Performance / Schedule / Cost Tradeoffs and Risk Analysis for the Acquisition of Aircraft Turbine Engines

This report discusses two applications of a cost-estimating model that incorporates quantitative measures of an engine's performance. A summary measure, called time of arrival (TOA), can be used in the decisionmaking process to trade off performance, schedule, and cost during the conceptual phase of aircraft turbine engines. The author briefly reviews the TOA measure and cost-estimating methodologies and then presents a trade-off and risk analysis of two present-day programs: the Rolls Royce RB211 engine program and a new, hypothetical, afterburning turbofan engine program. The analysis indicates: (1) The cost growth for the RB211 was due to an ambitious British program, in terms of performance level demanded for the specific schedule desired. (2) A schedule requiring a new engine "ahead of its time" results in a higher cost if it is achieved; it also exposes the engine, and the entire weapon system, to a higher risk of performance shortfall, schedule slippage, and cost growth. Future plans include an extension of the TOA methodology to the assessment of ownership costs for engines.