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

SODERTELGE SW 15 Sweden

   Designed by V Forssman and owing much to the Siemens-Schuckert D Ia - the drawings of which had been supplied by the German company to Baron Carl Cederstrom, the first Swedish aviator and manager of the Sodertelge Verkstader - the SW 15 was built in 1917. A single-seat fighting scout powered by a Vabis-built Benz Bz II six-cylinder water-cooled engine rated at 110 hp, the SW 15 was primarily of wooden construction with steel-tube wing spars and fabric skinning. An unequal-span single-bay staggered biplane, the prototype crashed on 17 June 1917, ground looping and killing its pilot, Bertil de Mare. The SW 15 was repaired and fitted with two 8-mm Schwarzlose m/14 machine guns with synchronization gear developed by Capt G von Porat and Ing Kolthoff. As a result of further flight testing, two more SW 15s were built for Flygvasendet, but these enjoyed strictly limited success, one flying 19 times and the other four times, both being finally grounded in December 1921.

Max speed, 78 mph (125 km/h) at sea level.
Span, 27 ft 1 1/4 in (8,26 m).
Length, 19 ft 4 1/4 in (5,90 m).
Height, 8 ft 2 1/3 in (2,50 m).

J.Forsgren Swedish Military Aircraft 1911-1926 (A Centennial Perspective on Great War Airplanes 68)

Sodertelge Verkstader SW15

  Better known as the Lottery Pursuit, and unofficially known as the Po-fighter (Po after Gosta von Porat), the Sodertelge Verkstader SW 15 was clearly inspired by contemporary German fighters. Drawings and technical information for a single-seat fighter were supplied to SW’s managing director Carl Cederstrom, apparently via Villehad Forssman, who at the time was working for Siemens-Schuckert.
  However, in 1916, Cederstrom was replaced by army pilot Gosta von Porat, with the designer Henry Kjellson soon joining the company. Kjellson and von Porat began preparing the drawings of a fighter aircraft. By mid-1916, a small, neat-looking biplane fighter, designated as the SW 15, was rolled out. The fuselage consisted of a welded steel-tube frame. The front fuselage was covered in aluminium sheet metal, while the rear fuselage was fabric covered. The fabric-covered wings were built entirely of wood. The SW 15 was powered by a 100 h.p. Vabis six-cylinder inline engine (the Mercedes D 1 built under licence by Vabis).
  Some Swedish sources state that the SW 15 was inspired by the Siemens-Schuckert D.Ia. Although the SW 15 was similar in configuration to the German fighter, confirmation of the Siemens-Schuckert D.Ia connection is lacking.
  The completed airplane was put on display in March 1917 at an exhibition organized by the Svenska Aeronautiska Sallskapet (Swedish Aeronautical Society, SAS). Interestingly, the as yet unflown SW 15 was the first prize in an SAS lottery! As a result, the SW 15 was nicknamed Lotterijagaren (The Lottery Pursuit)
  Following its maiden flight on June 17, 1917, the SW 15 prototype overturned on landing, with the pilot, Bertil de Mare, being killed. The aircraft had suffered little damage, and was quickly repaired. Gosta von Porat, who had replaced Carl Cederstrom as company executive, referred to the SW 15 as ‘The Beast’: “It had incredibly staggered (offset) wings, lacking a stabilizer (as well as a fin). The wheels were also undoubtedly located too far back, so that the airplane easily turned turtle. It would of course have been possible to make a “three-point landing”, ie with a low tail, without risks, but the test pilot, lieutenant Bertil de Mare, one of Flygkompaniet’s best, did what was usual at the time, namely a “wheel landing, with the tail section high up in the air, overturning and breaking his neck.
  Despite changes, nothing good ever came of the type.” Even though the SW 15 had claimed de Mare’s life, it had suffered very little damage, apart from a broken left wingstrut, returning to the air in September 1917. Modifications included fitting a fin and an enlarged rudder. The SW 15 was subsequently delivered to Flygkompaniet as serial number 825.
  A Schwarzlose m/14 machine gun was fitted, and ground firing trials initiated, using a synchronization mechanism developed by von Porat and Captain Kolthoff. However, during each trial, the synchronization mechanism failed, which resulted in the destruction of the propeller. For obvious reasons, no air firing trials were attempted.
  In March 1918, two further SW 15’s were, apparently with some reluctance, taken on charge by the AFK. Issued with the serial numbers 827 and 829 respectively, the SW 15’s were flown exclusively by Nils Rodehn. Between March 1918 and January 1919, serial number 827 was flown 19 times, and 829 on only four occasions. Rodehn did not particularly enjoy flying the SW 15’s, referring to them as “crocodiles”. In early 1919, the SW 15’s were consigned to storage, being accounted for as “In museum”. On December 5, 1921, the SW 15’s were officially struck off charge, having not flown for nearly three years.

Sodertelge Verkstader SW 15 Technical Data and Performance Characteristics
   Engine: 1 x 100 h.p. Vabis (licence-built Mercedes D.I)
   Wingspan: 8,26 m
   Length: 5,90 m
   Height: 2,50 m
   Empty weight: 500 kg
   Max take-off weight: 640 kg
   Maximum Speed: 125 km/h
   Armament: 2 x Schwarzlose machine guns