S 1 - FMV S 21/CFM S 25 (1926-1932)

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Helicopter Sweden

In 1921, the Army Aviation Company’s Workshops (FMV) at Malmen/Malmslätt near Linköping got an  preliminary order of ten reconnaissance aircraft of Henry Kjellson’s design. The aircraft got the designation S 21 (S = ”Spaning” = ”Reconnaissance” - 21 = 1921, the year of the design). The aircraft had a crew of two - pilot and observer. In these days, aircraft engines was an article in short supply in Sweden. When 22 airship (!) engines type Maybach IVA (260 hp) eventually were obtained from Germany, Kjellson, the chief engineer of FMV, had to design an airframe which suited this engine.  

The first S 21 was delivered in 1922. During the trials, several shortcomings were discovered. After some amendments, the other nine airframes were built in 1923-1924. Notwithstanding a long tail, the aircraft was nose-heavy. In the end of 1924, three of the ten aircraft were written off due to crashes. When the Air Force was established in July,1926, the six remaining S 21s were taken over under the new designation S 1.   

In 1924, FMV still had 25 Maybach-engines at its disposal. Therefore, a new batch of ten airframes was ordered by the Army Aviation Company. But as some modifications compared to the original design was made, the new aircraft was named S 25. The main alterations were a larger tailplane and a larger fin and side rudder. As the delivery took in the end of 1926 and in 1927, the new ten aircraft were delivered to the Swedish Air Force. The S 25s also got the designation S 1. Aircraft on floats were designated S 1HThe workshops at Malmen had been incorporated in the organization of the new fighting service. The name was changed to "Centrala Flygverkstaden i Malmslätt" (CFM).

In 1925, S 21 #4214 had been based at Boden in the north of Sweden for ambulance transports from remote areas. S 25 #45 got a canopy over the aft cockpit, which was used as room for a stretcher, and became spare ambulance for the Junkers F13 which was stationed at Boden in 1928. Finally, S 25 # 6220 got a heated stretcher space with a high canopy provided with windows (”the Flying Allotment Cottage”). The exhaust pipe was lengthened past the stretcher space. This aircraft was used as a flying ambulace at F 4 at Östersund 1927-1932.    

In spite of its shortcomings, S 1 made a good service as a reconnaissance aircraft until the beginning of the thirties, when it was replaced by the Fokker S 6 with its much more powerful engine.

The ordinary S 1s were armed with one fixed and one moveable 8 mm machine-gun m/22. 


Top - S 1 CVM S 25, probably # 3228, at Malmen.

Below - S 1 CVM S 25 # 3228 at Malmen, built in the same place 1927.

S 1 with wheel gear: Length: 8,6 m. Span: 15,1 m. MTOW: 1.815 kg. Max. speed: 168 km/h.


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© Lars Henriksson

Updated 2010-07-17