The PSU 94-097 airfoil has been designed for use on winglets of high-performance sailplanes. The design problem is difficult because the airfoil must operate over a wide range of Reynolds numbers, and this range includes values that are relatively low.

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A 1:17 scale model of a notional rotor hub of a large helicopter was tested in the Pennsylvania State University Applied Research Laboratory 12 in. test-section water tunnel. Objectives of the experiment were to quantify the effects of Reynolds number, advance ratio, and hub geometry configuration on the drag and shed wake of the rotor hub. A range of flow conditions was tested, with hub-diameter-based Reynolds numbers ranging from 1.0 × 10 6 to 2.6 × 10 6 and advance ratios ranging from 0.2 to 0.6, as well as nonrotating cases. Five hub geometry configurations were tested with various combinations of components including blade stubs, spiders, scissors, the swashplate, pitch links, and beanie fairing. Measurements included the steady and unsteady hub drag and particle image velocimetry at two downstream locations. Results include time-averaged and phase-averaged analyses of the unsteady drag and wake velocity. A strong dependence of the steady and unsteady hub drag and wake on the advance ratio, Reynolds number, and configuration was observed, demonstrating the importance of adequate Reynolds number scaling for model helicopter rotor hub tests.

In a number of instances, aircraft that have suffered in-flight damage to their airframe or control system were brought safely to the ground using unconventional means of control. The success in these cases depended greatly on the pilot having had some exposure to unconventional control strategies. Control strategies are considered for cases of aircraft with damage only to the primary control system, as well as cases in which the vertical tail is lost. The piloting strategies are developed using optimal control theory, which optimizes the control law for a desired maneuver and a chosen aircraft configuration. The results show that, despite the loss of the primary control system or of the vertical tail, control of the aircraft is often possible, although it requires the use of unconventional control strategies, in particular, of differential thrust. Especially in the case without a vertical tail, the maneuver in which adverse yaw induces a rolling moment opposite to the intended yaw direction is somewhat surprising and, initially, counterintuitive. Nomenclature= rolling moment coefficient, roll moment/ 1 2 ρV 2 ∞ Sb C m = pitching moment coefficient, pitch moment/ 1 2 ρV 2 ∞ Sc C n = yawing moment coefficient, yaw moment/ 1 2 ρV 2 ∞ Sb C Y = side force coefficient, side force/ 1 2 ρV 2 ∞ S c = mean aerodynamic chord H = weighting matrix (terminal) J = performance index K = Riccati matrix l = roll moment M = Mach number m = pitch moment n = yaw moment P = roll rate; positive when right wing moves down Q = pitch rate; positive when aircraft nose moves up Q = weighting matrix (tracking) R = yaw rate; positive when aircraft nose moves to right R = weighting matrix (control effort) r = desired state trajectory S = wing area s = command signal T = thrust U = forward velocity u = control vector V = side velocity; positive when aircraft moves to right V ∞ = flight speed W = downward velocity x = state vector α = angle of attack; positive when aircraft nose up β = sideslip angle; positive when aircraft moves to right δ A = aileron angle; positive when right aileron up δ E = elevator angle; positive when trailing edge up δ R = rudder angle; positive when trailing edge to left (negative yaw, but positive roll moment) = pitch angle; positive when aircraft nose up = bank angle; positive when left wing up = yaw angle; positive when aircraft nose points to right of flight path