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This model uses equations for estimating development and production costs and time of
arrival for U.S. military turbojet and turbofan engines. Interest in further investigation
of aircraft turbine engine cost estimating relationships (CERs) grew out of the
availability of data for engines recently developed, and experience with the CERs in
Rand's computer model for estimating Development and Procurement Costs of Aircraft
(DAPCA).
After establishing criteria for selecting explanatory variables and CERs, regression
analysis was applied to the expanded data base to develop improved relationships for the
cost of development to the model qualification test (MQT), total development cost, and the
cumulative average price at the 1000th production engine. The engine characteristics that
best explain development cost through MQT and production cost are maximum thrust of the
engine at sea-level-static conditions, an indicator of engine size; Mach number, a measure
of performance; and turbine inlet temperature, the dominant technical parameter in the
engine cycle. For total development cost, which includes the expenses involved in
developing a new engine to MQT, plus the cost to correct service related deficiencies and
costs for continual performance and reliability improvements over time, the derived
equation includes a production quantity term as well as thrust and Mach number.
The estimating relationship for time of arrival (TOA) was also refined in this study.
The TOA method links certain engine performance characteristics with time to provide a
measure of an engine's state of the art. The refined TOA model is based on 29 U.S.
military turbojet and turbofan engines developed and produced during the past 30 years.
The model predicts the man-rated MQT date as a function of certain of the engine's
performance and design parameters. The parameters include engine thrust to weight ratio,
turbine inlet temperature, and specific fuel consumption, which are the three most
important technical characteristics in the turbine engine development process.
These models are intended for use by long range military planners attempting to
determine costs for new systems - especially those of a technically advanced nature - so
that better estimates can be made. All parameters needed are readily available at an early
stage of planning for a new system. Care must be exercised in using these models to ensure
that inputs are consistent with the data base used in this study. For example, cost
estimates will reflect military technology and the manner in which programs were conducted
during the 1950s, 1960s, and 1970s. If an engine is developed that is not in the
mainstream trend, such as a variable cycle or lift engine, the estimating relationship
described may not apply. To the extent that a new program differs from historical
conditions, extrapolation will be necessary.
Source: "Development and Production Cost Estimating Relationships for Aircraft
Turbine Engines," J. L. Birkler, J. B. Garfinkle, K. E. Marks, Oct. 1982, Rand,
N-1882-AF
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