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V/STOL Flight Test Instrumentation Requirements for Extraction of Aerodynamic Coefficients

Report Number: AFFDL TR 68-154 Volume 1
Author: Hill, R. W.
Author: Bolling, N. F.
Author: Clinkenbeard, I. L.
Corporate Author: LTV Aerospace Corporation
Laboratory: Air Force Flight Dynamics Laboratory
Date of Publication: 1968-12
Pages: 310
Contract: F33615-68-C-1222
Project: 3170
Task: 317004
AD Number: AD0850956

The results of a synthesis of pertinent maneuvers with a mathematical model of the XC-142 V/STOL airplane have served to establish tolerances in the measurement of flight parameters which provide the time histories used in the derivation of aerodynamic coefficients. Extracting valid aerodynamic coefficients from flight test time histories requires highly accurate instruments or detailed a priori knowledge of instrumentation errors. Furthermore, the mathematical technique used should provide the capability of extracting many coefficients simultaneously and delineating the probable error of each coefficient. The method of multiple linear regression, a least squares algorithm, provides the requisite mathematical tool with adequate statistical credentials. A state-of-the-art survey and a vendor-product-line review have provided guidelines for a system that will meet the overall accuracy requirements established. Details of equipment installations, oriented toward minimizing environmental stresses (particularly vibrations), have been studied. Conclusions drawn from this program are that the assembly and application of a precision data acquisition system based on digital 'onboard' handling techniques, with the appropriate sensing instrumentation, is entirely feasible but that limited development of measurement techniques, hardware, and software are required.

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