## 3 Results
### IWT Tests  
Table 3 details the IWT test conditions selected by taking into account common performances of General Aviation, CS-25 (Test 1,2), and CS-23 (Test 4-6) categories [23]. The temperatures investigated ranged from \(-3\) to \(-23\)\({}^{\circ}\)C, at an altitude of 3000 m and an LWC of 0.3 g/m\({}^{3}\). Two different speeds were considered, i.e., 50 and 95 m/s, so the covered flight path (in clouds) ranged between about 7 and 13 km. Tests 1 referred to the CS-25  
Figure 9: Cutting and tape test carried out on S1 (**a,b**), S2 (**c,d**), C1 (**e,f**), and C2 (**g,h**) samples. On the top are the images of surfaces after the test; on the bottom, water droplets on tested surfaces to measure the residual wettability. vehicles category and investigated the lowest temperatures (\(-23\)\({}^{\circ}\)C), the highest speed (95m/s), and the highest LWC (0.5-0.6 g/m\({}^{3}\)). Test 2 replicated the test 1 conditions, but at sea level (altitude 83 m). Test 3-6 referred to the CS-23 vehicles category, investigating the temperature ranging between \(-3\) and \(-12\)\({}^{\circ}\)C, LWC was fixed to 0.3 g/m\({}^{3}\) and MVD at 20 \(\upmu\)m, and altitude at 3000 m, corresponding to severe icing cloud conditions which can occur at altitudes above 600 m [36]. In tests 3-6, along with the temperature, also the effect of speed was investigated (50 and 95 m/s). Figure 12 shows the pictures of both samples after each test. The surface of each sample was one-half superhydrophobic (A1 and A2 sites), whereas the other half was left as a reference (AR). First of all, it must be noted that the rime ice generated in tests 1, 2, and 5 (Figure 12a,b,e) covered quite uniformly the two samples, without taking into account the different wettability of the two half-sites of the samples. A deeper analysis of images revealed the presence of isolated frozen droplets along the airfoil, especially for coated surfaces which were evident in test 2 and test 5 (Figure 12b,e). Figure 11: Adhesion test results performed on C samples at 25\({}^{\circ}\)C and \(-30\)\({}^{\circ}\)C (**a**); schematic draw of most adhesion failures occurred during the testing of C samples (**b**). Figure 10: The Zwick Roll Z010 machine employed to perform the adhesion test (**a**), C samples before (**b**) and after the test (**c**). On the other hand, in glaze ice conditions, the low wettability of coated surfaces caused a reduction of the accreted ice, as highlighted in tests 3, 4, and 6 (Figure 12c,d,f), with a larger amount of isolated frozen droplets. This result seemed to provide evidence that, especially in glaze ice conditions, the high degree of surfaces' hydrophobicity caused the droplets to easily roll on the surface, reducing contact duration and thus ice accumulation. Additionally, in both rime and glaze ice, the isolated frozen droplets had a spherical shape, meaning that they preserved the low wettability at low temperatures and in dynamic conditions. The same behavior was observed at \(-5\,^{\circ}\)C by [PERSON] et al. [22] on hydrophobic and superhydrophobic surfaces (CA of 118-152\({}^{\circ}\)). Most of the droplets frozen as isolated ice had dimensions larger than the frozen droplets near the denser ice (_Lci_ in Figure 13a), probably because the droplets slipped on the superhydrophobic surface until they met an isolated iced droplet on which they could grow. Measurements of the accreted ice thickness, \(t_{ice}\), and the extension length of the compact ice, \(L_{ci}\), accreted along the airfoils (continuous blue zone in the schematic drawing in Figure 13a), were performed. In detail, for the measurements of \(t_{ice}\), seven marks were drawn on each airfoil at a 2 cm distance, and \(t_{ice}\) was measured as the difference in the chord length before and after the IWT tests (see pictures in Figure 13b,c).