[1] The S.40 was a graceful, low-wing cantilever monoplane of conventional design with fixed, tailwheel undercarriage.

The pilot and instructor sat in tandem cockpits, enclosed by sliding canopies.

[2] A single engine driving a two-blade propeller was mounted in the nose.

The main undercarriage units were fully independent, mounted under the wings, and enclosed in spats.

A small number were built for the Belgian military before the German invasion in 1940.