Bristol Orion

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The Bristol Orion was a two‑shaft turboprop engine designed for later Bristol Britannia versions and the Canadair CL-44. It went into development as the BE.25 Orion, but the British Ministry of Supply cancelled the project in January 1958 in favor of the Rolls-Royce Tyne, as jet airliners were becoming more popular.

Design and features
- The Orion used a shared-load low‑pressure (LP) turbine to drive both the seven‑stage LP compressor and the propeller, similar to the later Rolls‑Royce Tyne. This was different from Bristol Proteus, which used a free‑power turbine.
- A single-stage high‑pressure (HP) turbine drove a five‑stage all‑axial HP compressor.
- The combustor used separate flame cans.
- The engine was derated from a thermodynamic rating of 9,000 shp at sea level to about 5,150 equivalent hp (ehp) so it could maintain constant power up to 15,000 ft altitude.

Legacy and cancellation
- The Orion project cost about £4.75 million before it was cancelled.
- Although the Orion itself did not go into production, its gas‑generator concept helped influence other designs. French designer Wibault used it to power a vectored‑thrust aircraft that eventually became the Hawker Siddeley P.1127, using a Bristol Siddeley Orpheus gas generator that had a compressor derived from Orion’s low‑pressure section.