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As the everyday use of flying small to medium size Remotely Piloted Aircraft System (RPAS) continues to evolve, so does the need to fly them in icing environments. To investigate an RPAS’ ability to fly in these conditions, an outdoor test rig has been developed at the National Research Council Canada (NRC) in which a range of RPAS have been tested in icing environments. This rig has an available test area of 3.05 m × 3.05 m, and is 5.1 m high. An array of spray nozzles installed at the top of the test rig provides a cloud that, when operated at sub-zero temperatures, enables simulation of in-flight icing conditions. The spray cloud is calibrated to provide water concentration and drop size distributions consistent with Appendix C, freezing drizzle and freezing rain conditions.

The development and calibration of a new facility to test medium size rotors for Remotely Piloted Aircraft Systems (RPAS) under in-flight icing conditions is described. This facility has made use of a 3 m x 6 m cold room available at the NRC which includes a spray system to provide the icing cloud as well as a dedicated rotor stand assembly that incorporates a load cell and dynamometer. Calibration data of the spray drop sizes and liquid water content are provided and compared to conditions of the natural environment as detailed in icing regulations for transport category airplanes, i.e., CFR 14 Part 25 Appendix C and O. Data to examine the sensitivity of rotor performance, under a constant liquid water content to various droplet sizes are provided for a medium sized rotor. Tests have also been performed that examine the ability of the rotor to maintain predefined thrust, torque and power performance throughout an icing encounter of fixed duration.

A study has been conducted into icephobic properties of some highly durable “off-the-shelf” elastomer materials using a rotating ice adhesion test rig installed in the NRC’s Altitude Icing Wind Tunnel. This enabled the formation of ice at environmental conditions similar to those experienced during in-flight icing encounters. Initially, the tests indicated some very positive results with ice adhesion shear stress as low as 8KPa. On further examination, however, it became apparent that the test preparation process, in which the samples were cleaned with an ethanol alcohol solution, influenced the results due to absorption and prolonged retention of the cleaning fluid. The uptake of the ethanol alcohol solution by the elastomer was found to be a function of the surface temperature and remained absorbed into the coating during the ice accretion process changing the characteristics of the coating in such a way that led to a reduction in the ice/surface bond strength.