In US aviation in the 1920s there were just a few people who suspected that the high point of the battleship navies had been the Battle of Jutland, fought May 31-June 1, 1916.

The decline of the battleship was the rise of aircraft. The great guns of the floating fortresses could reach out 25 miles to smite their enemies, but it was clear to a few that soon, aircraft capable of carrying bombs over many times that distance would become a more versatile weapon. Those aircraft would be carried on special ships whose decks were designed to support aircraft operations – aircraft carriers.

US Navy Rear Admiral William Moffett was familiar with the record of existing liquid-cooled aircraft engines. Their power was good, but their reliability was not so good, with half their reported failures involving their cooling systems.

In summer, 1921, Congress established BuAero to manage naval aviation, with Adm. Moffett at its head. Not being an engine specialist he decided to send two men, Cdrs. Eugene Wilson and B.G. Leighton on a tour of US engine and accessory manufacturers.

When they returned they reported to the Admiral that if air-cooled engines were to receive anything like the R&D that liquid-cooled types had already received, they would become highly superior. Their qualities would be low system weight, simplicity, and ease of service. The word was, “It is as sensible to develop an air-cooled submarine as it is to build water-cooled aircraft.”

A very significant development was at the same time occurring. Glenn Curtiss’s boyhood friend Charlie Kirkham had joined him in the development of aircraft and their engines. He saw the low frontal area of a V-12 design with a compact 60-degree cylinder Vee angle for the performance advantage that it was (lots of cylinders, lined up behind a small frontal area, was a low-drag, high-speed machine). There were problems with making sound aluminum castings of such size.

This K12 engine was in 1920-’21 redesigned as the D12 by Arthur Nutt with a better balance between light weight (the K12) and reliability – most notably the adoption of seven main bearings in place of Kirkham’s four. Four bearings saved weight but subjected the crankshaft to excessive bending loads.

When the D12 was highly successful in the European Schneider Cup seaplane races, everyone was impressed by their power and speed. Eventually the Fairey Aircraft Co. imported a number of D12s into Britain and demonstrated their qualities by mounting one in a light bomber.

The result was faster than existing pursuit aircraft.

Eventually Rolls-Royce studied the D12 and produced its own early V12 – the Kestrel. This was soon replaced by the famous R-R ‘Merlin’ which powered Britain’s air defense fighters ‘Hurricane’ and ‘Spitfire,” which (with radar early warning) were so instrumental in winning the 1940 “Battle of Britain”.

Meanwhile, Frederick Rentschler, chairman of Wright Aeronautical Corp., was having trouble with his finance-minded board. Their view was that once an engine was made to run well, it should be produced as cheaply as possible to bring a return to the company. They saw engines as widgets.

Rentschler knew that if they did not push engine development every minute, the performance of their products would fall behind that of their competitors.

The conflict became so intense that Rentschler resigned.

Just at this point, Adm. Moffett let it be known that the Navy would buy no more liquid-cooled aircraft engines. He invited bids on a contract to build 200 air-cooled radial aircraft engines for the navy, to produce a minimum of 350 hp and to weigh no more than 600 lb.

Rentschler knew from one of his lieutenants, engineer George Mead, that there was high probability that such an engine could be built right now. Rentschler’s brother Gordon was an up-and-comer on Wall Street. The 1925 result of this association would be creation of Pratt & Whitney, who continue the manufacture of aircraft engines to this day.

George Mead and others who left Wright with Rentschler had a prototype running on Christmas, 1925 – the 9-cylinder R-1340 Wasp. On first test it gave 405 hp, steadily increasing with forceful R&D.

Yet another development was soon in progress – the cowling and cooling studies of the NACA (National Advisory Committee for Aeronautics, which would in 1957 be re-named NASA). Air-cooled radials have big frontal area (typically 14 square feet, versus 8.5 for a R-R Merlin V12). The goal of this NACA program was to reduce the drag and improve the cooling of large radials. It was remarkably successful, the work running roughly from 1927 to 1937.

When in September of 1941 English pilots first encountered the German FW190 fighter, powered by BMW’s 801 14-cylinder radial, they could not at first believe that a radial-powered aircraft could be so fast. In the Pacific, American fliers soon learned “never turn with a Zero” – its light wing loading of 24 lb/sq. ft. made it extremely dangerous. In a time when many fighters were armed with rifle-caliber guns, the Zero’s twin 20 mm cannon (0,787 inch) were serious firepower.The best way to engage a Zero, it was soon learned, was to make a high-speed firing pass, diving from superior altitude.

All US Navy carrier fighters in WW II were radial powered, including F4F Wildcat, F6F Hellcat and F4U Corsair.

During WW II the US produced 690,480 air-cooled radials and 125, 133 in-line liquid-cooled engines (69,998 Allisons and 55,135 Packard Merlins).

The last word goes on and on in the form of the continuing greater success of liquid-cooled in-line Merlin and Griffon-powered aircraft in the US national Air Races.