CHARACTERISED by fierce competition among the major producers, the civil powerplant market has recently had to come to terms with a new type of propulsion system which, if all its claims are fully realised, will bring large benefits in terms of fuel efficiency and economy of operation. The most effective size of these engines, whether of the unducted fan or geared fan configuration, has yet to be proved but it appears that they will not be produced for applications requiring very high thrust, at least not for the foreseeable future.