IMPACT: Numerical Study of Aerodynamics of an Iced Forward-Swept Tail with Leading Edge Extension 2023-01-1371

In-flight icing significantly influences the design of large passenger aircraft. Relevant aspects include sizing of the main aerodynamic surfaces, provision of anti-icing systems, and setting of operational restrictions. Empennages of large passenger aircraft are particularly affected due to the small leading edge radius, and the requirement to generate considerable lift for round out and flare, following an extended period of descent often in icing conditions. This paper describes a CFD-based investigation of the effects of sweep on the aerodynamic performance of a novel forward-swept horizontal stabilizer concept in icing conditions. The concept features an unconventional forward sweep, combined with a high lift leading edge extension (LEX) located within a fuselage induced droplet shadow zone, providing passive protection from icing. In-flight ice accretion was calculated, using Ansys FENSAP-ICE, on 10°, 15° and 20° (low, intermediate, and high) sweep horizontal stabilizers, with the tail as attached to the full-scale aircraft, for a 45-minute holding pattern. The aerodynamic analyses of the iced tails were carried out using Ansys Fluent Aero with angle of attacks from 0° to -15°. All three sweeps show reduction in lifting performance under icing conditions, due to early separation. However, comparisons of lift coefficient versus angle of attack (C_L-α) curves, spanwise lift distributions, and three-dimensional flow fields show that increasing sweep reduces the early separation tendency along the span, but also reduces LEX lifting performance. This leads overall to reduced icing associated lift degradation at higher sweep. This effort has been undertaken as part of the Cleansky 2 IMPACT project (GA no. 885052).