LAMINAR-FLOW CONTROL IS MATURING

Concerns about the practicality of laminar flow control are gradually fading as research shows that laminar flow can be reliable in flight and that the support system need not be complex. Early assessments of the fuel-saving potential assumed extensive laminar flow over the wings and empennage from either airfoil shaping or fuel chord suction. Shaping produces favorable pressure gradients for maintaining natural laminar flow (NLF), and laminar flow control (LFC) techniques such as full chord suction promise a fuel-saving payoff of up to 30% on long-range missions. NLF is most appealing because of its passive nature but is limited to low wing sweep and small chord Reynolds number. For large aircraft, current research is concentrated on hybrid laminar flow control (HLFC) concepts that combine suction and pressure-gradient control. This offers about half the fuel-savings potential of full chord LFC with a greatly simplified system.