The Kestrel engine was also sold to international air force customers; in this role it was used to power prototypes of the German Messerschmitt Bf 109 and the Junkers Ju 87 "Stuka" dive-bomber, as the Junkers Jumo 210 engines were not ready to be fitted.

The CR was powered by the recently introduced Curtiss D-12 engine, which replaced the individual cylinders with a cast aluminum block.

[4][5] Rowledge built a team to introduce a new engine using the cast block, but set the goal to surpass the D-12.

Previously, supercharging (and turbocharging) was primarily used for high-altitude designs to offset the loss of ambient air pressure as the aircraft climbed, and thereby maintain power.

The I-B variant saw widespread use in the Hawker Hart family of aircraft, a mainstay of British air power during the early 1930s.

The mark-XVI engine used in the Miles Master M.9 prototype delivered 745hp (500kW), and the XXX variant of 1940 saw service at 720hp (537kW).

The amount of heat rejected by an air-to-air cooling system is a function of the maximum coolant temperature and volume, so the resulting decrease in cooling capacity became a limiting factor for aero engine power in this period, as the coolant has to be kept below boiling point.

[9] During 1927, once the prototype of the Kestrel was complete, a need for a larger and more powerful engine was conceived for use in flying boats, and development began on an engine which utilised a 6" cylinder bore, compared to the Kestrel's 5", this became the Rolls-Royce Buzzard.

A handful of Rolls-Royce Kestrel engines remain airworthy as of March 2024, powering original or restored Hawker biplane types: Preserved examples of the Rolls-Royce Kestrel engine are on public display at the: Data from Lumsden[24] Related development