Modern commercial aircraft wings are far too large to be tested full-scale in existing icing wind tunnels and ice accretion scaling methods are not practical for large scale factors. Thus the use of hybrid scaling techniques, maintaining full-scale leading-edges and redesigned aft sections, is an attractive option for generating full-scale leading-edge ice accretions. The advantage lies in utilizing reduced chord models that minimize blockage effects in the icing tunnels. The present work discusses the design of hybrid airfoils with large scale factors that match the ice shapes of the full-scale airfoils predicted by LEWICE. Assessments of the effects of scale factor, extent of the full-scale leading-edge, nose droop angle, zero-angle of attack pitching moment coefficient (C m0 ), and droplet size are also presented. Hybrid or truncated airfoils are shown to produce ice shapes accurately, even at angles of attack different from the design angle of attack with the proper application of either flap, adjusted test angle of attack, or both. Further results suggest that hybrid circulation does not need to match full-scale circulation in order to match ice shapes, resulting in decreased loading for higher scale factor hybrid airfoils. Matching the flowfield around the hybrid airfoil to the full-scale flowfield provided a superior method for predicting ice shape agreement, stagnation point location being a first order and suction peak magnitude a second order parameter. This goal can be accomplished by varying the aft geometry, through C m0 and nose droop angle.Downloaded by UNIVERSITY OF ILLINOIS on August 14, 2013 | http://arc.aiaa.org |

Computational icing simulations of a hybrid, swept-wing model in the NASA IRT are presented. The results of these simulations are compared to those for the same icing conditions conducted on the full-scale reference wing. The effects of tunnel sidewalls, attachment line position, and altitude are considered. A discussion of icing scaling and the results of one scaling approach are given. The variation of impingement and ice shape with span in the tunnel for different angles of attack and flap deflection are presented.

A 3D swept hybrid wing design method using hybrid airfoils is presented for the purpose of icing wind tunnel testing of large commercial aircraft. Hybrid airfoils are those that present the same leading-edge geometry of the full-scale aircraft wing with a redesigned truncated aft section, such that models can fit inside icing wind tunnels and still reproduce full-scale flowfield and ice accretion with reduced chord. The effects of tunnel sidewalls, model sweep angle, aspect ratio, and wind tunnel blockage are presented. Attachment line location is used as a first-order parameter for matching full-scale ice shapes, and methods for controlling its spanwise variation are assessed including the use of gap between model and tunnel wall, aerodynamic twist, and segmented flaps. Finally, model design tradeoffs are presented between competing performance parameters such as full-scale ice accretion agreement, wind tunnel load/speed limits, and model manufacturing/operational complexity. NomenclatureAR = Aspect ratio α = Airfoil angle of attack c fs = Full-scale chord c hyb = Hybrid airfoil chord C p = Pressure coefficient C l = Lift coefficient C m0 = Quarter-chord zero-angle of attack pitching moment coefficient CRM = Common research model CRM65 = 65% scaled common research model δ = Flap deflection, positive down h/c = Tunnel height over model chord η = Wing spanwise position LE = Leading edge RANS = Reynolds-averaged Navier-Stokes equations SF = Scale factor (full-scale chord divided by hybrid chord) s/c = Normalized surface length coordinate