Nazi Germany (1940)
Light Transport and Trainer – Number built: 1,175

While often seen as less exciting than their combat counterparts, transport and auxiliary aircraft provided vital services in moving cargo, and training new pilots. Light transports which could combine both duties were thus extremely desirable during the war as theaters stretched across continents and pilot attrition was high. Luckily for the Luftwaffe, the Siebel company provided them with a simple but effective aircraft that could easily fulfill both roles. This was the Si 204, which saw wide-scale use both during, and after, the conflict.

Siebel company history

The story of  Siebel began back in 1936 when Hans Klemm opened a new aircraft factory the,  Flugzeugbau Halle GmbH.  This company would go on to produce license-built aircraft, including the Focke-Wulf Fw 44, and Heinkel He 46. Between 1936 and 1937, a new project led by Hans Klemm was initiated. This was a light twin-engined transport aircraft designated as Fh 104. While the work was going on, Klemm decided to hand over the factory to well-known aircraft enthusiast Fritz W. Siebel. The same year the name was changed to Siebel Flugzeugwerke Halle GmbH. Under new management, the work on the renamed Siebel Fh 104 continued. The Siebel Fh 104 would prove to be a solid design and was pressed into Luftwaffe service as a communication and liaison aircraft. In 1942 the production of this aircraft was terminated, by which time only some 46 were built. The Siebel factory would survive the war and even produce a few new aircraft designs. It would continue to exist up to 1968 when it was merged with Messerschmitt-Bolkow GmbH.

The Siebel 204 

Following the success of the Fh 104, Siebel received a request from the Luftwaffe officials in 1939 to design and build a new twin-engine, 8-passenger transport aircraft.  So Siebel and his team of engineers began working on such a design. While they may have used the experience gained while working on the Fh 104, their next project was a completely new design. The first prototype Si 204 V1 (D-AEFR) was completed in early 1940, and was flight tested on the 25th of May the same year. Sources disagree about the year when the maiden flight was made. For example, D. Nešić and M. Fratzke mentioned that it happened in 1941 while M. Griel placed it in 1940. The test flight proceeded without any major issues, so the development of this aircraft carried on. In October 1940 the Si 204 V2 (D-IMCH) was flight tested. Both of these would serve as bases for the pre-production A-0 series which were to be operated by the German Lufthansa airline. The first prototype was scrapped in 1942 while the second remained in use up to early 1944 when it was lost in an accident.

Following its successful testing, the first production version known as Si 204A was built. It was powered by two 360 hp, or 465 hp depending on the source, Argus As 410 engines. The Si 204A-0 and A-1 were put into production in 1941, the precise numbers are not clear but were likely limited. As the war dragged on these were mainly used for crew training, a role to which they proved well suited.

The Luftwaffe was generally satisfied with the Si 204A’s performance as a trainer but requested that a new version of it be built. This version was dedicated to various crew training tasks including; radio navigation, instrument flying, bombing, and communication. Other requests were made regarding its front canopy design and stronger power units. For this reason, the engines were replaced with two  600-hp Argus As 411 12-cylinder engines. Additionally, the original stepped canopy was replaced with a fully glazed canopy.

The new version was to be designated Si 204D. The fate of the skipped B and C versions is unclear, but these were likely only paper projects.  The Si 204V3 and V4 served as bases for the Si 204D aircraft. Both were flight tested in early 1941, withhe V3 being lost in an accident during mid-1942 while the fate of the V4 is not known.

Technical characteristics

The Si 204 was designed as a low-wing, twin-engine, all-metal transport, and training aircraft. Its fuselage was made of round-shaped formers each connected with a series of metal bars. These were covered with sheet metal plating. On the fuselage sides, there were four rectangular windows.

The wings and tail units were also of an all-metal construction. The wings were built using only a single spar. The dihedral tailplane was divided into two fins and rudders, which were located on their tips.

In the last months of the war, due to shortages of resources, Siebel attempted to replace some metal components using wooden materials. The end of the war prevented any of these wooden components from ever being used.

The pilot and his assistant were positioned in the front. As many German bombers had a fully glazed canopy, to help with the training and adaptation of new pilots, the Si 204 was also equipped with such a designed canopy. It largely resembled the one used on the He 111. Thanks to it the pilot had an excellent view during the flight.

As mentioned earlier, Si 204D was powered by two 600 hp Argus As 411 12-cylinder engines, these used two variable pitch blade propellers. The maximum speed achieved with these engines was around 364 km/h. With a fuel load of 1.090 liters, the maximum operational range was around 1.800 km.

The landing gear was more or less a standard design. It consisted of three wheels. The landing gear retracted back into the engine nacelles. These were not fully enclosed and part of the wheels was exposed. The tail wheel was not retractable.

While initially designed as a passenger transport aircraft, the Si 204 would be primarily used for crew training. For this reason, its interior compartment could be equipped with different training equipment depending on the need. Including radio, radar, or navigation equipment.

Production

Despite being Siebel’s own design, the factory itself lacked production capabilities as it was already heavily involved in the manufacturing of other designs including the Ju 88. The actual production was redistributed to two occupied foreign factories. The first were the SNCAC factories located in Fourchambault and Bourges in France, which came under German control after the successful end of the Western Campaign in 1940. The second production center was located at the  Czechoslovakian Aero factory, which was also occupied by the Germans even before the war started. Other companies like BMM and Walter were also involved in the production of this aircraft.

The production numbers were initially low, for example, the SNCAC only managed to build five aircraft per month during 1942. From 1942 to 1944 this company produced some 150 Si 204D aircraft. Czechoslovakian production capabilities proved to be better, managing to manufacture some 1007 such aircraft by the end of the war. The total production of all versions during the war is around 1.175 aircraft according to H. A. Skaarup. This number, as is the case with many German production numbers, may be different in other sources.

Service

As mentioned earlier the Si 204 was mainly used for crew training for various roles, transportation, and glider towing. While there is quite limited information on their precise service life, it appears to be quite a successful design and was praised by the Luftwaffe pilots. By the end of the war, some were even equipped with various radar equipment including FuG 217R and FuG 218V2R tail warning radars to train night fighter pilots. Interestingly the Si 204 was employed for the training of further Me 262 pilots.

It is often mentioned that the Si 204 was the last Luftwaffe aircraft to be shot down. Near Rodach in Bavaria, just a day before the Germans capitulated to the Allies. That kill is accredited to Lieutenant K. L. Smith, a pilot of a P-38 Lightning from the 474th Fighter Group. How valid this claim is difficult to know precisely due to the general chaotic state in Germany at that time.

Combat adaptation attempts

For fighting against Partisan movements in occupied Europe, older or modified aircraft were often reused, preserving the more modern aircraft for the front line use.  The Si 204 was seen as tempting for such a  modification, so the Siebel engineers tried to develop a fully armed combat version of this aircraft. To fulfill this role some extensive modifications were needed.

Inside its front fuselage, two 13 mm MG 131 heavy machine guns were placed. Each was supplied with 500 rounds of ammunition, stored in a metal ammunition bin. These were to be operated by the pilot. For this reason, he was provided with a Revi 16A-type gun sight. For protection against enemy aircraft, on top of the fuselage, a fully glazed turret armed with one 13 mm MG 131 was added. The turret movement was electrically controlled. Elevation was -10 to +80 while it could achieve a full 360 rotation.

The interior of the Si 204 received a bombing bay that could carry 12 70 kg bombs. External bomb racks with a capacity ranging from 50 to 500 kg were added. The pilot seat received armor plates for his protection from enemy fire on the Si 204E.  Due to its relatively slow speed, using this aircraft against a well equipped enemy was dangerous, so it was to be restricted to night bombing action only.

In 1944 two prototypes were completed and tested. Besides these two, the number of Si 204E’s built is unknown. Given its experimental nature, possibly only a few prototypes were ever completed. Allegedly these saw limited action fighting the Belarusian Partisans. The extent to which they were used in this role if used at all, remains unknown.

Carrier proposal

With the Allies slowly getting the upper hand in the air over Europe, the Luftwaffe became ever more desperate to find a solution to this problem. Mass production of cheap fighters was seen as a possible solution. One such project was proposed by Professor Alexander Lippisch, best known for designing a series of glider fly-wing designs. He was also involved in designing various bizarre aircraft projects, including the unusual  P 13a  aircraft.

While working on the P 13, Lippish was approached with a request from a group of students from Darmstadt and Munich universities who wanted to avoid conscription to join his work. Lippisch agreed to this and dispatched one of his assistants under the excuse that for his own project, a wooden glider was to be built and tested. They together managed to build an experimental  DM-1 glider.. However, this aircraft was not to be towed like any other glider. Instead, the DM-1 was to be placed above the Si 201 on brackets and carried.  However, nothing came of this project, and no such attempt at deploying the glider was made as the war ended.

After the war

When the war ended, the Si 204 would see more service in the hands of many other nations. The advancing Allies managed to capture a number of fully operational aircraft. These were immediately put to use either as transport, liaison, and evaluation purposes. At least one Si 204D was extensively used by the British pilot Captain Eric Brown, who was the chief test pilot of the Royal Aircraft Establishment at Farnborough. He was involved in a British project tasked with taking over German war research installations and interrogating technical personnel after the war.

He was generally impressed with the Si 204D’s overall performance, performing many flights on it. He later wrote about its performance. “The Si 204D was really a viceless airplane to handle, with inherently good stability about all three axes and good harmony of control. It was very well equipped for its tasks, and the later model I flew had an autopilot fitted. Like all German aircraft of that era, it was a mass of electrics, with extensive circuit breaker panels, and all very reliable.  However, the one thing the Germans never got right was wheel brakes, and the Sievel was no exception..”

The Siebels that were moved to Farnborough were extensively used during 1945 for various roles, like communication, providing navigational guidance, and transporting pilots to various captured Luftwaffe airfields. The last operational flight of the Si 204D at this base was recorded at the start of 1946.

After the war, the Si 204 saw the most common use in French and Czechoslovakia, which actually continued to produce this aircraft. In French service, these were known t as NC 700, powered with As 411 engines, NC 701 ‘Martinet’, powered by two Renault 12S  engines, and NC 702,  a modified version of the Si 204A. In total the French constructed over 300 aircraft of this type. Some would see service in French Asian and African colonies. The last operational flight was carried out in 1964. Two NC 702’s would be given to Maroko in 1960, but their use and fate is unknown.

After the war, the French sold 7 NC 701 to Poland. They were used mainly for mapping photography. These were operated until the mid-1950s’ before being put out of service.

By mid-1960 some 5 French-built Siebels were given to the Swedish National Geographic Institut. These were mainly used for taking meteorological photographs.

The second country that produced the Si 204 was Czechoslovakia. They were built in two versions, the C-3 for the army and C-103 for civilian use. Both were mainly operated in their original transport roles. From 1945 to 1950 some 179 would be built.

The Soviets also managed to capture an unknown number of operational Si 204. These were briefly pressed into service before being replaced by domestic-built designs.

Switzerland also operated at least one Si 204D. This aircraft and its crew escaped from Germany on the 7th of May 1945 and landed at Belp near Bern. The Si 204D  would remain in Switz use under the B-3 designation.

Production Versions

• Si 204 –  Prototype series
• Si 204A – Transport and training version built in small numbers
• Si 204B and C – Unknown fate, but likely paper projects only
• Si 204D – Model with a new glazed cockpit and powered with a stronger engine
• 204E – Experimental modification for combat operational use
• Flying carrier – One Si 204 was to be modified as a carrier for the Doctor Alexander Lippisch experimental all-wing fighter, but was never fully implemented

Operators

• Germany – Most produced planes were used by the Luftwaffe primarily used for crew training
• Czechoslovakia – Produced some 179 additional aircraft for military and civilian use
• France –  Over 300 modified aircraft (with French engines) were produced in France and saw wide service up to 1964.
• Soviet Union –Operated some captured  Si 204

• Poland – Brought 7  NC.701 from France after the war
• Macoro – Operated two French NC 702
• Sweden –  Operated five French-built Siebels
• Switzerland – Used at least one Si 204 under the designation B-3
• American and Great Britain – Both briefly operated a number of captured Si 204 after the war

Surviving aircraft

Today there are a number of partially or wholly survived aircraft Si 204. For example, the French Aviation Museum in Paris had one Si 204A and another located in the Escadrille du Souvenir close to Paris. One Si 204 is located at Sweden Lygvapen Museum.

Conclusion

While Germany in the Second World is better known for designing and producing a series of combat aircraft, their auxiliary aircraft are often overlooked. The Si 204 was one such case, despite its successful design, it is rather poorly documented in the sources. Its design was a success which can be seen in its after-war use, most notably by the French up to the mid-1960.

 

Si 204 D Specifications
Wingspans	21.33 m / 70 ft
Length	12 m / 39 ft 3 in
Height	4.25 m / 14 ft
Wing Area	46 m² / 495 ft²
Engines	Two Argus As 411 engines
Empty Weight	1.500 kg / 3.300 lbs
Maximum Takeoff Weight	3950 kg / 8,710 lbs
Climb Rate to 1 km	In  3 minute  30 seconds
Maximum Speed	364 km/h / 226 mph
Cruising speed	340 km/h / 210 mph
Range	1,800 km / 1,120 miles
Maximum Service Ceiling	7,500 m /  24,600 ft
Crew	Pilot and his assistants plus eight-passenger
Armament	None

Illustrations

Credits

• Article written by Marko P.
• Edited by  Henry H. & Stan L.
• Ported by Marko P.
• Illustrated By Ed Jackson

 

Sources

• D. Nešić (2008), Naoružanje Drugog Svetskog Rata Nemačka Beograd
• H. A. Skaarup (2012) Axis Warplane Survivors
• D. Mondey (2006). The Hamlyn Concise Guide To Axis Aircraft OF World War II, Bounty Books.
• D. Donald (1998) German Aircraft Of World War II, Blitz Publisher
• J. R Smith and A. L. Kay (1972) German Aircraft of the Second World War, Putnam
• Jean-Denis G.G. Lepage (2009), Aircraft Of The Luftwaffe 1935-1945, McFarland & Company Inc
• Captain E. ‘Winkle’ Brown (2010) Wings of the Luftwaffe, Hikoki Publication
• M. Griehl (2012) X-Planes German Luftwaffe Prototypes 1930-1945, Frontline books
• T. H. Hitchcock (1998) Jet Planes Of The Reich The Secret projects, Monogram Aviation Publication
• M. Frazke Siebel Fh 104/Si 204, Flugzeug Profile