Overshadowed by more famous and spectacular German aircraft, the Siebel Si 204 boasted a distinctive Dieselpunk appearance and played at least four different roles.
Used in substantial numbers by the Luftwaffe as a light communications aircraft and crew trainer, the Siebel Si 204 was essentially a scaled-up Fh 104 Hallore (which served as a personal transport of Field Marshal Albert Kesselring - see below). Two versions were produced, the Si 204A and Si 204D, the first of these flying in 1941.
The Si 204 was planned as a small passenger plane with 2 crew and 8 passengers for German airline Deutsche Luft Hansa. The development of this all-metal-plane was initiated in 1938. The contractor was, as usual, the RLM, but the development was conducted in close collaboration between Luft Hansa and Siebel in Halle. After the beginning of the war the plane was re-designed as a trainer aircraft with a full "stepless" glass cockpit, with no separate flat windscreen for the pilot (much as almost all German bomber aircraft of the time were being designed with), which seemed to be better for blind flying in the Si 204's case.
The first two prototypes only were delivered as passenger planes with the old cockpit. The maiden flight of the first prototype was before September 1940, possibly on 25 May 1940, that of the second prototype before February 1941. The third prototype was re-designed as a trainer aircraft for blind flying. As a result of this, the maiden flight was not earlier than the end of 1941 or the beginning of 1942.
At that time Siebel produced the Junkers Ju 88 under licence, and therefore only 15 prototypes were able to be built in Halle. As a result, SNCAN in France produced the passenger plane A-1 and the pre-series A-0 between April 1942 and November 1943. ČKD/BMM in the Czech Protectorate delivered the first blind flying trainer D-0 in January 1943 followed by the production of a further 44 D-0 pre-series planes. The D-1 series was begun in March 1943 by the Aero company, also located in the Czech Protectorate, and by BMM in June or July 1943. In August 1943, SNCAN also delivered the first D-1.
The production of the D-3 was started in October 1944 by the Aero company. The D-3 had wooden wings and a tail plane made of wood and metal. In France, production of the D-1 was ended in August 1944 as a result of the Liberation. All in all 168 Si 204 were built by SNCAN. BMM produced the plane until October 1944 and then changed to the production of spare parts for the Si 204. The Aero company was scheduled to cease production of the D-1 in March 1945 after building 486 planes and then switch to D-3 only. The aircraft, however, was only built until January 1945 with 541 completed. Therefore the total production was 1,216 including the prototypes.
The use of the Si 204D was mainly in B- and C-Schools (advanced schools) and by FÜG 1 (delivery wing of the Luftwaffe), probably as a taxi plane for crews who had delivered other planes to fighting units. The utilization in blind flying schools was sporadic; for radio schools there is no evidence of use. The Si 204A flew mainly with communications squadrons and flying services for senior officers, but also with schools.
In July 1944 five Si 204 were destined to be converted to night combat planes, but no further planes were allotted. They were probably intended for the pre-series Si 204 E-0. There is, however, no evidence that these planes were ever used in combat situations.
Luft Hansa received at least four Si 204: The first prototype, D-AEFR, was evaluated from March to May 1941 by Luft Hansa Prague. From spring 1942 to spring 1943 the second prototype, D-ASGU, was used on regular routes as a freight carrier.
An Si 204 was likely the last German aircraft shot down on the Western Front. At 8 PM on the evening of May 8, 1945, 2nd Lt. K.L. Smith of the 9th Air Force's 474th Fighter Group, flying a P-38 Lightning, downed a Siebel three miles southeast of Rodach, Bavaria.
At the end of the war one Si 204D remained in Berlin-Tempelhof (named “Rhein”). One flew to Enns in Austria, where it was captured by the Allies. Captured Si 204s flew in a variety of roles in the Soviet Union, including with Aeroflot and TsAGI (and Polar aviation, as we see below), but were all quickly phased out of service as local aircraft manufacturing was re-established.
After the war, a production of Si 204 continued in Czechoslovakia and France. In Czechoslovakia Aero Vodochody produced 179 Si 204D, developed into military trainer variants Aero C-3A and C-3B (the later for bombardier training), passenger variant C-103 and military transport variant Aero D-44 until 1949.
Aero C-3A by A.Nilssen Photography, on Flickr
In France SNCAC, commonly known as Aérocentre, produced 240 transport NC.701 Martinets and a number (110?) of passenger NC.702 Martinets. The NC.701 was distinguished by three-blade propellers and was powered by 440 kW (590 hp) Renault 125-00 engines. The NC.702 had a modified nose.
But the most interesting role intended for the Si 204 was that of a flying carrier. In 1937, Doctor Alexander Lippisch assumed the leadership of a design team developing the RLM's Projekt X, which was eventually to become the Me 163 rocket-powered interceptor. Five years later he left the project, just as the first Komet production prototypes were being completed, to lead another research team consisting of students of aircraft construction from Darmstadt and Munich universities.
Working with the help of the DFS on a program intended to lead to the development of a fast interceptor, Lippisch and the students produced a series of revolutionary aircraft, designated with a DM prefix in recognition of the two universities. The DM-1 Experimental Glider prototype of the P-13a Supersonic Fighter was found in an incomplete state at the end of the war by the Americans.
It was originally intended to carry the DM-1 on the back of a Siebel Si 204 to a height of 25,900 ft, from which it would dive to an anticipated speed of 348 mph. At a later stage the DM- 1 was to be flown at a speed of 497 mph under the power of a rocket motor. At the other end of the speed range, the aerodynamic characteristics of this little single-seat aircraft were such that a landing speed of only 44 mph was expected.
It was the end of the war that prevented further development beyond this unpowered DM-1 test glider. The Americans shipped the prototype back to the USA for completion and flight testing, and the resulting data were incorporated into the design of the many US delta-wing aircraft. After the war, Lippisch, working with American aircraft designer Convair, developed and tested the XF-92 based on his designs, leading to the eventual adoption of the F-102 Delta Dagger and its successor, the F-106 Delta Dart. But it's another story...
Sources: Virtual Aircraft Museum, Wikipedia, Fiddlers Green Paper Models
Headline picture: Aero C-3A by A.Nilssen Photography, on Flickr