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Session 2202

Cost Estimating Software for General Aviation Aircraft Design Charles N. Eastlake, Harry W. Blackwell Embry-Riddle Aeronautical University/Lockheed Martin Corporation

Abstract

The widely used DAPCA IV cost model for estimating aircraft acquisition cost is based on Department of Defense data and thus, not surprisingly, overpredicts the cost of general aviation (GA) aircraft. These equations were modified by the author for use as a tool for aircraft design classes at Embry-Riddle Aeronautical University in 1986. The first phase of modification was an intuitive adjustment based upon personal experience with the differences between designing military and civilian aircraft. Then a second phase of adjustment was made to force the equations to predict the correct current price of a Cessna 172. The equations were programmed in Basic and named LiteCost. The DAPCA equations were programmed almost “as is” to use for executive jet type projects and were named ExecCost. Then companion programs called LiteOps and ExecOps were written from scratch to estimate operations costs in dollars per flight hour. These were fairly fundamental book keeping type calculations based on inputs of flight hours per year, cost of fuel, amount of money borrowed to purchase the aircraft, and specification of design features which are more complex to maintain. This set of four programs has been in continuous use since then, and has been provided to several other universities.

In 1999 the co-author acquired the programs for use in a graduate school project. To enhance usability, he ported the existing code for the four programs into a newly created Windows-based graphical interface application using Microsoft Visual Basic. The convenience and user- friendliness of the programs are dramatically increased.

1. Introduction

The senior aircraft design course sequence at Embry-Riddle Aeronautical University has a long history of using general aviation aircraft as the assigned design specification. The incorporation of cost analysis into the design process has always been viewed as an important segment of the learning process. In the last two decades the concepts of Life Cycle Cost and Design to Cost have evolved from merely important to absolutely essential. The quandary provided by this situation is that the accepted cost models are based heavily on military acquisition data. Specifically, the DAPCA IV cost model (Reference 1) for aircraft acquisition cost is derived from military aircraft data. And as one would expect it predicts costs that are unrealistically high when applied to the relatively small and simple general aviation aircraft typified by civilian flight trainers and personal aircraft. In the case of the Cessna 172, the aircraft of this type which has been produced in the greatest numbers, the DAPCA IV model predicted a cost over three times the actual sale price. Coupled with this consistent overprediction of acquisition cost, there is not a commonly accepted model for the operational support cost portion of life cycle cost which is well suited for use with the limited amount of data available in student projects.

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Blackwell, H. W., & Eastlake, C. N. (2000, June), Cost Estimating Software For General Aviation Aircraft Design Paper presented at 2000 Annual Conference, St. Louis, Missouri. 10.18260/1-2--8243