11115 50 D3060-3109/18 D.IV
26 July 1918 11163 60 D6150-6209/18 D.IV
10 Sep. 1918 FW38 50 D9000-9049/18 D.IV
16 Oct. 1918 FW90 100 D11500-11599/18 D.IV
End Oct. 1918 FW92? 100 2 D.IV
In addition to the three D.III prototypes and three D.IV prototypes, Siemens records show a total of 80 production D.III aircraft and 280 production D.IV aircraft were ordered as shown in the table above. Another order for 100 D.IV at the end of October is not listed in the Siemens records but may be Siemens order FW92, for which no other details were recorded. The total number actually delivered is not known, but it is very unlikely all the D.IV aircraft ordered were delivered. There are small discrepancies between order dates given above and those listed in the Siemens records, possibly caused by change orders.


SSW Fighter Deliveries in Spring 1918
Date Unit Qty. Serial Numbers
16 March JGIII 6 D.III 8340-8345/17
6 April JGII 9 D.III 8346-8354/17
15 April JGII 1 D.IV 7553/17
19 April JGII 10 D.III 8355-8359/17, 1600-1603 & 1605/18
30 April JGII 6 D.III 1604, 1606-1608, 1611, 1612/18
13 May JGII 6 D.III 1614-1619/18
18 May JGII 4 D.III 1610, 1613, 1621, 1624/18

M.Dusing German Aviation Industry in WWI. Volume 2 (A Centennial Perspective on Great War Airplanes 85)

Siemens-Schuckert-Werke, Abt. Flugzeugbau, Siemensstadt b. Berlin (SSW)

Aircraft Development:

Siemensstadt:

<...>
  On the basis of these experimental experiences and detailed scientific calculations, the aircraft SSW D.III and SSW D.IV were then developed. These aircraft, as well as the Gotha G.IV license, were then mass produced.
  The parallel development of D aircraft led to the success of the SSW D.III with 160 hp Siemens-Halske engine (Sh. Ill) in September 1917, which was followed by an initial order for 20 aircraft at the end of 1917. This type, developed from the SSW D.I, featured an improved design as well as climbability and maneuverability.
  In addition to the D.I and R.I aircraft mentioned above, other types were developed and some were delivered to the front in smaller series. These were B-, D-, E-airplanes from own development as well as licensed Alb C.IIIc and Go G.IV equipped with Daimler, Maybach, Argus or NAG engines.
<...>

W.Green, G.Swanborough The Complete Book of Fighters

SIEMENS-SCHUCKERT (SSW) D II Germany

   Late in 1916, at the suggestion of the Idflieg, SSW began work on a new single-seat fighter designed by Dipl Ing Harald Wolff around the new 11-cylinder Siemens-Halske Sh III geared rotary engine rated at 160 hp. The result, the D II, was a rotund single-bay biplane primarily of wooden construction, the wings featuring two hollow box spars and the fuselage being a circular-section semi-monocoque of three-ply, intended armament being two 7,9-mm LMG 08/15 machine guns. Three prototypes were initially built, the D II, the D IIa and the D IIb. Although completed early 1917, delays in availability of the Sh III engine prevented flight test of the prototypes, the first of these flying in June. Erratic engine behaviour notwithstanding, the D IIs demonstrated excellent climb performance - the D IIb attaining 16,405 ft (5 000 m) in 15.5 min during August - and three more development aircraft were ordered. Two of these, designated D IIc kurz (short) and D IIc lang (long), differed in wing span and area. The D IIc kurz had a span of 27 ft 10 2/3 in (8,50 m) and a wing area of 208.8 sq ft (19,40 m2) whereas the D IIc lang had a span and area of 29 ft 6 1/3 in (9,00 m) and 193.97 sqft (18,02 m2) respectively, and reduced chord on the upper wing. The third aircraft, the D IIe, had dural wing spars, broad-chord I-type interplane struts and unbraced wings. The D IIc kurz entered flight test on 22 October 1917, the D IIc lang following on 15 November, and an initial order for 20 series aircraft, designated D III and based on the D IIc kurz was placed in December. The D IIc wing cellule was found to lack rigidity in flight, dictating introduction of interplane bracing cables which negated the original purpose of the dural spars, this aircraft later being rebuilt to D IV standards.


SIEMENS-SCHUCKERT (SSW) D III Germany
  
   With the choice of the D IIc kurz (short) as the basis for the initial production Sh III-powered SSW fighter biplane to which the designation D III was assigned, an order for 20 aircraft was placed in December 1917, this being augmented by an order for a further 30 in February 1918. The first two series D IIIs initially had a two-bladed propeller similar to that of the D II, but this was replaced by a smaller-diameter four-bladed propeller which permitted a reduction in the height of the undercarriage chassis. The Siemens-Halske Sh III 11-cylinder rotary engine had a nominal rating of 160 hp, but its maximum output was 210 hp at sea level. The standard armament of twin 7,9-mm LMG 08/15 synchronised machine guns was fitted. The first D IIIs came off the line in January 1918, and, between March and May, a total of 41 was sent to the Front where they demonstrated good handling qualities and outstanding climb capabilities. The Sh III engine proved troublesome, however, having been placed in service prematurely, and all D IIIs were returned to SSW for modification. This involved introduction of the improved Sh IIIa engine and the cutting away of the lower portion of the engine cowling to improve cooling. In addition, some revision was made to the rudder contours. These modifications were also incorporated in a further 30 D IIIs ordered in the interim, to bring total production to 80 aircraft. A modified version, the D IIIa with ailerons on the upper wing only, participated in the second D-type contest (17 May - 28 June 1918), but was not found to offer worthwhile advantages over the standard model.

Max speed, 110 mph (177 km/h) at sea level.
Time to 3,280 ft (1000 m), 1.75 min.
Range, 224 mis (360 km).
Empty weight, 1,153 lb (523 kg).
Loaded weight, 1,598 lb (725 kg).
Span, 27 ft 7 7/8 in (8,43 m).
Length, 18 ft 8 1/2 in (5,70 m).
Height, 9 ft 2 1/4 in (2,80 m).
Wing area, 202.8 sq ft (18,84 m2).


SIEMENS-SCHUCKERT (SSW) D IV Germany
  
   By the end of 1917, the Idflieg regarded the D III as an interim development and was pressing for acceleration of work on the D IV. Retaining the Sh IIIa engine and twin LMG 08/15 gun armament, the D IV differed from its predecessor fundamentally in having a revised wing configuration developed by Heinrich Kann, the basic structure remaining unchanged. The D IV utilised an improved wing profile, the chord of the upper wing being reduced to that of the lower wing, resulting in a reduction of 40 sqft (3,72 m2) in gross area. Rate of climb remained virtually unchanged from that of the D III, but most other aspects of the performance were improved. No fewer than 280 D IVs were ordered in March 1918, although the type did not attain operational use until August, and no more than 50-60 were to achieve active service. Production did not cease with the Armistice, continuing through January 1919, a total of 119 having been completed prior to the end of World War I. A number of D IVs (and D IIIs) continued to be operated by the Reichswehr and by the Grenzschutz Ost (Border Protection East) force, flown by volunteers to protect the German population against the Red Army in the Baltic states and Germany's eastern borders.

Max speed, 114 mph (184 km/h).
Time to 3,280 ft (1000 m), 1.9 min.
Range, 239 mis (385 km).
Empty weight, 1,190 lb (540 kg).
Loaded weight, 1,627 lb (738 kg).
Span, 27 ft 4 3/4 in (8,35 m).
Length, 18 ft 8 1/2 in (5,70 m).
Wing area, 162.75 sg ft (15,12 m2).


SIEMENS-SCHUCKERT (SSW) D V Germany

   Developed in parallel with the D IV, the D V was an essentially similar Sh IIIa-powered fighter differing only in having a two-bay wing cellule. Three prototypes of the D V were ordered, the first of these participating in the second D-type contest at Adlershof in May-June 1918, and the third being completed in August. By consensus the D V held less promise than the D IV, two of the prototypes being rebuilt to D IV configuration and one being lost during flight test.

Time to 3,280 ft (1000 m), 1.8 min.
Empty weight, 1,133 lb (514 kg).
Loaded weight, 1,618 lb (734 kg).
Span, 29 ft 0 3/4 in (8,86 m).
Length, 18 ft 8 1/2 in (5,70 m).

Журнал Flight

Flight, March 13, 1919.

THE SIEMENS TYPE D IV SINGLE-SEATER FIGHTER

   DURING the latter part of the War, a good deal was heard of the Siemens Single-Seater, but little reliable information concerning this machine was available. It was said that it had an extraordinarily good (for a German) climb, manoeuvred exceptionally well, and was strong enough to be "spun" with the engine running. The engine was thought to be a Siemens rotary, said to give exceptional power for its weight, and to be particularly good for altitude work. The reports, as is so often the case in such circumstances, differed greatly, and varied from the statement that this machine was no good at all, to the opinion that it was better than anything we had at the time. As frequently happens, the truth judging from the following description, which is translated from the German aviation journal Flugsport, is somewhere in between the two extremes. The machine is undoubtedly one of the best German machines of which detailed particulars are available, but at the same time does not come up to our best. Thus Flugsport :-
   In January, 1918, the Siemens-Schuckert Works brought out, in a competition for this class at Adlexshof, a single-seater fighter known as the D III. This machine, which had a Siemens-Halske rotary motor with 11 cylinders, had a climb that greatly exceeded the specifications of that time, and had at the same time a sufficient horizontal speed and good manoeuvrability. In order to improve upon this type, the speed was increased at the cost of climb, and the shape and section of the main planes were altered accordingly. The new machine, type D IV, is shown in the accompanying illustrations.
   The total span of the D IV is 8m.35, with a chord of 1 m. There is neither dihedral nor sweepback. The weight of the machine empty is 525 kg.
   Concerning the Siemens rotary engine, only a brief reference will be made to this, a more detailed description being reserved for a future occasion. The 200 h.p. 11-cylinder motor is a development of the previous 9-cylinder engine of 110 h.p. It differs from that engine in that, whereas in the smaller motor the crankshaft was stationary and the cylinders revolved, in the new engine the crankshaft revolves in one direction and the cylinders in the opposite direction. The cylinders revolve at the rate of 900 r.p.m. in one direction, and the crankshaft makes 900 r.p.m. in the opposite direction. This is equivalent to an engine speed of 1,800 r.p.m., while the speed of the airscrew is only 900 r.p.m.
   The arrangement of having the two masses rotating in opposite directions is attended by the following special advantages: The low speed of the airscrew results in a better propeller efficiency, which means a greater useful thrust. On account of the low speed of the cylinders the centrifugal force is smaller, which makes for reliability. The high virtual speed of the engine (by having cylinders and shaft revolving in opposite directions - Editor FLIGHT) results in greater power and lighter engine weight. On account of the low speed of the cylinders, air resistance is decreased, resulting in a better efficiency. By having the masses revolving in opposite directions gyroscopic force is approximately eliminated, which is an advantage for manoeuvring. The petrol consumption is far lower than that of any other rotary, and is about the same as that of stationary engines.
   The Siemens rotary can be throttled down from 900 r.p.m. to 350 r.p.m. The cylinders can be easily removed, and by fitting dual magnetos the reliability is increased. The engine can be started by means of a hand-operated magneto. Both inlet and exhaust valves are mechanically operated, and the motor is over-dimensioned, and consequently suitable for work at great altitudes. The normal brake horse-power is 200 h.p. and the maximum power 240 h.p., for a total engine weight, ready for running, of 194 kg. This gives a weight per horse-power of 0.81 kg. If one at the same time bears in mind the low speed of the airscrew, resulting in a good efficiency, of 68 per cent, or so, the value of the engine will be apparent. (A propeller efficiency of 68 per cent, does not impress one particularly. - Editor FLIGHT.) The value of the ratio (lbs. thrust / lbs. weight of engine + weight of screw), should be very good.
   The engine is hung on its three supports in a wrought-iron frame, which is attached by suitable fittings to the four longerons of the fuselage. Later types are improved by making the engine quickly removable with its cowling arrangement. The aluminium cowl round the motor ensures proper cooling and prevents the used oil from being thrown out. The oil tank is mounted behind the engine in order to protect it from the cold, and a short distance behind it is mounted the petrol tank which is arranged for gravity feed. The two tanks are bolted together, and may be put into and taken out of the machine as a unit. In later types the oil tank is built with double walls, the space between which is packed with heat-insulating material so that the oil, even at the greatest altitudes, retains its proper consistency.
   The air screw is a four-bladed tractor, with the four blades glued together in one plane. Its diameter is 2m.80 and the pitch 3m.90. The four-bladed screw, as shown by experiments, has certain advantages over the two-bladed, without, in the present case, having a lower efficiency than the latter. Thus the under-carriage is lower, which facilitates landing at the high speed of this machine.
   The fuselage is built of three-ply wood, and is designed for the lowest possible head resistance. The framework is formed by a series of transverse formers or bulkheads and four pine longerons, and to this the three-ply planking is tacked. Of particular interest are the diagonal formers running from bulkhead to bulkhead. These give great rigidity to the structure. Growing out of the main body and built integral with it are the vertical fin and horizontal tail plane, as well as the lower fin, which forms a support for the tail skid. The tail plane, which is of the symmetrical type, is set at an angle of incidence of 0 deg. while the vertical fin is cambered on one side only, in order to counteract the turning moment caused by the propeller torque. To the tail plane is hinged in the usual manner the one-piece, balanced elevator. The rudder is placed wholly above the elevator. Both rudder and elevator are built up of steel tubes with ribs of sheet steel, and the control cables, which are in duplicate, are so arranged as to nowhere pass over pulleys. The pilot's seat is mounted on duralumin tubes and is adjustable in two directions. The safety belt is attached to the upper longerons via coil springs. One of the accompanying illustrations shows the interior of the pilot's cockpit, which is equipped with the usual instruments: Revolutions-counter, compass, altimeter, throttle levers, switches, magneto switches, and petrol tap, etc. The control lever carries at its upper end a handle of the type that has been standardised by the German authorities (Heeresverwaltung), and the left side of which is arranged as a throttle lever. By a special locking arrangement, the control lever may be locked in any position. The longitudinal rocking shaft, which is forked round the control lever, carries at its front end a double crank for the aileron control. The latter is in the form of steel tubing throughout in order to minimise danger of damage by bullets.
   To the front part of the fuselage is attached the undercarriage, which is built of steel tube throughout. It is held together by a cross tube behind the axle and by diagonal bracing in the rear bay only. The wheel axle, which is a nickel chrome steel tube of 55 mm. diameter, is slung from the struts by coil springs wrapped around the axle. As circular section tubes are employed for the undercarriage struts, these have been streamlined with sheet aluminium. The upper plane is in one piece, and has spars of the box type, the spars being made by spindling out two halves to the desired section. Where struts, etc., occur, the spars are left solid. The ribs are built up of webs of 1.5 mm. three-ply wood, with flanges of pine. The ribs, which are placed 160 mm. apart, are carefully secured to the spars by small blocks of wood, glued on. The internal wing bracing is in the form of steel tube compression struts and steel wires. The wing fabric is stitched to the ribs. All the wing spar fittings are so designed as to surround the spars, thus avoiding piercing. There are four ailerons of the balanced type, which are hinged to the rear spar. The ailerons are operated by steel tubes lying inside the plane, an arrangement which in addition to the advantage already referred to of safety against bullets, gives less head resistance than cables placed on the outside of the wing. (This is evidently a "crib" of the Nieuport type of control. - Editor FLIGHT.) The inter-plane struts are in the form of Vees, which have their pointed end secured to a bridge piece of wood between the lower plane spars. Both front and rear struts of the Vee are of streamline section, and are hollowed out for lightness. The canopy (Baldachin) or centre section struts are braced by cables in such a manner that, by utilising the machine-gun bridge in the construction, they do not interfere with the sighting and use of the guns. The main wing bracing consists of two cables with a very high factor of safety, while an external drift wire to the nose of the body is provided to afford extra safety during a long steep dive.
   The armament consists of two machine-guns, rigidly mounted, and synchronised to fire through the propeller. Adjustment of the guns is made at the rear support.
   Sand tests carried out on the machine have given results far above the official specifications. During the most severe tests in the air, including dives and upside-down flights, no defects were found, and not a single part had taken a permanent set or stretch after the very severe test flights.
   One of the accompanying illustrations shows a barograph record taken under official tests and with the machine carrying its service load of 105 kg. The climbs are only to be described as exceptionally good, and have not, so far as is known, been equalled by our enemies. (This is not correct. - Editor FLIGHT.) The speed and manoeuvrability has drawn favourable comment from all quarters, and the machine has become a leading weapon in the hands of our skilful pilots. The Armistice has prevented the machine from appearing in quantities on the front. The enemy Press had already learned of the appearance of this machine, and we find in tne Matin, during August, an article dealing with it, and English technical journals conclude a description of the Siemens by challenging the English industry to overtake, by intensive work, the lead which the German industry has gained with this machine and motor.