Gnome 9N Monosoupape

One of the most famous Gnome engines was the 9N Monosoupape (single-valve). Having no intake valve, its fuel mixture entered the cylinders through holes cut in the cylinder walls. The 9N was introduced around 1917.
The concept of the rotary engine was that (unlike the radial engine) the propeller was bolted firmly to the engine which rotated as a unit around a stationary crankshaft. The torque generated tended to make aircraft powered by rotary engines tricky to fly.


  • 9N: 160 hp (119 kW)


  • 9-cylinder rotary piston engine
  • Air-cooled
  • Displacement: 970 cubic inches (15.9 litres)

used by

  • Nieuport 28