Rolls-Royce and Its Aircraft Engines

By T.A. Heppenheimer, U.S. Centennial of Flight Commission

There were two men in England, one rich and one poor. The rich man, Charles Stuart Rolls, was the son of the wealthy Lord Llangattock. He sold imported cars to well-heeled friends in London early in the 20th century.

The poor man, Frederick Henry Royce, had started his career by selling newspapers at age 10. He pieced together the elements of a technical education and set up a factory in Manchester that built dynamos and heavy electrical equipment. In 1904 he built a 10-horsepower (7.5-kilowatt) automobile, which ran well.

A mutual acquaintance brought the two men together, and Rolls agreed to sell cars manufactured by Royce. This launched the firm of Rolls-Royce. A Rolls-Royce company director, Claude Johnson, urged them to build a top-of-the-line car that would set a standard for quality. The automobile that resulted, the Silver Ghost, entered production in 1906. Long and elegant in appearance, it made Rolls-Royce famous.

When World War I broke out in 1914, officials of the Admiralty and the War Office asked Rolls-Royce to build aircraft engines. The company had experience only with motorcars but responded with a 12-cylinder aero engine, the Eagle. Tested initially at 225 horsepower (168 kilowatts) in March 1915, its later versions produced as much as 360 horsepower (268 kilowatts). It powered important twin-engine bombers including the Handley Page 0/400 that later became a successful airliner and the Vickers Vimy that, in 1919, became the first airplane to fly across the Atlantic Ocean.

Rolls-Royce also built smaller engines. These included the 240-horsepower (179-kilowatt) Falcon for fighter aircraft, one of which was the successful Bristol Fighter. A six-cylinder motor, the Hawk, powered blimps and could run continually for days. At the war's end the company was reaching for particularly high power. The Condor engine, which became available early in 1919, delivered up to 675 horsepower (503 kilowatts).

Rolls-Royce supplied more than 60 percent of all the British-built aircraft engines used in the First World War. However, peace brought a marked falloff in demand for such motors, and company leaders turned again to their motorcars. This did not last long. During the mid-1920s, the planebuilder Sir Richard Fairey spurred Rolls-Royce to make a renewed commitment to aero engines.

Fairey crafted a fine light bomber called the Fox. He powered it with the Curtiss D-12—an American engine. This did not suit the Air Ministry, so it sent a D-12 over to Rolls-Royce and invited the company to learn from its design. This led to a new line of engines: the Kestrel series, with versions that gave from 550 to 745 horsepower (410 to 556 kilowatts). The Kestrels reestablished Rolls-Royce in aviation.

The Schneider Cup seaplane races soon gave engine manufacturers an opportunity to build aero motors of particularly high horsepower although they only had to hold together long enough to win. Britain won the 1927 race with an aircraft that traveled at 281 miles per hour (452 kilometers per hour). Rolls-Royce then developed versions of a new motor—the R engine—that won the Schneider Trophy in both 1929 and 1931. These engines used high-performance fuels along with superchargers, which pumped additional air into the cylinders to burn more fuel. The 1931 version introduced cooled engine valves that kept fuel in the cylinders from igniting prematurely. The Rolls-Royce R engine and the Supermarine S6B plane, designed by R.J. Mitchell who would go on to design the famous Spitfire of World War II, set a 1931 world speed record of 407 miles per hour (655 miles per hour). The engine also produced 2,783 horsepower (2,075 kilowatts) on a test stand. (Engineers mount engines on a test stand in a laboratory to measure its power when it is not installed in a vehicle. A dynamometer is used to measure the amount of horsepower the engine produces.)

L-1011 RB-211 Engines A smoky start to the Rolls Royce RB-211 engines on 4R-ULB - an Sri Lankan Airlines (Air Lanka) TriStar - seen in Switzerland in 1998. Image courtesy of AirNikon. Find more of his photos at Airliners.net

The R engine pointed a clear path to the future. But it had a very short operating life and relied on costly and highly specialized fuels. Rolls-Royce now faced the challenge of building engines of similar power that could achieve long life while burning conventional aviation gasoline. The company met this challenge with its great wartime series: the Merlin, which entered development in 1933.

An early version, the Merlin 46, produced 720 horsepower (537 kilowatts) in a plane flying at an altitude of 30,000 feet (9,144 meters). An advanced supercharger boosted this power to 1,020 horsepower (761 kilowatts) by more strongly compressing the incoming air. Compressed air is hot and it prematurely ignited the fuel in the cylinders of these Merlins that were built for higher performance. Hence, an air cooler was installed. This cooler, together with the use of fuel injection, yielded 1,420 horsepower (1,059 kilowatts). High-octane gasolines, imported from the United States, raised the output even more to 2,050 horsepower (1,529 kilowatts). In this manner, the basic Merlin nearly tripled its rated power.

Merlins helped the Allies win World War II. They powered Spitfire and Hurricane fighters that won the Battle of Britain, saving that country from Nazi invasion. Fitted with Merlins, the four-engine Lancaster bomber carried an 11-ton bomb. Fleets of Lancasters, carrying high explosive and incendiary bombs, burned the city of Hamburg to the ground in July 1943. America's P-51 fighters, powered by Merlins that were built in the United States by Packard, won air superiority above German cities. When the senior Nazi leader Hermann Goering saw that the bombers attacking Berlin were escorted by these fighters, he told his staff, "The war is over."

Rolls-Royce built some 160,000 of these engines, in 52 versions. Yet, as its engineers sought continuing improvements, the firm's management turned to the next step—the jet. Frank Whittle, a British inventor, had built some of the first jet engines before the war. A jet engine required a compressor to feed it with a flow of compressed air, and Rolls-Royce's experience with superchargers was highly pertinent. Beginning early in 1942, the company drew on Whittle's work and began to develop a succession of engines named for English rivers: the Welland and the Derwent. In March 1944, the firm began work on the Nene, which went on to develop 5,000 pounds (22,241 newtons) of thrust.

Germany was also building jets and led in this field. The best Nazi jet fighter, the Messerschmitt Me 262, topped 520 miles per hour (837 kilometers per hour). Its British rival, the Gloster Meteor, initially lacked thrust and achieved only 460 miles per hour (740 kilometers per hour). But in November 1945, fitted with two Derwent 5 engines, a Meteor set a world speed record flying at 606 miles per hour (975 kilometers per hour).

Rolls-Royce jet engines proved to be good enough to win sales in the demanding market of the United States. Late in 1946, officials of the U.S. Navy selected the new Nene for a carrier-based jet fighter, the Grumman Panther. In Connecticut, the firm of Pratt & Whitney proceeded to build it under license. Later versions of the Panther flew with the Rolls-Royce Tay, a Nene follow-on.

Germany's wartime jet engines had used a simple internal layout that made them slender, reducing the drag. Rolls-Royce adopted this design for its Avon and Conway series, in 1953. The Avon powered the Hawker Hunter, an important fighter of the 1950s. Twin Avons gave thrust to the English Electric Canberra bomber, built in the United States as the Martin B-57. Avons also found use in an early jet airliner, France's Caravelle.

The Conway introduced the "bypass" principle. It featured a large fan toward the front of the engine that resembled a propeller. This produced greater thrust and improved fuel economy. Conways powered the four-engine Vickers VC-10 jetliner, along with some Boeing 707s and Douglas DC-8s built in the United States. A smaller bypass engine, the Rolls Royce Spey, also was built under license in the United States. It powered an attack plane, the A-7, which flew for both the U. S. Navy and Air Force.

However, Rolls-Royce fell into severe difficulties when it set out to build a new engine, the RB-211, for use with Lockheed's L-1011 airliner. The RB-211 was one of the first "high bypass" designs, with an enormous front fan and a rated thrust of some 40,000 pounds (177,929 newtons). This design certainly broke new ground, but its development proved to be very costly, which brought Rolls-Royce to the brink of financial ruin. Early in 1971, company directors learned that they had no prospect of raising the funds they needed. They placed Rolls-Royce into bankruptcy, expecting that the firm would be broken up and sold.

Lockheed's chairman, Dan Haughton, rescued Rolls-Royce by arranging for the U.S. Congress to guarantee a new loan of $250 million. This gave Rolls-Royce the money it needed. The firm emerged from bankruptcy and turned the RB-211 into a successful engine. Rolls-Royce remains active in its field as its new Trent series of engines vie for sales in the ongoing competitions of commercial aviation.

Note: This article was commissioned by and first appeared on NASA's U.S. Centennial of Flight web site. It appears here with permission. We gratefully acknowledge both the author and NASA.