CORRELATION OF FULL-SCALE DRAG PREDICTIONS WITH FLIGHT MEASUREMENTS ON THE C-141A AIRCRAFT – PHASE Ⅱ, WING TUNNEL TEST, ANALYSIS, AND PREDICTION TECHNIQUES. VOLUME 1 – DRAG PREDICTION WIND TUNNEL DATA ANALYSIS AND CORRELATION

摘要

A research program has been conducted to determine the degree of cruise-drag correlation on the C-141A aircraft between predictions based on wind-tunnel test data, and flight test results. Volume 1 contains an analysis of wind-tunnel tests which were conducted in the NASA Langley 8-foot transonic wind tunnel on a 0.0275 scale C-141A model at Reynolds numbers up to 3.05 x 105/MAC. Model support interference corrections were evaluated through a systematic series of tests, and the fully-corrected model data analyzed to provide details of the model component interference factors. Detailed estimates of profile drag were conducted, including a review of flat plate skin friction, airfoil and wing form drag.nIt is shown that predicted, subcritical minimum profile drag of the complete configuration agrees within 0.7% of flight test data, through a wind-tunnel extrapolation method based on flat plate skin friction and component shape factors which, in turn, were based on average supervelocity calculations. The-full-scale estimated roughness drag is, therefore, assumed to be substantially correct from this correlation. An alternative method of extrapolation, based on computed profile drag from a subsonic viscous theory, resulted in a prediction which was four percent lower than flight.