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In recent years, the National Aeronautics and Space Administration (NASA) in cooperation with U.S. industry has performed flight and wind-tunnel investigations aimed at demonstrating the feasibility of obtaining significant amounts of laminar boundary-layer flow at moderate Reynolds numbers on the swept-back wings of commercial transport aircraft. Significant local drag reductions have been recorded with the use of a hybrid laminar flow control (HLFC) concept. In this paper, we address the potential application of HLFC to the external surface of an advanced, high bypass ratio turbofan engine nacelle with a wetted area which approaches 15 percent of the wing total wetted area of future commercial transports. A pressure distribution compatible with HLFC is specified and the corresponding nacelle geometry is computed utilizing a predictor/corrector design method. Linear stability calculations are conducted to provide predictions of the extent of the laminar boundary layer.

The results of a study that evaluates the application of hybrid laminar flow control (HLFC) to a long-range, twin-engine subsonic transport aircraft are presented. The study was performed using the Flight Optimization System (FLOPS), a rapid and flexible conceptual design and analysis code. This code is a multidisciplinary system of computer programs for conceptual and preliminary design and evaluation of advanced aircraft concepts. A 300 passenger, twin-engine baseline aircraft was defined for a 6,500 n.mi. design range. All operational and regulatory requirements and constraints, such as fuel reserves, balanced field length and second segment climb are satisfied during the design process. The baseline configuration was sized to account for 50 percent chord laminar flow on the wing upper surface and both surfaces of the horizontal and vertical tails. In addition, the benefits of achieving various amounts of laminar flow on the engine nacelles were also studied.