Prediction of Antisymmetric Buffet Loads on Horizontal Stabilizers in Massively Separated Flows, Phase II.

Abstract : The Federal Aviation Administration (FAA) has a continuing program to collect data and develop predictive methods for aircraft flight loads. Some of the most severe and potentially catastrophic flight loads are produced by separated flows. Structural response to the aerodynamic excitation produced by separated flows is defined as buffeting. A low-cost technique for the prediction of full-scale buffet loads on horizontal stabilizers of aircraft is described. A 1/13-scale rigid generic wind tunnel model with a t-tail configuration (based on the Beech Super King Air 200) was constructed and tested at the Wichita State University 7x10 ft. subsonic wind tunnel. The test matrix included a dynamic pressure range of 25 to 45 psf; an angle-of-attack range of -5 to 20 degrees, and a sideslip range of 0 to 20 degrees. The stabilizer was instrumented with differential pressure transducers and strain gages. The measured pressure power spectra and cross-spectral densities were scaled and used to excite a full-scale aeroelastic finite element model which included the tail structure and aft tail cone. The computed horizontal stabilizer rolling moment power spectra are used to determine the number of exceedences (within a known probability) of a specified rolling moment level per a given maneuver (e.g., stall). Representative pressure, strain gage, and rolling moment power spectra are discussed as is a selected exceedence estimate.