05/21/2003. Remarks by Johan Visschedijk: "This two-seater biplane was designed to provide both an initial and acrobatic training. The fuselage was of welded steel tubes covered partly by sheet metal and partly by fabric. The wings had a covering of bakelite-plywood and fabric. Both radial or in-line power plants could be used. A number were built by the firm of Kromhout.

Span: 31 ft 4 in (9.55 m)
Length: 25 ft 1 in (7.65 m)
Height: 9 ft 6 in (2.90 m)
Weights: empty 1,529 lb (694 kg), gross 2,145 lb (973 kg)
Maximum speed: 115 mph (185 kmh)

From 1938 to 1940 the RNethAAF used 20 S.IX with an 165 hp Armstrong Siddeley Genet Major radial engine. Between May 10 and 15, 1940 some were flown to France, before the surrender of the Dutch forces, to escape capture by the German invaders. The Dutch Navy purchased 15 S.IX with an 168 hp Menasco Buccaneer in-line engine. These were all destroyed at the navy-camp De Kooy."