SNCASE SE 100, a prototype heavy fighter

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NOTE : This suggestion was passed for consideration in the previous forum. As I believe it is now fair game to post that kind of stuff again, here was my contribution at the time for this aircraft.




The SNCASE SE 100 could provide a welcome addition in the French heavy fighter line. Benefitting from a unique armament, powerful engines and, if Gaijin’s willing, a couple bomb racks, it could make for a logical evolution from the Potez/Breguet line.


France launched, in 1934, a program for a 3 seats escort fighter called “Commandement à la chasse” (Command Fighter). The competition that followed this program gave birth to the Potez 63 serie of fighters and the Breguet 690, which disappointed the French military. They were used in different roles, recon for the Potez 63, light bombing for the breguet 693. This brought the chief commander of the French air force to launch a new program, in 1936, to study heavier planes, more powerful, better armed, for a new category of heavy fighters called C3 (3 seats fighters) to replace the Potez 630 and 631 which went into production as nothing else was available. The company Lioré et Olivier decided to make the most unconventional, experimental and original fighter possible, to beat all competitions thanks to futuristic ideas. The Leo 50 was born.


Lioré & Olivier LEO 50 (project only, became the SE 100)



The first demonstrator, the Leo 48, was designed early 1937. The main objective of the design : to create a brand new aerodynamic frame that would reduce to the maximum the efforts the plane would have to face once in the air. The demonstrator had a very short career, as it ultimately crashed during the 3rd flight at the end of the runway (small crash, nothing serious). From this concept plane was born the LEO 50. A 7 tons escort fighter, the idea was to make a day fighter which would have 2 MAC mgs in the nose and 2 MAC mgs for the gunner in the back. The night fighter version would have 2 HS404 in the nose, and 1 HS 404 for the gunner. The main reservoir could have possibly been replaced by a bomb bay. To reduce the weight of the landing gears, he had the idea of using a tricycle configuration. The LEO 50 was still on the drawing board when Lioré & Olivier was nationalised.

SNCASE SE 100 (only prototype built and tested)





The LEO 50 was unfit for the new C3 program when the SNCASE took control, so its designer, Mercier integrated the modification asked by the new C3 program : a 1200 km autonomy, 3 hours endurance with 90% max speed, and said max speed at 500km/h minimum. The fuselage became a little larger, the engines were switched to GR 14N : This new configuration was called SNCASE SE 100, and it was the first prototype built and tested. The construction of the SE 100 started in april 1938, and was delayed several times due to the non stop modifications of the program that forced the constructor to modify the prototype. In the end, it was finished on February 10th, 1939.

Its first flight was on March 29th, 1939. The take-off speed was 130 km/h, the landing was done at 125 km/h. Until the 9th of May, several other test flight were made to test the longitudinal stability of the plane, which was an issue. Several modifications and corrections later, a fly test on May 9th, 1939 showed it could fly well with only 1 engine working, and that the brakes worked perfectly. That same day, it reached 4000m in 8’20" , at a mass of 6900 kg. It reached 6000m at 13’40" , and reached a speed of 547 km/h.

Mass production of the aircraft was decided in autumn 1938, and was the reason for a lot of modifications, mainly in the armament configuration, during the year that followed. Many other variants of the plane were predicted, but none of them made it past the concept stage. As the plane was being moved in Southern France, WW2 started. The plane was then painted with a military camo on december 31st, its fuselage was switched with the one from the 2nd prototype, and several more tests were performed. The last batch of tests were on March 26th, 1940. The plane weighted 7400 tons, including 60 kg of lest in the gunner seat. It reached 580 km/h instead of the 600 km/h that the pilots had hoped for, and its service ceiling was 9000m. The overall performances were encouraging, although slightly disappointing.

On April 5th, 1940, after over a 100h of test flight, tragedy struck. The prototype crashed during a morning test flight, killing both the pilot and the engineer. The plane had been distabilized by the vibration of the propeller blades (it was also possible that the landing gear deployed by mistake, although it was never confirmed ) and fell in a low altitude spin from which it couldn’t recover. 2 months later, the Armistice came to be, and the second prototype, never finished, was definitely abandonned.


construction : prototype ordered in 1937, 1st flight on 3/29/1939, destroyed on 4/5/1940

Category : C3/C2/CN2

engines : GR 14N48/49 (1/20/1940)

wingspan : 15,70m

length : 11,75m

height : 3,80m (on the ground)

Wing area : 31 m2, 34,4m2 including the wings in the fuselage

Weight : 7400 kg (3/1940)

Armament front : 2 x HS 404 (90 rounds each) 5 x MAC 1934 M39 (500 rounds each)

Armament gunner : 1 x HS 404 on a AB170bis turret (120 rounds) or 1 x HS9 (90 rounds) or 3 x MAC (500 rounds each), later 5 x MAC machineguns ( 2 in the belly)

Internal : 1 x 500L fuel + 2 x 500 L fuel (fuselage) + 2 x 180 L fuel (engine pods)

External : 2 x gardy bomb racks with 4 x 50kg bombs each (project only)

Max speed : 560/580 km/h @ 6000 meters.

Climbing speed : 4000m in 8’20", 6000m in 13’40" (4/1939), 8000m in 15 minutes (3/1940)

Service ceiling : around 9000m (without weapons)

SNCASE SE 101 (later renamed SE 100-02, second unfinished prototype)

This second prototype was started at the same time as the first, but due to delays and constant changes in the demands of the French air force, it was never finished. It served as a test bench for various weapon configuration, and, ultimately, its fuselage was used to modify the original SE 100. This is the prototype which, in fact gave birth to the ludicrous weapon configuration mentioned above, as it was created with the intent to fit the best firepower possible, which would be six HS 404 in the nose, 2 in the turret, and 1 in the belly of the plane. Needless to say, this ideal loadout was completely unrealistic. It was 50% finished when the Armistice was declared.

SNCASE SE 103/105 (mass-production, projects only)

Evolutions of the prototype as per requested by the STAé for the Mass production versions. Hesitant and unsure of the pursuit of the prototype, only the the SE 105 gave birth to a project of prototype, which was laid down in August 1940 before being shut down.





The last and most relevant weapon configuration available for the prototype SNCASE SE 100 was the one ordered by the STAé on January 24, 1940. The author explains : “It was to receive 5 MAC machinguns in the front (one being in the nose) one below each HS 404 canon and two more further back on the upper front part of the fuselage (…).” This would mean a configuration as follow :


RED are the machinguns

BLUE are the HS 404 canons

The plane was also meant to be able to carry Gardy rack to fit 2 x 4 50kg bombs, as well as 2 x MAC machinguns in the belly, but it wasn’t specified how. the rear HS 404 could be replaced by 3 MAC 34 machineguns.

Photo of the gunner turret armed with a 20mm



Visibility of the gunner from the tail :



Front landing gear :




tail landing gear



Fuselage :




Engines :



Interior :




RICCO Philippe, DOCUMENT’AIR N°4, “SNCASE SE 100 Chasseur lourd polyvalent”, Avia Editions, 2006

Sources mentioned in the book :

Musée de l’air et de l’espace

Service Historique de l’Armée de l’Air

Archives Nationales

Institut National de la Propriété Industrielle



Centre d’Archives de l’Armement

Lioré & Olivier association “Les Mohicans”

As well as various other individuals.


Looks like a lot of fun! Though if it was already passed, you didn’t need to suggest it again. Nevertheless, +1!

As far as I know, even the suggestions passed for consideration are fair game now. They’re leaving behind everything that was on the previous forum.



A must have and very original plane for France.

1 Like

A highly unorthodox and less-than-sexy aircraft, but one with massive strike fighter potential. Incorporate the prototype and planned production versions as a subsection.

I would hope for the 6x20mm version, but such a different plane and quite cool.

As explained in the suggestion, the 6x20mm loadout never really existed. It was a test bed to see how much firepower the fuselage could handle, but it never was a realistic configuration for the aircraft (which was already quite heavy).