Cirrus aero engines

The Cirrus and Hermes or Cirrus-Hermes are a series of British aero engines manufactured, under various changes of ownership, from the 1920s until the 1950s.

The engines were all air-cooled, four-cylinder inline types, with earlier ones upright and later designs inverted.

[2] The uprated Cirrus II, with slightly greater displacement, delivered 75 horsepower (56 kW) from 1926.

The Cirrus III was introduced in 1928 with even greater displacement and power of 85 horsepower (63 kW).

[6][7][8] Having developed the American Cirrus III engine at New Jersey, the company moved to Marysville, Michigan, where it set up production.

[10][11][12] The Hi-Drive was supplied in direct and geared drive options, and was designed to accept a de Palma supercharger for increased performance.

was taken over by Menasco, who developed the inverted engine as the Pirate, sold from 1936, and a six-cylinder derivative as the Buccaneer.

The resulting high propeller line allowed the top of the engine to be lowered, which significantly improved the pilot's view in a single-engined type.

[21][22] The Blackburn Cirrus Midget was a smaller version developed in 1938 but it failed to enter production.

In 1948 it introduced the Blackburn Cirrus Bombardier with fuel injection and a higher compression ratio, giving increased output.