Erosion Resistant Surfaces on Aircraft Leading Edges

Leading edges of aircraft are highly susceptible to erosion caused by environmental factors during flight, such as rain, sand, and ice crystals, necessitating robust surface protection. In-service experience shows that among the solutions used today only steel foils consistently resist erosion throughout an aircraft's operational lifespan. While slight erosion on Aluminium parts like 2024 clad slats is expected and deemed acceptable for serial aircraft, provided a uniform appearance is maintained, new aircraft designs demand specific requirements. These include low roughness and the absence of disturbances for natural laminar flow (NLF) conditions, or the use of alternative materials for slats and more efficient manufacturing processes. Consequently, the development of alternative erosion resistant coating concepts is of high interest.

Beyond coating development itself, defining appropriate test specifications for evaluating these technologies are challenging. With rotating arm test facilities, lab water jet methods and gas jet tests using sand particles specific conditions for rain and sand erosion can be simulated, but a direct correlation with the highly variable in-service life of aircrafts and defining a quantitative requirement for passing the tests is difficult.

Within the EU funded Ultra-Performance (UP) Wing project new surface technologies for protecting an ultra-performance slat are developed and characterised. Elastomeric and hard coating concepts are under consideration. The impact of mechanical properties of the coating and the underlying substrate (Aluminum, Thermoplastic) on erosion resistance is determined by Pulsating Jet and Rotating Arm test, while varying test speeds between 160 and 225 m/sec, and by applying up to 200 g sand by means of gas jet test. Furthermore, first attempts to simulate rain erosion impacts are made by studying single rain droplet impacts on Aluminum. The ultimate goal is the prediction of erosion behavior of coatings based on intrinsic material properties.