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The Learjet 85 is a business jet with an unpowered manual elevator control and is designed for a maximum dive Mach number of 0.89. During the early design, it was found that the stick force required for a 1.5g pull-up from a dive would exceed the limit set by FAA regulations. A design improvement of the tailplane was initiated, using 2D and 3D Navier-Stokes CFD codes. It was discovered that a small amount of positive camber could reduce the elevator hinge moment for the same tail download at high Mach numbers. This was the result of the stabilizer forebody carrying more of the tail download and the elevator carrying less. Consequently, the elevator hinge-moment during recovery from a high-speed dive was lower than for the original tail. Horizontal tails are conventionally designed with zero or negative camber since a positive camber can have adverse effects on tail stall and drag.

There are many different numerical approaches to ice accretion simulation. Little comparison has been made between those approaches to identify the best tool for a given application. This paper presents a comparison exercise between 2D codes (CANICE-BA and LEWICE) and 3D codes (CANICE3D-BA, LEWICE3D and FENSAP-ICE). It also compares the 3D first generation code (panel method with Lagrangian droplet trajectory tracking) CANICE3D-BA to the 3D second generation code (Navier-Stokes with Eulerian droplet tracking) FENSAP-ICE. The paper includes a description of the different methodologies. The first comparison exercise is done using three 2D cases for which experimental ice shapes are available. The second exercise addresses a water collection efficiency over an isolated tail for which experimental data is available. Finally, an ice accretion comparison is presented in a DLR4 wing-body configuration.