Composites in 1969

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Let's talk about a pioneer jet engine that used carbon fiber composites in 1969!

During the mid-sixties, both aircraft and engine manufacturers were in the process of updating their products from those of the initial jet era. There were new large aircraft that needed more powerful and economical engines. Three engine manufacturers were looking at these new requirements. General Electric started with its TF-39 (developed into the CF-6), and Pratt and Whitney were developing their JT9D to address the USAF Very Large Transport competition requirements. Ironically, the JT9D and Boeing were the losing designs, however, out of these grew the 747 air-frame and engine combination.

During research into a basic design for the long-term development of the company, Rolls-Royce determined that if they could develop a three spool engine then they would be able to match the air mass flow better to the compressors, provide superior fuel consumption and a much better path to even higher thrust engines. The RB211 was one of a proposed family of these engines. Now while the triple spool design had advantages, it was also over 450kg heavier than the competing engines.

One of the innovations proposed for this engine was the material proposed for the main front fan stage – a new, high strength, lightweight carbon fiber material called Hyfil. The first engine runs were in 1969 and the initial thrust of ~33,000 lb was gradually increased with testing, to ~40,000 lb. In May 1970 however, the massive 33 blade carbon fiber fan failed bird strike tests and Rolls Royce had to switch to using a heavier titanium alloy.

Unfortunately, at the time, composite technology was not ready for such a big leap. Nevertheless, nowadays, the usage of carbon fiber composites blades is increasing considerably!

Source: Article "Rolls Royce RB211 Turbofan Jet Aero Engine", published by the HARS Aviation Museum.

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