From Measurement Uncertainty to Measurement Communications, Credibility, and Cost Control in Propulsion Ground Test Facilities

In the past several years significant advances have been made in altitude ground test facilities with respect to measurement accuracy and measurement cost control. To a large measure, the advances have been the result of the application of comprehensive measurement uncertainty evaluation programs. This paper discusses the specific measurement evaluation process used in the Engine Test Facility, Arnold Engineering Development Center. To explain this process, the reader is guided through the measurement process for engine thrust, an extremely critical parameter for propulsion performance testing. Although this paper focuses on the measurement of engine thrust, the overall objective is the general measurement evaluation process and its uses. The approach presented can be applied to any type measurement system. First, an overview of the measurement uncertainty methodology and its application in altitude engine test cells is presented. The paper concludes with a discussion of how measurement uncertainty results can be utilized to improve measurement understanding and presents the means to identify factors that must be controlled to achieve a reliable and accurate measurement assessment.