Design and Calibration of a Flowfield Survey Rake for Inlet Flight Research

Abstract

The Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center is a unique test platform available for use on NASA's F-15B aircraft, tail number 836, as a modular host for a variety of aerodynamics and propulsion research. For future flight data from this platform to be valid, more information must be gathered concerning the quality of the airflow underneath the body of the F-15B at various flight conditions, especially supersonic conditions. The flow angularity and Mach number must be known at multiple locations on any test article interface plane for measurement data at these locations to be valid. To determine this prerequisite information, flight data will be gathered in the Rake Airflow Gauge Experiment using a custom-designed flowfield rake to probe the airflow underneath the F-15B at the desired flight conditions. This paper addresses the design considerations of the rake and probe assembly, including the loads and stress analysis using analytical methods, computational fluid dynamics, and finite element analysis. It also details the flow calibration procedure, including the completed wind-tunnel test and posttest data reduction, calibration verification, and preparation for flight-testing. = total pressure at probe n total pressure port, psf q = dynamic pressure, psf RAGE = Rake Airflow Gauge Experiment T t = wind tunnel or CFD total temperature, °R x = distance from centroid along x-axis, in. y = distance from centroid along y-axis, in. z = distance from centroid along z-axis, in. 2D = two-dimensional 3D = three-dimensional α = angle of attack, deg β = angle of sideslip, deg βq = product of sideslip angle and dynamic pressure β b = body axis angle of sideslip, deg β t = true angle of sideslip, deg δ 0 = wind-tunnel horizontal bias (misalignment) angle, deg θ = probe pitch angle (wind-tunnel), deg θ n = probe pitch angle corrected for bias, deg θ 0 = wind-tunnel pitch bias (misalignment) angle, deg σ n = normal stress, ksi σ x = normal stress, psi σ xx,max = maximum axial stress, ksi σ yield = yield stress, ksi φ = probe roll angle (wind-tunnel), deg φ n = probe roll angle corrected for bias, deg 3

Flight Test Results from the Rake Airflow Gage Experiment on the F-15B

“…As described in Ref. 5, each probe was not calibrated individually; instead, the rake was calibrated as a unit in a wind tunnel. Nonuniformities in the wind-tunnel flow had unquantifiable effects on the calibration of all of the probes except possibly the center probe, because this probe was the only one that was fixed in space in the tunnel as the calibration data were obtained.…”