The Gnome Monosoupape 9B2 was a 9-cylinder rotary engine delivering about 100 hp (75 kW). As part of the successful "Monosoupape" (single-valve) family developed by the Société des Moteurs Gnome in France, it offered a simpler valve system, reduced weight, and greater reliability than many earlier rotary designs. These qualities made the 9B2 one of the most widely used Allied engines of the mid-war period.

Aircraft powered by the Gnome Monosoupape 9B2

• Nieuport 11 "Bébé" – the famous French scout of 1916, small and highly maneuverable.
• Nieuport 16 – an improved and strengthened version of the Bébé, fitted with the 9B2.
• Nieuport 17 (early production) – first production batches flew with the 9B2 before upgrading to stronger Le Rhône engines.
• Morane-Saulnier Type N – the streamlined "Bullet" fighter, used by French and British forces.
• Morane-Saulnier Types I and V – developments of the Type N, also powered by the 9B2.
• Airco DH.2 – Britain’s pioneering single-seat pusher fighter, designed around the 100 hp Monosoupape, which helped end the "Fokker Scourge" in 1916.
• Sopwith Pup (early prototypes) – tested with the 9B2 before production standardized on the Clerget 9Z.
• Training and experimental aircraft – the engine was also fitted to various prototypes and trainers between 1915 and 1917.

Historical significance

The 9B2 represented a critical step in rotary engine development. With more power than the early 80 hp units, it enabled aircraft like the Nieuport 11 and Airco DH.2 to restore Allied air superiority during 1916. Although later surpassed by heavier 130–160 hp engines such as the Le Rhône 9J and Clerget 9B, the 9B2 powered many of the fighters that defined the middle years of the First World War.{{freeshipping_code_1}}{{payment}}