The Rolls-Royce aero engine that was the first to use a three-shaft design was the RB211.
The RB211 was the first production three-spool, or three-shaft, turbofan engine. Its low-, intermediate- and high-pressure compressor sections were driven by separate concentric shafts, allowing each section to operate closer to its most efficient speed. That arrangement was more complex than a conventional two-shaft layout, but it offered important gains in efficiency, compactness and performance.
Rolls-Royce began developing the RB211 in the 1960s for the Lockheed L-1011 TriStar. The engine combined high-bypass technology with a carbon-fibre fan developed under the Hyfil programme. It was certified in April 1972, and the first TriStar entered service with Eastern Air Lines later that month.
The Conway was an earlier Rolls-Royce turbofan with a two-shaft design, while the Olympus was primarily an axial-flow turbojet and later turbofan family. Trent is not the answer because it is a later family that inherited and refined the RB211’s three-shaft principle. In fact, the RB211 became the technical foundation for the Trent line.