09/30/2011. Remarks by Johan Visschedijk: "With the issue of an official specification for a twin-engined fighter to replace the Potez 631, Pierre Mercier and Jacques Lecarme of the Société Nationale de Constructions Aéronautiques de Sud-Est (SNCASE) projected an unconventional three-seat aircraft carrying an armament of three 0.787 in (20 mm) cannon, powered by two 800 hp Gnome & Rhône 14 Super-Mars radials and designated LeO 50 (the Liore-et-Olivier works being a part of the SNCASE).

It was soon obvious that the LeO 50 would be underpowered and would not meet the specification's performance requirements. The basic design was, therefore, scaled-up, 1,030 hp Gnome & Rhône 14N fourteen-cylinder air-cooled radial engines were incorporated and, redesignated S.E. 100, prototype construction commenced in April 1938 at La Courneuve, near Paris.

The wing was of wooden construction and comprised a one-piece torsion box of spruce to which the leading and trailing edges were attached with steel strips. The torsion box housed fuel tanks between the fuselage and engine nacelles, and in order to provide the maximum flap area, the ailerons articulated obliquely at the extreme tips of the wings. The Mercier engine cowlings were similar to those of the LeO 451 bomber, and the fuselage was a welded steel-tube structure with duralumin skinning.

Outrigger landing gear under construction (Kees Kort Collection)

The landing gear was unusual in that it comprised a single large nose wheel with small outrigger wheels retracting into the vertical tail surfaces. The nose wheel was steerable and was claimed to be the first of its type to be tested. The outrigger or auxiliary wheels were taken from a Dewoitine D.500 fighter.

The S.E.100-01 longe-range escort and attack fighter was flown for the first time from Villacoublay on March 29, 1939. During the ensuing tests a small retractable ventral fin was added and, in February 1940, the aircraft was ferried from Villacoublay to Marignane in 1 hr 17 min.

At Marignane, as a result of various refinements, including improved wing root fairings and new airscrew spinners, the maximum speed was increased from 348 to 360 mph (560 to 579 kmh), and the prototype performed extremely well until, in April 1940, the S.E.100-01 crashed when the pitch of one airscrew was reversed inadvertently at low altitude.

In the meantime, a second prototype had been built at La Courneuve, this differing from its predecessor in some respects. The forward-firing armament was increased from two to three 0.787 in (20 mm) cannon, and rear-firing armament was boosted from one 0.787 in (20 mm) cannon on a SAMM electro-pneumatic mount in the observer's cockpit to two 0.787 in (20 mm) cannon in a dorsal turret and one 0.787 in (20 mm) cannon on a ventral mount.

The communications tunnel between the cockpits was removed in order to increase fuselage fuel capacity, and the lower fuselage tank was made removable so that bomb racks could be installed in its place. The German occupation of Paris prevented the S.E.100-02 being flown at Villacoublay and no further examples were build."