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SPAD S.XX (Herbemont) Sud Est Aviation

The two-seater competition aircraft SPAD S.20bis was created after the war for military purposes and was designed shortly before the end of the war by André Herbémont and modeled after the SPAD S.XX. The brawny but fast aircraft which was originally designed as a one-seater fighter was described as a "protected one-seater" because the second crew member and pilot were to be protected by a transversable MG in the rear section of the cockpit. The Blériot-SPAD S.XX (Herbémont) model originated shortly before the end of the war from the military aircraft SPAD S.XVIII which was a larger and stronger version of the successful model SPAD S.XIII.

The prototype of the SPAD flew for the first time on August 7, 1918. After a successful test flight, the Aéronautique Militaire ordered 300 aircrafts per month. Nevertheless, the end of the war interruped the series production. 100 aircrafts were completed. 95 copies were delivered to the French Armed Forces. Three were delivered to Japan and one copy was exported to Bolivia.

It was reported that the S.XX was easily manageable and that the pilot had a clear frontal and rear view.

After the end of the war, Herbémont strengthened his ambitions and used them to continue developments of former military aircrafts. The fast SPAD S.XX served as an initial version for an entire line of civil variations from one-seater racing aircrafts to several-seater passenger airplanes.

In contention with designers from the Nieuport company, some special versions for racing and record purposes were constructed. With the new name SPAD Herbemont S.20 bis, there were finally several variations of a comfortable racing aircraft that broke several altitude and speed records of the time.

In order to achieve higher speeds, air resistance had to be minimized. Initially, the second seat was uncovered, streamlined covers were used for experimentation and the upper wings were altered into a lighter V-shape. Through each new variation the wing span was gradually minimized and the wing form was aerodynamically improved. The aircrafts were powered by 300 PS strong Hispano-Suiza engines.

In 1918, a world speed record was set by a SPAD S.20 carrying passengers at a speed of 230 km/h and in July 1919, a high altitude record of 8,900 m was established. On September 1919, the pilot Sadi Leconte achieved another top speed record of approximately 249 km/h in a SPAD 20bis-1 which he had piloted its initial flight the day before. In October, Leconte achieved this record with a S.20bis-2 with shortened wings during the first post-war air exhibition in France and the competition was the "Prix Henry Deutsch de la Meurthe" with a speed of 248 km/h. Already 5 days later, he surpassed his own record with a speed of approximately 252 km/h while piloting a S.20bis-3 with an even shortened span.

The successful records of the SPAD's survived this time period and remained constant. With various versions of the SPAD S.20bis, both pilots Jean Casale and Bernard de Romanet set three world speed records in 1920 within a very brief time span: on February 28, Casale achieved a record speed of 283.464 km/h on a Prix-German stretch piloting a SPAD S.20bis-4 with a wing span of only 6.60 m. On October 9, de Romanet surpassed this with a speed of 292.682 km/h and exceeded his own record on November 4 with a new world record of 309.012 km/h with a SPAD S.20bis-6 which was powered by a 320 PS strong (235 kW) special model of a Hispano Suiza engine.

The SPAD S.20 was a biplane with a Monocoque fuselage and an 8 cylinder Hispano-Suiza 8 engine which was encased in a special oval hood. The Lumiére wooden air bolts possessed a diameter of 2.40 m. The S.XX aircraft posessed a planked plywood fuselage which was covered with fabric and well lacquered. The wings were made out of wood. The ailerons were situated on the under side and were at right angles to the fuselage. The larger wings were above and at a 7° angle. Both wings were connected by a shaft which braced the fuselage and the undercarriage. The surfaces and empennage were covered with material. The undercarriage was situated directly under the engine cover and was braced between the front and rear stays. The wheels were lined with rubber.

  • Variations:
    • SPAD S.XXbis: a modified S.XX with expanded wings and empennage and unbalanced side rudders. A copy was purchased by Japan.
    • SPAS S.20bis-1, bis-2, bis-3: in order to keep up in racing, the former two-seater was transformed into a one-seater, the wing span was shortened and the wing area was made smaller.
    • SPAD S.20bis-4: further shortening of the wing span to 6.60 m
    • SPAD S.20bis-5: 15 qm reduced wing span area, portions of the baldachin were removed and the upper wings were directly connected to the fuselage
    • SPAD S.20bis-6: Initial flight on October 7, 1920, powered by a Hispano-Suiza 320 PS (235 kW) engine, the upper wings were supported by a shorter baldachin over the fuselage.
    • SPAD S.26: swimmer aircraft with 340-PS strong Hispano-Suiza engine
    • SPAD S.31: ocean aircraft with the fuselage of the S.XX and the wing span area of 31 qm; it was constructed for racing for the Schneider prize in 1929 in Venice, however it did not participate. The further development, the SPAD S.31 was constructed with new floaters by Tellier and was armed with two synchronized MG's. A copy was sold to Japan in 1921.

Technical data

Blériot-SPAD S.XX (Herbémont)

Type two-seater fighter aircraft, later changed to a one-seater
Power plant a Hispano-Suiza in-line engine with 300 PS (221 kW)
Year of construction 1918

Performance

Top speed 229 km/h at an altitude of 3,000 m
217 km/h at an altitude of 4,000 m
High altitude 8,000 m
Operational range 400 km

Weight

Empty weight 867 kg
Max. take-off weight 1,306 kg

Dimensions

Span 9.72 m
Length 7.30 m
Height 2.80 m
Wing span area 30.0 qm
Crew 1-2 persons
Useful load/armament two synchronized, forward-firing 7.7-mm Vickers machine guns and one or two 7.7 mm Lew MG at the rear of the cockpit
Production quantity 100 copies

Technical data

Blériot-SPAD S.XX (Herbémont)

Type competition aircraft
Manufacturer Blériot-SPAD
Power plant a liquid-cooled V-8-Hispano-Suiza 8 eb-engine with 320 PS (235.3 kW)
Year of construction 1920

Performance

Top speed 309 km/h

Weight

Empty weight 890 kg
Max. take-off weight 1,050 kg
Performance when fully fueled 3.3 kg/PS
Surface load 75 kg/qm

Dimensions

Span 6.48
Fuselage length 7.50 m
Surface area 2.80 m
Wing span area 15.2 qm
Crew 1 person




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