Cycle Flexibility: It’s Impact on V/STOL Tactical Aircraft Propulsion Systems

The design of a V/STOL aircraft, incorporating only one lift-cruise engine places great emphasis on the flexibility of its propulsion system to provide sufficient thrust for take-off and efficient fuel consumption for cruise. In order to attain a reasonable range with a lightweight vehicle this inconsistency of thrust and SFC mis-match must be resolved. A brief survey of engine technology predictions for the next decade indicates that future aircraft systems would be offered a wider choice of cycle characteristics, higher technology levels, and added cycle flexibility. A comparative parametric study was conducted to determine the effect of these advancements on a postulated 1983 V/STOL aircraft. In particular the effect of increasing thrust through the use of thrust lapse-rating and variable turbine geometry were compared to more conventional augmentors such as duct burning and water injection. Additionally, the effects of varying cycle characteristics to realize SFC improvements were investigated.