Workshop session on propulsion of future aircraft

The principal findings and conclusions of our workshop were: we agreed that high fuel costs will continue over the long term, but the past pessimistic outlook has been tempered somewhat. Hence, we have more time to develop advanced technology into the next and succeeding cycles of equipment. Even so, those of us involved in advanced technology will not relax our efforts to continue those advances.

Fuel cost has become a major portion of direct operating cost - now over 50% - so improved fuel efficiency in the propulsion system is a key driver. However, it will not and cannot be achieved at the cost of increased complexity, shortened engine life, or in any way that worsens environmental impact. Considerable progress has been made in improving engine efficiency and reducing fuel consumption in current high-bypass ratio engines. However, there remains a considerable carrot for further reductions, particularly when it is recognized that some 70% of the fuel burned in an engine is associated with thermal and parasitic losses in the gas generator, power transfer losses, and installation drag. These represent wasted energy, some of which can be converted into useful work and improved propulsive efficiency.