# FVM J 23

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The **FVM J 23** was a [Swedish](/source/Sweden) single seat, single engine, [parasol wing](/source/Parasol_wing) [fighter aircraft](/source/Fighter_aircraft) built in the mid-1920s. Five were flown but the type never reached operational status because of structural concerns raised by a fatal accident.

## Design and development

The parasol wing of the J 23 had a thick [airfoil](/source/Airfoil) section, a straight [leading edge](/source/Leading_edge) and a [trailing edge](/source/Trailing_edge) which curved forwards to elliptical tips. In the central region the wing became thinner and the [chord](/source/Chord_(aircraft)) decreased in front of the cockpit.[1][2] It was of wooden, two [spar](/source/Spar_(aviation)) construction[3] and [plywood](/source/Plywood) covered apart from the [ailerons](/source/Aileron).[4] These were angled, [fabric covered](/source/Aircraft_fabric_covering) and small but slotted to improve their efficiency. Parallel pairs of airfoil section [flying struts](/source/Strut) ran on each side from the lower [fuselage](/source/Fuselage) to the wing spars at about one third span. Over the fuselage a pair of N-form [cabane struts](/source/Cabane_strut) leaned inwards to meet at the wing's centre.[2]

Like the wing, the fuselage and empennage of the J 23 were wooden structures. The elliptical cross section fuselage consisted of pre-shaped, stress bearing plywood panels around a light framework of [frames](/source/Frame_(aircraft)) and [stringers](/source/Stringer_(aircraft)).[2][4] The pilot's open [cockpit](/source/Cockpit) was just aft of the trailing edge, from where he could see both over the wing and through the narrow gap between wing and fuselage. The six cylinder [BMW IIIa](/source/BMW_IIIa) engine had a fixed pair of [machine gun](/source/Machine_gun) over it in the forward fuselage and its honeycomb [radiator](/source/Radiator_(engine_cooling)) was in the nose, with the [propeller shaft](/source/Propeller_shaft) set low.[1] This was a high [compression](/source/Compression_ratio) engine which could only develop full power at altitude, enabling the J 23 to fly high and fast.[2][5] Its top speed was claimed to be 220 km/h (137 mph) at 1,000 m (3,280 ft) but 250 km/h (155 mph) at 3,000 m (9,840 ft).[2] The 8 mm (0.3 in) m/22 were [synchronized](/source/Synchronization_gear), firing through the [propeller](/source/Propeller_(aircraft)).[4] At the rear the ply covered [fin](/source/Fin) was surprisingly[2] small and low, though the fabric covered [rudder](/source/Rudder) extended down to the keel. The rudder carried a [trim tab](/source/Trim_tab).[2][4] The J 23's [cantilever](/source/Cantilever), low [aspect ratio](/source/Aspect_ratio_(wing)), D-shaped, ply covered [tailplane](/source/Tailplane) was mounted on top of the fuselage, carrying [balanced](/source/Balanced_rudder) [elevators](/source/Elevator_(aircraft)) with cut outs for rudder movement.[1]

Its [fixed undercarriage](/source/Landing_gear) had mainwheels on a rigid axle, rubber sprung from the crosspiece between two tall V-form legs mounted on the fuselage at the same points as the interplane struts. [1][4] The axle and crosspiece were enclosed within an airfoil section [fairing](/source/Fairing_(aircraft)), which provided some additional lift.[4]

The J 23 first flew in June 1923 and was tail heavy, a fault rectified by an increase in length[4] (several sources, e.g.[1] put the length at about 6.90 m (22 ft 8 in) but L'Aérophile, a year after the first flight,[3] gives 8.50 m (27 ft 11 in)). By July five examples had been built and all appeared at the Gothenburg International Aero Show[1] late in that month.[2] On 10 August 1923 one set a Swedish altitude record of 8,000 m (26,247 ft).[3] Military testing proceeded until 15 March 1924, when there was a fatal, structural wing failure on one J 23. Though work on the aircraft continued and some modifications like an increase in tail area were made, the J 23 was thereafter seen as too fragile for service use.[1]

Work had also been proceeding on the **J 24**, similar to the J 23 but with a much more powerful 224 kW (300 hp) [Hispano-Suiza 8F](/source/Hispano-Suiza_8F) [V-8 engine](/source/V-8_engine). Following the J 23 accident, the sole J 24 was converted into a [single bay biplane](/source/Biplane#Bays) designated the **J 24B**. It was flown in 1925 but, overweight, its performance was not good enough to interest the military.[1]

## Variants

Data from Green and Swanborough p. 235[1]

**J 23**- Five BMW powered aircraft, first modified then scrapped after the March 1924 accident.
**J 24**- Similar to the J 23 but with a more powerful, 224 kW (300 hp) [Hispano-Suiza 8F](/source/Hispano-Suiza_8F) [V-8](/source/V-8_engine). One only.
**J 24B**- The J .24 rebuilt after the March 1924 J 23 accident as a biplane. One only, flown in 1925.

## References

1. Green, William & Swanborough, Gordon (1994). *The Complete Book of Fighters*. Godalming, UK: Salamander Books. p. 235. ISBN 1-85833-777-1.

1. ["The Gothenburg International Aero Exhibition - The Swedish Exhibit"](http://www.flightglobal.com/pdfarchive/view/1923/1923%20-%200450.html). *[Flight](/source/Flight_International)*. Vol. XV, no. 31. 9 September 1923. pp. 448–450.

1. ["Autre Pays"](http://gallica.bnf.fr/ark:/12148/bpt6k6554816n/f106). *L'Aérophile*. Vol. 1924, no. 5-6. 1–15 March 1924. pp. 99–100.

1. ["FVM J 23"](https://translate.google.com/translate?hl=en&sl=de&u=http://www.fliegerweb.com/geschichte/flugzeuge/lexikon.php%3Fshow%3Dlexikon-603&prev=/search%3Fq%3DFVM%2BJ23%26client%3Dfirefox-a%26hs%3D3mJ%26rls%3Dorg.mozilla:en-GB:official%26channel%3Dsb). Retrieved 2 September 2014.

1. Gunston, Bill (1989). *World Encyclopaedia of Aero Engines*. 2 ed. Wellingborough: Patrick Stephens Ltd. p. 25. ISBN 1-85260-163-9.

## Bibliography

- Cortet, Pierre (November 1997). "Rétros du Mois" [Retros of the Month] (in French). *Avions: Toute l'aéronautique et son histoire*. '***(56): 5. [ISSN 1243-8650](https://www.worldcat.org/issn/1243-8650)***
- Forsgren, Jan (July 2020). "Swewden's Parasol Fighters: The FVM J 23 & J 24/J 24B". *The Aviation Historian*. '***(32): 114–118. [ISSN 2051-1930](https://www.worldcat.org/issn/2051-1930)***

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Adapted from the Wikipedia article [FVM J 23](https://en.wikipedia.org/wiki/FVM_J_23) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/FVM_J_23?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.